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Question 1
Incorrect
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For calculation of cardiac output by Fick's principle, which of the following vessels is the best source of venous blood to determine the arterial-to-venous oxygen tension difference?
Your Answer: Pulmonary vein
Correct Answer: Pulmonary artery
Explanation:Fick’s principle states that the total uptake (or release) of a substance by peripheral tissues is equal to the product of the blood flow to the peripheral tissues and the arterial– venous concentration difference (gradient) of the substance. It is used to measure the cardiac output, and the formula is Cardiac output = oxygen consumption divided by arteriovenous oxygen difference. Assuming there are no shunts across the pulmonary system, the pulmonary blood flow equals the systemic blood flow. The arterial and venous blood oxygen content is measured by sampling from the pulmonary artery (low oxygen content) and pulmonary vein (high oxygen content). Peripheral arterial blood is used as a surrogate for the pulmonary vein.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 2
Correct
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Calculate the cardiac stroke volume of a patient whose oxygen consumption (measured by analysis of mixed expired gas) is 300 ml/min, arterial O2 content is 20 ml/100 ml blood, pulmonary arterial O2 content is 15 ml/100 ml blood and heart rate is 60/min.
Your Answer: 100 ml
Explanation:By Fick’s principle, VO2 = Q × (CA (O2) − CV (O2)) where VO2 = O2 consumption, Q = cardiac output and CA(O2) and CV(O2) are arterial and mixed venous O2 content respectively. Thus, in the given problem, 300 ml O2/min = Q × (20−15) ml O2/100 ml. Thus, Q = 6000 ml blood/min. Then, we can calculate stroke volume by dividing the cardiac output with heart rate. Thus, stroke volume = 6000 ml/min divided by 60/min stroke volume = 100 ml.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 3
Incorrect
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An 8 year old boy presents with a history of repeated bacterial/pyogenic infections. He had a normal recovery from chickenpox and measles and shows normal antibody response. A decrease in which of the cell types can best explain this history of repeated pyogenic infections?
Your Answer: B lymphocytes
Correct Answer: Neutrophils
Explanation:A decrease in the number of granulocytes, particularly neutrophils is known as agranulocytosis and it increases the susceptibility of an individual towards recurrent infections. Neutropenia can be either due to decreased production or increased elimination of neutrophils.
Ineffective agranulopoiesis is seen in: 1. myeloid stem cell suppression, 2. disease conditions associated with granulopoiesis such as megaloblastic anaemia and myelodysplastic syndromes, 3. rare genetic diseases, 4. splenic sequestration and 5. increased peripheral utilization.
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This question is part of the following fields:
- Inflammation & Immunology
- Pathology
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Question 4
Incorrect
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What is the normal glomerular filtration rate?
Your Answer: 75 mL/min
Correct Answer: 125 mL/min
Explanation:The normal glomerular filtration rate (GFR) in humans is 125 mL/min. After the age of 40, GFR decreases progressively by about 0.4–1.2 mL/min per year.
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This question is part of the following fields:
- Physiology
- Renal
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Question 5
Correct
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Which of the following toxins most likely results in continuous cAMP production, which pumps H2O, sodium, potassium, chloride and bicarbonate into the lumen of the small intestine and results in rapid dehydration?
Your Answer: Cholera toxin
Explanation:The cholera toxin (CTX or CT) is an oligomeric complex made up of six protein subunits: a single copy of the A subunit (part A), and five copies of the B subunit (part B), connected by a disulphide bond. The five B subunits form a five-membered ring that binds to GM1 gangliosides on the surface of the intestinal epithelium cells. The A1 portion of the A subunit is an enzyme that ADP-ribosylates G proteins, while the A2 chain fits into the central pore of the B subunit ring. Upon binding, the complex is taken into the cell via receptor-mediated endocytosis. Once inside the cell, the disulphide bond is reduced, and the A1 subunit is freed to bind with a human partner protein called ADP-ribosylation factor 6 (Arf6). Binding exposes its active site, allowing it to permanently ribosylate the Gs alpha subunit of the heterotrimeric G protein. This results in constitutive cAMP production, which in turn leads to secretion of H2O, Na+, K+, Cl−, and HCO3− into the lumen of the small intestine and rapid dehydration. The gene encoding the cholera toxin was introduced into V. cholerae by horizontal gene transfer.
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This question is part of the following fields:
- Microbiology
- Pathology
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Question 6
Correct
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A 33-year old lady presented to the gynaecology clinic with amenorrhoea for 6 months and a recent-onset of milk discharge from her breasts. She was not pregnant or on any medication. On enquiry, she admitted to having frequent headaches the last 4 months. Which of the following findings would you expect to see in her condition?
Your Answer: Hyperprolactinaemia
Explanation:Excessively high levels of prolactin in the blood is called hyperprolactinaemia. Normally, prolactin levels are less than 580 mIU/l in females and less than 450 mIU/l in men. The biologically inactive macroprolactin can lead to a false high reading. However, the patient remains asymptomatic. Dopamine down-regulates prolactin whereas oestrogen upregulates it. Hyperprolactinaemia can be caused due to lack of inhibition (compression of pituitary stalk or low dopamine levels), or increased production due to a pituitary adenoma (prolactinoma). Either of these causes can lead to a prolactin level of 1000-5000 mIU/l. However, levels more than 5000mIU/l are usually associated due to an adenoma and >100,000 mIU/l are seen in macroadenomas (tumours < 1cm in diameter). Increased prolactin causes increased dopamine release from the arcuate nucleus of hypothalamus. This increased dopamine in turn, inhibits the GnRH (Gonadotrophin Releasing Hormone) thus blocking gonadal steroidogenesis resulting in the symptoms of hyperprolactinaemia. In women, it includes hypoestrogenism, anovulatory infertility, decreased or irregular menstruation or complete amenorrhoea. It can even cause production of breast milk, loss of libido, vaginal dryness and osteoporosis. In men, the symptoms include impotence, decreased libido, erectile dysfunction and infertility. In men, treatment can be delayed due to late diagnosis as they have no reliable indicator such as menstruation that might indicate a problem. Most of the male patients seek help only when headaches and visual defects start to surface.
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This question is part of the following fields:
- Endocrine
- Pathology
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Question 7
Incorrect
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Pain in the epigastric region occurring typically 2-3 hours after meals and causing the patient to wake up at night is characteristic of which of the following conditions?
Your Answer: Zollinger–Ellison syndrome
Correct Answer: Duodenal ulcer
Explanation:The description is typical for duodenal ulcers. There is no pain upon waking in the morning however it appears around mid-morning and is relieved by ingestion of food. The pain also often causes the patient to wake up at night.
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This question is part of the following fields:
- Gastrointestinal; Hepatobiliary
- Pathology
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Question 8
Correct
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If a 70-year-old man with known atrial fibrillation dies suddenly, which of these is the most likely cause of death?
Your Answer: Thromboembolism
Explanation:In atrial fibrillation, the abnormal atrial contraction can cause blood to stagnate in the left atrium and form a thrombus, which may then embolize. The patient’s history of AF suggest an embolic disease, which lead to his death.
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This question is part of the following fields:
- Cardiovascular
- Pathology
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Question 9
Incorrect
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Causes of metabolic acidosis with a normal anion gap include:
Your Answer: Lactic acidosis
Correct Answer: Diarrhoea
Explanation:Excess acid intake and excess bicarbonate loss as in diarrhoea, are causes of metabolic acidosis with a normal anion gap. The other conditions all result in an increased anion gap.
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This question is part of the following fields:
- Fluids & Electrolytes
- Physiology
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Question 10
Correct
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Which of these substances is secreted by pericytes in the juxtaglomerular cells?
Your Answer: Renin
Explanation:The juxtaglomerular cells synthesise, store and secrete the enzyme renin in the kidney. They are specialised smooth muscle cells in the wall of the afferent arteriole that delivers blood to the glomerulus and thus play a critical role in the renin– angiotensin system and so in renal autoregulation.
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This question is part of the following fields:
- Physiology
- Renal
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Question 11
Correct
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Increased resistance to flow of blood in cerebral vessels is most likely seen in:
Your Answer: Elevation in systemic arterial pressure from 100 to 130 mmHg
Explanation:Constant cerebral blood flow is maintained by autoregulation in the brain, which causes an increase in local vascular resistance to offset an increase in blood pressure. There will be an increase in cerebral blood flow (and decrease in resistance to cerebral blood flow) with a decrease in arterial oxygen or an increase in arterial CO2. Similarly, a decrease in viscosity will also increase the blood flow. Due to increased brain metabolism and activity during a seizure, there will also be an increase in the cerebral blood flow.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 12
Correct
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Which of the following compensatory parameters is responsible for causing an increase in the blood pressure in a 30 year old patient with a BP of 40 mmHg?
Your Answer: Baroreceptor reflex
Explanation:The baroreflex or baroreceptor reflex is one of the body’s homeostatic mechanisms for regulating blood pressure. It provides a negative feedback response in which an elevated blood pressure will causes blood pressure to decrease; similarly, decreased blood pressure depresses the baroreflex, causing blood pressure to rise. The system relies on specialised neurones (baroreceptors) in the aortic arch, carotid sinuses and elsewhere to monitor changes in blood pressure and relay them to the brainstem. Subsequent changes in blood pressure are mediated by the autonomic nervous system. Baroreceptors include those in the auricles of the heart and vena cava, but the most sensitive baroreceptors are in the carotid sinuses and aortic arch. The carotid sinus baroreceptors are innervated by the glossopharyngeal nerve (CN IX); the aortic arch baroreceptors are innervated by the vagus nerve (CN X).
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 13
Correct
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Which tumour marker is associated with medullary carcinoma of thyroid?
Your Answer: Calcitonin
Explanation:Medullary carcinoma of thyroid accounts for 3% of thyroid cancers. It arises from the parafollicular cells (C cells) of the thyroid gland that produce calcitonin. It is often familial and caused by mutation of ret proto-oncogene, but can occasionally be sporadic. The familial cases can also occur as part of MEN syndromes IIA and IIB. The high calcitonin leads to down-regulation of the receptors, which does not affect the calcium levels significantly. Medullary carcinoma of thyroid shows characteristic amyloid deposits that stain positively with Congo red. The initial presentation consists of an asymptomatic thyroid nodule. Many cases are diagnosed due to routine screening of relatives of patients with MEN IIA and IIB. Medullary carcinoma can also cause ectopic production of other hormones/peptides such as adrenocorticotrophic hormone, vasoactive intestinal polypeptide, kallikreins and serotonin.
Metastasis from medullary carcinoma spread via the lymphatics to cervical and mediastinal nodes, and can also affect the liver, lungs and bone. Diagnosis is by raised serum calcitonin levels. A provocative test with calcium (15 mg/kg intravenously over 4 hours) also aids in diagnosis by leading to excessive secretion of calcitonin. X-ray might also show dense, conglomerate calcification.
CA-125 is frequently elevated in ovarian carcinomas. CA 15-3 is often associated with breast carcinomas. Alpha-fetoprotein is seen raised in hepatomas and gonadal tumours. Elevated HCG is associated with normal pregnancies, gonadal tumours, and choriocarcinomas. Thyroglobulin is used for surveillance in papillary carcinoma of thyroid. CA 19-9 is used in the management of pancreatic cancer.
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This question is part of the following fields:
- Endocrine
- Pathology
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Question 14
Correct
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Decreased velocity of impulse conduction through the atrioventricular node (AV node) in the heart will lead to:
Your Answer: Increased PR interval
Explanation:AV node damage may lead to an increase in the PR interval to as high as 0.25 – 0.40 s (normal = 0.12 – 0.20 s). In the case of severe impairment, there might be a complete failure of passage of impulses leading to complete block. In this case, the atria and ventricles will beat independently of each other.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 15
Incorrect
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A 34-year-old woman is diagnosed with cerebral oedema after suffering a severe head trauma. Which of the following conditions is not likely to be associated with the extracellular oedema?
Your Answer: Lymphatic blockage
Correct Answer: Increased plasma colloid osmotic pressure
Explanation:Cerebral oedema is extracellular fluid accumulation in the brain. Increased capillary permeability, increased capillary pressure, increased interstitial fluid colloid osmotic pressure and lymphatic blockage would increase fluid movement into the interstitial spaces. Increased plasma colloid osmotic pressure, however, would oppose fluid movement from the capillaries into the interstitial compartment.
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This question is part of the following fields:
- Fluids & Electrolytes
- Physiology
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Question 16
Correct
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Langhans giant cells are characteristically seen in which type of inflammation?
Your Answer: Granulomatous inflammation
Explanation:Langhans giant cells are characteristically seen in granulomatous inflammation. They form when epithelioid cells fuse together. They usually contain a nuclei with a horseshoe-shaped pattern in the periphery of the cell.
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This question is part of the following fields:
- Inflammation & Immunology
- Pathology
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Question 17
Incorrect
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A 62-year-old male smoker, presented with shortness of breath, chronic cough and haemoptysis over the last three months. He has developed a fat pad in the base of his neck, rounded face, acne and osteoporosis. Which of the following is the most likely pulmonary disease that is causing these symptoms and findings?
Your Answer: Pulmonary adenocarcinoma
Correct Answer: Small-cell anaplastic carcinoma
Explanation:Small cell lung cancer is a highly aggressive form of lung cancer. It is thought to originate from neuroendocrine cells in the bronchus called Feyrter cells and is often associated to ectopic production of hormones like ADH and ACTH that result in paraneoplastic syndromes and Cushing’s syndrome.
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This question is part of the following fields:
- Pathology
- Respiratory
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Question 18
Correct
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A 45-year-old woman was brought to the emergency department due to fever and chills. She has a history of recurrent UTI and complains of dysuria and urinary frequency. Urinary white blood cell count is >200 cell/high power field. If urine culture is performed, what is the most likely organism that will grow?
Your Answer: Escherichia coli
Explanation:The pathogen that most likely causes recurrent urinary tract infection in young women are E. coli, Enterococcus and Staphylococcus saprophyticus.
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This question is part of the following fields:
- Microbiology
- Pathology
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Question 19
Correct
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An 26-year-old man sought admission due to persistent non-bloody diarrhoea. The patient is HIV-positive. Examination of stool sample showed numerous acid-fast cysts. Which of the following organism is the most likely cause of diarrhoea?
Your Answer: Cryptosporidium parvum
Explanation:Cryptosporidium parvum is one of several species that causes cryptosporidiosis, a parasitic disease of the mammalian intestinal tract. Primary symptoms of C. parvum infection are acute, watery, and non-bloody diarrhoea. C. parvum infection is of particular concern in immunocompromised patients, where diarrhoea can reach 10–15 l per day.
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This question is part of the following fields:
- Microbiology
- Pathology
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Question 20
Correct
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Which of the following is the most abundant WBC seen in a smear from a healthy person.
Your Answer: Neutrophils
Explanation:neutrophils are the most abundant cell type of the WBC. These phagocytes are found normally in the blood and increase in number are seen during an acute inflammation. These the percentages of WBC in blood Neutrophils: 40 to 60%
Lymphocytes: 20 to 40%
Monocytes: 2 to 8%
Eosinophils: 1 to 4%
Basophils: 0.5 to 1%
Band (young neutrophil): 0 to 3%. eosinophils, basophils, neutrophils are known as granulocytes and monocytes and lymphocytes as agranulocytes.
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This question is part of the following fields:
- Inflammation & Immunology
- Pathology
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