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Question 1
Correct
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When two medical conditions are related through the presence of a confounding factor, the association is said to be:
Your Answer: Indirect
Explanation:Association and Causation: Understanding the Difference
Association refers to the relationship between two variables where one is more commonly found in the presence of the other. However, not all associations are causal. There are three types of association: spurious, indirect, and direct. Spurious associations are those that arise by chance and are not real, while indirect associations are due to the presence of another factor, also known as a confounding variable. Direct associations, on the other hand, are true associations not linked by a third variable.
To establish causation, the Bradford Hill Causal Criteria are used. These criteria include strength, temporality, specificity, coherence, and consistency. The strength of the association is an important factor in determining causation, as a stronger association is more likely to be truly causal. Temporality refers to whether the exposure precedes the outcome, while specificity asks whether the suspected cause is associated with a specific outcome or disease. Coherence considers whether the association fits with other biological knowledge, and consistency looks at whether the same association is found in many studies.
Understanding the difference between association and causation is important in research and decision-making. While an association may suggest a relationship between two variables, it does not necessarily mean that one causes the other. By using the Bradford Hill Causal Criteria, researchers can determine whether an association is truly causal and make informed decisions based on their findings.
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This question is part of the following fields:
- General Principles
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Question 2
Incorrect
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A 45-year-old man comes to the emergency department with a complaint of waking up with a severe headache for the past three days. He has been feeling increasingly nauseated and has vomited three times in the last 24 hours. During the examination, it was found that he has reduced power in his left upper limb and bilateral papilloedema. A CT scan of his head revealed a mass on the right side, close to the midline in the posterior frontal lobe. The mass is blocking the drainage of cerebrospinal fluid (CSF) into the third ventricle, causing enlargement of the lateral ventricle on the right side. Can you identify the structure through which CSF from the lateral ventricle drains into the third ventricle?
Your Answer: Cerebral aqueduct
Correct Answer: Interventricular foramen
Explanation:The interventricular foramina allow the two lateral ventricles to drain into the third ventricle, which is located in the midline between the thalami of the two hemispheres. The third ventricle is connected to the fourth ventricle via the cerebral aqueduct (of Sylvius). CSF flows from the third ventricle into the fourth ventricle and exits through one of four openings: the median aperture (foramen of Magendie), either of the two lateral apertures (foramina of Luschka), or the central canal at the obex.
The patient described in the question is exhibiting symptoms and signs that suggest an increase in intracranial pressure, which can be caused by various factors such as mass lesions and neoplasms. In this case, a mass is obstructing the normal flow of CSF through the ventricular system, leading to an increase in intracranial pressure and resulting in a motor deficit on the opposite side of the body. Symptoms of raised ICP may include vomiting, headaches that worsen when lying down or upon waking, changes in mental state, and papilloedema.
Cerebrospinal Fluid: Circulation and Composition
Cerebrospinal fluid (CSF) is a clear, colorless liquid that fills the space between the arachnoid mater and pia mater, covering the surface of the brain. The total volume of CSF in the brain is approximately 150ml, and it is produced by the ependymal cells in the choroid plexus or blood vessels. The majority of CSF is produced by the choroid plexus, accounting for 70% of the total volume. The remaining 30% is produced by blood vessels. The CSF is reabsorbed via the arachnoid granulations, which project into the venous sinuses.
The circulation of CSF starts from the lateral ventricles, which are connected to the third ventricle via the foramen of Munro. From the third ventricle, the CSF flows through the cerebral aqueduct (aqueduct of Sylvius) to reach the fourth ventricle via the foramina of Magendie and Luschka. The CSF then enters the subarachnoid space, where it circulates around the brain and spinal cord. Finally, the CSF is reabsorbed into the venous system via arachnoid granulations into the superior sagittal sinus.
The composition of CSF is essential for its proper functioning. The glucose level in CSF is between 50-80 mg/dl, while the protein level is between 15-40 mg/dl. Red blood cells are not present in CSF, and the white blood cell count is usually less than 3 cells/mm3. Understanding the circulation and composition of CSF is crucial for diagnosing and treating various neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 3
Incorrect
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A 94-year-old male, previously diagnosed with Parkinson's disease, passed away due to aspirational pneumonia and underwent a post-mortem examination. As part of the examination, a histological analysis of the basal ganglia was conducted. What types of inclusion bodies are anticipated to be observed?
Your Answer: Heinz bodies
Correct Answer: Lewy bodies
Explanation:Lewy bodies are commonly associated with Parkinson’s disease, but they can also be present in other conditions. These bodies are characterized by the presence of neuromelanin pigment and are typically found in the remaining Dopaminergic neurons in the substantia nigra pars compacta (SNc). They can be identified through staining for various proteins, including a-synuclein and ubiquitin. While their exact function is not yet fully understood, it is believed that Lewy bodies may play a role in managing proteins that are not properly broken down due to protein dysfunction.
Parkinson’s disease is a progressive neurodegenerative disorder that occurs due to the degeneration of dopaminergic neurons in the substantia nigra. This leads to a classic triad of symptoms, including bradykinesia, tremor, and rigidity, which are typically asymmetrical. The disease is more common in men and is usually diagnosed around the age of 65. Bradykinesia is characterized by a poverty of movement, shuffling steps, and difficulty initiating movement. Tremors are most noticeable at rest and typically occur in the thumb and index finger. Rigidity can be either lead pipe or cogwheel, and other features include mask-like facies, flexed posture, and drooling of saliva. Psychiatric features such as depression, dementia, and sleep disturbances may also occur. Diagnosis is usually clinical, but if there is difficulty differentiating between essential tremor and Parkinson’s disease, 123I‑FP‑CIT single photon emission computed tomography (SPECT) may be considered.
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This question is part of the following fields:
- Neurological System
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Question 4
Incorrect
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A 6-year-old boy presents to the clinic after experiencing his seventh fracture. Upon examination, his x-rays reveal dense bones with multiple cortical layers. He also has a mild normocytic anemia and low platelets, but his sclera appear white. What is the probable diagnosis?
Your Answer: Non-accidental injury
Correct Answer: Osteopetrosis
Explanation:Osteopetrosis and its Distinction from Other Bone Disorders
Osteopetrosis is a congenital condition that affects bone reabsorption, leading to the appearance of a ‘bone within a bone’ from multiple cortical layers. Despite the increased density, bones become brittle and prone to fracture, and there is no room for the marrow to grow, causing bone marrow failure and peripheral cytopenias. Additionally, bones expand and frequently cause neural compression symptoms.
When diagnosing osteopetrosis, it is important to exclude non-accidental injury (NAI) due to the repeated bone injury, but NAI alone cannot account for the x-ray findings or the blood counts. However, a diagnosis of osteopetrosis does not rule out the possibility of NAI co-existing with the condition.
Other bone disorders, such as acute lymphocytic leukemia and aplastic anemia, may present with peripheral cytopenias but not the x-ray appearances or multiple fractures. On the other hand, osteogenesis imperfecta (OI) is a congenital condition of brittle bones susceptible to multiple fractures due to a mutation in type I collagen. The most common form, type I OI, is inherited as an autosomal dominant condition and is associated with blue sclerae and neural deafness from bone overgrowth. X-rays show reduced bone density with cortical disorganization.
In summary, the distinct features of osteopetrosis and its differentiation from other bone disorders is crucial in making an accurate diagnosis and providing appropriate treatment.
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This question is part of the following fields:
- Rheumatology
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Question 5
Incorrect
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A 68-year-old female comes in with a sudden onset of back pain that radiates down her lower limb while she was gardening and bending forward. During a neurological examination of her lower limb, it was discovered that she has reduced power when flexing her hip and extending her knee. Her patellar reflex was also reduced, and there is decreased sensation in the anteromedial aspect of her thigh. Can you determine the level at which the intervertebral disc herniation is located based on these examination findings?
Your Answer: L2-L3
Correct Answer: L3-L4
Explanation:If there is a disc herniation at the L3-L4 level, it can impact the L4 spinal nerve and lead to issues with the femoral nerve’s function. A herniation at the L2-L3 level can cause L3 radiculopathy and result in weakness in hip adduction. On the other hand, a herniation at the L3-L4 level can cause L4 radiculopathy and lead to weakness in knee extension, with a greater contribution from L4 than L3, as well as a decrease in the patellar reflex.
Understanding Prolapsed Disc and its Features
A prolapsed disc in the lumbar region can cause leg pain and neurological deficits. The pain is usually more severe in the leg than in the back and worsens when sitting. The features of the prolapsed disc depend on the site of compression. For instance, compression of the L3 nerve root can cause sensory loss over the anterior thigh, weak quadriceps, reduced knee reflex, and a positive femoral stretch test. On the other hand, compression of the L4 nerve root can cause sensory loss in the anterior aspect of the knee, weak quadriceps, reduced knee reflex, and a positive femoral stretch test.
Similarly, compression of the L5 nerve root can cause sensory loss in the dorsum of the foot, weakness in foot and big toe dorsiflexion, intact reflexes, and a positive sciatic nerve stretch test. Lastly, compression of the S1 nerve root can cause sensory loss in the posterolateral aspect of the leg and lateral aspect of the foot, weakness in plantar flexion of the foot, reduced ankle reflex, and a positive sciatic nerve stretch test.
The management of prolapsed disc is similar to that of other musculoskeletal lower back pain, which includes analgesia, physiotherapy, and exercises. However, if the symptoms persist even after 4-6 weeks, referral for an MRI is appropriate. Understanding the features of prolapsed disc can help in early diagnosis and prompt management.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 6
Incorrect
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What is true about the Salmonella species?
Your Answer: Salmonella typhi can be categorised into type A, B and C
Correct Answer: A relative bradycardia is often seen in typhoid fever
Explanation:Enteric fever, also known as typhoid or paratyphoid, is caused by Salmonella typhi and Salmonella paratyphi respectively. These bacteria are not normally found in the gut and are transmitted through contaminated food and water or the faecal-oral route. The symptoms of enteric fever include headache, fever, and joint pain, as well as abdominal pain and distension. Constipation is more common in typhoid than diarrhoea, and rose spots may appear on the trunk in 40% of patients with paratyphoid. Possible complications of enteric fever include osteomyelitis, gastrointestinal bleeding or perforation, meningitis, cholecystitis, and chronic carriage. Chronic carriage is more likely in adult females and occurs in 1% of cases.
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This question is part of the following fields:
- General Principles
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Question 7
Incorrect
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Adrenaline is commonly released into the bloodstream during a normal physiological stress response. Upon entering the systemic circulation, adrenaline interacts with different adrenergic receptors, such as the β1 receptor.
What is the outcome of stimulating this receptor?Your Answer: Negative chronotropic effect on the myocardium
Correct Answer: Positive inotropic effect on the myocardium
Explanation:Stimulation of β1 adrenergic receptors leads to the contraction of cardiac muscle. This is because β1 receptor agonism results in positive inotropic and chronotropic effects, which increase the force and rate of cardiac contractions. It is important to note that β2 receptor agonism causes dilation of respiratory smooth muscle, while α2 receptor agonism inhibits insulin release from pancreatic β cells. The negative chronotropic effect on the myocardium is not caused by β1 receptor agonism, but rather by β1 receptor antagonism. Therefore, adrenaline would have a positive chronotropic effect on the myocardium.
Adrenergic receptors are a type of G protein-coupled receptors that respond to the catecholamines epinephrine and norepinephrine. These receptors are primarily involved in the sympathetic nervous system. There are four types of adrenergic receptors: α1, α2, β1, and β2. Each receptor has a different potency order and primary action. The α1 receptor responds equally to norepinephrine and epinephrine, causing smooth muscle contraction. The α2 receptor has mixed effects and responds equally to both catecholamines. The β1 receptor responds equally to epinephrine and norepinephrine, causing cardiac muscle contraction. The β2 receptor responds much more strongly to epinephrine than norepinephrine, causing smooth muscle relaxation.
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This question is part of the following fields:
- General Principles
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Question 8
Incorrect
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A 49-year-old man with a history of uncontrolled HIV presents with dyspnea and hemoptysis. Diagnostic tests reveal invasive aspergillosis, and he is prescribed amphotericin B. What is the mode of action of amphotericin B?
Your Answer: Inhibits DNA polymerase
Correct Answer: Binds with ergosterol
Explanation:The mechanism of action of Amphotericin B involves binding with ergosterol, a key component of fungal cell membranes. This binding results in the formation of pores that cause the cell wall to lyse, ultimately leading to fungal cell death.
Flucytosine, on the other hand, is converted by cytosine deaminase to 5-fluorouracil. This compound inhibits thymidylate synthase, which in turn disrupts fungal protein synthesis.
Caspofungin works by inhibiting the synthesis of beta-glucan, a major component of the fungal cell wall.
Griseofulvin interacts with microtubules, leading to the disruption of the mitotic spindle.
Anti-viral agents like acyclovir function by inhibiting viral DNA polymerase.
Antifungal agents are drugs used to treat fungal infections. There are several types of antifungal agents, each with a unique mechanism of action and potential adverse effects. Azoles work by inhibiting 14α-demethylase, an enzyme that produces ergosterol, a component of fungal cell membranes. However, they can also inhibit the P450 system in the liver, leading to potential liver toxicity. Amphotericin B binds with ergosterol to form a transmembrane channel that causes leakage of monovalent ions, but it can also cause nephrotoxicity and flu-like symptoms. Terbinafine inhibits squalene epoxidase, while griseofulvin interacts with microtubules to disrupt mitotic spindle. However, griseofulvin can induce the P450 system and is teratogenic. Flucytosine is converted by cytosine deaminase to 5-fluorouracil, which inhibits thymidylate synthase and disrupts fungal protein synthesis, but it can cause vomiting. Caspofungin inhibits the synthesis of beta-glucan, a major fungal cell wall component, and can cause flushing. Nystatin binds with ergosterol to form a transmembrane channel that causes leakage of monovalent ions, but it is very toxic and can only be used topically, such as for oral thrush.
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This question is part of the following fields:
- General Principles
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Question 9
Incorrect
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A 60-year-old man visits an after-hours medical facility in the late evening with a complaint of a severe headache that is focused around his left eye. He mentions experiencing haloes in his vision and difficulty seeing clearly. The patient has a medical history of hypertension and diabetes. During the examination, the sclera appears red, and the cornea is hazy with a dilated pupil.
What condition is the most probable diagnosis?Your Answer: Subarachnoid haemorrhage
Correct Answer: Acute closed-angle glaucoma
Explanation:The patient’s symptoms are consistent with acute closed-angle glaucoma, which is an urgent ophthalmological emergency. They are experiencing a headache with unilateral eye pain, reduced vision, visual haloes, a red and congested eye with a cloudy cornea, and a dilated, unresponsive pupil. These symptoms may be triggered by darkness or dilating eye drops. Treatment should involve laying the patient flat to relieve angle pressure, administering pilocarpine eye drops to constrict the pupil, acetazolamide orally to reduce aqueous humour production, and providing analgesia. Referral to secondary care is necessary.
It is important to differentiate this condition from other potential causes of the patient’s symptoms. Central retinal vein occlusion, for example, would cause sudden painless loss of vision and severe retinal haemorrhages on fundoscopy. Migraines typically involve a visual or somatosensory aura followed by a unilateral throbbing headache, nausea, vomiting, and photophobia. Subarachnoid haemorrhages present with a sudden, severe headache, rather than a gradually worsening one accompanied by eye signs. Temporal arteritis may cause pain when chewing, difficulty brushing hair, and thickened temporal arteries visible on examination. However, the presence of a dilated, fixed pupil with conjunctival injection should steer the clinician away from a diagnosis of migraine.
Acute angle closure glaucoma (AACG) is a type of glaucoma where there is a rise in intraocular pressure (IOP) due to a blockage in the outflow of aqueous humor. This condition is more likely to occur in individuals with hypermetropia, pupillary dilation, and lens growth associated with aging. Symptoms of AACG include severe pain, decreased visual acuity, a hard and red eye, haloes around lights, and a semi-dilated non-reacting pupil. AACG is an emergency and requires urgent referral to an ophthalmologist. The initial medical treatment involves a combination of eye drops, such as a direct parasympathomimetic, a beta-blocker, and an alpha-2 agonist, as well as intravenous acetazolamide to reduce aqueous secretions. Definitive management involves laser peripheral iridotomy, which creates a tiny hole in the peripheral iris to allow aqueous humor to flow to the angle.
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This question is part of the following fields:
- Neurological System
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Question 10
Incorrect
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A 82-year-old man visits the urology department complaining of a painful swelling in his left testicle that has been present for the past month. Upon examination, it is diagnosed as a left varicocele. Further CT scans reveal enlarged lymph nodes obstructing the venous drainage in the middle portion of his abdomen. Which vein is most likely to be compressed?
Your Answer: Pampiniform plexus of veins
Correct Answer: Left renal vein
Explanation:The left renal vein collects venous blood from the left testis through the left testicular/gonadal vein.
Both the left and right testes are drained by their respective testicular/gonadal veins. The right testicular vein empties directly into the inferior vena cava, while the left testicular vein drains into the left renal vein before joining the inferior vena cava.
Anatomy of the Inferior Vena Cava
The inferior vena cava (IVC) originates from the fifth lumbar vertebrae and is formed by the merging of the left and right common iliac veins. It passes to the right of the midline and receives drainage from paired segmental lumbar veins throughout its length. The right gonadal vein empties directly into the cava, while the left gonadal vein usually empties into the left renal vein. The renal veins and hepatic veins are the next major veins that drain into the IVC. The IVC pierces the central tendon of the diaphragm at the level of T8 and empties into the right atrium of the heart.
The IVC is related anteriorly to the small bowel, the first and third parts of the duodenum, the head of the pancreas, the liver and bile duct, the right common iliac artery, and the right gonadal artery. Posteriorly, it is related to the right renal artery, the right psoas muscle, the right sympathetic chain, and the coeliac ganglion.
The IVC is divided into different levels based on the veins that drain into it. At the level of T8, it receives drainage from the hepatic vein and inferior phrenic vein before piercing the diaphragm. At the level of L1, it receives drainage from the suprarenal veins and renal vein. At the level of L2, it receives drainage from the gonadal vein, and at the level of L1-5, it receives drainage from the lumbar veins. Finally, at the level of L5, the common iliac vein merges to form the IVC.
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This question is part of the following fields:
- Cardiovascular System
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Question 11
Incorrect
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A different patient, who has also been diagnosed with primary hyperparathyroidism due to elevated calcium and PTH levels, is wondering about the hormone's role in calcium metabolism within the kidneys.
Your Answer: Increases reabsorption of calcium in the collecting duct
Correct Answer: Increases tubular reabsorption of calcium
Explanation:The reabsorption of phosphate in the kidneys is increased by calcitriol. Parathyroid hormone, on the other hand, enhances the conversion of 25-hydroxycholecalciferol to calcitriol. Calcitriol, which is the active form of vitamin D, plays a crucial role in calcium metabolism in both the bones and the kidneys. Specifically, it promotes the reabsorption of calcium in the tubules of the kidneys, primarily in the proximal convoluted tubule, as well as in the thick ascending limb and distal convoluted tubule.
Hormones Controlling Calcium Metabolism
Calcium metabolism is primarily controlled by two hormones, parathyroid hormone (PTH) and 1,25-dihydroxycholecalciferol (calcitriol). Other hormones such as calcitonin, thyroxine, and growth hormone also play a role. PTH increases plasma calcium levels and decreases plasma phosphate levels. It also increases renal tubular reabsorption of calcium, osteoclastic activity, and renal conversion of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol. On the other hand, 1,25-dihydroxycholecalciferol increases plasma calcium and plasma phosphate levels, renal tubular reabsorption and gut absorption of calcium, osteoclastic activity, and renal phosphate reabsorption. It is important to note that osteoclastic activity is increased indirectly by PTH as osteoclasts do not have PTH receptors. Understanding the actions of these hormones is crucial in maintaining proper calcium metabolism in the body.
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This question is part of the following fields:
- General Principles
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Question 12
Incorrect
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A 19-year-old male is admitted with acute asthma. He has been treated with steroid, bronchodilators and 15 l/min of oxygen.
His pulse rate is 125/min, oxygen saturation 89%, respiratory rate 24/min, blood pressure 140/88 mmHg and he has a peak flow rate of 150 l/min. On auscultation of his chest, he has bilateral wheezes.
Arterial blood gas (ABG) result taken on 15 l/min oxygen shows:
pH 7.42 (7.36-7.44)
PaO2 8.4 kPa (11.3-12.6)
PaCO2 5.3 kPa (4.7-6.0)
Standard HCO3 19 mmol/L (20-28)
Base excess −4 (+/-2)
Oxygen saturation 89%
What is the most appropriate action for this man?Your Answer: Repeat arterial blood gas analysis, as it is likely to be a venous sample
Correct Answer: Call ITU to consider intubation
Explanation:Urgent Need for Ventilation in Life-Threatening Asthma
This patient is experiencing life-threatening asthma with a dangerously low oxygen saturation level of less than 92%. Despite having a normal PaCO2 level, the degree of hypoxia is inappropriate and requires immediate consideration for ventilation. The arterial blood gas (ABG) result is consistent with the clinical presentation, making a venous blood sample unnecessary. Additionally, the ABG and bedside oxygen saturation readings are identical, indicating an arterialised sample.
It is crucial to note that in cases of acute asthma, reducing the amount of oxygen below the maximum available is not recommended. Hypoxia can be fatal and must be addressed promptly. Therefore, urgent intervention is necessary to ensure the patient’s safety and well-being.
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This question is part of the following fields:
- Respiratory System
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Question 13
Incorrect
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Sarah is a 28-year-old teacher who has presented to the emergency department with a sudden onset of a severe headache and visual disturbances. Her medical history is significant only for asthma. She does not take any medications, does not smoke nor drink alcohol.
Upon examination, Sarah is alert and oriented but in obvious pain. Neurological examination reveals a fixed, dilated, non-reactive left pupil that is hypersensitive to light. All extra ocular movements are intact and there is no relative afferent pupillary defect. Systematic enquiry reveals no other abnormalities.
What is the most likely cause of Sarah's symptoms?Your Answer: Epilepsy
Correct Answer: Posterior communicating artery aneurysm
Explanation:Understanding Third Nerve Palsy: Causes and Features
Third nerve palsy is a neurological condition that affects the third cranial nerve, which controls the movement of the eye and eyelid. The condition is characterized by the eye being deviated ‘down and out’, ptosis, and a dilated pupil. In some cases, it may be referred to as a ‘surgical’ third nerve palsy due to the dilation of the pupil.
There are several possible causes of third nerve palsy, including diabetes mellitus, vasculitis (such as temporal arteritis or SLE), uncal herniation through tentorium if raised ICP, posterior communicating artery aneurysm, and cavernous sinus thrombosis. In some cases, it may also be a false localizing sign. Weber’s syndrome, which is characterized by an ipsilateral third nerve palsy with contralateral hemiplegia, is caused by midbrain strokes. Other possible causes include amyloid and multiple sclerosis.
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This question is part of the following fields:
- Neurological System
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Question 14
Incorrect
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A 59-year-old man is referred to an ophthalmologist by his physician due to complaints of blurry vision and floaters. He has a medical history of type II diabetes and hypertension.
During the slit lamp examination, the ophthalmologist observes a posterior vitreous detachment.
The ophthalmologist explains that the cause of his symptoms is likely due to a defect in the collagen that makes up the vitreous membrane, leading to its separation from the retina.
What type of collagen is the ophthalmologist referring to?Your Answer: Type IV collagen
Correct Answer: Type II collagen
Explanation:Type II collagen is the main component of the vitreous membrane, and any abnormalities in this collagen can raise the risk of vitreous haemorrhage. For more information on the various types of collagen and their respective locations, please refer to the notes provided.
Understanding Collagen and its Associated Disorders
Collagen is a vital protein found in connective tissue and is the most abundant protein in the human body. Although there are over 20 types of collagen, the most important ones are types I, II, III, IV, and V. Collagen is composed of three polypeptide strands that are woven into a helix, with numerous hydrogen bonds providing additional strength. Vitamin C plays a crucial role in establishing cross-links, and fibroblasts synthesize collagen.
Disorders of collagen can range from acquired defects due to aging to rare congenital disorders. Osteogenesis imperfecta is a congenital disorder that has eight subtypes and is caused by a defect in type I collagen. Patients with this disorder have bones that fracture easily, loose joints, and other defects depending on the subtype. Ehlers Danlos syndrome is another congenital disorder that has multiple subtypes and is caused by an abnormality in types 1 and 3 collagen. Patients with this disorder have features of hypermobility and are prone to joint dislocations and pelvic organ prolapse, among other connective tissue defects.
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This question is part of the following fields:
- General Principles
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Question 15
Incorrect
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Lily is a 32-year-old female who has been in a relationship for 3 years. Lily and her partner have been trying to conceive regularly for over a year without success. They have visited their doctor to arrange some tests to investigate a potential cause. What is the hormone that is released after ovulation and can be utilized as an indicator of fertility?
Your Answer: Testosterone
Correct Answer: Progesterone
Explanation:To test for ovulation in women with regular cycles, Day 21 progesterone (mid-luteal cycle progesterone) is used. However, for those with irregular cycles, progesterone should be tested a week before the predicted menstruation. Ovulation is necessary for fertilization to occur, as it indicates the release of an egg.
Oestrogen and Progesterone: Their Sources and Functions
Oestrogen and progesterone are two important hormones in the female body. Oestrogen is primarily produced by the ovaries, but can also be produced by the placenta and blood via aromatase. Its functions include promoting the development of genitalia, causing the LH surge, and increasing hepatic synthesis of transport proteins. It also upregulates oestrogen, progesterone, and LH receptors, and is responsible for female fat distribution. On the other hand, progesterone is produced by the corpus luteum, placenta, and adrenal cortex. Its main function is to maintain the endometrium and pregnancy, as well as to thicken cervical mucous and decrease myometrial excitability. It also increases body temperature and is responsible for spiral artery development.
It is important to note that these hormones work together in regulating the menstrual cycle and preparing the body for pregnancy. Oestrogen promotes the proliferation of the endometrium, while progesterone maintains it. Without these hormones, the menstrual cycle and pregnancy would not be possible. Understanding the sources and functions of oestrogen and progesterone is crucial in diagnosing and treating hormonal imbalances and reproductive disorders.
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This question is part of the following fields:
- Reproductive System
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Question 16
Incorrect
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Which one of the following cranial foramina pairings are incorrect?
Your Answer: Optic canal and ophthalmic artery.
Correct Answer: Optic canal and ophthalmic nerve.
Explanation:The optic nerve is transmitted through the optic canal, while the superior orbital fissure is traversed by the ophthalmic nerve.
Foramina of the Base of the Skull
The base of the skull contains several openings called foramina, which allow for the passage of nerves, blood vessels, and other structures. The foramen ovale, located in the sphenoid bone, contains the mandibular nerve, otic ganglion, accessory meningeal artery, and emissary veins. The foramen spinosum, also in the sphenoid bone, contains the middle meningeal artery and meningeal branch of the mandibular nerve. The foramen rotundum, also in the sphenoid bone, contains the maxillary nerve.
The foramen lacerum, located in the sphenoid bone, is initially occluded by a cartilaginous plug and contains the internal carotid artery, nerve and artery of the pterygoid canal, and the base of the medial pterygoid plate. The jugular foramen, located in the temporal bone, contains the inferior petrosal sinus, glossopharyngeal, vagus, and accessory nerves, sigmoid sinus, and meningeal branches from the occipital and ascending pharyngeal arteries.
The foramen magnum, located in the occipital bone, contains the anterior and posterior spinal arteries, vertebral arteries, and medulla oblongata. The stylomastoid foramen, located in the temporal bone, contains the stylomastoid artery and facial nerve. Finally, the superior orbital fissure, located in the sphenoid bone, contains the oculomotor nerve, recurrent meningeal artery, trochlear nerve, lacrimal, frontal, and nasociliary branches of the ophthalmic nerve, and abducent nerve.
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This question is part of the following fields:
- Neurological System
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Question 17
Incorrect
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A 20-year-old man experienced recurrent episodes of breathlessness and palpitations lasting approximately 20 minutes and resolving gradually. No unusual physical signs were observed. What is the probable cause of these symptoms?
Your Answer: Paroxysmal supraventricular tachycardia
Correct Answer: Panic attacks
Explanation:Likely Diagnosis for Sudden Onset of Symptoms
When considering the sudden onset of symptoms, drug abuse is an unlikely cause as the symptoms are short-lived and not accompanied by other common drug abuse symptoms. Paroxysmal SVT would present with sudden starts and stops, rather than a gradual onset. Personality disorder and thyrotoxicosis would both lead to longer-lasting symptoms and other associated symptoms. Therefore, the most likely diagnosis for sudden onset symptoms would be panic disorder. It is important to consider all possible causes and seek medical attention to properly diagnose and treat any underlying conditions.
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This question is part of the following fields:
- Cardiovascular System
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Question 18
Incorrect
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A pair comes to your endocrine clinic. The woman has achondroplasia and her partner does not. They want to discuss with you the factors to consider before having a baby. What is accurate about achondroplasia?
Your Answer: It is caused by a mutation in the growth hormone (GH) receptor
Correct Answer: It is unlikely to respond to growth hormone therapy
Explanation:Achondroplasia is a condition that causes dwarfism due to a growth disorder. It is inherited in an autosomal dominant manner, and most affected individuals can expect to have a normal lifespan. However, if both parents have achondroplasia, there is a 25% chance that their child will inherit two copies of the gene, which can be fatal either before or shortly after birth. The cause of achondroplasia is a mutation in the fibroblast growth factor (FGF) receptor, which means that growth hormone therapy is unlikely to be effective.
Achondroplasia is a genetic disorder that causes short stature due to abnormal cartilage development. It is caused by a mutation in the FGFR-3 gene and is inherited in an autosomal dominant manner. The condition is characterized by short limbs with shortened fingers, a large head with frontal bossing and narrow foramen magnum, midface hypoplasia with a flattened nasal bridge, ‘trident’ hands, and lumbar lordosis. In most cases, it occurs as a sporadic mutation, with advancing parental age being a risk factor.
There is currently no specific treatment for achondroplasia. However, some individuals may benefit from limb lengthening procedures, which involve the use of Ilizarov frames and targeted bone fractures. It is important to have a clearly defined need and end point for these procedures in order to achieve success.
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This question is part of the following fields:
- General Principles
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Question 19
Incorrect
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A 30-year-old woman has recently returned from a trip to south-east Asia. She is experiencing a swinging fever and shows signs of jaundice. Additionally, she has been complaining of headaches and has started to lose consciousness and experience convulsions. Given the symptoms, it is suspected that there may be cerebral involvement.
Upon examination of a blood film, it is found that a significant number of red blood cells (RBCs) contain inclusion bodies that resemble 'signet rings'. Approximately 20% of the RBCs have multiple inclusion bodies.
What is the most likely organism responsible for these symptoms?Your Answer: Plasmodium knowlesi
Correct Answer: Plasmodium falciparum
Explanation:The most common cause of cerebral malaria is Plasmodium falciparum, also known as ‘malignant’ malaria. This parasitic disease is important to recognize, especially in individuals who have recently traveled to high-risk areas. Other plasmodium species, such as Plasmodium knowlesi, Plasmodium malariae, and Plasmodium ovale, are not typically associated with cerebral malaria.
Understanding Malaria: Causes, Types, and Protective Factors
Malaria is a disease caused by Plasmodium protozoa, which is transmitted through the bite of a female Anopheles mosquito. There are four different species of Plasmodium that can cause malaria in humans, with Plasmodium falciparum being the most severe. The other three types, including Plasmodium vivax, cause a milder form of the disease known as benign malaria.
Several protective factors against malaria have been identified, including sickle-cell trait, G6PD deficiency, HLA-B53, and the absence of Duffy antigens. These factors can help reduce the risk of contracting the disease.
To better understand the life cycle of the malaria parasite, an illustration is provided by the National Institute of Allergy and Infectious Diseases (NIAID). By understanding the causes, types, and protective factors of malaria, we can work towards preventing and treating this deadly disease.
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This question is part of the following fields:
- General Principles
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Question 20
Incorrect
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What is the cell type in the glomerulus that has a role in phagocytosis?
Your Answer: Podocytes
Correct Answer: Mesangial cells
Explanation:The Structure of the Glomerulus
The glomerulus is composed of glomerular capillaries that are lined by a basement membrane and podocyte processes. Podocytes are connected to the epithelial cells of Bowman’s capsule, which are then connected to the cells of the proximal convoluted tubule. Supporting cells called mesangial cells are located between the capillary endothelial cells and podocytes. These cells produce the extracellular matrix that supports the structure of the glomerulus and remove dead cells through phagocytosis. Additionally, mesangial cells may play a role in regulating glomerular blood flow. Overall, the glomerulus is a complex structure that plays a crucial role in the filtration of blood in the kidneys.
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This question is part of the following fields:
- Histology
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Question 21
Correct
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A 67-year-old woman presents to the clinic with a gradual onset of dyspnea on exertion over the past 6 months. She has a medical history of severe COPD and is currently receiving long-term oxygen therapy. During the examination, you observe pitting edema up to the mid-thighs, an elevated JVP with a prominent V wave, a precordial heave, and a loud P2. What is the most probable mechanism involved in this diagnosis?
Your Answer: Pulmonary arteries vasoconstriction due to hypoxia
Explanation:Hypoxia causes vasoconstriction of pulmonary arteries, leading to a diagnosis of right heart failure secondary to hypoxic lung disease, also known as cor pulmonale.
The Effects of Hypoxia on Pulmonary Arteries
When the partial pressure of oxygen in the blood decreases, the pulmonary arteries undergo vasoconstriction. This means that the blood vessels narrow, allowing blood to be redirected to areas of the lung that are better aerated. This response is a natural mechanism that helps to improve the efficiency of gaseous exchange in the lungs. By diverting blood to areas with more oxygen, the body can ensure that the tissues receive the oxygen they need to function properly. Overall, hypoxia triggers a physiological response that helps to maintain homeostasis in the body.
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This question is part of the following fields:
- Respiratory System
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Question 22
Incorrect
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You are requested to evaluate a patient in your clinic who has developed lesions on his penis. He reports that he has recently come back from Thailand, where he had unprotected sexual intercourse with multiple partners on three occasions. He denies any discomfort or pain while urinating, and there is no discharge. On examination, you notice a small group of fleshy lesions on the glans, but there is no ulceration.
What is the most probable pathogen responsible for the patient's symptoms?Your Answer: Chlamydia trachomatis
Correct Answer: HPV 6 or 11
Explanation:Genital warts are caused by HPV subtypes 6 and 11, which are non-carcinogenic. These warts are sexually transmitted and can also affect the larynx. While they do not pose a cancer risk, they can be psychologically distressing and require treatment such as podophyllotoxin ointment, cryotherapy, or surgical removal. Recurrence is possible due to HPV ability to remain dormant.
In contrast, HPV subtypes 16 and 18 are carcinogenic and linked to various cancers, but do not cause warts.
Syphilis, caused by Treponema pallidum, presents with a painless ulcer during the primary stage and can develop wart-like lesions during secondary syphilis, although this is rare compared to genital warts. Chlamydia trachomatis is another common sexually transmitted infection with various symptoms.
HPV Infection and Cervical Cancer
Human papillomavirus (HPV) infection is the primary risk factor for cervical cancer, with subtypes 16, 18, and 33 being the most carcinogenic. Other common subtypes, such as 6 and 11, are associated with genital warts but are not carcinogenic. When endocervical cells become infected with HPV, they may undergo changes that lead to the development of koilocytes. These cells have distinct characteristics, including an enlarged nucleus, irregular nuclear membrane contour, hyperchromasia (darker staining of the nucleus), and a perinuclear halo. These changes are important diagnostic markers for cervical cancer and can be detected through Pap smears or other screening methods. Early detection and treatment of HPV infection and cervical cancer can greatly improve outcomes and reduce the risk of complications.
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This question is part of the following fields:
- Haematology And Oncology
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Question 23
Incorrect
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Sophie is a 22-year-old woman who was diagnosed with hypertrophic cardiomyopathy 4 years ago. Since then she has developed pulmonary hypertension which has added to her symptom load. To alleviate this, Sophie's doctor considers prescribing ambrisentan, an endothelin receptor antagonist. By inhibiting the mediator, endothelin, the doctor hopes to improve Sophie's symptoms until she receives a heart transplant.
What are the main physiological impacts of this mediator?Your Answer: Increased renal reabsorption of sodium and excretion of potassium
Correct Answer: Vasoconstriction and bronchoconstriction
Explanation:Endothelin is a potent vasoconstrictor and bronchoconstrictor that is secreted by endothelial cells and plays a crucial role in vascular homeostasis. However, excessive production of endothelin has been linked to various pathologies, including primary pulmonary hypertension. Inhibiting endothelin receptors can help lower pulmonary blood pressure.
It’s important to note that endothelin does not affect systemic vascular resistance or sodium excretion, which are regulated by atrial and ventricular natriuretic peptides. Aldosterone, on the other hand, is responsible for increasing sodium reabsorption in the kidneys, and it’s believed that endothelin and aldosterone may work together to regulate sodium homeostasis.
While endothelin causes vasoconstriction, it does not cause bronchodilation. Adrenaline, on the other hand, causes both vasoconstriction and bronchodilation, allowing for improved oxygen absorption from the lungs while delivering blood to areas of the body that require it for action.
Finally, endothelin does not increase endovascular permeability, which is a function of histamine released by mast cells in response to noxious stimuli. Histamine enhances the recruitment of leukocytes to an area of inflammation by causing vascular changes.
Understanding Endothelin and Its Role in Various Diseases
Endothelin is a potent vasoconstrictor and bronchoconstrictor that is secreted by the vascular endothelium. Initially, it is produced as a prohormone and later converted to ET-1 by the action of endothelin converting enzyme. Endothelin interacts with a G-protein linked to phospholipase C, leading to calcium release. This interaction is thought to be important in the pathogenesis of many diseases, including primary pulmonary hypertension, cardiac failure, hepatorenal syndrome, and Raynaud’s.
Endothelin is known to promote the release of angiotensin II, ADH, hypoxia, and mechanical shearing forces. On the other hand, it inhibits the release of nitric oxide and prostacyclin. Raised levels of endothelin are observed in primary pulmonary hypertension, myocardial infarction, heart failure, acute kidney injury, and asthma.
In recent years, endothelin antagonists have been used to treat primary pulmonary hypertension. Understanding the role of endothelin in various diseases can help in the development of new treatments and therapies.
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This question is part of the following fields:
- Cardiovascular System
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Question 24
Incorrect
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Which statement regarding ligand gated ion channels (LGIC) is accurate?
Your Answer: Channel ion selectivity is dependent upon pore size
Correct Answer: Agonist recognition and ion channel are intrinsic to a single protein complex
Explanation:Ligand Gated Ion Channels: A Brief Overview
Ligand gated ion channels (LGICs) are protein complexes that have both agonist recognition and ion channel functions. These functions are intrinsic to a single protein complex, which is usually pentameric in nature. For example, the nicotinic acetylcholine receptor (nAChR) is composed of a2ßδγ subunits. Each monomer of the LGIC has four transmembrane domains (TMSD) labeled M1-M4. The M2 domain forms a putative alpha-helix within the membrane.
LGICs typically have a charged entrance that plays a role in ion selectivity. For instance, the nAChR has a negatively charged entrance that attracts Na and K ions. This selectivity is crucial for the proper functioning of the LGIC. the structure and function of LGICs is important for developing drugs that target these channels. By targeting LGICs, researchers can develop drugs that modulate the activity of these channels, which can have therapeutic benefits for a variety of diseases.
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This question is part of the following fields:
- Pharmacology
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Question 25
Incorrect
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A middle-aged woman who is obese comes in with complaints of polyuria. She has a history of squamous cell lung carcinoma. What could be the possible reason for her polyuria?
Your Answer: Type 2 diabetes mellitus
Correct Answer: Hyperparathyroidism
Explanation:Polyuria is caused by all the options listed above, except for syndrome of inappropriate ADH secretion. However, the patient’s age does not match the typical onset of type 1 diabetes, which usually occurs in young individuals. Furthermore, squamous cell lung carcinoma is commonly associated with a paraneoplastic syndrome that results in the release of excess parathyroid hormone by the tumor, leading to hypercalcemia and subsequent polyuria, along with other symptoms such as renal and biliary stones, bone pain, abdominal discomfort, nausea, vomiting, depression, and anxiety.
Lung cancer can present with paraneoplastic features, which are symptoms caused by the cancer but not directly related to the tumor itself. Small cell lung cancer can cause the secretion of ADH and, less commonly, ACTH, which can lead to hypertension, hyperglycemia, hypokalemia, alkalosis, and muscle weakness. Lambert-Eaton syndrome is also associated with small cell lung cancer. Squamous cell lung cancer can cause the secretion of parathyroid hormone-related protein, leading to hypercalcemia, as well as clubbing and hypertrophic pulmonary osteoarthropathy. Adenocarcinoma can cause gynecomastia and hypertrophic pulmonary osteoarthropathy. Hypertrophic pulmonary osteoarthropathy is a painful condition involving the proliferation of periosteum in the long bones. Although traditionally associated with squamous cell carcinoma, some studies suggest that adenocarcinoma is the most common cause.
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This question is part of the following fields:
- Respiratory System
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Question 26
Incorrect
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A 49-year-old female presents to her family physician with complaints of post-coital pain. She initially attributed it to her age, but lately, she has been experiencing a constant dull pain in her pelvis. Additionally, she reports having a foul-smelling discharge from her vagina. Her medical and surgical history is unremarkable, but she mentions having multiple sexual partners during her teenage years and twenties. She has been smoking ten cigarettes a day for the past decade and does not consume alcohol. During the examination, the doctor discovers an irregular mass on her cervix. What is the primary mechanism behind the most significant risk factor for this patient's condition?
Your Answer: Cigarette smoking produces dysplasia of the squamocolumnar junction leading to cervical cancer
Correct Answer: Human papillomavirus 16 and 18 produces oncoproteins which causes inhibition of the tumor suppressor genes causing cervical carcinoma
Explanation:The patient is displaying typical signs and symptoms of cervical carcinoma, with a constant dull pelvic pain indicating possible invasion of pelvic structures and nerves. The strongest risk factor for this patient is having had multiple sexual partners at a young age, which increases the likelihood of being infected with the human papillomavirus.
1: Multiple sexual partners are the strongest risk factor for cervical carcinoma due to the increased chance of contracting the human papillomavirus, specifically the 16 and 18 viral strains that inhibit the tumor suppressor genes p53 and RB, triggering carcinogenesis.
2: While cigarette smoking can have an oncogenic effect, it is not the primary risk factor in this case.
3: HIV is a risk factor for cervical carcinoma, but it is less common than the human papillomavirus.
4: The human papillomavirus is the primary risk factor, but it does not activate oncogenes. Instead, it inhibits tumor suppressor genes.
5: Age alone is not a risk factor for cervical carcinoma. However, an older person who has been exposed to the human papillomavirus may have a higher risk due to the longer exposure time for the virus to induce carcinogenesis via the inhibition of tumor suppressor genes.HPV Infection and Cervical Cancer
Human papillomavirus (HPV) infection is the primary risk factor for cervical cancer, with subtypes 16, 18, and 33 being the most carcinogenic. Other common subtypes, such as 6 and 11, are associated with genital warts but are not carcinogenic. When endocervical cells become infected with HPV, they may undergo changes that lead to the development of koilocytes. These cells have distinct characteristics, including an enlarged nucleus, irregular nuclear membrane contour, hyperchromasia (darker staining of the nucleus), and a perinuclear halo. These changes are important diagnostic markers for cervical cancer and can be detected through Pap smears or other screening methods. Early detection and treatment of HPV infection and cervical cancer can greatly improve outcomes and reduce the risk of complications.
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This question is part of the following fields:
- Haematology And Oncology
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Question 27
Incorrect
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A 38-year-old woman who had a kidney transplant 3 years ago visits the transplant clinic for follow-up. She has been in good health and is currently on tacrolimus medication to prevent transplant rejection.
What is the mode of action of tacrolimus?Your Answer: Pyrimidine metabolism antagonist
Correct Answer: Calcineurin inhibitor
Explanation:Tacrolimus functions as a calcineurin inhibitor, which is a type of immunosuppressant used to prevent transplant rejection. Alkylating agents like cyclophosphamide and platinum compounds are also used for immunosuppression in autoimmune diseases. Methotrexate, a folic acid analogue, inhibits the synthesis of tetrahydrofolate to exhibit its immunosuppressive action. Azathioprine and similar medications work by antagonizing purine metabolism to maintain immunosuppression after a transplant.
Tacrolimus: An Immunosuppressant for Transplant Rejection Prevention
Tacrolimus is an immunosuppressant drug that is commonly used to prevent transplant rejection. It belongs to the calcineurin inhibitor class of drugs and has a similar action to ciclosporin. The drug works by reducing the clonal proliferation of T cells by decreasing the release of IL-2. It binds to FKBP, forming a complex that inhibits calcineurin, a phosphatase that activates various transcription factors in T cells. This is different from ciclosporin, which binds to cyclophilin instead of FKBP.
Compared to ciclosporin, tacrolimus is more potent, resulting in a lower incidence of organ rejection. However, it is also associated with a higher risk of nephrotoxicity and impaired glucose tolerance. Despite these potential side effects, tacrolimus remains an important drug in preventing transplant rejection and improving the success of organ transplantation.
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This question is part of the following fields:
- General Principles
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Question 28
Correct
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Infusion with which of the following blood products is most likely to result in an urticarial reaction?
Rewritten: Infusion of which blood product is most likely to cause urticarial reactions?Your Answer: Fresh frozen plasma
Explanation:Transfusion of packed red cells is frequently associated with pyrexia as an adverse event, while infusion of FFP often leads to urticaria as the most common adverse event.
Blood product transfusion complications can be categorized into immunological, infective, and other complications. Immunological complications include acute haemolytic reactions, non-haemolytic febrile reactions, and allergic/anaphylaxis reactions. Infective complications may arise due to transmission of vCJD, although measures have been taken to minimize this risk. Other complications include transfusion-related acute lung injury (TRALI), transfusion-associated circulatory overload (TACO), hyperkalaemia, iron overload, and clotting.
Non-haemolytic febrile reactions are thought to be caused by antibodies reacting with white cell fragments in the blood product and cytokines that have leaked from the blood cell during storage. These reactions may occur in 1-2% of red cell transfusions and 10-30% of platelet transfusions. Minor allergic reactions may also occur due to foreign plasma proteins, while anaphylaxis may be caused by patients with IgA deficiency who have anti-IgA antibodies.
Acute haemolytic transfusion reaction is a serious complication that results from a mismatch of blood group (ABO) which causes massive intravascular haemolysis. Symptoms begin minutes after the transfusion is started and include a fever, abdominal and chest pain, agitation, and hypotension. Treatment should include immediate transfusion termination, generous fluid resuscitation with saline solution, and informing the lab. Complications include disseminated intravascular coagulation and renal failure.
TRALI is a rare but potentially fatal complication of blood transfusion that is characterized by the development of hypoxaemia/acute respiratory distress syndrome within 6 hours of transfusion. On the other hand, TACO is a relatively common reaction due to fluid overload resulting in pulmonary oedema. As well as features of pulmonary oedema, the patient may also be hypertensive, a key difference from patients with TRALI.
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This question is part of the following fields:
- Haematology And Oncology
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Question 29
Incorrect
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A 31-year-old woman with hypothyroidism is visiting the endocrinology clinic for a check-up. She has been prescribed levothyroxine. Can you explain the characteristics of this medication, which acts by targeting thyroid hormone receptors to regulate gene transcription?
Your Answer: Hydrophilic, activates messenger proteins
Correct Answer: Lipophilic, diffuses through cell membrane
Explanation:For drugs to effectively target nuclear receptors, they need to possess lipid solubility to enable them to penetrate the cell membrane.
Pharmacodynamics refers to the effects of drugs on the body, as opposed to pharmacokinetics which is concerned with how the body processes drugs. Drugs typically interact with a target, which can be a protein located either inside or outside of cells. There are four main types of cellular targets: ion channels, G-protein coupled receptors, tyrosine kinase receptors, and nuclear receptors. The type of target determines the mechanism of action of the drug. For example, drugs that work on ion channels cause the channel to open or close, while drugs that activate tyrosine kinase receptors lead to cell growth and differentiation.
It is also important to consider whether a drug has a positive or negative impact on the receptor. Agonists activate the receptor, while antagonists block the receptor preventing activation. Antagonists can be competitive or non-competitive, depending on whether they bind at the same site as the agonist or at a different site. The binding affinity of a drug refers to how readily it binds to a specific receptor, while efficacy measures how well an agonist produces a response once it has bound to the receptor. Potency is related to the concentration at which a drug is effective, while the therapeutic index is the ratio of the dose of a drug resulting in an undesired effect compared to that at which it produces the desired effect.
The relationship between the dose of a drug and the response it produces is rarely linear. Many drugs saturate the available receptors, meaning that further increased doses will not cause any more response. Some drugs do not have a significant impact below a certain dose and are considered sub-therapeutic. Dose-response graphs can be used to illustrate the relationship between dose and response, allowing for easy comparison of different drugs. However, it is important to remember that dose-response varies between individuals.
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This question is part of the following fields:
- General Principles
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Question 30
Incorrect
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A 36-year-old man has been referred to the sleep clinic by his GP due to reports from his partner of sleepwalking and appearing frightened during the night. Additionally, he has been known to scream while sleeping and recently experienced an episode of bedwetting. At which stage of sleep do these symptoms typically occur?
Your Answer: Non-REM stage 1
Correct Answer: Non-REM stage 3
Explanation:Understanding Sleep Stages: The Sleep Doctor’s Brain
Sleep is a complex process that involves different stages, each with its own unique characteristics. The Sleep Doctor’s Brain provides a simplified explanation of the four main sleep stages: N1, N2, N3, and REM.
N1 is the lightest stage of sleep, characterized by theta waves and often associated with hypnic jerks. N2 is a deeper stage of sleep, marked by sleep spindles and K-complexes. This stage represents around 50% of total sleep. N3 is the deepest stage of sleep, characterized by delta waves. Parasomnias such as night terrors, nocturnal enuresis, and sleepwalking can occur during this stage.
REM, or rapid eye movement, is the stage where dreaming occurs. It is characterized by beta-waves and a loss of muscle tone, including erections. The sleep cycle typically follows a pattern of N1 → N2 → N3 → REM, with each stage lasting for different durations throughout the night.
Understanding the different sleep stages is important for maintaining healthy sleep habits and identifying potential sleep disorders. By monitoring brain activity during sleep, the Sleep Doctor’s Brain can provide valuable insights into the complex process of sleep.
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This question is part of the following fields:
- Neurological System
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Question 31
Incorrect
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A couple has approached you for genetic counselling. The husband, Felix, is worried about passing on a mitochondrial disease to his future child as his sister died at a young age due to complications associated with the same disease. The wife, Melissa, has no family history of any such disease. Both parents identify as cisgender.
Felix undergoes testing for the mitochondrial disease, and the results come back positive.
What is the probability of their first child being affected by this mitochondrial disease?Your Answer: 100%
Correct Answer: 0%
Explanation:Mitochondrial diseases are caused by a small amount of double-stranded DNA present in the mitochondria, which encodes protein components of the respiratory chain and some special types of RNA. These diseases are inherited only via the maternal line, as the sperm contributes no cytoplasm to the zygote. None of the children of an affected male will inherit the disease, while all of the children of an affected female will inherit it. Mitochondrial diseases generally encode rare neurological diseases, and there is poor genotype-phenotype correlation due to heteroplasmy, which means that within a tissue or cell, there can be different mitochondrial populations. Muscle biopsy typically shows red, ragged fibers due to an increased number of mitochondria. Examples of mitochondrial diseases include Leber’s optic atrophy, MELAS syndrome, MERRF syndrome, Kearns-Sayre syndrome, and sensorineural hearing loss.
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This question is part of the following fields:
- General Principles
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Question 32
Correct
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Sophie, a 6-week-old baby, presents to the emergency department for evaluation. Her mother has observed that Sophie has been experiencing shortness of breath for the past 3 weeks, particularly during feeding. Sophie was born at 36 weeks and her mother reports no other issues since birth.
During the examination, a continuous machinery murmur with a left-sided sub-clavicular thrill is detected, and a diagnosis of patent ductus arteriosus is made. Surgery is not deemed necessary, but a medication that inhibits prostaglandin synthesis is recommended.
What is the most probable pharmacological treatment that will be offered?Your Answer: Indomethacin
Explanation:The inhibition of prostaglandin synthesis in infants with patent ductus arteriosus is achieved through the use of indomethacin. This medication (or ibuprofen) is effective in promoting closure of the ductus arteriosus by inhibiting prostaglandin synthesis.
Beta-blockers such as bisoprolol are not used in the management of PDA, making this answer incorrect.
Steroids like dexamethasone and prednisolone are not typically used in the treatment of PDA, although they may be given to the mother if premature delivery is expected. Therefore, these answers are also incorrect.
Understanding Patent Ductus Arteriosus
Patent ductus arteriosus is a type of congenital heart defect that is generally classified as ‘acyanotic’. However, if left uncorrected, it can eventually result in late cyanosis in the lower extremities, which is termed differential cyanosis. This condition is caused by a connection between the pulmonary trunk and descending aorta. Normally, the ductus arteriosus closes with the first breaths due to increased pulmonary flow, which enhances prostaglandins clearance. However, in some cases, this connection remains open, leading to patent ductus arteriosus.
This condition is more common in premature babies, those born at high altitude, or those whose mothers had rubella infection in the first trimester. The features of patent ductus arteriosus include a left subclavicular thrill, continuous ‘machinery’ murmur, large volume, bounding, collapsing pulse, wide pulse pressure, and heaving apex beat.
The management of patent ductus arteriosus involves the use of indomethacin or ibuprofen, which are given to the neonate. These medications inhibit prostaglandin synthesis and close the connection in the majority of cases. If patent ductus arteriosus is associated with another congenital heart defect amenable to surgery, then prostaglandin E1 is useful to keep the duct open until after surgical repair. Understanding patent ductus arteriosus is important for early diagnosis and management of this condition.
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This question is part of the following fields:
- Cardiovascular System
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Question 33
Incorrect
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You are a third year medical student assisting a plastic surgeon in theatre. The plastic surgeon hands you a surgical retractor and asks you to retract the latissimus dorsi muscle. Once you have successfully done so, the surgeon inquires about the nerve responsible for innervating this muscle.
What is the nerve that innervates the latissimus dorsi muscle?Your Answer: Axillary nerve
Correct Answer: Thoracodorsal nerve
Explanation:The Functions of Different Nerves in the Brachial Plexus
The brachial plexus is a network of nerves that originate from the spinal cord and provide innervation to the upper limb. Each nerve in the brachial plexus has a specific function and innervates a particular muscle or group of muscles. the functions of these nerves is essential for diagnosing and treating various neurological conditions.
One of the nerves in the brachial plexus is the thoracodorsal nerve, which originates from the posterior cord of the brachial plexus. Its primary function is to provide somatic innervation to the latissimus dorsi muscle, which is a large muscle in the posterior thorax involved in shoulder joint movement.
Another nerve in the brachial plexus is the upper subscapular nerve, which innervates the subscapularis muscle. The long thoracic nerve, on the other hand, innervates the serratus anterior muscle, and damage to this nerve can cause a winging effect on the scapula.
The axillary nerve is another nerve in the brachial plexus that originates from the posterior cord. Its primary motor supply is to the deltoid muscle, which is involved in shoulder abduction.
Lastly, the lateral pectoral nerve is a branch of the lateral cord and innervates the pectoralis major muscle. The pectoralis major muscle also receives innervation from the medial pectoral nerve, which is a branch of the median cord of the brachial plexus.
In summary, each nerve in the brachial plexus has a specific function and innervates a particular muscle or group of muscles. the functions of these nerves is crucial for diagnosing and treating various neurological conditions.
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This question is part of the following fields:
- Clinical Sciences
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Question 34
Incorrect
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A 65-year-old male presents with a six month history of weight loss and tiredness. He is a smoker of 10 cigarettes per day and drinks approximately 10 units of alcohol daily.
On examination, he appears slightly plethoric, but otherwise has no obvious abnormality. Investigations reveal a haemoglobin level of 202 g/L (130-180), platelets of 310 ×109/L (150-400), and a white cell count of 9.2 ×109/L (4-11). His U+Es are normal and his glucose level is 5.5 mmol/L (3.0-6.0). Urine analysis reveals blood 2+.
What is the most appropriate investigation for this patient that will aid in the diagnosis?Your Answer: Oral glucose tolerance test
Correct Answer: Abdominal ultrasound scan
Explanation:Salient Features and Possible Causes of Polycythaemia
The patient presents with weight loss, no obvious physical abnormalities, and a polycythaemia with 2+ blood on dipstick analysis. These symptoms suggest the need for investigation of a genitourinary (GU) malignancy, with an ultrasound abdomen being the most appropriate test. It is important to note that smoking may cause polycythaemia, but it could also be caused by a hypernephroma that produces ectopic erythropoietin. Therefore, further investigation is necessary to determine the underlying cause of the patient’s polycythaemia.
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This question is part of the following fields:
- Renal System
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Question 35
Correct
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During pronation and supination, which bones are involved in movement?
Your Answer: Rotation of the radius on the ulna
Explanation:The movement of the arm’s pronation and supination is caused by the rotation of the radius bone, while the ulna bone remains still. This movement involves two joints: the proximal and distal radio-ulnar joints. The humerus bone remains stationary during this process, while the radial head rotates on the humerus’s capitulum. It’s worth noting that the distal carpal bones don’t move in relation to the distal radius during pronation and supination.
Anatomy of the Radius Bone
The radius bone is one of the two long bones in the forearm that extends from the lateral side of the elbow to the thumb side of the wrist. It has two expanded ends, with the distal end being the larger one. The upper end of the radius bone has articular cartilage that covers the medial to lateral side and articulates with the radial notch of the ulna by the annular ligament. The biceps brachii muscle attaches to the tuberosity of the upper end.
The shaft of the radius bone has several muscle attachments. The upper third of the body has the supinator, flexor digitorum superficialis, and flexor pollicis longus muscles. The middle third of the body has the pronator teres muscle, while the lower quarter of the body has the pronator quadratus muscle and the tendon of supinator longus.
The lower end of the radius bone is quadrilateral in shape. The anterior surface is covered by the capsule of the wrist joint, while the medial surface has the head of the ulna. The lateral surface ends in the styloid process, and the posterior surface has three grooves that contain the tendons of extensor carpi radialis longus and brevis, extensor pollicis longus, and extensor indicis. Understanding the anatomy of the radius bone is crucial in diagnosing and treating injuries and conditions that affect this bone.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 36
Incorrect
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A 32-year-old female patient visits your clinic complaining of fatigue and unexplained weight gain. She mentions feeling extremely sensitive to cold temperatures. You suspect hypothyroidism and decide to conduct a test on her serum levels of thyroid stimulating hormone (TSH) and free thyroxine (T4). Which of the following hormones is not secreted from the anterior pituitary gland, where TSH is released?
Your Answer: Growth hormone
Correct Answer: antidiuretic hormone
Explanation:The hormone ADH (also known as vasopressin) is secreted by the posterior pituitary gland and acts in the collecting ducts of the kidneys to increase water reabsorption. Unlike ADH, all of the other hormone options presented are released from the anterior pituitary. ACTH is a component of the hypothalamic-pituitary-axis and increases the production and release of cortisol from the adrenal gland. GH (also called somatotropin) is an anabolic hormone that stimulates growth in childhood and has metabolic effects on protein, glucose, and lipids. FSH is a gonadotropin that promotes the maturation of germ cells.
Thyroid disorders are commonly encountered in clinical practice, with hypothyroidism and thyrotoxicosis being the most prevalent. Women are ten times more likely to develop these conditions than men. The thyroid gland is a bi-lobed structure located in the anterior neck and is part of a hypothalamus-pituitary-end organ system that regulates the production of thyroxine and triiodothyronine hormones. These hormones help regulate energy sources, protein synthesis, and the body’s sensitivity to other hormones. Hypothyroidism can be primary or secondary, while thyrotoxicosis is mostly primary. Autoimmunity is the leading cause of thyroid problems in the developed world.
Thyroid disorders can present in various ways, with symptoms often being the opposite depending on whether the thyroid gland is under or overactive. For example, hypothyroidism may result in weight gain, while thyrotoxicosis leads to weight loss. Thyroid function tests are the primary investigation for diagnosing thyroid disorders. These tests primarily look at serum TSH and T4 levels, with T3 being measured in specific cases. TSH levels are more sensitive than T4 levels for monitoring patients with existing thyroid problems.
Treatment for thyroid disorders depends on the cause. Patients with hypothyroidism are given levothyroxine to replace the underlying deficiency. Patients with thyrotoxicosis may be treated with propranolol to control symptoms such as tremors, carbimazole to reduce thyroid hormone production, or radioiodine treatment.
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This question is part of the following fields:
- Endocrine System
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Question 37
Incorrect
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A 28-year-old female, who is 5 months postpartum, presents with a 4-week history of weight loss, heat intolerance, tremor, palpitation and diarrhoea. Pregnancy and birth were uncomplicated. On further questioning, she admits having taken off-license weight loss medication bought from the internet 2 months ago. Past medical history and family history are insignificant. She does not smoke or drink alcohol.
On physical examination, she has exophthalmos, brisk reflexes and fine tremor. Her vital signs were heart rate 100/minute, blood pressure 138/78 mmHg, temperature 36.6ºC. The thyroid gland was diffusely enlarged.
Thyroid Stimulating Hormone (TSH) 0.01 mU/l
Free thyroxine (T4) 25 pmol/l
Total thyroxine (T4) 155 nmol/l
What is the most likely diagnosis?Your Answer: Hashimoto's thyroiditis
Correct Answer: Graves' Disease
Explanation:During the postnatal period, Graves’ disease may either present for the first time or worsen. Exophthalmos is a distinctive symptom of Graves’ disease that is not observed in other hyperthyroid conditions. Hypothyroidism is caused by Hashimoto’s thyroiditis. postpartum thyroiditis is characterized by initial hyperthyroidism after childbirth, followed by normal or occasionally reduced thyroid levels.
During pregnancy, there is an increase in the levels of thyroxine-binding globulin (TBG), which causes an increase in the levels of total thyroxine. However, this does not affect the free thyroxine level. If left untreated, thyrotoxicosis can increase the risk of fetal loss, maternal heart failure, and premature labor. Graves’ disease is the most common cause of thyrotoxicosis during pregnancy, but transient gestational hyperthyroidism can also occur due to the activation of the TSH receptor by HCG. Propylthiouracil has traditionally been the antithyroid drug of choice, but it is associated with an increased risk of severe hepatic injury. Therefore, NICE Clinical Knowledge Summaries recommend using propylthiouracil in the first trimester and switching to carbimazole in the second trimester. Maternal free thyroxine levels should be kept in the upper third of the normal reference range to avoid fetal hypothyroidism. Thyrotropin receptor stimulating antibodies should be checked at 30-36 weeks gestation to determine the risk of neonatal thyroid problems. Block-and-replace regimes should not be used in pregnancy, and radioiodine therapy is contraindicated.
On the other hand, thyroxine is safe during pregnancy, and serum thyroid-stimulating hormone should be measured in each trimester and 6-8 weeks postpartum. Women require an increased dose of thyroxine during pregnancy, up to 50% as early as 4-6 weeks of pregnancy. Breastfeeding is safe while on thyroxine. It is important to manage thyroid problems during pregnancy to ensure the health of both the mother and the baby.
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This question is part of the following fields:
- Endocrine System
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Question 38
Correct
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Samantha is a 42-year-old woman who has presented with new-onset urinary retention over the past 8 hours. She was previously diagnosed with non-Hodgkin's lymphoma and is currently undergoing chemotherapy treatment for this. She notes that prior to this, her urine had a reddish-tinge.
A 3-way catheter was inserted and blood-stained urine with clots was seen within the catheter bag. Urinalysis showed significant blood but no leukocytes or nitrites were seen. A cystoscopy performed did not show any masses and biopsies taken did not show any malignancy. It was felt that this was a likely side effect of one of these chemotherapy agents.
What is the underlying mechanism of action of the culprit chemotherapy agent?Your Answer: Promotes cross-linking of DNA
Explanation:The chemotherapy regime R-CHOP, which is likely being used to manage the patient’s non-Hodgkin’s lymphoma, includes cyclophosphamide, a drug that functions as an alkylating agent and promotes cross-linking of DNA. This can lead to haemorrhagic cystitis, which is likely the cause of the patient’s haematuria. Other drugs in the regime have different mechanisms of action, such as inhibition of microtubule formation with vincristine, inhibition of topoisomerase II and DNA/RNA synthesis with doxorubicin, and monoclonal antibody targeting of CD20 with rituximab. Pyrimidine analogues like 5-fluorouracil, which block thymidylate synthase and induce cell cycle arrest and apoptosis, are not commonly used in the management of non-Hodgkin’s lymphoma.
Cytotoxic agents are drugs that are used to kill cancer cells. There are several types of cytotoxic agents, each with their own mechanism of action and potential adverse effects. Alkylating agents, such as cyclophosphamide, work by causing cross-linking in DNA. However, they can also cause haemorrhagic cystitis, myelosuppression, and transitional cell carcinoma. Cytotoxic antibiotics, like bleomycin and anthracyclines, degrade preformed DNA and stabilize DNA-topoisomerase II complex, respectively. However, they can also cause lung fibrosis and cardiomyopathy. Antimetabolites, such as methotrexate and fluorouracil, inhibit dihydrofolate reductase and thymidylate synthesis, respectively. However, they can also cause myelosuppression, mucositis, and liver or lung fibrosis. Drugs that act on microtubules, like vincristine and docetaxel, inhibit the formation of microtubules and prevent microtubule depolymerisation & disassembly, respectively. However, they can also cause peripheral neuropathy, myelosuppression, and paralytic ileus. Topoisomerase inhibitors, like irinotecan, inhibit topoisomerase I, which prevents relaxation of supercoiled DNA. However, they can also cause myelosuppression. Other cytotoxic drugs, such as cisplatin and hydroxyurea, cause cross-linking in DNA and inhibit ribonucleotide reductase, respectively. However, they can also cause ototoxicity, peripheral neuropathy, hypomagnesaemia, and myelosuppression.
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This question is part of the following fields:
- Haematology And Oncology
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Question 39
Incorrect
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A 29-year-old woman visits the antenatal clinic for her week 28 anti-D injection during her first pregnancy. Blood tests were conducted, and the following outcomes were obtained:
pH 7.47 (7.35 - 7.45)
PO2 10 kPa (11 - 15)
PCO2 4.0 kPa (4.6 - 6.4)
Bicarbonate 20 mmol/L (22 - 29)
What pregnancy-related physiological alteration is accountable for these findings?Your Answer: Increase in cardiac output
Correct Answer: Increase in pulmonary ventilation and tidal volume
Explanation:A haemoglobin level of 105 g/L is considered normal at 28 weeks of pregnancy, with the non-pregnant reference range being 115-165 g/L.
During pregnancy, a woman’s body undergoes various physiological changes. The cardiovascular system experiences an increase in stroke volume, heart rate, and cardiac output, while systolic blood pressure remains unchanged and diastolic blood pressure decreases in the first and second trimesters before returning to normal levels by term. The enlarged uterus may cause issues with venous return, leading to ankle swelling, supine hypotension, and varicose veins.
The respiratory system sees an increase in pulmonary ventilation and tidal volume, with oxygen requirements only increasing by 20%. This can lead to a sense of dyspnea due to over-breathing and a fall in pCO2. The basal metabolic rate also increases, potentially due to increased thyroxine and adrenocortical hormones.
Maternal blood volume increases by 30%, with red blood cells increasing by 20% and plasma increasing by 50%, leading to a decrease in hemoglobin levels. Coagulant activity increases slightly, while fibrinolytic activity decreases. Platelet count falls, and white blood cell count and erythrocyte sedimentation rate rise.
The urinary system experiences an increase in blood flow and glomerular filtration rate, with elevated sex steroid levels leading to increased salt and water reabsorption and urinary protein losses. Trace glycosuria may also occur.
Calcium requirements increase during pregnancy, with gut absorption increasing substantially due to increased 1,25 dihydroxy vitamin D. Serum levels of calcium and phosphate may fall, but ionized calcium levels remain stable. The liver experiences an increase in alkaline phosphatase and a decrease in albumin levels.
The uterus undergoes significant changes, increasing in weight from 100g to 1100g and transitioning from hyperplasia to hypertrophy. Cervical ectropion and discharge may increase, and Braxton-Hicks contractions may occur in late pregnancy. Retroversion may lead to retention in the first trimester but usually self-corrects.
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This question is part of the following fields:
- Reproductive System
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Question 40
Incorrect
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A 65-year-old man with a history of type 2 diabetes is being seen by his primary care physician.
He is currently taking metformin 1g twice daily and lisinopril for his high blood pressure.
His most recent HbA1c result is:
HbA1c 58 mmol/L (<42)
After further discussion, he has agreed to add a second medication for his diabetes. He has been informed that potential side effects may include weight gain, hypoglycemia, and gastrointestinal issues.
What is the mechanism of action for this new medication?Your Answer:
Correct Answer: Binding to KATP channels on pancreatic beta cell membrane
Explanation:Sulfonylureas are a type of medication used to treat type 2 diabetes mellitus. They work by increasing the amount of insulin produced by the pancreas, but only if the beta cells in the pancreas are functioning properly. Sulfonylureas bind to a specific channel on the cell membrane of pancreatic beta cells, known as the ATP-dependent K+ channel (KATP).
While sulfonylureas can be effective in managing diabetes, they can also cause some adverse effects. The most common side effect is hypoglycemia, which is more likely to occur with long-acting preparations like chlorpropamide. Another common side effect is weight gain. However, there are also rarer side effects that can occur, such as hyponatremia (low sodium levels) due to inappropriate ADH secretion, bone marrow suppression, hepatotoxicity (liver damage), and peripheral neuropathy.
It is important to note that sulfonylureas should not be used during pregnancy or while breastfeeding.
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This question is part of the following fields:
- Endocrine System
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