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Question 1
Correct
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What is the function of aldosterone in the kidney?
Your Answer: Retain sodium and excrete potassium
Explanation:The Role of Aldosterone in Sodium and Potassium Balance
Aldosterone is a hormone that plays a crucial role in regulating the balance of sodium and potassium in the body. It is the final stage of the renin-angiotensin-aldosterone axis, which is triggered by reduced flow to the kidneys. The main function of aldosterone is to retain sodium at the expense of potassium. This helps to increase fluid volume by retaining water, which is important for maintaining blood pressure and electrolyte balance.
To maintain electrochemical balance, potassium has to be excreted to retain sodium. This means that when aldosterone levels are high, the body will excrete more potassium in the urine. Conversely, when aldosterone levels are low, the body will retain more potassium and excrete more sodium. This delicate balance is essential for proper functioning of the body’s cells and organs.
In summary, aldosterone is a hormone that helps to regulate the balance of sodium and potassium in the body. It is triggered by reduced flow to the kidneys and works to retain sodium at the expense of potassium. This helps to increase fluid volume and maintain electrolyte balance.
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This question is part of the following fields:
- Clinical Sciences
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Question 2
Incorrect
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An 82-year-old man arrives at the emergency department with sepsis of unknown origin. During a thorough examination, it is discovered that his big toe is swollen, black, and tender. A fluid collection is also present at the nail bed. The patient has a history of uncontrolled type 1 diabetes mellitus. An MRI confirms the diagnosis of osteomyelitis. What is the probable causative organism?
Your Answer: Staphylococcus epidermidis
Correct Answer: Staphylococcus aureus
Explanation:The most common cause of osteomyelitis is Staphylococcus aureus, a bacteria that is normally found on the skin and mucus membranes but can become pathogenic in individuals who are immunocompromised or have risk factors for infections. Clostridium perfringens, Pseudomonas aeruginosa, and Staphylococcus epidermidis are not common causes of osteomyelitis, although they may cause other types of infections.
Understanding Osteomyelitis: Types, Causes, and Treatment
Osteomyelitis is a bone infection that can be classified into two types: haematogenous and non-haematogenous. Haematogenous osteomyelitis is caused by bacteria in the bloodstream and is usually monomicrobial. It is more common in children and can be caused by risk factors such as sickle cell anaemia, intravenous drug use, immunosuppression, and infective endocarditis. On the other hand, non-haematogenous osteomyelitis is caused by the spread of infection from adjacent soft tissues or direct injury to the bone. It is often polymicrobial and more common in adults, with risk factors such as diabetic foot ulcers, pressure sores, diabetes mellitus, and peripheral arterial disease.
Staphylococcus aureus is the most common cause of osteomyelitis, except in patients with sickle-cell anaemia where Salmonella species are more prevalent. To diagnose osteomyelitis, MRI is the imaging modality of choice, with a sensitivity of 90-100%.
The treatment for osteomyelitis involves a course of antibiotics for six weeks. Flucloxacillin is the preferred antibiotic, but clindamycin can be used for patients who are allergic to penicillin. Understanding the types, causes, and treatment of osteomyelitis is crucial in managing this bone infection.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 3
Incorrect
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A 67-year-old patient is being evaluated after being admitted for treatment of a persistent Clostridium difficile infection. The patient had received treatment for a previous infection three weeks ago, but the symptoms did not subside, and she continued to experience diarrhoea. The patient was hospitalized three days ago due to a life-threatening Clostridium difficile infection.
The patient has been receiving oral vancomycin and IV metronidazole for the past few days, but there has been no improvement in her symptoms. What would be the venous blood gas results in this case?Your Answer: Metabolic acidosis + hyperkalaemia
Correct Answer: Metabolic acidosis + hypokalaemia
Explanation:If a patient experiences prolonged diarrhoea, they may develop metabolic acidosis and hypokalaemia. This is likely the case for a patient with a history of prolonged Clostridium difficile infection, as the loss of bicarbonate ions from the GI tract during diarrhoea can lead to metabolic acidosis. Prolonged diarrhoea can also result in hypokalaemia due to the direct loss of potassium from the GI tract, which the body may be unable to compensate for. Therefore, metabolic acidosis and hypokalaemia are the expected outcomes in this scenario.
Understanding Metabolic Acidosis
Metabolic acidosis is a condition that can be classified based on the anion gap, which is calculated by subtracting the sum of chloride and bicarbonate from the sum of sodium and potassium. The normal range for anion gap is 10-18 mmol/L. If a question provides the chloride level, it may be an indication to calculate the anion gap.
Hyperchloraemic metabolic acidosis is a type of metabolic acidosis with a normal anion gap. It can be caused by gastrointestinal bicarbonate loss, prolonged diarrhea, ureterosigmoidostomy, fistula, renal tubular acidosis, drugs like acetazolamide, ammonium chloride injection, and Addison’s disease. On the other hand, raised anion gap metabolic acidosis is caused by lactate, ketones, urate, acid poisoning, and other factors.
Lactic acidosis is a type of metabolic acidosis that is caused by high lactate levels. It can be further classified into two types: lactic acidosis type A, which is caused by sepsis, shock, hypoxia, and burns, and lactic acidosis type B, which is caused by metformin. Understanding the different types and causes of metabolic acidosis is important in diagnosing and treating the condition.
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This question is part of the following fields:
- Renal System
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Question 4
Incorrect
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A 68-year-old man arrives at the emergency department complaining of intense abdominal pain that spreads to his back. His medical history shows that he has an abdominal aortic aneurysm. During a FAST scan, it is discovered that the abdominal aorta is widely dilated, with the most significant expansion occurring at the point where it divides into the iliac arteries. What vertebral level corresponds to the location of the most prominent dilation observed in the FAST scan?
Your Answer: L3
Correct Answer: L4
Explanation:The abdominal aorta divides into two branches at the level of the fourth lumbar vertebrae. At the level of T12, the coeliac trunk arises, while at L1, the superior mesenteric artery branches off. The testicular artery and renal artery originate at L2, and at L3, the inferior mesenteric artery is formed.
The aorta is a major blood vessel that carries oxygenated blood from the heart to the rest of the body. At different levels along the aorta, there are branches that supply blood to specific organs and regions. These branches include the coeliac trunk at the level of T12, which supplies blood to the stomach, liver, and spleen. The left renal artery, at the level of L1, supplies blood to the left kidney. The testicular or ovarian arteries, at the level of L2, supply blood to the reproductive organs. The inferior mesenteric artery, at the level of L3, supplies blood to the lower part of the large intestine. Finally, at the level of L4, the abdominal aorta bifurcates, or splits into two branches, which supply blood to the legs and pelvis.
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This question is part of the following fields:
- Cardiovascular System
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Question 5
Correct
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An 82-year-old male patient visits their GP with a swollen and red knee joint that has been hot for the past 3 days. The patient has a medical history of diabetes and osteoarthritis, leading the GP to suspect septic arthritis. During the humoral response to an infection, what receptor is present on Helper T cells that allows them to interact with MHC II molecules on antigen-presenting cells to eliminate pathogens?
Your Answer: CD4
Explanation:Helper T cells express CD4, which interacts with MHC II molecules on antigen presenting cells. CD20 is present on B cells from late pro-B cells through memory cells, but not on early pro-B cells or plasma cells. CD8 is expressed on cytotoxic T cells and binds with MHC I molecules.
The adaptive immune response involves several types of cells, including helper T cells, cytotoxic T cells, B cells, and plasma cells. Helper T cells are responsible for the cell-mediated immune response and recognize antigens presented by MHC class II molecules. They express CD4, CD3, TCR, and CD28 and are a major source of IL-2. Cytotoxic T cells also participate in the cell-mediated immune response and recognize antigens presented by MHC class I molecules. They induce apoptosis in virally infected and tumor cells and express CD8 and CD3. Both helper T cells and cytotoxic T cells mediate acute and chronic organ rejection.
B cells are the primary cells of the humoral immune response and act as antigen-presenting cells. They also mediate hyperacute organ rejection. Plasma cells are differentiated from B cells and produce large amounts of antibody specific to a particular antigen. Overall, these cells work together to mount a targeted and specific immune response to invading pathogens or abnormal cells.
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This question is part of the following fields:
- General Principles
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Question 6
Incorrect
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A 60-year-old man is experiencing bone pain and declining kidney function. Bence-Jones proteins have been detected in his urine and a whole-body MRI has shown osteolytic lesions. To confirm the diagnosis, his physician orders a bone marrow aspiration.
Which cells are being sought in the bone marrow examination?Your Answer: Reed-Sternberg cells
Correct Answer: B-cells
Explanation:Plasma cells would be visible in a bone marrow aspirate to diagnose multiple myeloma, which is characterized by osteolytic lesions, decreased renal function, bony pain, and the presence of Bence-Jones proteins. This condition is a type of B-cell neoplasm affecting plasma cells.
Understanding Multiple Myeloma: Features and Investigations
Multiple myeloma is a type of cancer that affects the plasma cells in the bone marrow. It is most commonly found in patients aged 60-70 years. The disease is characterized by a range of symptoms, which can be remembered using the mnemonic CRABBI. These include hypercalcemia, renal damage, anemia, bleeding, bone lesions, and increased susceptibility to infection. Other features of multiple myeloma include amyloidosis, carpal tunnel syndrome, neuropathy, and hyperviscosity.
To diagnose multiple myeloma, a range of investigations are required. Blood tests can reveal anemia, renal failure, and hypercalcemia. Protein electrophoresis can detect raised levels of monoclonal IgA/IgG proteins in the serum, while bone marrow aspiration can confirm the diagnosis if the number of plasma cells is significantly raised. Imaging studies, such as whole-body MRI or X-rays, can be used to detect osteolytic lesions.
The diagnostic criteria for multiple myeloma require one major and one minor criteria or three minor criteria in an individual who has signs or symptoms of the disease. Major criteria include the presence of plasmacytoma, 30% plasma cells in a bone marrow sample, or elevated levels of M protein in the blood or urine. Minor criteria include 10% to 30% plasma cells in a bone marrow sample, minor elevations in the level of M protein in the blood or urine, osteolytic lesions, or low levels of antibodies in the blood. Understanding the features and investigations of multiple myeloma is crucial for early detection and effective treatment.
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This question is part of the following fields:
- Haematology And Oncology
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Question 7
Incorrect
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A 29-year-old female is 24 weeks pregnant and visits the midwife for a check-up. The foetal heart rate is detected on the Doppler scan and growth rates are appropriate for the gestational age. The mother reports to the midwife that she has been experiencing increased breathing rate lately. The midwife explains that this is a common occurrence during pregnancy.
What other physiological alterations are typical during pregnancy?Your Answer: Stroke volume decreases
Correct Answer: Red blood cell volume increases
Explanation:During pregnancy, women are checked for anaemia twice – once at the initial booking visit (usually at 8-10 weeks) and again at 28 weeks. The National Institute for Health and Care Excellence (NICE) has set specific cut-off levels to determine if a woman requires oral iron therapy. For the first trimester, the cut-off is less than 110 g/L, for the second and third trimesters, it is less than 105 g/L, and for the postpartum period, it is less than 100 g/L. If a woman falls below these levels, she should receive oral ferrous sulfate or ferrous fumarate. Treatment should continue for three months after iron deficiency is corrected to allow for the replenishment of iron stores.
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This question is part of the following fields:
- Reproductive System
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Question 8
Incorrect
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As a new resident on the medical assessment unit, you are attending a consultant-led ward round. A 45-year-old male with a history of alcohol-related liver failure becomes agitated and threatens to punch the consultant. He displays coarse tremors in both hands and appears highly anxious.
The patient is a chronic alcoholic.
What is the preferred medication for managing his symptoms?Your Answer: Naloxone
Correct Answer: Lorazepam
Explanation:To prevent increased sedation, lorazepam is the preferred medication for alcohol withdrawal syndrome in patients with hepatic failure, rather than chlordiazepoxide. Naloxone is used for opioid overdose and respiratory depression caused by opioids, while flumazenil is not used for alcohol withdrawal management as it counteracts the effects of benzodiazepines.
Alcohol withdrawal occurs when an individual who has been consuming alcohol chronically suddenly stops or reduces their intake. This is due to the fact that chronic alcohol consumption enhances GABA-mediated inhibition in the central nervous system (CNS), similar to benzodiazepines, and inhibits NMDA-type glutamate receptors. When alcohol consumption is stopped, the opposite occurs, resulting in decreased inhibitory GABA and increased NMDA glutamate transmission.
Symptoms of alcohol withdrawal typically start within 6-12 hours and include tremors, sweating, tachycardia, and anxiety. Seizures are most likely to occur at around 36 hours, while delirium tremens, which is characterized by coarse tremors, confusion, delusions, auditory and visual hallucinations, fever, and tachycardia, is most likely to occur at around 48-72 hours.
Patients with a history of complex withdrawals from alcohol, such as delirium tremens, seizures, or blackouts, should be admitted to the hospital for monitoring until their withdrawals stabilize. The first-line treatment for alcohol withdrawal is long-acting benzodiazepines, such as chlordiazepoxide or diazepam, which are typically given as part of a reducing dose protocol. Lorazepam may be preferable in patients with hepatic failure. Carbamazepine is also effective in treating alcohol withdrawal, while phenytoin is said not to be as effective in the treatment of alcohol withdrawal seizures.
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This question is part of the following fields:
- Psychiatry
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Question 9
Correct
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Which of the following is not a cause of hyperkalemia?
Your Answer: Severe malnutrition
Explanation:There are various factors that can lead to an increase in serum potassium levels, which are abbreviated as MACHINE. These include certain medications such as ACE inhibitors and NSAIDs, acidosis (both metabolic and respiratory), cellular destruction due to burns or traumatic injury, hypoaldosteronism, excessive intake of potassium, nephrons, and renal failure, and impaired excretion of potassium. Additionally, familial periodic paralysis can have subtypes that are associated with either hyperkalemia or hypokalemia.
Hyperkalaemia is a condition where there is an excess of potassium in the blood. The levels of potassium in the plasma are regulated by various factors such as aldosterone, insulin levels, and acid-base balance. When there is metabolic acidosis, hyperkalaemia can occur as hydrogen and potassium ions compete with each other for exchange with sodium ions across cell membranes and in the distal tubule. The ECG changes that can be seen in hyperkalaemia include tall-tented T waves, small P waves, widened QRS leading to a sinusoidal pattern, and asystole.
There are several causes of hyperkalaemia, including acute kidney injury, drugs such as potassium sparing diuretics, ACE inhibitors, angiotensin 2 receptor blockers, spironolactone, ciclosporin, and heparin, metabolic acidosis, Addison’s disease, rhabdomyolysis, and massive blood transfusion. Foods that are high in potassium include salt substitutes, bananas, oranges, kiwi fruit, avocado, spinach, and tomatoes.
It is important to note that beta-blockers can interfere with potassium transport into cells and potentially cause hyperkalaemia in renal failure patients. In contrast, beta-agonists such as Salbutamol are sometimes used as emergency treatment. Additionally, both unfractionated and low-molecular weight heparin can cause hyperkalaemia by inhibiting aldosterone secretion.
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This question is part of the following fields:
- Renal System
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Question 10
Correct
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A 15-year-old boy complains of muscle pain and early fatigue during exercise, along with dark urine. He is diagnosed with McArdle's disease.
What is the enzyme that limits the defective pathway in this condition?Your Answer: Glycogen phosphorylase
Explanation:Glycogen phosphorylase is the enzyme that limits the rate of glycogenolysis, which is the breakdown of glycogen into glucose for energy use and blood glucose maintenance. McArdle’s disease, a type V glycogen storage disease, is caused by a deficiency of myophosphorylase, which is involved in glycogenolysis in muscle. Isocitrate dehydrogenase is the rate limiting enzyme for the citric acid cycle, while phosphofructokinase-1 limits the rate of glycolysis. Glycogen synthase is the enzyme that limits the rate of glycogenesis.
Rate-Determining Enzymes in Metabolic Processes
Metabolic processes involve a series of chemical reactions that occur in living organisms to maintain life. Enzymes play a crucial role in these processes by catalyzing the reactions. However, not all enzymes have the same impact on the rate of the reaction. Some enzymes are rate-determining, meaning that they control the overall rate of the process. The table above lists the rate-determining enzymes involved in common metabolic processes.
For example, in the TCA cycle, isocitrate dehydrogenase is the rate-determining enzyme. In glycolysis, phosphofructokinase-1 controls the rate of the process. In gluconeogenesis, fructose-1,6-bisphosphatase is the rate-determining enzyme. Similarly, glycogen synthase controls the rate of glycogenesis, while glycogen phosphorylase controls the rate of glycogenolysis.
Other metabolic processes, such as lipogenesis, lipolysis, cholesterol synthesis, and ketogenesis, also have rate-determining enzymes. Acetyl-CoA carboxylase controls the rate of lipogenesis, while carnitine-palmitoyl transferase I controls the rate of lipolysis. HMG-CoA reductase is the rate-determining enzyme in cholesterol synthesis, while HMG-CoA synthase controls the rate of ketogenesis.
The urea cycle, de novo pyrimidine synthesis, and de novo purine synthesis also have rate-determining enzymes. Carbamoyl phosphate synthetase I controls the rate of the urea cycle, while carbamoyl phosphate synthetase II controls the rate of de novo pyrimidine synthesis. Glutamine-PRPP amidotransferase is the rate-determining enzyme in de novo purine synthesis.
Understanding the rate-determining enzymes in metabolic processes is crucial for developing treatments for metabolic disorders and diseases. By targeting these enzymes, researchers can potentially regulate the rate of the process and improve the health outcomes of individuals with these conditions.
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This question is part of the following fields:
- General Principles
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Question 11
Correct
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A patient arrives at the emergency department with complaints of abdominal pain in the right iliac fossa. Upon palpation, the patient experiences pain in the right iliac fossa when pressure is applied to the left iliac fossa. What is the term used to describe this sign?
Your Answer: Rovsing's sign
Explanation:Rovsing’s sign is a diagnostic indicator of appendicitis, characterized by pain in the right lower abdomen when the left lower abdomen is palpated. The Psoas sign is another indicator of appendicitis, where flexing the right hip causes irritation of the psoas muscle. The Obturator sign is also a sign of appendicitis, where discomfort is felt in the obturator internus muscle when both the hip and knees are flexed to 90 degrees. However, McBurney’s sign, which refers to pain in the right lower abdomen 2/3 of the way from the umbilicus to the right anterior superior iliac spine, is not a reliable indicator of appendicitis.
Acute appendicitis is a common condition that requires surgery and can occur at any age, but is most prevalent in young people aged 10-20 years. The pathogenesis of acute appendicitis involves lymphoid hyperplasia or a faecolith, which leads to obstruction of the appendiceal lumen. This obstruction causes gut organisms to invade the appendix wall, resulting in oedema, ischaemia, and possibly perforation.
The most common symptom of acute appendicitis is abdominal pain, which is typically peri-umbilical and radiates to the right iliac fossa due to localised peritoneal inflammation. Other symptoms include mild pyrexia, anorexia, and nausea. Examination may reveal generalised or localised peritonism, rebound and percussion tenderness, guarding and rigidity, and classical signs such as Rovsing’s sign and psoas sign.
Diagnosis of acute appendicitis is typically based on raised inflammatory markers and compatible history and examination findings. Imaging may be used in certain cases, such as ultrasound in females where pelvic organ pathology is suspected. Management of acute appendicitis involves appendicectomy, which can be performed via an open or laparoscopic approach. Patients with perforated appendicitis require copious abdominal lavage, while those without peritonitis who have an appendix mass should receive broad-spectrum antibiotics and consideration given to performing an interval appendicectomy. Intravenous antibiotics alone have been trialled as a treatment for appendicitis, but evidence suggests that this is associated with a longer hospital stay and up to 20% of patients go on to have an appendicectomy within 12 months.
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This question is part of the following fields:
- Gastrointestinal System
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Question 12
Incorrect
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Mrs. Johnson presents to her GP with pain in her left eye and a strange feeling that something is bothering her eye. After a corneal reflex test, it is observed that the corneal reflex on the left is impaired, specifically due to a lesion affecting the nerve serving as the afferent limb of the pathway.
What is the name of the nerve that serves as the afferent limb of the corneal pathway, detecting stimuli?Your Answer: Maxillary branch of the trigeminal nerve
Correct Answer: Ophthalmic branch of the trigeminal nerve
Explanation:The corneal reflex pathway involves the detection of stimuli by the ophthalmic branch of the trigeminal nerve, which then travels to the trigeminal ganglion. The brainstem, specifically the trigeminal nucleus, detects this signal and sends signals to both the left and right facial nerve. This causes the orbicularis oculi muscle to contract, resulting in a bilateral blink. The oculomotor nerve, on the other hand, innervates the extraocular muscles responsible for eye movement and does not provide any sensory function.
Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.
In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 13
Correct
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A 44-year-old man from India is staying with relatives in the UK. He presents to the doctor with concerns about difficulty reading the newspaper in the morning. He is unsure if it is due to blurry vision or difficulty distinguishing colors. He has a medical history of tuberculosis and is currently undergoing quadruple therapy. Which medication in his regimen could be causing his symptoms?
Your Answer: Ethambutol
Explanation:The standard quadruple therapy consists of ethambutol, isoniazid, pyrazinamide, and rifampicin.
Tuberculosis is a bacterial infection that can be treated with a combination of drugs. Each drug has a specific mechanism of action and can also cause side-effects. Rifampicin works by inhibiting bacterial DNA dependent RNA polymerase, which prevents the transcription of DNA into mRNA. However, it is a potent liver enzyme inducer and can cause hepatitis, orange secretions, and flu-like symptoms.
Isoniazid, on the other hand, inhibits mycolic acid synthesis. It can cause peripheral neuropathy, which can be prevented with pyridoxine (Vitamin B6). It can also cause hepatitis and agranulocytosis, but it is a liver enzyme inhibitor.
Pyrazinamide is converted by pyrazinamidase into pyrazinoic acid, which inhibits fatty acid synthase (FAS) I. However, it can cause hyperuricaemia, leading to gout, as well as arthralgia and myalgia. It can also cause hepatitis.
Finally, Ethambutol inhibits the enzyme arabinosyl transferase, which polymerizes arabinose into arabinan. However, it can cause optic neuritis, so it is important to check visual acuity before and during treatment. The dose also needs adjusting in patients with renal impairment.
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This question is part of the following fields:
- General Principles
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Question 14
Incorrect
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Which of the following statements regarding psoriasis is inaccurate?
Your Answer: Nail signs include pitting and onycholysis
Correct Answer: Mediated by type 2 helper T cells
Explanation:Psoriasis is caused by type 1 helper T cells that participate in the cellular immune response, as opposed to type 2 helper T cells.
Psoriasis: A Chronic Skin Disorder with Various Subtypes and Complications
Psoriasis is a prevalent chronic skin disorder that affects around 2% of the population. It is characterized by red, scaly patches on the skin, but it is now known that patients with psoriasis are at an increased risk of arthritis and cardiovascular disease. The pathophysiology of psoriasis is multifactorial and not yet fully understood. It is associated with genetic factors such as HLA-B13, -B17, and -Cw6, and abnormal T cell activity that stimulates keratinocyte proliferation. Environmental factors such as skin trauma, stress, streptococcal infection, and sunlight exposure can worsen, trigger, or improve psoriasis.
There are several recognized subtypes of psoriasis, including plaque psoriasis, flexural psoriasis, guttate psoriasis, and pustular psoriasis. Each subtype has its own unique characteristics and affects different areas of the body. Psoriasis can also cause nail signs such as pitting and onycholysis, as well as arthritis.
Complications of psoriasis include psoriatic arthropathy, metabolic syndrome, cardiovascular disease, venous thromboembolism, and psychological distress. It is important for patients with psoriasis to receive proper management and treatment to prevent these complications and improve their quality of life.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 15
Incorrect
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A 70-year-old man with lung cancer is having a left pneumonectomy. The left main bronchus is being divided. Which thoracic vertebrae is located behind this structure?
Your Answer: T1
Correct Answer: T6
Explanation:Anatomy of the Lungs
The lungs are a pair of organs located in the chest cavity that play a vital role in respiration. The right lung is composed of three lobes, while the left lung has two lobes. The apex of both lungs is approximately 4 cm superior to the sternocostal joint of the first rib. The base of the lungs is in contact with the diaphragm, while the costal surface corresponds to the cavity of the chest. The mediastinal surface contacts the mediastinal pleura and has the cardiac impression. The hilum is a triangular depression above and behind the concavity, where the structures that form the root of the lung enter and leave the viscus. The right main bronchus is shorter, wider, and more vertical than the left main bronchus. The inferior borders of both lungs are at the 6th rib in the mid clavicular line, 8th rib in the mid axillary line, and 10th rib posteriorly. The pleura runs two ribs lower than the corresponding lung level. The bronchopulmonary segments of the lungs are divided into ten segments, each with a specific function.
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This question is part of the following fields:
- Respiratory System
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Question 16
Correct
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A 32-year-old male is undergoing renal transplant surgery. Shortly after the donor kidney has been inserted, the transplanted organ begins to lose its color and becomes limp. Is hyperacute transplant rejection the likely cause of this? What is the underlying mechanism behind it?
Your Answer: Pre-existing recipient antibodies against donor HLA/ABO antigens
Explanation:Hyperacute transplant rejection is a rapid rejection of a donor organ that can occur within minutes to hours after transplantation. This rejection is caused by pre-existing antibodies against ABO or HLA antigens in the donor organ. If the rejection is widespread, it can activate the coagulation cascade and lead to occlusive thrombosis of the donated organ. Donor organs are carefully matched to recipients to minimize the risk of rejection.
Mast cell degranulation is an allergic reaction that is mediated by IgE and results in the release of histamine.
Acute rejection occurs days to weeks after transplantation and is an inflammatory process against the donated organ. Immunosuppressives can be used to slow down this process.
Chronic rejection occurs months to years after transplantation and is characterized by atrophy of the organ and arteriosclerosis, rather than acute inflammatory processes.
Graft vs Host disease occurs when donor T-cells mount a cell-mediated response against host tissues. This can lead to cholestasis, jaundice, a widespread rash, and diarrhea. It typically occurs within the first year following transplantation.
The HLA system, also known as the major histocompatibility complex (MHC), is located on chromosome 6 and is responsible for human leucocyte antigens. Class 1 antigens include A, B, and C, while class 2 antigens include DP, DQ, and DR. When matching for a renal transplant, the importance of HLA antigens is ranked as DR > B > A.
Graft survival rates for renal transplants are high, with a 90% survival rate at one year and a 60% survival rate at ten years for cadaveric transplants. Living-donor transplants have even higher survival rates, with a 95% survival rate at one year and a 70% survival rate at ten years. However, postoperative problems can occur, such as acute tubular necrosis of the graft, vascular thrombosis, urine leakage, and urinary tract infections.
Hyperacute rejection can occur within minutes to hours after a transplant and is caused by pre-existing antibodies against ABO or HLA antigens. This type of rejection is an example of a type II hypersensitivity reaction and leads to widespread thrombosis of graft vessels, resulting in ischemia and necrosis of the transplanted organ. Unfortunately, there is no treatment available for hyperacute rejection, and the graft must be removed.
Acute graft failure, which occurs within six months of a transplant, is usually due to mismatched HLA and is caused by cell-mediated cytotoxic T cells. This type of failure is usually asymptomatic and is detected by a rising creatinine, pyuria, and proteinuria. Other causes of acute graft failure include cytomegalovirus infection, but it may be reversible with steroids and immunosuppressants.
Chronic graft failure, which occurs after six months of a transplant, is caused by both antibody and cell-mediated mechanisms that lead to fibrosis of the transplanted kidney, known as chronic allograft nephropathy. The recurrence of the original renal disease, such as MCGN, IgA, or FSGS, can also cause chronic graft failure.
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This question is part of the following fields:
- Renal System
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Question 17
Incorrect
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A 55-year-old man comes to his physician complaining of severe morning headaches. The doctor conducts a neurological evaluation to detect any neurological impairments. During the assessment, the patient exhibits normal responses for all tests except for the absence of corneal reflex.
Which cranial nerve is impacted?Your Answer: Oculomotor nerve
Correct Answer: Trigeminal nerve
Explanation:The loss of corneal reflex is associated with the trigeminal nerve, specifically the ophthalmic branch. This reflex tests the sensation of the eyeball when cotton wool is used to touch it, causing the eye to blink in response. The glossopharyngeal nerve is not associated with the eye but is involved in the gag reflex. The optic nerve is responsible for vision and does not provide physical sensation to the eyeball. The oculomotor nerve is primarily a motor nerve and only provides sensory information in response to bright light. The trochlear nerve is purely motor and has no sensory innervations.
Cranial nerves are a set of 12 nerves that emerge from the brain and control various functions of the head and neck. Each nerve has a specific function, such as smell, sight, eye movement, facial sensation, and tongue movement. Some nerves are sensory, some are motor, and some are both. A useful mnemonic to remember the order of the nerves is Some Say Marry Money But My Brother Says Big Brains Matter Most, with S representing sensory, M representing motor, and B representing both.
In addition to their specific functions, cranial nerves also play a role in various reflexes. These reflexes involve an afferent limb, which carries sensory information to the brain, and an efferent limb, which carries motor information from the brain to the muscles. Examples of cranial nerve reflexes include the corneal reflex, jaw jerk, gag reflex, carotid sinus reflex, pupillary light reflex, and lacrimation reflex. Understanding the functions and reflexes of the cranial nerves is important in diagnosing and treating neurological disorders.
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This question is part of the following fields:
- Neurological System
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Question 18
Incorrect
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A 43-year-old man presents to his GP with a 3-month history of occasional frank haematuria. He has come in today as he began to experience intense, cramping loin pain over the weekend. Upon further questioning, the patient discloses that he has unintentionally lost 7kg of weight over the last 3 months.
The patient has been a smoker of 20 cigarettes a day for the past 26 years and has a BMI of 36kg/m2.
During the examination, a mass is palpated when balloting the kidneys. There are no other signs to elicit on examination.
What is the most common histological subtype given the likely diagnosis?Your Answer: Urothelial
Correct Answer: Clear cell
Explanation:The most common subtype of renal cell carcinoma is clear cell, while squamous epithelial is a subtype of bladder cancer and not typically associated with renal carcinoma.
Renal cell cancer, also known as hypernephroma, is a primary renal neoplasm that accounts for 85% of cases. It originates from the proximal renal tubular epithelium and is commonly associated with smoking and conditions such as von Hippel-Lindau syndrome and tuberous sclerosis. The clear cell subtype is the most prevalent, comprising 75-85% of tumors.
Renal cell cancer is more common in middle-aged men and may present with classical symptoms such as haematuria, loin pain, and an abdominal mass. Other features include endocrine effects, such as the secretion of erythropoietin, parathyroid hormone-related protein, renin, and ACTH. Metastases are present in 25% of cases at presentation, and paraneoplastic syndromes such as Stauffer syndrome may also occur.
The T category criteria for renal cell cancer are based on tumor size and extent of invasion. Management options include partial or total nephrectomy, depending on the tumor size and extent of disease. Patients with a T1 tumor are typically offered a partial nephrectomy, while alpha-interferon and interleukin-2 may be used to reduce tumor size and treat metastases. Receptor tyrosine kinase inhibitors such as sorafenib and sunitinib have shown superior efficacy compared to interferon-alpha.
In summary, renal cell cancer is a common primary renal neoplasm that is associated with various risk factors and may present with classical symptoms and endocrine effects. Management options depend on the extent of disease and may include surgery and targeted therapies.
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This question is part of the following fields:
- Renal System
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Question 19
Incorrect
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A 75-year-old woman with a history of type 2 diabetes mellitus and atrial fibrillation visits her GP complaining of a rash on her arm. The rash has been present for two days and she has been feeling generally unwell with a mild fever. Upon examination, the GP observes a well-defined, raised, reddish patch on her left forearm that is most red at the border. Additionally, there is associated axillary lymphadenopathy. The GP orders a full blood count, CRP, and a swab of the lesion. What is the most likely pathogen responsible for this condition?
Your Answer: Herpes zoster
Correct Answer: Streptococcus pyogenes
Explanation:Erysipelas is a skin infection that is localized and caused by Streptococcus pyogenes. It is often seen in elderly patients with weakened immune systems, such as those with diabetes mellitus. Symptoms include a raised, painful rash with clear boundaries.
Ringworm is commonly caused by Trichophyton rubrum. This results in a circular, scaly, and itchy rash that is red in color.
While Staphylococcus epidermidis is a normal part of the skin’s flora, it is more commonly associated with infections of foreign devices and endocarditis rather than skin infections.
Understanding Erysipelas: A Superficial Skin Infection
Erysipelas is a skin infection that is caused by Streptococcus pyogenes. It is a less severe form of cellulitis, which is a more widespread skin infection. Erysipelas is a localized infection that affects the skin’s upper layers, causing redness, swelling, and warmth. The infection can occur anywhere on the body, but it is most commonly found on the face, arms, and legs.
The treatment of choice for erysipelas is flucloxacillin, an antibiotic that is effective against Streptococcus pyogenes. Other antibiotics may also be used, depending on the severity of the infection and the patient’s medical history.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 20
Incorrect
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A perimenopausal woman in her late 40s is prescribed Hormone Replacement Therapy consisting of oestrogen and progesterone. What roles do these hormones play in HRT?
Your Answer: Progesterone enhances the effects of oestrogen
Correct Answer: Oestrogen is for symptomatic relief and progesterone is protective against oestrogenic adverse effects
Explanation:The main cause of menopausal symptoms is low levels of oestrogen, which is why hormone replacement therapy (HRT) aims to alleviate these symptoms by supplementing oestrogen. However, oestrogen can lead to thickening of the endometrium, which increases the risk of neoplasia. To counteract this risk, progesterone is also included in HRT to prevent endometrial thickening and any associated malignancy.
Therefore, any statement suggesting that progesterone is used for symptomatic relief, that oestrogen is protective, or that progesterone and oestrogen work together in a synergistic manner is incorrect.
Symptoms of Menopause
Menopause is a natural biological process that marks the end of a woman’s reproductive years. It is characterized by a decrease in the levels of female hormones, particularly oestrogen, which can lead to a range of symptoms. One of the most common symptoms is a change in periods, including changes in the length of menstrual cycles and dysfunctional uterine bleeding.
Around 80% of women experience vasomotor symptoms, which can occur daily and last for up to five years. These symptoms include hot flushes and night sweats. Urogenital changes are also common, affecting around 35% of women. These changes can include vaginal dryness and atrophy, as well as urinary frequency.
In addition to physical symptoms, menopause can also have psychological effects. Approximately 10% of women experience anxiety and depression during this time, as well as short-term memory impairment. It is important to note that menopause can also have longer-term complications, such as an increased risk of osteoporosis and ischaemic heart disease.
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This question is part of the following fields:
- Reproductive System
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Question 21
Correct
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A 68-year-old male presents with sudden and severe abdominal pain. He has a medical history of ischaemic heart disease and takes nitrates, atenolol and amlodipine for it. Upon examination, his pulse is irregularly irregular and measures 115 bpm, his blood pressure is 104/72 mmHg, and his temperature is 37.4°C. The abdomen is diffusely tender and bowel sounds are absent. What is the probable diagnosis?
Your Answer: Mesenteric ischaemia
Explanation:Narrowing Down the Differential Diagnosis for Acute Abdomen
When presented with a patient experiencing an acute abdomen, the differential diagnosis can be extensive. However, by taking note of the key points in the patient’s history and conducting a thorough examination, one can narrow down the potential causes. In the case of a man with absent bowel sounds, atrial fibrillation, and a history of ischemic heart disease, the most likely cause of his presentation is mesenteric ischemia. This is due to the fact that he is not obstructed and has vascular disease. For further information on acute mesenteric ischemia, Medscape provides a helpful resource. By utilizing these tools and resources, healthcare professionals can more accurately diagnose and treat patients with acute abdominal symptoms.
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This question is part of the following fields:
- Gastrointestinal System
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Question 22
Incorrect
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A new drug is being trialled for joint pain and its pharmacology and pharmacokinetics are being reviewed. A patient in their 40s receives drug X of 500mg strength with the initial plasma concentration being recorded as 8.0mg/L. Calculate the drug’s volume of distribution.
60L
6%
65.5L
4%
62.5L
83%
64L
6%
63L
1%
In order to calculate volume of distribution you must be familiar with the equation.
Vd = Dose/Plasma concentration
Since the units here all related we don’t have to change anything but ensure that the units are compatible before plugging them into the formula. Here the drug dose was 500mg and the concentration was 8.0mg/L.
500mg/8.0mg/L = 62.5L?Your Answer: 64L
Correct Answer: 62.5L
Explanation:To determine the volume of distribution, one should be acquainted with the formula Vd = Dose/Plasma concentration. It is important to ensure that the units used are compatible before substituting them into the equation. For instance, if the drug dose is 500mg and the concentration is 8.0mg/L, the volume of distribution would be 62.5L.
Understanding Volume of Distribution in Pharmacology
The volume of distribution (VD) is a concept in pharmacology that refers to the theoretical volume that a drug would occupy to achieve the same concentration as it currently has in the blood plasma. The VD is used to determine how a drug is distributed in the body and can be classified as low, medium, or high. Low VD drugs are confined to the plasma, while medium VD drugs are distributed in the extracellular space, and high VD drugs are distributed in the tissues.
Several factors influence the VD of a drug, including liver and renal failure, pregnancy, dehydration, large molecules, high plasma protein, hydrophilicity, and high charge. For instance, drugs with high plasma protein binding tend to have a low VD because they are confined to the plasma. On the other hand, drugs that are highly hydrophilic or charged tend to have a low VD because they cannot penetrate cell membranes.
Examples of high VD drugs include tricyclic antidepressants, morphine, digoxin, phenytoin, chloroquine, and salicylates. These drugs are distributed widely in the body and can penetrate cell membranes. In contrast, low VD drugs include heparin, insulin, and warfarin, which are confined to the plasma due to their large size or high plasma protein binding. Understanding the VD of a drug is crucial in determining its pharmacokinetics and optimizing its therapeutic effects.
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This question is part of the following fields:
- General Principles
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Question 23
Incorrect
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A 28-year-old woman visits her GP after experiencing a sudden deterioration of vision in her left eye 10 days ago. She reports that her vision became blurry and has only partially improved since. Additionally, the patient describes intermittent sensations of pain and burning around her left eye. She has no significant medical history.
During the examination, the direct pupillary light reflex is weaker in her left eye. Her left eye has a visual acuity of 6/12, while her right eye has a visual acuity of 6/6. The patient experiences pain when her left eye is abducted.
What is the most frequent cause of this presentation?Your Answer: Myasthenia gravis
Correct Answer: Multiple sclerosis
Explanation:Optic neuritis, which is characterized by unilateral vision loss and pain, is most commonly caused by multiple sclerosis. This is an inflammatory disease that affects the central nervous system and is more prevalent in individuals of white ethnicity living in northern latitudes. Behcet’s disease, a rare vasculitis, can also cause optic neuritis but is less strongly associated with the condition. Conjunctivitis, on the other hand, does not cause vision loss and is characterized by redness and irritation of the outer surface of the eye. Myasthenia gravis, an autoimmune condition that causes muscle weakness, does not cause optic neuritis but can affect ocular muscles and lead to symptoms such as drooping eyelids and double vision.
Understanding Optic Neuritis: Causes, Features, Investigation, Management, and Prognosis
Optic neuritis is a condition that causes a decrease in visual acuity in one eye over a period of hours or days. It is often associated with multiple sclerosis, diabetes, or syphilis. Other features of optic neuritis include poor discrimination of colors, pain that worsens with eye movement, relative afferent pupillary defect, and central scotoma.
To diagnose optic neuritis, an MRI of the brain and orbits with gadolinium contrast is usually performed. High-dose steroids are the primary treatment for optic neuritis, and recovery typically takes 4-6 weeks.
The prognosis for optic neuritis is dependent on the number of white-matter lesions found on an MRI. If there are more than three lesions, the five-year risk of developing multiple sclerosis is approximately 50%. Understanding the causes, features, investigation, management, and prognosis of optic neuritis is crucial for early diagnosis and effective treatment.
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This question is part of the following fields:
- Neurological System
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Question 24
Incorrect
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An older gentleman was discovered to have an asymptomatic midline abdominal mass. What physical feature during examination would suggest a diagnosis of an abdominal aortic aneurysm (AAA)?
Your Answer: Tender
Correct Answer: Expansile
Explanation:Abdominal Aortic Aneurysm:
An abdominal aortic aneurysm (AAA) is frequently found incidentally in men, particularly in older age groups. As a result, ultrasound screening has been introduced in many areas to detect this condition. However, the diagnosis of AAA cannot be made based on pulsatility alone, as it is common for pulsations to be transmitted by the organs that lie over the aorta. Instead, an AAA is characterized by its expansile nature. If a tender, pulsatile swelling is present, it may indicate a perforated AAA, which is a medical emergency. Therefore, it is important for men to undergo regular screening for AAA to detect and manage this condition early. -
This question is part of the following fields:
- Gastrointestinal System
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Question 25
Incorrect
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A 75-year-old man is experiencing symptoms of mesenteric ischemia. During his diagnostic evaluation, a radiologist is attempting to cannulate the coeliac axis from the aorta. Typically, at which vertebral level does this artery originate?
Your Answer: T10
Correct Answer: T12
Explanation:The coeliac trunk is a major artery that arises from the aorta and gives off three branches on the left-hand side: the left gastric, hepatic, and splenic arteries.
The Coeliac Axis and its Branches
The coeliac axis is a major artery that supplies blood to the upper abdominal organs. It has three main branches: the left gastric, hepatic, and splenic arteries. The hepatic artery further branches into the right gastric, gastroduodenal, right gastroepiploic, superior pancreaticoduodenal, and cystic arteries. Meanwhile, the splenic artery gives off the pancreatic, short gastric, and left gastroepiploic arteries. Occasionally, the coeliac axis also gives off one of the inferior phrenic arteries.
The coeliac axis is located anteriorly to the lesser omentum and is related to the right and left coeliac ganglia, as well as the caudate process of the liver and the gastric cardia. Inferiorly, it is in close proximity to the upper border of the pancreas and the renal vein.
Understanding the anatomy and branches of the coeliac axis is important in diagnosing and treating conditions that affect the upper abdominal organs, such as pancreatic cancer or gastric ulcers.
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This question is part of the following fields:
- Cardiovascular System
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Question 26
Correct
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What is the cause of the tubercle bacillus' pathogenicity?
Your Answer: Delayed hypersensitivity reaction against bacteria
Explanation:The cell mediated immunity response to mycobacteria is targeted and effective in reducing infection, but it also causes tissue damage through delayed hypersensitivity. Although necrosis can occur in tuberculosis, it typically occurs within the granuloma.
Understanding Tuberculosis: The Pathophysiology and Risk Factors
Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis. The pathophysiology of tuberculosis involves the migration of macrophages to regional lymph nodes, forming a Ghon complex. This complex leads to the formation of a granuloma, which is a collection of epithelioid histiocytes with caseous necrosis in the center. The inflammatory response is mediated by a type 4 hypersensitivity reaction. While healthy individuals can contain the disease, immunocompromised individuals are at risk of developing disseminated (miliary) TB.
Several risk factors increase the likelihood of developing tuberculosis. These include having lived in Asia, Latin America, Eastern Europe, or Africa for years, exposure to an infectious TB case, and being infected with HIV. Immunocompromised individuals, such as diabetics, patients on immunosuppressive therapy, malnourished individuals, or those with haematological malignancies, are also at risk. Additionally, silicosis and apical fibrosis increase the likelihood of developing tuberculosis. Understanding the pathophysiology and risk factors of tuberculosis is crucial in preventing and treating this infectious disease.
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This question is part of the following fields:
- General Principles
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Question 27
Incorrect
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A 50-year-old woman visits the rheumatology clinic due to worsening joint pain caused by her longstanding rheumatoid arthritis. Her symptoms have progressed to the point where she can no longer perform her daily activities. She is interested in trying infliximab after hearing about it from a friend and reading about it online. She wants to know how the drug works and how it can potentially alleviate her symptoms.
What is the mechanism of action of infliximab?Your Answer:
Correct Answer: Anti-TNF
Explanation:Infliximab targets TNF through its monoclonal antibody action, while rituximab targets CD20, cetuximab acts as an antagonist to epidermal growth factor receptor, alemtuzumab targets CD52, and OKT3 targets CD3.
Understanding Tumour Necrosis Factor and its Inhibitors
Tumour necrosis factor (TNF) is a cytokine that plays a crucial role in the immune system. It is mainly secreted by macrophages and has various effects on the immune system, such as activating macrophages and neutrophils, acting as a costimulator for T cell activation, and mediating the body’s response to Gram-negative septicaemia. TNF also has anti-tumour effects and binds to both the p55 and p75 receptor, inducing apoptosis and activating NFkB.
TNF has endothelial effects, including increased expression of selectins and production of platelet activating factor, IL-1, and prostaglandins. It also promotes the proliferation of fibroblasts and their production of protease and collagenase. TNF inhibitors are used to treat inflammatory conditions such as rheumatoid arthritis and Crohn’s disease. Examples of TNF inhibitors include infliximab, etanercept, adalimumab, and golimumab.
Infliximab is also used to treat active Crohn’s disease unresponsive to steroids. However, TNF blockers can have adverse effects such as reactivation of latent tuberculosis and demyelination. Understanding TNF and its inhibitors is crucial in the treatment of various inflammatory conditions.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 28
Incorrect
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A 68-year-old woman has been diagnosed with laryngeal cancer and has quit smoking. Surgery is planned to remove the cancer through a laryngectomy. What vertebral level/levels will the organ be located during the procedure?
Your Answer:
Correct Answer: C3 to C6
Explanation:The larynx is situated in the front of the neck at the level of the C3-C6 vertebrae. This is the correct location for accessing the larynx during a laryngectomy. The larynx is not located at the C1-C2 level, as these are the atlas bones. It is also not located at the C2-C3 level, which is where the hyoid bone can be found. The C7 level is where the isthmus of the thyroid gland is located, not the larynx.
Anatomy of the Larynx
The larynx is located in the front of the neck, between the third and sixth cervical vertebrae. It is made up of several cartilaginous segments, including the paired arytenoid, corniculate, and cuneiform cartilages, as well as the single thyroid, cricoid, and epiglottic cartilages. The cricoid cartilage forms a complete ring. The laryngeal cavity extends from the laryngeal inlet to the inferior border of the cricoid cartilage and is divided into three parts: the laryngeal vestibule, the laryngeal ventricle, and the infraglottic cavity.
The vocal folds, also known as the true vocal cords, control sound production. They consist of the vocal ligament and the vocalis muscle, which is the most medial part of the thyroarytenoid muscle. The glottis is composed of the vocal folds, processes, and rima glottidis, which is the narrowest potential site within the larynx.
The larynx is also home to several muscles, including the posterior cricoarytenoid, lateral cricoarytenoid, thyroarytenoid, transverse and oblique arytenoids, vocalis, and cricothyroid muscles. These muscles are responsible for various actions, such as abducting or adducting the vocal folds and relaxing or tensing the vocal ligament.
The larynx receives its arterial supply from the laryngeal arteries, which are branches of the superior and inferior thyroid arteries. Venous drainage is via the superior and inferior laryngeal veins. Lymphatic drainage varies depending on the location within the larynx, with the vocal cords having no lymphatic drainage and the supraglottic and subglottic parts draining into different lymph nodes.
Overall, understanding the anatomy of the larynx is important for proper diagnosis and treatment of various conditions affecting this structure.
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This question is part of the following fields:
- Respiratory System
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Question 29
Incorrect
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Which of the following statements about interleukin 1 (IL-1) is accurate?
Your Answer:
Correct Answer: It is released mainly by macrophages/monocytes
Explanation:The Role of Interleukin 1 in the Immune Response
Interleukin 1 (IL-1) is a crucial mediator of the immune response, secreted primarily by macrophages and monocytes. Its main function is to act as a costimulator of T cell and B cell proliferation. Additionally, IL-1 increases the expression of adhesion molecules on the endothelium, leading to vasodilation and increased vascular permeability. This can cause shock in sepsis, making IL-1 one of the mediators of this condition. Along with IL-6 and TNF, IL-1 also acts on the hypothalamus, causing pyrexia.
Due to its significant role in the immune response, IL-1 inhibitors are increasingly used in medicine. Examples of these inhibitors include anakinra, an IL-1 receptor antagonist used in the management of rheumatoid arthritis, and canakinumab, a monoclonal antibody targeted at IL-1 beta used in systemic juvenile idiopathic arthritis and adult-onset Still’s disease. These inhibitors help to regulate the immune response and manage conditions where IL-1 plays a significant role.
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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 37-year-old woman presents with fatigue, weight gain and cold intolerance.
She has no past medical history and does not take any regular medications.
Her blood tests show the following:
Thyroid stimulating hormone (TSH) 15.0 mU/L (0.5 - 5.5)
Free thyroxine (T4) 7.5 pmol/L (9.0 - 18)
Thyroid peroxidase antibodies 120 IU/mL (<60)
Which type of receptor does the medication she agreed to start act on?Your Answer:
Correct Answer: Nuclear receptor
Explanation:Levothyroxine exerts its effects by binding to nuclear receptors, which leads to the regulation of gene transcription and translation. This process is slower compared to other signal transduction pathways but results in a more prolonged effect. In the case of primary hypothyroidism with raised anti-TPO antibodies, which is likely due to autoimmune thyroiditis (Hashimoto’s thyroiditis), levothyroxine is the standard treatment.
Other types of receptors include G-protein coupled receptors, such as opioid receptors and beta-adrenoceptors, which trigger a sequence of events leading to the production of secondary messengers and activation of further transduction pathways. Ligand-gated ion channel receptors, such as nicotinic acetylcholine receptors and GABA receptors, open channels upon activation, allowing specific ions to pass through 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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