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Question 1
Incorrect
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A 29-year-old Jewish woman comes to a doctor complaining of mouth ulcers and skin blistering. During the examination, the doctor observes Nikolsky's sign. The doctor informs her that she has an autoimmune disease where her body's own cells are being attacked by antibodies. What is the specific target for these antibodies in her condition?
Your Answer: TSH receptor
Correct Answer: Desmoglein 3
Explanation:Pemphigus vulgaris is characterized by the presence of antibodies against desmoglein 3, while Grave’s disease is associated with antibodies against TSH receptors. Cardiac myopathy is linked to antibodies against desmoglein 2, while pemphigus foliaceus is associated with antibodies against desmoglein 1. Hashimoto’s hypothyroidism is characterized by the presence of antibodies against thyroid peroxidase.
Pemphigus vulgaris is an autoimmune condition that occurs when the body’s immune system attacks desmoglein 3, a type of cell adhesion molecule found in epithelial cells. This disease is more prevalent in the Ashkenazi Jewish population. The most common symptom is mucosal ulceration, which can be the first sign of the disease. Oral involvement is seen in 50-70% of patients. Skin blistering is also a common symptom, with easily ruptured vesicles and bullae. These lesions are typically painful but not itchy and may appear months after the initial mucosal symptoms. Nikolsky’s sign is a characteristic feature of pemphigus vulgaris, where bullae spread following the application of horizontal, tangential pressure to the skin. Biopsy results often show acantholysis.
The first-line treatment for pemphigus vulgaris is steroids, which help to reduce inflammation and suppress the immune system. Immunosuppressants may also be used to manage the disease.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 2
Incorrect
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Roughly what percentage of saliva production comes from the submandibular glands?
Your Answer: 40%
Correct Answer: 70%
Explanation:Anatomy of the Submandibular Gland
The submandibular gland is located beneath the mandible and is surrounded by the superficial platysma, deep fascia, and mandible. It is also in close proximity to various structures such as the submandibular lymph nodes, facial vein, marginal mandibular nerve, cervical branch of the facial nerve, deep facial artery, mylohyoid muscle, hyoglossus muscle, lingual nerve, submandibular ganglion, and hypoglossal nerve.
The submandibular duct, also known as Wharton’s duct, is responsible for draining saliva from the gland. It opens laterally to the lingual frenulum on the anterior floor of the mouth and is approximately 5 cm in length. The lingual nerve wraps around the duct, and as it passes forward, it crosses medial to the nerve to lie above it before crossing back, lateral to it, to reach a position below the nerve.
The submandibular gland receives sympathetic innervation from the superior cervical ganglion and parasympathetic innervation from the submandibular ganglion via the lingual nerve. Its arterial supply comes from a branch of the facial artery, which passes through the gland to groove its deep surface before emerging onto the face by passing between the gland and the mandible. The anterior facial vein provides venous drainage, and the gland’s lymphatic drainage goes to the deep cervical and jugular chains of nodes.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 3
Correct
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A 70-year-old woman with osteoporosis experiences a fall resulting in a fully displaced intracapsular femoral neck fracture. What is the primary vessel responsible for supplying blood to the femoral head?
Your Answer: Circumflex femoral arteries
Explanation:The anastomoses encircling the femoral head are created by vessels originating from the medial and lateral circumflex femoral arteries, typically sourced from the profunda femoris artery.
Anatomy of the Hip Joint
The hip joint is formed by the articulation of the head of the femur with the acetabulum of the pelvis. Both of these structures are covered by articular hyaline cartilage. The acetabulum is formed at the junction of the ilium, pubis, and ischium, and is separated by the triradiate cartilage, which is a Y-shaped growth plate. The femoral head is held in place by the acetabular labrum. The normal angle between the femoral head and shaft is 130 degrees.
There are several ligaments that support the hip joint. The transverse ligament connects the anterior and posterior ends of the articular cartilage, while the head of femur ligament (ligamentum teres) connects the acetabular notch to the fovea. In children, this ligament contains the arterial supply to the head of the femur. There are also extracapsular ligaments, including the iliofemoral ligament, which runs from the anterior iliac spine to the trochanteric line, the pubofemoral ligament, which connects the acetabulum to the lesser trochanter, and the ischiofemoral ligament, which provides posterior support from the ischium to the greater trochanter.
The blood supply to the hip joint comes from the medial circumflex femoral and lateral circumflex femoral arteries, which are branches of the profunda femoris. The inferior gluteal artery also contributes to the blood supply. These arteries form an anastomosis and travel up the femoral neck to supply the head of the femur.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 4
Incorrect
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A 65-year-old man is set to undergo a surgical procedure to drain an abscess situated on the medial side of his lower leg. The anaesthetist plans to administer a saphenous nerve block by injecting a local anaesthetic through the adductor canal's roof. What is the muscular structure that the needle for the local anaesthetic must pass through?
Your Answer: Vastus lateralis
Correct Answer: Sartorius
Explanation:The Adductor Canal: Anatomy and Contents
The adductor canal, also known as Hunter’s or the subsartorial canal, is a structure located in the middle third of the thigh, immediately distal to the apex of the femoral triangle. It is bordered laterally by the vastus medialis muscle and posteriorly by the adductor longus and adductor magnus muscles. The roof of the canal is formed by the sartorius muscle. The canal terminates at the adductor hiatus.
The adductor canal contains three important structures: the saphenous nerve, the superficial femoral artery, and the superficial femoral vein. The saphenous nerve is a sensory nerve that supplies the skin of the medial leg and foot. The superficial femoral artery is a major artery that supplies blood to the lower limb. The superficial femoral vein is a large vein that drains blood from the lower limb.
In order to expose the contents of the adductor canal, the sartorius muscle must be removed. Understanding the anatomy and contents of the adductor canal is important for medical professionals who perform procedures in this area, such as nerve blocks or vascular surgeries.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 5
Incorrect
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A 25-year-old man comes to the doctor complaining of difficulty with bowel movements. He reports having a good appetite and drinking enough fluids. He denies experiencing weight loss, night sweats, or fevers. The patient has a history of rhinitis and indigestion. He takes two medications regularly, but he cannot recall their names. Additionally, he has a learning disability.
Which of the following medications could be responsible for his constipation?Your Answer: Cimetidine
Correct Answer: Chlorphenamine
Explanation:Antihistamines for Allergic Rhinitis and Urticaria
Antihistamines, specifically H1 inhibitors, are effective in treating allergic rhinitis and urticaria. Sedating antihistamines like chlorpheniramine have antimuscarinic properties that can cause dry mouth and urinary retention. On the other hand, non-sedating antihistamines like loratadine and cetirizine are less likely to cause drowsiness. However, there is some evidence that cetirizine may still cause some level of drowsiness compared to other non-sedating antihistamines. Overall, antihistamines are a valuable treatment option for those suffering from allergic rhinitis and urticaria.
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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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A 16-year-old male presents to the physician with severe right dorsoradial wrist pain, which had a gradual onset over the past week. He had tripped over the pavement one month ago, breaking his fall with his outstretched right hand. However, he did not seek medical attention for it as the pain was not severe then.
Clinical examination reveals tenderness in the anatomical snuffbox, and the range of motion of the wrist is limited by pain. There is no overlying skin changes. His sensation over the median, radial and ulnar distributions of the hand was intact.
Radiographs of the wrist show collapse and fragmentation. The patient was diagnosed with a scaphoid fracture and informed that he has a complication due to delaying medical attention. He is then promptly scheduled for surgery.
What is the reason for the development of this complication in a 16-year-old male with a scaphoid fracture who delayed seeking medical attention?Your Answer: Blood supply from the superficial palmar arch is disrupted, resulting in avascular necrosis of the scaphoid.
Correct Answer: Blood supply from the dorsal carpal branch is disrupted, resulting in avascular necrosis of the scaphoid.
Explanation:The radial vein is not involved in avascular necrosis of the scaphoid. The abductor pollicis brevis muscle, which is responsible for thumb movement and located near the scaphoid bone, is supplied by the superficial palmar arch and is not typically affected by avascular necrosis in scaphoid fractures. Nonunion refers to the failure of bony union beyond a certain period of time, but as it has only been one month since the injury and only one radiograph has been taken, it is premature to diagnose non-union in this patient.
A scaphoid fracture is a type of wrist fracture that usually occurs when a person falls onto an outstretched hand or during contact sports. It is important to identify scaphoid fractures as they can lead to avascular necrosis due to the unusual blood supply of the scaphoid bone. Patients with scaphoid fractures typically experience pain along the radial aspect of the wrist and loss of grip or pinch strength. Clinical examination involves checking for tenderness over the anatomical snuffbox, wrist joint effusion, pain on telescoping of the thumb, tenderness of the scaphoid tubercle, and pain on ulnar deviation of the wrist. Plain film radiographs and scaphoid views are used to diagnose scaphoid fractures, but MRI is considered the definitive investigation. Initial management involves immobilization with a splint or backslab and referral to orthopaedics. Orthopaedic management depends on the type of fracture, with undisplaced fractures typically treated with a cast and displaced fractures requiring surgical fixation. Complications of scaphoid fractures include non-union and avascular necrosis.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 7
Correct
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A 45-year-old carpenter comes to your medical practice complaining of weakness and numbness in his right hand. During the examination, you observe a decrease in sensation on the palmar side of his index finger, middle finger, and the radial half of his ring finger. Tinel's sign is positive, leading you to diagnose carpal tunnel syndrome. Which nerve is the most probable cause of this condition?
Your Answer: Median
Explanation:The carpal tunnel only allows the median nerve to pass through it, providing sensory innervation to the palmar aspect of the thumb, index, middle, and radial aspect of the ring finger. If the median nerve is damaged, it can also cause weakness in wrist flexion.
If any of the other nerves are affected, they would cause different patterns of sensory disturbance. For example, an ulnar nerve palsy would typically cause paresthesia on the ulnar half of the ring finger, the entire little finger, and the dorsal medial (ulnar) aspect of the hand. A radial nerve palsy would cause paresthesia on the dorsal lateral (radial) aspect of the hand, but not beyond the metacarpal-phalangeal joint. An axillary nerve palsy would only cause paresthesia in the deltoid area and not affect the sensation in the hands. Finally, a musculocutaneous nerve palsy would cause paresthesia along the lateral aspect of the forearm, but the sensation in the hand would remain intact.
Carpal tunnel syndrome is a condition that occurs when the median nerve in the carpal tunnel is compressed. This can cause pain and pins and needles sensations in the thumb, index, and middle fingers. In some cases, the symptoms may even travel up the arm. Patients may shake their hand to alleviate the discomfort, especially at night. During an examination, weakness in thumb abduction and wasting of the thenar eminence may be observed. Tapping on the affected area may also cause paraesthesia, and flexing the wrist can trigger symptoms.
There are several potential causes of carpal tunnel syndrome, including idiopathic factors, pregnancy, oedema, lunate fractures, and rheumatoid arthritis. Electrophysiology tests may reveal prolongation of the action potential in both motor and sensory nerves. Treatment options may include a six-week trial of conservative measures such as wrist splints at night or corticosteroid injections. If symptoms persist or are severe, surgical decompression may be necessary, which involves dividing the flexor retinaculum.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 8
Correct
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A 32-year-old man is rushed to the operating room for aortic dissection. Upon observation, he displays tall stature, pectus excavatum, and arachnodactyly. Which protein defect is primarily responsible for his condition?
Your Answer: Fibrillin
Explanation:The underlying cause of Marfan’s syndrome is a genetic mutation in the fibrillin-1 protein, which plays a crucial role as a substrate for elastin.
Understanding Marfan’s Syndrome
Marfan’s syndrome is a genetic disorder that affects the connective tissue in the body. It is caused by a defect in the FBN1 gene on chromosome 15, which codes for the protein fibrillin-1. This disorder is inherited in an autosomal dominant pattern and affects approximately 1 in 3,000 people.
Individuals with Marfan’s syndrome often have a tall stature with an arm span to height ratio greater than 1.05. They may also have a high-arched palate, arachnodactyly (long, slender fingers), pectus excavatum (sunken chest), pes planus (flat feet), and scoliosis (curvature of the spine). In addition, they may experience cardiovascular problems such as dilation of the aortic sinuses, mitral valve prolapse, and aortic aneurysm, which can lead to aortic dissection and aortic regurgitation. Other symptoms may include repeated pneumothoraces (collapsed lung), upwards lens dislocation, blue sclera, myopia, and ballooning of the dural sac at the lumbosacral level.
In the past, the life expectancy of individuals with Marfan’s syndrome was around 40-50 years. However, with regular echocardiography monitoring and medication such as beta-blockers and ACE inhibitors, the life expectancy has significantly improved. Despite this, cardiovascular problems remain the leading cause of death in individuals with Marfan’s syndrome.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 9
Incorrect
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A 28-year-old man visits his GP with complaints of ongoing stiffness and pain in his lower back for the past 6 months. He reports no specific injury that could have caused his symptoms and mentions that he leads an active lifestyle. The pain is particularly severe in the morning but improves with physical activity. Following imaging tests, he is diagnosed with ankylosing spondylitis. What is the gene linked to this condition?
Your Answer: Human leucocyte antigen- B47
Correct Answer: Human leucocyte antigen- B27
Explanation:Ankylosing spondylitis is associated with the HLA-B27 serotype, with approximately 90% of patients with the condition testing positive for it. Adrenal 21-hydroxylase deficiency is thought to be linked to HLA-B47, while HLA-DQ2 is associated with coeliac disease and the development of autoimmune diseases. HLA-DR4 is primarily linked to rheumatoid arthritis, while HLA-DR2 is associated with systemic lupus erythematosus, multiple sclerosis, and leprosy, but not ankylosing spondylitis.
Ankylosing spondylitis is a type of spondyloarthropathy that is associated with HLA-B27. It is more common in males aged 20-30 years old. Inflammatory markers such as ESR and CRP are often elevated, but normal levels do not rule out ankylosing spondylitis. HLA-B27 is not very useful in making the diagnosis as it is positive in 90% of patients with ankylosing spondylitis and 10% of normal patients. The most useful diagnostic tool is a plain x-ray of the sacroiliac joints, which may show subchondral erosions, sclerosis, squaring of lumbar vertebrae, bamboo spine, and syndesmophytes. If the x-ray is negative but suspicion for AS remains high, an MRI may be obtained to confirm the diagnosis. Spirometry may show a restrictive defect due to pulmonary fibrosis, kyphosis, and ankylosis of the costovertebral joints.
Management of ankylosing spondylitis includes regular exercise such as swimming, NSAIDs as first-line treatment, physiotherapy, and disease-modifying drugs such as sulphasalazine if there is peripheral joint involvement. Anti-TNF therapy such as etanercept and adalimumab may be given to patients with persistently high disease activity despite conventional treatments, according to the 2010 EULAR guidelines. Research is ongoing to determine whether anti-TNF therapies should be used earlier in the course of the disease.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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Question 10
Correct
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A 26-year-old medical student visits his doctor with a complaint of experiencing dry mouth, particularly at night, which has been affecting his sleep. He has a medical history of allergic rhinitis and is currently taking chlorphenamine for it.
What is the correct explanation for the mechanism of action of chlorphenamine?Your Answer: H1 receptor antagonist
Explanation:Chlorphenamine is a medication.
Antihistamines for Allergic Rhinitis and Urticaria
Antihistamines, specifically H1 inhibitors, are effective in treating allergic rhinitis and urticaria. Sedating antihistamines like chlorpheniramine have antimuscarinic properties that can cause dry mouth and urinary retention. On the other hand, non-sedating antihistamines like loratadine and cetirizine are less likely to cause drowsiness. However, there is some evidence that cetirizine may still cause some level of drowsiness compared to other non-sedating antihistamines. Overall, antihistamines are a valuable treatment option for those suffering from allergic rhinitis and urticaria.
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This question is part of the following fields:
- Musculoskeletal System And Skin
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