MBBS (Bachelor of Medicine and Bachelor of Surgery) Professional Examination — Questions and Answers

Question 1: Which nerve is most commonly injured in a midshaft fracture of the humerus?

Radial nerve (Correct answer)
Ulnar nerve
Musculocutaneous nerve
Median nerve

Correct answer: Radial nerve

The radial nerve winds around the posterior aspect of the humerus in the spiral groove and is vulnerable to injury in midshaft humeral fractures.

Question 2: A patient presents with acute limb ischemia — which of the 6 Ps is NOT part of the classic presentation?

Pruritus (Correct answer)
Pulselessness
Pain
Pallor

Correct answer: Pruritus

The 6 Ps of acute limb ischemia are: Pain, Pallor, Pulselessness, Paresthesia, Paralysis, and Perishing cold (poikilothermia) — pruritus is not included.

Question 3: What is the most common cause of community-acquired pneumonia (CAP) in adults?

Haemophilus influenzae
Legionella pneumophila
Mycoplasma pneumoniae
Streptococcus pneumoniae (Correct answer)

Correct answer: Streptococcus pneumoniae

Streptococcus pneumoniae is the most common cause of bacterial community-acquired pneumonia in adults across all age groups.

Question 4: A 70-year-old man arrives at the hospital after falling while hanging Christmas lights on his roof. He claims to be experiencing right-side chest pain and shortness of breath. His right breath sounds have significantly decreased, according to a physical examination. The moment you insert a chest tube on the right, 850ml of blood start to flow back. Which course of action in his management is best?

Suction then remove and seal chest tube site
Keep tube to suction, watch pressures and output (Correct answer)
OR for operative exploration
Remove chest tube and place dressing

Correct answer: Keep tube to suction, watch pressures and output

The patient's symptoms and the significant blood return from the chest tube indicate a hemothorax. While 850ml of blood is a considerable amount, the initial management for a hemothorax is to continue chest tube drainage, monitor the patient's vital signs, and assess the rate of ongoing blood loss. Operative exploration is typically reserved for persistent, massive bleeding (e.g., >1500ml initially or >200ml/hour for several hours), which is not yet indicated here.

Question 5: A woman visits the emergency room six days after starting warfarin therapy with severe, black eschars on her arm, breast, buttocks, and foot. Your presumed illness is probably caused by a lack in one of the following:

Vitamin K
Vitamin C
Platelets
Protein C (Correct answer)

Correct answer: Protein C

The patient's severe, black eschars developing shortly after starting warfarin therapy are characteristic of warfarin-induced skin necrosis. This rare but serious complication is caused by a transient hypercoagulable state resulting from the rapid depletion of Protein C, a natural anticoagulant, before the depletion of procoagulant factors. This imbalance leads to microthrombosis and subsequent skin necrosis.

Question 6: In the urea cycle, the final step converts arginine to urea and which other product?

Ornithine (Correct answer)
Aspartate
Citrulline
Fumarate

Correct answer: Ornithine

Arginase cleaves arginine to yield urea (excreted) and ornithine, which re-enters the cycle to accept another carbamoyl group.

Question 7: ACE inhibitors reduce angiotensin II levels and are contraindicated in pregnancy primarily because they cause:

Fetal renal dysgenesis and oligohydramnios (Correct answer)
Cardiac septal defects
Neural tube defects
Cleft palate

Correct answer: Fetal renal dysgenesis and oligohydramnios

ACE inhibitors in the 2nd and 3rd trimester cause fetal renal tubular dysplasia, leading to oligohydramnios, limb contractures, and neonatal renal failure.

Question 8: Reed-Sternberg cells are pathognomonic of which condition?

Non-Hodgkin lymphoma
Burkitt lymphoma
Chronic lymphocytic leukemia
Hodgkin lymphoma (Correct answer)

Correct answer: Hodgkin lymphoma

Reed-Sternberg cells (large binucleated cells with prominent 'owl eye' nucleoli) are the hallmark of Hodgkin lymphoma.

Question 9: Which of the following typically becomes severely depleted and is frequently administered after large and enormous blood transfusions:

Potassium
Vitamin K
Calcium (Correct answer)
Glucose

Correct answer: Calcium

Massive blood transfusions frequently lead to hypocalcemia due to the citrate anticoagulant present in stored blood products. Citrate binds to ionized calcium in the recipient's bloodstream, effectively chelating it and reducing its physiological availability. This can cause various symptoms, including cardiac dysfunction, necessitating careful monitoring and often calcium supplementation during large volume transfusions.

Question 10: The Ziehl-Neelsen stain is used to identify organisms that are acid-fast. Which property makes mycobacteria acid-fast?

Presence of teichoic acids
High peptidoglycan content
Presence of mycolic acids in the cell wall (Correct answer)
Thick polysaccharide capsule

Correct answer: Presence of mycolic acids in the cell wall

Mycolic acids are long-chain fatty acids in the mycobacterial cell wall that retain the carbol fuchsin dye even after acid-alcohol decolorization.

Question 11: Which neurotransmitter is released at the neuromuscular junction?

Norepinephrine
Dopamine
Serotonin
Acetylcholine (Correct answer)

Correct answer: Acetylcholine

Acetylcholine is released from motor neurons at the neuromuscular junction and binds nicotinic receptors on skeletal muscle.

Question 12: What is the most common complication following splenectomy?

Portal vein thrombosis
Left-sided pleural effusion (Correct answer)
Pancreatic fistula
Overwhelming post-splenectomy infection (OPSI)

Correct answer: Left-sided pleural effusion

Left-sided reactive pleural effusion is the most common early complication after splenectomy; OPSI is the most feared late complication but occurs less frequently.

Question 13: Which amino acid is the precursor for catecholamine synthesis (dopamine, norepinephrine, epinephrine)?

Histidine
Phenylalanine/Tyrosine (Correct answer)
Glutamate
Tryptophan

Correct answer: Phenylalanine/Tyrosine

Tyrosine (derived from phenylalanine) is converted to L-DOPA and then sequentially to dopamine, norepinephrine, and epinephrine in catecholamine synthesis.

Question 14: Which organism is the most common cause of community-acquired pneumonia in adults?

Mycoplasma pneumoniae
Klebsiella pneumoniae
Streptococcus pneumoniae (Correct answer)
Haemophilus influenzae

Correct answer: Streptococcus pneumoniae

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia in adults, accounting for approximately 30-70% of cases.

Question 15: Which enzyme converts fibrinogen to fibrin in the coagulation cascade?

Thrombin (Correct answer)
Prothrombin
Plasmin
Factor X

Correct answer: Thrombin

Thrombin (activated from prothrombin by Factor Xa/Va) cleaves fibrinopeptides A and B from fibrinogen, generating fibrin monomers that polymerize into a clot.

Question 16: Mallory bodies (Mallory-Denk bodies) in hepatocytes are associated with which condition?

Viral hepatitis B
Alcoholic liver disease (Correct answer)
Primary biliary cirrhosis
Hemochromatosis

Correct answer: Alcoholic liver disease

Mallory bodies are aggregates of cytokeratin intermediate filaments found in hepatocytes damaged by alcohol, representing a hallmark of alcoholic hepatitis.

Question 17: Which of the following is the reversal agent for heparin toxicity?

Protamine sulfate (Correct answer)
Tranexamic acid
Fresh frozen plasma
Vitamin K

Correct answer: Protamine sulfate

Protamine sulfate is a positively charged molecule that binds and neutralizes negatively charged heparin, reversing its anticoagulant effect.

Question 18: In colorectal cancer staging using the TNM system, what does N1 indicate?

No regional lymph node metastasis
Metastasis in 1–3 regional lymph nodes (Correct answer)
Distant organ metastasis
Metastasis in 4 or more regional lymph nodes

Correct answer: Metastasis in 1–3 regional lymph nodes

N1 in colorectal TNM staging indicates metastasis in 1–3 regional lymph nodes (N0 = none, N1 = 1–3 nodes, N2 = ≥4 nodes).

Question 19: Which class of drugs inhibits cyclooxygenase (COX) enzymes and reduces prostaglandin synthesis?

Antihistamines
NSAIDs (Correct answer)
Leukotriene antagonists
Corticosteroids

Correct answer: NSAIDs

NSAIDs inhibit COX-1 and COX-2 enzymes, reducing prostaglandin and thromboxane synthesis to provide anti-inflammatory, analgesic, and antipyretic effects.

Question 20: Cystic fibrosis is caused by a defect in which protein?

Spectrin
Dystrophin
CFTR (Cystic Fibrosis Transmembrane conductance Regulator) (Correct answer)
Collagen type IV

Correct answer: CFTR (Cystic Fibrosis Transmembrane conductance Regulator)

CF is caused by mutations in the CFTR gene encoding a chloride channel; the most common mutation (ΔF508) causes protein misfolding and failure to reach the cell surface.

Question 21: The first-pass metabolism effect is most significant for drugs administered by which route?

Transdermal
Sublingual
Oral (Correct answer)
Intravenous

Correct answer: Oral

Orally administered drugs pass through the gut wall and liver before reaching systemic circulation, where extensive first-pass metabolism can significantly reduce bioavailability.

Question 22: Prions are infectious agents associated with transmissible spongiform encephalopathies. What is the defining characteristic of prion proteins?

They are misfolded proteins that induce normal proteins to misfold (Correct answer)
They are lipid-coated viral particles
They replicate using reverse transcriptase
They contain RNA but no protein

Correct answer: They are misfolded proteins that induce normal proteins to misfold

Prions are abnormally folded PrP^Sc proteins that act as templates to convert normal cellular PrP^C into the pathological conformation, propagating without any nucleic acid.

Question 23: Which type of hypersensitivity reaction is the mechanism behind tuberculin skin test (Mantoux test) positivity?

Type III (immune complex)
Type II (cytotoxic)
Type IV (delayed-type/cell-mediated) (Correct answer)
Type I (IgE-mediated)

Correct answer: Type IV (delayed-type/cell-mediated)

The Mantoux reaction is a classic Type IV (delayed-type) hypersensitivity, mediated by sensitized T lymphocytes that react to tuberculin antigen 48-72 hours after injection.

Question 24: Warfarin's anticoagulant effect is due to inhibition of which enzyme?

Factor Xa
Vitamin K epoxide reductase (Correct answer)
Thrombin
Antithrombin III

Correct answer: Vitamin K epoxide reductase

Warfarin inhibits vitamin K epoxide reductase, preventing regeneration of reduced vitamin K needed for carboxylation of clotting factors II, VII, IX, and X.

Question 25: The mechanism of action of statins involves inhibition of which enzyme?

Lipoprotein lipase
Pancreatic lipase
Cholesterol ester transfer protein
HMG-CoA reductase (Correct answer)

Correct answer: HMG-CoA reductase

Statins inhibit HMG-CoA reductase, the rate-limiting enzyme in cholesterol synthesis, leading to upregulation of LDL receptors and decreased plasma LDL.

Question 26: Which suture material is most appropriate for closing the abdominal fascia (linea alba) in a midline laparotomy?

Silk (non-absorbable braided)
Chromic catgut (absorbable)
Rapid-absorbing polyglactin
Polypropylene (non-absorbable monofilament) (Correct answer)

Correct answer: Polypropylene (non-absorbable monofilament)

Polypropylene (Prolene) or slowly absorbable sutures like PDS are preferred for fascial closure due to their prolonged tensile strength reducing wound dehiscence risk.

Question 27: Which dermatome covers the medial aspect of the thigh?

L2 (Correct answer)
S1
L1
L3

Correct answer: L2

The L2 dermatome covers the medial and anterior aspect of the upper thigh.

Question 28: Which of the following best describes metaplasia?

Increase in cell number
Decrease in cell size due to reduced workload
Increase in cell size
Replacement of one differentiated cell type by another (Correct answer)

Correct answer: Replacement of one differentiated cell type by another

Metaplasia is the reversible replacement of one mature cell type by another, typically as an adaptation to chronic irritation or stress.

Question 29: Which sign is elicited in acute appendicitis by pressing on the left iliac fossa causing pain in the right iliac fossa?

McBurney's sign
Psoas sign
Obturator sign
Rovsing's sign (Correct answer)

Correct answer: Rovsing's sign

Rovsing's sign is positive when palpation of the left iliac fossa causes pain in the right iliac fossa due to transmitted pressure over an inflamed appendix.

Question 30: Which vitamin deficiency leads to impaired collagen synthesis and is associated with scurvy?

Vitamin K
Vitamin C (Correct answer)
Vitamin A
Vitamin D

Correct answer: Vitamin C

Vitamin C (ascorbic acid) is required for hydroxylation of proline and lysine residues in collagen, and its deficiency causes scurvy with poor wound healing and bleeding gums.

Question 31: Amyloid deposits in systemic amyloidosis are identified with which stain?

Congo red with apple-green birefringence under polarized light (Correct answer)
Oil Red O
Periodic acid-Schiff (PAS)
Prussian blue

Correct answer: Congo red with apple-green birefringence under polarized light

Congo red stain identifies amyloid deposits, which show characteristic apple-green birefringence under polarized light microscopy.

Question 32: Which foramen transmits the optic nerve and ophthalmic artery?

Foramen rotundum
Superior orbital fissure
Optic canal (Correct answer)
Inferior orbital fissure

Correct answer: Optic canal

The optic canal transmits the optic nerve (CN II) and the ophthalmic artery.

Question 33: Which antibiotic acts by inhibiting bacterial cell wall synthesis by binding to the D-Ala-D-Ala terminus of peptidoglycan precursors?

Penicillin
Rifampin
Ciprofloxacin
Vancomycin (Correct answer)

Correct answer: Vancomycin

Vancomycin binds to the D-Ala-D-Ala terminus of peptidoglycan precursors, preventing transglycosylation and transpeptidation, thereby inhibiting cell wall synthesis.

Question 34: Which hormone is responsible for the long-loop negative feedback on the hypothalamo-pituitary axis in thyroid regulation?

TRH
Calcitonin
T3 and T4 (Correct answer)
TSH

Correct answer: T3 and T4

T3 and T4 exert negative feedback on both the pituitary (inhibiting TSH) and hypothalamus (inhibiting TRH) to regulate their own production.

Question 35: In ATLS (Advanced Trauma Life Support), what is the first priority in the primary survey?

Circulation and hemorrhage control
Airway maintenance with cervical spine protection (Correct answer)
Breathing and ventilation
Disability (neurological status)

Correct answer: Airway maintenance with cervical spine protection

The ATLS primary survey follows the ABCDE sequence: Airway (with C-spine protection) is always assessed and managed first.

Question 36: Which virulence factor of Staphylococcus aureus allows it to resist phagocytosis by inhibiting opsonization?

Coagulase
Leukocidin
Hyaluronidase
Protein A (Correct answer)

Correct answer: Protein A

Protein A binds to the Fc region of IgG antibodies, preventing opsonization and thereby inhibiting phagocytosis by neutrophils.

Question 37: Gaucher disease results from deficiency of which enzyme?

Hexosaminidase A
Glucocerebrosidase (beta-glucosidase) (Correct answer)
Sphingomyelinase
Alpha-galactosidase A

Correct answer: Glucocerebrosidase (beta-glucosidase)

Gaucher disease is the most common lysosomal storage disorder, caused by glucocerebrosidase deficiency, leading to glucocerebroside accumulation in macrophages.

Question 38: Which of the following statements about the lymphatic drainage of the lungs is true?

The thymus gland drains the anterior portions of both lungs
Flow of lymph from the left lower lobe may drain to the right mediastinal (paratracheal) lymph nodes (Correct answer)
The thoracic duct picks up tributaries along its route through the mediastinum, providing most of the drainage of the left lung
The upper 2/3 of each lung drains to the hilum, while the bottom 1/3 drains below the diaphragm

Correct answer: Flow of lymph from the left lower lobe may drain to the right mediastinal (paratracheal) lymph nodes

The lymphatic drainage of the lungs is complex and can involve cross-midline pathways, particularly from the lower lobes. Lymph from the left lower lobe can indeed drain to the right mediastinal (paratracheal) lymph nodes. This anatomical detail is clinically significant for understanding the potential spread of lung cancer and for accurate staging.

Question 39: A dental operation is being performed on a 45-year-old male who had a prosthetic aortic valve replaced five years prior. Given its better absorption, which preventive antibiotics are advised?

Oral amoxicillin (Correct answer)
Oral Vancomycin
IV penicillin
IV Ampicillin

Correct answer: Oral amoxicillin

For patients with prosthetic heart valves undergoing dental procedures, antibiotic prophylaxis is recommended to prevent infective endocarditis. Oral amoxicillin is the first-line antibiotic of choice due to its broad spectrum against common oral bacteria and its excellent oral absorption. This ensures adequate antibiotic levels are achieved to protect against bacteremia during the procedure.

Question 40: Which bacteria produce an exotoxin that causes food poisoning by pre-formed toxin ingestion, with symptoms beginning within 1-6 hours of eating?

Salmonella enteritidis
Staphylococcus aureus (Correct answer)
Bacillus cereus
Clostridium perfringens

Correct answer: Staphylococcus aureus

Staphylococcus aureus produces heat-stable enterotoxins in food; because the toxin is preformed, symptoms of nausea, vomiting, and cramping begin rapidly within 1-6 hours of ingestion.

Question 41: Which mechanism of antibiotic resistance involves enzymatic inactivation of aminoglycosides by modification through acetylation, adenylation, or phosphorylation?

Enzymatic modification of the drug (Correct answer)
Altered target site
Efflux pump upregulation
Reduced outer membrane permeability

Correct answer: Enzymatic modification of the drug

Aminoglycoside-modifying enzymes (acetyltransferases, adenylyltransferases, phosphotransferases) chemically modify aminoglycosides, preventing them from binding the 30S ribosomal subunit.

Question 42: What is the normal resting membrane potential of a cardiac ventricular myocyte?

-110 mV
-70 mV
-90 mV (Correct answer)
-55 mV

Correct answer: -90 mV

The resting membrane potential of ventricular myocytes is approximately -90 mV, maintained primarily by K+ leak channels.

Question 43: In the complement system, which component acts as the convergence point for both the classical and alternative pathways?

C9
C1q
C3 (Correct answer)
C5

Correct answer: C3

C3 is the central convergence point; both the classical pathway (via C4b2a C3 convertase) and the alternative pathway (via C3bBb C3 convertase) cleave C3 into C3a and C3b.

Question 44: Which organism causes 'walking pneumonia' and lacks a cell wall, making it intrinsically resistant to beta-lactam antibiotics?

Mycoplasma pneumoniae (Correct answer)
Bordetella pertussis
Chlamydia pneumoniae
Legionella pneumophila

Correct answer: Mycoplasma pneumoniae

Mycoplasma pneumoniae lacks a cell wall entirely, making it resistant to all beta-lactam antibiotics; it causes atypical 'walking pneumonia' with mild symptoms and a dry cough.

Question 45: Which condition is described by the triad of hematemesis, aortic stenosis, and gastrointestinal angiodysplasia?

Osler-Weber-Rendu syndrome
Dieulafoy lesion
Mallory-Weiss syndrome
Heyde's syndrome (Correct answer)

Correct answer: Heyde's syndrome

Heyde's syndrome is the association between calcific aortic stenosis and gastrointestinal bleeding from angiodysplasia, mediated by loss of von Willebrand factor multimers.

Question 46: DNA replication proceeds in which direction?

5' to 3' only
Both 3' to 5' and 5' to 3' simultaneously
Bidirectional from multiple origins but always 5' to 3' (Correct answer)
3' to 5' only

Correct answer: Bidirectional from multiple origins but always 5' to 3'

DNA replication is bidirectional from origins of replication, but each new strand is synthesized only in the 5' to 3' direction by DNA polymerase.

Question 47: The anatomical snuffbox is bounded laterally by which tendons?

Extensor pollicis longus and brevis
Abductor pollicis longus and extensor pollicis brevis (Correct answer)
Extensor indicis and extensor pollicis longus
Flexor pollicis longus and abductor pollicis brevis

Correct answer: Abductor pollicis longus and extensor pollicis brevis

The lateral border of the anatomical snuffbox is formed by the tendons of abductor pollicis longus and extensor pollicis brevis.

Question 48: After an MVC, an ambulance transports a 43-year-old woman who has numerous left rib fractures and respiratory problems to the emergency department. She exhibits tachycardia, tachypnea, and hypoxia. Chest XR shows the tip of the NG tube in the left chest after an NG tube is inserted. Which statement about the issue with this patient is accurate?

This injury occurs more commonly on the left side (Correct answer)
NG tubes commonly puncture the esophagus if care is not taken in placement
Rib fractures can obscure NG location on XR and CT scan should be performed
NG tube is in the left airway and should be removed

Correct answer: This injury occurs more commonly on the left side

The presence of an NG tube in the left chest after multiple left rib fractures indicates a traumatic diaphragmatic rupture. This injury occurs more commonly on the left side because the liver on the right side provides a protective barrier to the right hemidiaphragm, making it less prone to rupture from blunt trauma. The NG tube's position confirms herniation of abdominal contents into the thoracic cavity.

Question 49: Which reaction produces the most ATP per molecule of substrate in cellular respiration?

Oxidative phosphorylation via the electron transport chain (Correct answer)
Beta-oxidation of fatty acids
Substrate-level phosphorylation in the Krebs cycle
Glycolysis

Correct answer: Oxidative phosphorylation via the electron transport chain

Oxidative phosphorylation via the electron transport chain generates approximately 32–34 ATP per glucose, far exceeding the 2 ATP from glycolysis and 2 GTP from the Krebs cycle.

Question 50: The blood supply to the head of the femur in adults comes primarily from which artery?

Obturator artery
Lateral circumflex femoral artery
Superior gluteal artery
Medial circumflex femoral artery (Correct answer)

Correct answer: Medial circumflex femoral artery

The medial circumflex femoral artery provides the primary blood supply to the femoral head in adults, which is why femoral neck fractures can lead to avascular necrosis.

Question 51: Clostridium tetani produces tetanospasmin, which causes spastic paralysis. What is its mechanism of action?

Cleaves SNARE proteins at peripheral synapses
Inhibits release of inhibitory neurotransmitters glycine and GABA (Correct answer)
Blocks acetylcholine release at the neuromuscular junction
Activates adenylyl cyclase in neurons

Correct answer: Inhibits release of inhibitory neurotransmitters glycine and GABA

Tetanospasmin cleaves synaptobrevin (a SNARE protein) in inhibitory interneurons, blocking release of glycine and GABA, resulting in unopposed motor neuron excitation and spastic paralysis.

Question 52: During exercise, which of the following best explains the increase in cardiac output?

Increased sympathetic activity and venous return (Correct answer)
Peripheral vasoconstriction reducing afterload
Decreased heart rate with increased stroke volume only
Increased vagal tone

Correct answer: Increased sympathetic activity and venous return

During exercise, sympathetic activation increases heart rate and contractility while increased venous return (via muscle pump) boosts stroke volume.

Question 53: Which hormone causes water reabsorption in the collecting duct by inserting aquaporin-2 channels?

Aldosterone
Atrial natriuretic peptide
Parathyroid hormone
Antidiuretic hormone (ADH) (Correct answer)

Correct answer: Antidiuretic hormone (ADH)

ADH (vasopressin) binds V2 receptors in the collecting duct, triggering aquaporin-2 insertion and increasing water reabsorption.

Question 54: What is the effect of increased plasma protein concentration on plasma oncotic pressure?

Has no effect on fluid balance
Increases hydrostatic pressure
Increases oncotic pressure, drawing fluid into capillaries (Correct answer)
Decreases oncotic pressure, promoting edema

Correct answer: Increases oncotic pressure, drawing fluid into capillaries

Increased plasma proteins raise oncotic pressure, which retains fluid within capillaries and opposes edema formation.

Question 55: What is the most common cause of right heart failure in the United States?

Pulmonary embolism
Left heart failure (Correct answer)
Tricuspid regurgitation
Primary pulmonary hypertension

Correct answer: Left heart failure

Left heart failure leading to pulmonary hypertension and right ventricular pressure overload is the most common cause of right heart failure.

Question 56: The Frank-Starling mechanism of the heart states that:

Cardiac output is independent of preload
Stroke volume increases with increased end-diastolic volume (Correct answer)
Heart rate increases with increased venous return
Contractility decreases with increased stretch

Correct answer: Stroke volume increases with increased end-diastolic volume

The Frank-Starling mechanism states that stroke volume increases as end-diastolic volume increases, up to a physiological limit.

Question 57: Alpha-1-antitrypsin deficiency causes emphysema through which mechanism?

Impaired surfactant production
Increased collagen deposition in lung parenchyma
Unopposed neutrophil elastase activity destroying alveolar walls (Correct answer)
Increased mucus production blocking small airways

Correct answer: Unopposed neutrophil elastase activity destroying alveolar walls

Alpha-1-antitrypsin normally inhibits elastase; its deficiency allows neutrophil elastase to destroy alveolar walls, causing panacinar emphysema predominantly in the lung bases.

Question 58: The left recurrent laryngeal nerve hooks around which structure?

Left common carotid artery
Right subclavian artery
Aortic arch (Correct answer)
Left brachiocephalic vein

Correct answer: Aortic arch

The left recurrent laryngeal nerve hooks under and around the arch of the aorta before ascending to the larynx.

Question 59: Which type of bacterial genetic transfer involves bacteriophages carrying bacterial DNA from one bacterium to another?

Transformation
Transposition
Transduction (Correct answer)
Conjugation

Correct answer: Transduction

Transduction is the process by which bacteriophages accidentally package and transfer bacterial DNA from a donor bacterium to a recipient bacterium.

Question 60: Which Glasgow Coma Scale (GCS) score indicates severe traumatic brain injury?

8 or below (Correct answer)
9–12
5–7
13–15

Correct answer: 8 or below

A GCS score of 8 or below defines severe TBI; endotracheal intubation is generally indicated at this level to protect the airway.

Question 61: Which of the following correctly describes the location of the ureter in relation to the uterine artery?

The ureter passes anterior and inferior to the uterine artery (Correct answer)
The ureter passes posterior to the uterine artery
The ureter passes lateral to the uterine artery
The ureter passes superior to the uterine artery

Correct answer: The ureter passes anterior and inferior to the uterine artery

The ureter passes inferior to the uterine artery ('water under the bridge'), which is clinically important during hysterectomy to avoid ureteric injury.

Question 62: What is the primary stimulus for erythropoietin (EPO) secretion?

Tissue hypoxia detected by renal peritubular cells (Correct answer)
Low hemoglobin concentration
High altitude exposure
Low serum iron

Correct answer: Tissue hypoxia detected by renal peritubular cells

EPO is secreted by peritubular interstitial cells of the kidney in response to tissue hypoxia, mediated by HIF-1α transcription factor.

Question 63: Which histological finding is characteristic of Crohn's disease but NOT ulcerative colitis?

Goblet cell depletion
Mucosal inflammation
Non-caseating granulomas (Correct answer)
Crypt abscesses

Correct answer: Non-caseating granulomas

Non-caseating granulomas are found in approximately 50% of Crohn's disease cases and represent a hallmark distinguishing it from ulcerative colitis.

Question 64: Which of the following shifts the oxygen-hemoglobin dissociation curve to the right?

Decreased temperature
Decreased PCO2
Increased pH
Increased 2,3-DPG (Correct answer)

Correct answer: Increased 2,3-DPG

Increased 2,3-DPG reduces hemoglobin's affinity for oxygen, shifting the curve to the right and facilitating oxygen unloading to tissues.

Question 65: Chyle leaks are frequently treated by adding extra of the following fatty acids to the patient's diet:

Short-chain
Long-chain
Medium-chain (Correct answer)
Very Long-chain

Correct answer: Medium-chain

Chyle leaks involve the leakage of lymphatic fluid, which is rich in long-chain triglycerides (LCTs) absorbed via the lymphatic system. To reduce lymphatic flow and promote healing of the leak, a diet supplemented with medium-chain fatty acids (MCFAs) is often prescribed. MCFAs are absorbed directly into the portal venous system, bypassing the lymphatic system, thereby decreasing the volume and LCT content of chyle.

Question 66: Which of the following is an example of Type III hypersensitivity (immune complex-mediated)?

Contact dermatitis
Anaphylaxis
Goodpasture syndrome
Serum sickness (Correct answer)

Correct answer: Serum sickness

Serum sickness is a Type III (immune complex-mediated) hypersensitivity reaction where antigen-antibody complexes deposit in vessel walls and tissues.

Question 67: Which tumor marker is elevated in hepatocellular carcinoma?

PSA
Alpha-fetoprotein (AFP) (Correct answer)
CEA
CA 19-9

Correct answer: Alpha-fetoprotein (AFP)

AFP is elevated in approximately 70% of hepatocellular carcinoma cases and is also elevated in yolk sac tumors.

Question 68: Which drug is used to reverse benzodiazepine overdose?

Atropine
Naloxone
N-acetylcysteine
Flumazenil (Correct answer)

Correct answer: Flumazenil

Flumazenil is a competitive antagonist at GABA-A benzodiazepine receptors and can reverse benzodiazepine sedation, but has a short half-life.

Question 69: Which ion is primarily responsible for the pacemaker potential (funny current) in the SA node?

Ca2+
Na+ (Correct answer)
K+
Cl-

Correct answer: Na+

The funny current (If) in SA node pacemaker cells is mainly carried by Na+ influx through HCN channels during hyperpolarization, initiating spontaneous depolarization.

Question 70: Which drug is a competitive antagonist at the beta-1 adrenergic receptor used in heart failure?

Metoprolol (Correct answer)
Dobutamine
Phenylephrine
Milrinone

Correct answer: Metoprolol

Metoprolol is a cardioselective beta-1 blocker that reduces heart rate and myocardial oxygen demand, improving outcomes in heart failure with reduced ejection fraction.

Question 71: Which cell type is the primary effector in granuloma formation?

Neutrophils
Plasma cells
NK cells
Epithelioid macrophages and giant cells (Correct answer)

Correct answer: Epithelioid macrophages and giant cells

Granulomas consist primarily of activated epithelioid macrophages and multinucleated giant cells, organized to wall off persistent antigens.

Question 72: Which maneuver is used intraoperatively to expose the retroperitoneal structures (kidney, aorta, IVC) during abdominal surgery?

Pringle maneuver
Mattox maneuver (Correct answer)
Cattell-Braasch maneuver
Kocher maneuver

Correct answer: Mattox maneuver

The Mattox maneuver involves medial visceral rotation of the left-sided abdominal organs to expose the suprarenal aorta and left retroperitoneal structures.

Question 73: What is the best initial investigation for suspected acute appendicitis in a child?

CT abdomen with contrast
Ultrasound abdomen (Correct answer)
Diagnostic laparoscopy immediately
MRI abdomen

Correct answer: Ultrasound abdomen

Ultrasound is the first-line investigation in children and pregnant patients to avoid radiation; it has high specificity but lower sensitivity than CT.

Question 74: Which structure passes through the foramen ovale of the skull base?

Middle meningeal artery
CN VI (abducens nerve)
CN V2 (maxillary nerve)
CN V3 (mandibular nerve) (Correct answer)

Correct answer: CN V3 (mandibular nerve)

The mandibular division of the trigeminal nerve (CN V3) passes through the foramen ovale.

Question 75: A patient with AIDS develops ring-enhancing lesions on brain MRI. Which organism is most likely responsible?

Toxoplasma gondii (Correct answer)
Cryptococcus neoformans
Aspergillus fumigatus
JC virus

Correct answer: Toxoplasma gondii

Toxoplasma gondii is the most common cause of ring-enhancing brain lesions in AIDS patients with CD4 counts below 100 cells/μL, caused by reactivation of latent infection.

Question 76: Which antibiotic class inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs)?

Fluoroquinolones
Aminoglycosides
Beta-lactams (Correct answer)
Macrolides

Correct answer: Beta-lactams

Beta-lactam antibiotics (penicillins, cephalosporins, carbapenems) inhibit cell wall synthesis by irreversibly binding to PBPs, preventing peptidoglycan cross-linking.

Question 77: Which diuretic acts on the thick ascending limb of the loop of Henle?

Acetazolamide
Hydrochlorothiazide
Spironolactone
Furosemide (Correct answer)

Correct answer: Furosemide

Furosemide is a loop diuretic that inhibits the Na-K-2Cl cotransporter (NKCC2) in the thick ascending limb, producing potent diuresis.

Question 78: A 3-year-old presents with a 'barking cough' and inspiratory stridor. Which virus is the most common cause of this condition (croup)?

Influenza A virus
Parainfluenza virus (Correct answer)
Respiratory syncytial virus
Adenovirus

Correct answer: Parainfluenza virus

Parainfluenza virus type 1 is the most common cause of croup (laryngotracheobronchitis), characterized by subglottic edema producing the classic barking cough and inspiratory stridor.

Question 79: Which enzyme catalyzes the rate-limiting step of glycolysis?

Phosphoglucose isomerase
Hexokinase
Phosphofructokinase-1 (PFK-1) (Correct answer)
Pyruvate kinase

Correct answer: Phosphofructokinase-1 (PFK-1)

PFK-1 is the rate-limiting enzyme of glycolysis, catalyzing the conversion of fructose-6-phosphate to fructose-1,6-bisphosphate, and is regulated by ATP, AMP, and citrate.

Question 80: Which vitamin serves as a coenzyme for pyruvate dehydrogenase?

Thiamine (B1) (Correct answer)
Biotin (B7)
Riboflavin (B2)
Niacin (B3)

Correct answer: Thiamine (B1)

Thiamine pyrophosphate (TPP) is a required cofactor for pyruvate dehydrogenase; its deficiency impairs aerobic metabolism, causing Wernicke's encephalopathy.

Question 81: A 73-year-old man who has a history of atrial fibrillation and hypertension appears with mid-abdominal pain that started out of nowhere. A little while afterwards, I had a black, liquid bowel movement. There are no signs of peritonitis on an abdominal exam. The patient does, however, have leukocytosis. He is brought into the surgery room to be examined. The ascending colon, cecum, and distal small bowel appear dark and purple. What will management do next?

Revascularization followed by bowel resection (Correct answer)
Warm the bowel and re-evaluate in 24 hours
Bowel resection and anastomosis
Systemic heparinization

Correct answer: Revascularization followed by bowel resection

The patient's acute mid-abdominal pain, black bowel movement, history of atrial fibrillation, leukocytosis, and ischemic bowel findings in the operating room are classic for acute mesenteric ischemia, likely due to an embolic event. The priority in managing ischemic bowel is to restore blood flow as quickly as possible to salvage viable tissue. Therefore, revascularization (e.g., embolectomy or bypass) followed by resection of any irreversibly damaged bowel is the most appropriate course of action.

Question 82: Which segment of the nephron is impermeable to water under all conditions?

Thick ascending loop of Henle (Correct answer)
Proximal convoluted tubule
Thin descending loop of Henle
Collecting duct

Correct answer: Thick ascending loop of Henle

The thick ascending limb of the loop of Henle is always impermeable to water but actively transports NaCl, creating the medullary concentration gradient.

Question 83: Which opioid analgesic has the highest oral bioavailability and is often used in opioid maintenance therapy?

Fentanyl
Codeine
Morphine
Methadone (Correct answer)

Correct answer: Methadone

Methadone has high oral bioavailability (~80%), a long half-life, and is used in opioid use disorder maintenance therapy.

Question 84: Vitamin B12 deficiency causes megaloblastic anemia through impaired synthesis of which molecule?

Heme
Thymidine (dTMP) (Correct answer)
Globin chains
Ferritin

Correct answer: Thymidine (dTMP)

B12 deficiency impairs methionine synthesis, trapping folate as methyl-THF and preventing thymidine synthesis, impairing DNA replication and causing megaloblastic anemia.

Question 85: The femoral triangle is bounded superiorly by which structure?

Inguinal ligament (Correct answer)
Poupart's ligament
Adductor longus muscle
Sartorius muscle

Correct answer: Inguinal ligament

The inguinal ligament forms the superior boundary of the femoral triangle.

Question 86: Which drug class is used as first-line treatment for type 2 diabetes and acts by reducing hepatic glucose production?

Biguanides (Metformin) (Correct answer)
Thiazolidinediones
Sulfonylureas
DPP-4 inhibitors

Correct answer: Biguanides (Metformin)

Metformin (a biguanide) primarily reduces hepatic gluconeogenesis by activating AMPK and is first-line therapy for type 2 diabetes.

Question 87: Which muscle is innervated by both the anterior and posterior divisions of the obturator nerve?

Adductor longus
Obturator externus
Gracilis
Adductor magnus (Correct answer)

Correct answer: Adductor magnus

Adductor magnus receives dual innervation: the adductor portion from the obturator nerve and the hamstring portion from the sciatic nerve.

Question 88: Which lipoprotein is responsible for transporting cholesterol from peripheral tissues to the liver (reverse cholesterol transport)?

VLDL
LDL
Chylomicrons
HDL (Correct answer)

Correct answer: HDL

HDL mediates reverse cholesterol transport, collecting cholesterol from peripheral tissues and transporting it to the liver for excretion.

Question 89: You are visiting a patient in the SICU whose attempt to wean off the ventilator has been unsuccessful for the previous three days. The patient has a history of trauma, is tube-fed, and has been on a ventilator for ten days. To determine a respiratory quotient (RQ), you choose to order a metabolic cart. This patient has an RQ of 1.45. You tell the dietician that the patient requires:

reduced amount of tube feeds overall (Correct answer)
increased amount of tube feeds overall
reduced amount of protein in tube feeds
reduced amount of fat in tube feeds

Correct answer: reduced amount of tube feeds overall

A respiratory quotient (RQ) of 1.45 is significantly elevated, indicating that the patient is being overfed, particularly with carbohydrates. Excess carbohydrate metabolism leads to increased carbon dioxide production, which places an additional burden on the respiratory system and can hinder successful ventilator weaning. Therefore, reducing the overall amount of tube feeds is necessary to decrease the metabolic load and CO2 production, facilitating the weaning process.

Question 90: Which fungal infection is most commonly seen in immunocompromised patients and presents with a 'soap bubble' appearance on brain imaging?

Mucormycosis
Aspergillosis
Cryptococcosis (Correct answer)
Candidiasis

Correct answer: Cryptococcosis

Cryptococcus neoformans causes cryptococcal meningitis in immunocompromised patients; the mucoid capsule produces the 'soap bubble' lesions seen on CT/MRI of the brain.

Question 91: Your patient's end-tidal CO2 after anesthesia induction is observed to be noticeably elevated despite enhanced minute ventilation. What do you do if your diagnosis is as suspected?

Give bolus of something
Suction airway
Increase tidal volume
Give dantrolene and abort case (Correct answer)

Correct answer: Give dantrolene and abort case

A sudden and noticeably elevated end-tidal CO2 despite increased minute ventilation during anesthesia induction is a hallmark sign of malignant hyperthermia (MH). MH is a rare, life-threatening genetic disorder characterized by a hypermetabolic state in skeletal muscles. The immediate and critical management involves administering dantrolene, a specific muscle relaxant, and aborting the surgical case to prevent further complications and stabilize the patient.

Question 92: Which of the following best describes the role of surfactant in the lungs?

Facilitates oxygen diffusion across the alveolar membrane
Increases surface tension to stabilize alveoli
Reduces surface tension to prevent alveolar collapse (Correct answer)
Neutralizes inhaled pathogens

Correct answer: Reduces surface tension to prevent alveolar collapse

Surfactant (dipalmitoyl phosphatidylcholine) reduces alveolar surface tension, preventing collapse during expiration and reducing work of breathing.

Question 93: Hemoglobin S (sickle cell) differs from hemoglobin A by a substitution of which amino acid?

Lysine replaces glutamate at position 6 of the alpha chain
Glutamate replaces valine at position 6 of the beta chain
Serine replaces threonine at position 6 of the beta chain
Valine replaces glutamate at position 6 of the beta chain (Correct answer)

Correct answer: Valine replaces glutamate at position 6 of the beta chain

Sickle cell disease results from a single point mutation causing valine to replace glutamic acid at position 6 of the beta-globin chain.

Question 94: Which muscle is responsible for depression of the mandible against resistance?

Lateral pterygoid
Digastric (Correct answer)
Masseter
Temporalis

Correct answer: Digastric

The digastric muscle, along with the mylohyoid and geniohyoid, depresses the mandible and opens the mouth against resistance.

Question 95: A Gram-negative organism causes urethritis and is the leading cause of bacterial STI in the United States. What is the causative agent?

Treponema pallidum
Neisseria gonorrhoeae
Haemophilus ducreyi
Chlamydia trachomatis (Correct answer)

Correct answer: Chlamydia trachomatis

Chlamydia trachomatis is the most common bacterial STI in the United States; it is an obligate intracellular organism that causes urethritis, cervicitis, and pelvic inflammatory disease.

Question 96: The 'Rule of Nines' is used in burns assessment — what percentage of body surface area does the anterior trunk represent?

9%
36%
27%
18% (Correct answer)

Correct answer: 18%

In the Rule of Nines, the anterior trunk accounts for 18% of total body surface area (TBSA), equal to the posterior trunk.

Question 97: Which segment of the liver is adjacent to the inferior vena cava?

Segment I (caudate lobe) (Correct answer)
Segment II
Segment IV
Segment VI

Correct answer: Segment I (caudate lobe)

The caudate lobe (Segment I) lies directly anterior to the inferior vena cava and drains directly into it.

Question 98: Which chamber of the heart forms the majority of the anterior surface?

Left atrium
Right ventricle (Correct answer)
Left ventricle
Right atrium

Correct answer: Right ventricle

The right ventricle forms the majority of the anterior (sternocostal) surface of the heart.

Question 99: Which antiepileptic drug acts by prolonging the inactivation state of voltage-gated sodium channels?

Valproate
Ethosuximide
Phenytoin (Correct answer)
Clonazepam

Correct answer: Phenytoin

Phenytoin stabilizes the inactive state of voltage-gated Na+ channels, preventing rapid repetitive neuronal firing without affecting normal neural function.

Question 100: Kartagener syndrome is characterized by bronchiectasis, sinusitis, and situs inversus due to defect in which structure?

Gap junctions
Microtubules in cilia (dynein arms) (Correct answer)
Actin microfilaments
Intermediate filaments

Correct answer: Microtubules in cilia (dynein arms)

Kartagener syndrome (primary ciliary dyskinesia) results from absent or defective dynein arms in ciliary microtubules, causing immotile cilia.

Question 101: Which cofactor is required for carboxylation reactions in fatty acid synthesis and gluconeogenesis?

Thiamine pyrophosphate
Lipoic acid
Biotin (Correct answer)
Pyridoxal phosphate

Correct answer: Biotin

Biotin is covalently bound to carboxylases (pyruvate carboxylase, acetyl-CoA carboxylase) and acts as a CO2 carrier in carboxylation reactions.

Question 102: Which antipsychotic is associated with agranulocytosis and requires mandatory blood count monitoring?

Clozapine (Correct answer)
Haloperidol
Olanzapine
Risperidone

Correct answer: Clozapine

Clozapine causes agranulocytosis in 1–2% of patients, requiring weekly CBC monitoring for the first 6 months then bi-weekly.

Question 103: The inhaled anesthetic you intend to employ has an extremely high MAC. High minimum alveolar concentration (MAC) anesthetics typically:

More potent
Very slow onset
Less lipid soluble (Correct answer)
Little of it is needed for adequate anesthesia

Correct answer: Less lipid soluble

Minimum Alveolar Concentration (MAC) is inversely related to anesthetic potency; a high MAC indicates that a large concentration of the anesthetic is required to produce its effect, meaning it is less potent. Anesthetics with high MAC (low potency) are typically less lipid soluble. Lipid solubility is a key determinant of an anesthetic's potency, as it dictates how readily the drug can cross cell membranes and exert its effects within the central nervous system.

Question 104: Which enzyme is deficient in Phenylketonuria (PKU)?

Homogentisate oxidase
Phenylalanine transaminase
Phenylalanine hydroxylase (Correct answer)
Tyrosine aminotransferase

Correct answer: Phenylalanine hydroxylase

PKU is caused by deficiency of phenylalanine hydroxylase, which converts phenylalanine to tyrosine, leading to phenylalanine accumulation and intellectual disability.

Question 105: You are looking at a 34-year-old, 100-pound patient who has just been admitted. Both of her arms and her entire back, from the neck to the buttocks, are burned. What IV fluids will be prescribed in your entrance orders?

10.8 Liters of fluid, with 5.4L replaced in first 8 hours from now and 5.4 over the next 24 hours
10.8 Liters of fluid, with 5.4L replaced in first 8 hours from now and 5.4 over the next 16 hours
5.4 Liters of fluid, with 2.7L replaced in first 12 hours from now and 2.7L over the next 12 hours
10.8 Liters of fluid, with 5.4L replaced in the first 8 hours from the time of burn and 5.4 over the next 16 hours (Correct answer)

Correct answer: 10.8 Liters of fluid, with 5.4L replaced in the first 8 hours from the time of burn and 5.4 over the next 16 hours

The Parkland formula for fluid resuscitation in burn patients is 4 mL x patient weight (kg) x % Total Body Surface Area (TBSA) burned. Half of the calculated fluid is administered in the first 8 hours from the time of the burn, and the remaining half over the subsequent 16 hours. Assuming a total body surface area (TBSA) burn of 60% for a 100-pound (approximately 45 kg) patient, the total fluid needed would be 4 mL x 45 kg x 60% = 10,800 mL (10.8 Liters). Therefore, 5.4 Liters would be administered in the first 8 hours, and the remaining 5.4 Liters over the subsequent 16 hours.

Question 106: Which antimalarial drug can cause hemolytic anemia in patients with G6PD deficiency?

Primaquine (Correct answer)
Mefloquine
Chloroquine
Artemether

Correct answer: Primaquine

Primaquine generates reactive oxygen species that cause hemolysis in G6PD-deficient patients who cannot regenerate NADPH to protect red blood cells.

Question 107: In which organelle does the citric acid (Krebs) cycle occur?

Cytoplasm
Nucleus
Smooth endoplasmic reticulum
Mitochondrial matrix (Correct answer)

Correct answer: Mitochondrial matrix

The citric acid cycle occurs in the mitochondrial matrix, where acetyl-CoA is oxidized to CO2 with generation of NADH, FADH2, and GTP.

Question 108: Which type of infarction is characterized by pale, firm tissue without hemorrhage?

Septic infarction
Venous infarction
Red (hemorrhagic) infarction
White (anemic) infarction (Correct answer)

Correct answer: White (anemic) infarction

White (anemic) infarctions occur in solid organs with single arterial supply (heart, spleen, kidney) where blood cannot re-enter the necrotic tissue.

Question 109: The pudendal nerve exits the pelvis through which foramen?

Obturator foramen
Lesser sciatic foramen only
Greater sciatic foramen only
Greater sciatic foramen, then re-enters through the lesser sciatic foramen (Correct answer)

Correct answer: Greater sciatic foramen, then re-enters through the lesser sciatic foramen

The pudendal nerve exits through the greater sciatic foramen, crosses the ischial spine, and re-enters the perineum through the lesser sciatic foramen.

Question 110: The McBurney's point, used to locate appendiceal tenderness, is located at what anatomical position?

Midpoint of the right iliac fossa
1/3 of the way from the right ASIS to the umbilicus (Correct answer)
Midpoint of a line from umbilicus to right ASIS
2/3 of the way from the umbilicus to the right ASIS

Correct answer: 1/3 of the way from the right ASIS to the umbilicus

McBurney's point is located one-third of the distance from the right anterior superior iliac spine (ASIS) to the umbilicus.

Question 111: Psammoma bodies are calcified concentric rings found in which tumor?

Small cell lung cancer
Glioblastoma multiforme
Hepatocellular carcinoma
Papillary thyroid carcinoma (Correct answer)

Correct answer: Papillary thyroid carcinoma

Psammoma bodies are found in papillary thyroid carcinoma, papillary serous ovarian carcinoma, and meningiomas.

Question 112: Which type of shock is characterized by high cardiac output and low systemic vascular resistance?

Obstructive shock
Distributive (septic) shock (Correct answer)
Cardiogenic shock
Hypovolemic shock

Correct answer: Distributive (septic) shock

Distributive shock (classically septic shock) features massive vasodilation (low SVR) with a compensatory high cardiac output ('warm shock') in early stages.

Question 113: Which malaria parasite is associated with tertian fever occurring every 48 hours and can remain dormant in the liver as hypnozoites?

Plasmodium knowlesi
Plasmodium falciparum
Plasmodium malariae
Plasmodium vivax (Correct answer)

Correct answer: Plasmodium vivax

Plasmodium vivax causes benign tertian malaria with 48-hour fever cycles and forms dormant hypnozoites in the liver, responsible for relapses months to years after initial infection.

Question 114: What is the normal pH range of arterial blood?

7.25–7.35
7.30–7.40
7.35–7.45 (Correct answer)
7.45–7.55

Correct answer: 7.35–7.45

Normal arterial blood pH is 7.35–7.45, maintained primarily by the bicarbonate buffer system, lungs, and kidneys.

Question 115: Digoxin toxicity is worsened by which electrolyte imbalance?

Hyperkalemia
Hypokalemia (Correct answer)
Hyponatremia
Hypermagnesemia

Correct answer: Hypokalemia

Hypokalemia increases digoxin binding to Na+/K+-ATPase, potentiating its toxic effects including arrhythmias.

Question 116: Which structure forms the floor of the cubital fossa?

Supinator only
Pronator teres and brachioradialis
Brachialis and supinator (Correct answer)
Biceps brachii tendon and brachialis

Correct answer: Brachialis and supinator

The floor of the cubital fossa is formed by the brachialis muscle medially and the supinator laterally.

Question 117: Which of the following is a content of the carotid sheath?

Internal carotid artery, external jugular vein, glossopharyngeal nerve
External carotid artery, internal jugular vein, phrenic nerve
Common carotid artery, subclavian vein, vagus nerve
Internal jugular vein, common carotid artery, vagus nerve (Correct answer)

Correct answer: Internal jugular vein, common carotid artery, vagus nerve

The carotid sheath contains the common carotid artery, internal jugular vein, and vagus nerve (CN X).

Question 118: An 82-year-old woman presents with post-prandial dull abdomen pain that has been present for almost a year. She dropped 25 pounds in the previous three months as a result of avoiding oral intake due to worsening discomfort symptoms. Her symptoms have not improved after repeated normal upper endoscopies and long-term proton-pump inhibitor medication. She underwent a laparoscopic cholecystectomy six months earlier for several tiny gallstones, which were discovered during a right upper quadrant ultrasound. Four months ago, a colonoscopy revealed a solitary, fully excised pedunculated tubular adenoma. A CT scan was conducted, and it reveals no indication of cancer (see below). The patient is cachectic upon examination. Her abdomen is soft and not painful to the touch, and no lumps are visible. An analysis of the lab results reveals microcytic anemia and an albumin level of 2.4. The most effective course of treatment for this patient would be:

Placement of a jejuna feeding tube
Selective angiography (Correct answer)
Total parenteral nutrition
High-dose megestrol acetate

Correct answer: Selective angiography

The patient's symptoms of chronic post-prandial abdominal pain, significant weight loss, microcytic anemia, and low albumin, despite normal upper endoscopy and colonoscopy, are highly suggestive of chronic mesenteric ischemia. This condition results from insufficient blood flow to the intestines, typically due to atherosclerotic narrowing of the mesenteric arteries. Selective angiography is the most effective diagnostic tool, as it directly visualizes these arteries and can often be combined with therapeutic revascularization (e.g., stenting) to restore blood flow.

Question 119: The oncogene RAS encodes a protein with what function?

Tumor suppressor
Tyrosine kinase receptor
Transcription factor
GTPase signal transduction protein (Correct answer)

Correct answer: GTPase signal transduction protein

RAS encodes a GTP-binding protein; mutations lock it in the active GTP-bound state, constitutively activating downstream proliferation signals.

Question 120: What is the Charcot's triad of acute cholangitis?

Fever, jaundice, and right upper quadrant pain (Correct answer)
Jaundice, dark urine, and pale stools
Right upper quadrant pain, Murphy's sign, and leukocytosis
Fever, nausea, and epigastric pain

Correct answer: Fever, jaundice, and right upper quadrant pain

Charcot's triad of acute cholangitis consists of fever (rigors), jaundice, and right upper quadrant pain, caused by biliary obstruction with ascending infection.

Question 121: The DNA double helix is held together by which type of bonds between base pairs?

Hydrogen bonds (Correct answer)
Covalent bonds
Ionic bonds
Disulfide bonds

Correct answer: Hydrogen bonds

Complementary base pairs (A-T and G-C) in DNA are held together by hydrogen bonds; G-C pairs have 3 hydrogen bonds and A-T pairs have 2.

Question 122: Which investigation is considered the gold standard for diagnosing deep vein thrombosis (DVT)?

Compression ultrasonography
Contrast venography (Correct answer)
CT pulmonary angiography
D-dimer blood test

Correct answer: Contrast venography

Contrast venography remains the gold standard for DVT diagnosis, though duplex compression ultrasonography is the preferred first-line investigation due to its non-invasive nature.

Question 123: A biological mechanism for each of the following bacteria's antibiotic resistance is correctly matched, WITH THE EXCEPTION OF:

Methicillin Resistant Staph aureus: mutation in Penicillin Binding Protein (PBP) on the cell membrane
Carbapenem Resistant Klebsiella pneumonia (KPC): Carbapenemase production
Vancomycin Resistant Enterococcus: mutation in Penicillin Binding Protein (PBP) on the cell membrane
Gentamycin Resistant Enterococcus: mutation in Penicillin Binding Protein (PBP) on the cell membrane (Correct answer)

Correct answer: Gentamycin Resistant Enterococcus: mutation in Penicillin Binding Protein (PBP) on the cell membrane

Gentamicin resistance in Enterococcus is typically mediated by aminoglycoside-modifying enzymes that inactivate the antibiotic, not by mutations in Penicillin Binding Proteins (PBPs). PBP mutations are primarily associated with resistance to beta-lactam antibiotics, such as methicillin resistance in Staph aureus or vancomycin resistance in Enterococcus (though VRE often involves altered peptidoglycan precursors, not directly PBP mutation for vancomycin itself).

Question 124: A 59-year-old man who has a slight fullness behind his right knee but no pain or restrictions in knee motion presents. He smokes 30 packs a year, consumes 1 to 2 beers socially each year, and takes hydrochlorothiazide to control his hypertension. He was examined because of a noticeable popliteal pulse, and duplex ultrasonography revealed a 3.4 cm popliteal aneurysm. His left lower extremity pulses are normal, as are the femoral and distal pulses on his right leg. The best course of action for management would be:

Abdominal ultrasound (Correct answer)
Open aneurysmal exclusion with bypass
Endovascular popliteal artery stent placement
Surveillance duplex ultrasonography in 1 year

Correct answer: Abdominal ultrasound

Popliteal aneurysms have a strong association with abdominal aortic aneurysms (AAAs); a significant percentage of patients with one will also have the other. Therefore, upon diagnosis of a popliteal aneurysm, it is crucial to screen for an AAA to identify any coexisting pathology. An abdominal ultrasound is a non-invasive and effective method for screening for AAAs.

Question 125: Which organism is the most common cause of neonatal meningitis and is acquired from the maternal vaginal flora during delivery?

Listeria monocytogenes
Streptococcus agalactiae (Group B Strep) (Correct answer)
Escherichia coli
Neisseria meningitidis

Correct answer: Streptococcus agalactiae (Group B Strep)

Streptococcus agalactiae (Group B Streptococcus) is the most common cause of neonatal meningitis and sepsis, transmitted vertically from colonized mothers during delivery.

Question 126: Which of the following is the primary product of the pentose phosphate pathway?

Oxaloacetate and FADH2
Acetyl-CoA and NADH
ATP and pyruvate
NADPH and ribose-5-phosphate (Correct answer)

Correct answer: NADPH and ribose-5-phosphate

The pentose phosphate pathway generates NADPH (for reductive biosynthesis and antioxidant defense) and ribose-5-phosphate (for nucleotide synthesis).

Question 127: Which type of edema is caused by increased vascular permeability due to inflammation?

Lymphedema
Exudate (Correct answer)
Pitting edema from hypoalbuminemia
Transudate

Correct answer: Exudate

Inflammatory edema is an exudate, characterized by high protein content and specific gravity >1.020, reflecting increased vascular permeability.

Question 128: Virchow's triad describes the three factors predisposing to thrombosis. Which of the following is NOT part of the triad?

Hypercoagulability
Thrombocytopenia (Correct answer)
Abnormal blood flow (stasis or turbulence)
Endothelial injury

Correct answer: Thrombocytopenia

Virchow's triad consists of endothelial injury, abnormal blood flow, and hypercoagulability; thrombocytopenia actually reduces thrombosis risk.

Question 129: Which clinical sign is pathognomonic of a tension pneumothorax?

Dullness to percussion on the affected side
Tracheal deviation away from the affected side with absent breath sounds (Correct answer)
Subcutaneous emphysema alone
Bilateral decreased breath sounds

Correct answer: Tracheal deviation away from the affected side with absent breath sounds

Tension pneumothorax classically causes tracheal deviation to the contralateral side, absent breath sounds on the affected side, and hemodynamic compromise.

Question 130: Which phase of the cardiac action potential is responsible for the plateau in ventricular myocytes?

Phase 2 — plateau (Correct answer)
Phase 3 — rapid repolarization
Phase 1 — early repolarization
Phase 0 — rapid depolarization

Correct answer: Phase 2 — plateau

Phase 2 (plateau) is caused by sustained Ca2+ influx through L-type calcium channels balanced by K+ efflux, preventing early repolarization.

Question 131: Treatment for a 38-year-old woman with primary Raynaud's syndrome included calcium channel blockers and cold avoidance. She still has significant, refractory symptoms though. The distal second, third, and fourth digits of her left upper extremity were critically ischemic and ulcerated when she was recently admitted. With a wrist-brachial index of 1.03, the palmar arch, radial, and ulnar pulses were all present. She had intravenous prostaglandin therapy, topical nitrates, and a heparin infusion as treatment. She gradually advanced, nevertheless, to the point where her second and third digits lost all of their tissue, necessitating a distal amputation. Which of the following approaches to this patient would be reasonable?

Implanted catheter for continuous nitrate infusion
Cervical sympathectomy (Correct answer)
Upper extremity bypass graft
Upper extremity angiogram with radial and ulnar stenting

Correct answer: Cervical sympathectomy

The patient's severe, refractory Raynaud's syndrome with critical ischemia and tissue loss, despite comprehensive medical management, indicates a need for more aggressive intervention. Cervical sympathectomy is a surgical option considered for severe, limb-threatening Raynaud's that has failed conservative and pharmacological treatments. By interrupting the sympathetic nerve supply to the upper extremity, it promotes vasodilation and improves blood flow to the affected digits, aiming to prevent further tissue damage and aid healing.

Question 132: A patient presents with rice-water stools and severe dehydration. The causative organism produces a toxin that permanently activates Gs protein. Which organism is responsible?

Salmonella typhi
Shigella dysenteriae
Vibrio cholerae (Correct answer)
Campylobacter jejuni

Correct answer: Vibrio cholerae

Vibrio cholerae produces cholera toxin that permanently ADP-ribosylates Gs alpha subunit, leading to constitutive activation of adenylyl cyclase, massive chloride secretion, and rice-water diarrhea.

Question 133: What is the most common cause of small bowel obstruction in adults?

Adhesions from previous surgery (Correct answer)
Hernias
Crohn's disease
Tumors

Correct answer: Adhesions from previous surgery

Post-operative intraperitoneal adhesions account for approximately 60–75% of all small bowel obstruction cases in adults.

Question 134: What is the GFR (glomerular filtration rate) in a healthy adult?

125 mL/min (Correct answer)
180 mL/min
60 mL/min
90 mL/min

Correct answer: 125 mL/min

The normal GFR in a healthy adult is approximately 125 mL/min (180 L/day), with approximately 99% of the filtrate reabsorbed.

Question 135: You are seeing a patient in the emergency department who banged his head after falling while skiing. He lost consciousness, according to his buddies who were with him, and they brought him to the lodge while dialing for an ambulance. He "woke up" on the ambulance ride to the hospital and briefly appeared to be fine, but he is now unconscious once more. Which vessel is typically at fault given the diagnosis you suspect?

Basilar artery
Middle meningeal artery (Correct answer)
Posterior meningeal artery
Anterior meningeal artery

Correct answer: Middle meningeal artery

The patient's presentation of initial loss of consciousness, a lucid interval, and subsequent re-loss of consciousness is a classic sign of an epidural hematoma. This type of intracranial hemorrhage is most commonly caused by trauma to the temporal bone, which can rupture the middle meningeal artery. The arterial bleeding rapidly accumulates between the dura mater and the skull, leading to increasing intracranial pressure and neurological deterioration.

Question 136: Which type of necrosis is characteristically seen in tuberculosis?

Caseous necrosis (Correct answer)
Liquefactive necrosis
Coagulative necrosis
Fat necrosis

Correct answer: Caseous necrosis

Tuberculosis produces caseous necrosis, which appears cheese-like grossly and consists of amorphous pink granular material microscopically.

Question 137: A 56-year-old guy who underwent a heart catheterization earlier in the day is brought to your attention. He expresses pain in the femoral region (site of procedure). A painful, pulsating lump is palpable, and ultrasound results support your probable diagnosis of pseudoaneurysm. The tumor had kept growing despite fruitless attempts to treat the compression of the ultrasonography probe and thrombin injection. What should we do next?

covered stent placement
ultrasound-guided thrombin injection
surgical ligation (Correct answer)
ultrasound probe compression

Correct answer: surgical ligation

A pseudoaneurysm is a contained rupture of an artery. When less invasive methods like ultrasound-guided compression and thrombin injection fail to resolve a growing, painful, pulsating lump, it indicates a persistent and potentially worsening problem. Surgical ligation or repair becomes necessary to directly close or excise the pseudoaneurysm, preventing further expansion, rupture, or complications like distal ischemia.

Question 138: Which test is used to distinguish Streptococcus pyogenes (Group A Strep) from other beta-hemolytic streptococci?

Bacitracin sensitivity (Correct answer)
CAMP test
Optochin sensitivity
Bile solubility

Correct answer: Bacitracin sensitivity

Streptococcus pyogenes (Group A Strep) is sensitive to bacitracin, which differentiates it from Group B and other beta-hemolytic streptococci.

Question 139: Which drug is used to treat acetaminophen (paracetamol) overdose?

Flumazenil
N-acetylcysteine (Correct answer)
Activated charcoal (alone)
Naloxone

Correct answer: N-acetylcysteine

N-acetylcysteine replenishes glutathione stores, neutralizing the hepatotoxic NAPQI metabolite of acetaminophen and preventing liver failure.

Question 140: Which of the following statements about a tumor marker and the malignancy it is typically linked with is true?

CA 125 and thyroid cancer
Alpha-fetoprotein and brain tumors
CA 19-9 and pancreatic cancer (Correct answer)
Carcinoembryonic antigen (CEA) and melanoma

Correct answer: CA 19-9 and pancreatic cancer

CA 19-9 is a well-established tumor marker primarily associated with pancreatic cancer. It is commonly used to monitor treatment response and detect recurrence in patients diagnosed with pancreatic adenocarcinoma. While not specific enough for screening, its elevation is a strong indicator in the context of pancreatic malignancy.

Question 141: Which nerve is at greatest risk during a thyroidectomy due to its proximity to the inferior thyroid artery?

Glossopharyngeal nerve
Superior laryngeal nerve (external branch)
Recurrent laryngeal nerve (Correct answer)
Hypoglossal nerve

Correct answer: Recurrent laryngeal nerve

The recurrent laryngeal nerve runs close to the inferior thyroid artery and the tracheo-esophageal groove; injury causes hoarseness or vocal cord paralysis.

Question 142: What is the normal central venous pressure (CVP) range?

15–20 mmHg
0–2 mmHg
8–12 mmHg
2–6 mmHg (Correct answer)

Correct answer: 2–6 mmHg

Normal CVP is 2–6 mmHg, reflecting right atrial filling pressure and serving as an estimate of preload.

Question 143: Which genetic mutation is associated with chronic myeloid leukemia (CML)?

MYC translocation t(8;14)
BCR-ABL fusion t(9;22) Philadelphia chromosome (Correct answer)
PML-RARA fusion t(15;17)
BCL-2 translocation t(14;18)

Correct answer: BCR-ABL fusion t(9;22) Philadelphia chromosome

CML is characterized by the Philadelphia chromosome, resulting from t(9;22) translocation creating BCR-ABL fusion, a constitutively active tyrosine kinase.

Question 144: Which statement about the Renin-Angiotensin System is TRUE?

Angiotensinogen is secreted by the kidney
Renin stimulates the conversion from Angiotensin I to Angiotensin II
ACE converts Angiotensinogen to Angiotensin I
Decreased renal perfusion stimulates renin production (Correct answer)

Correct answer: Decreased renal perfusion stimulates renin production

The Renin-Angiotensin System (RAS) is a vital regulatory pathway for blood pressure and fluid balance. Renin, an enzyme produced by the juxtaglomerular cells in the kidneys, is primarily stimulated by decreased renal perfusion. This reduction in blood flow to the kidneys, often due to low blood pressure or hypovolemia, triggers the release of renin to initiate the cascade that ultimately raises blood pressure.

Question 145: Which aminoglycoside antibiotic is associated with nephrotoxicity and ototoxicity?

Azithromycin
Gentamicin (Correct answer)
Vancomycin
Clindamycin

Correct answer: Gentamicin

Gentamicin accumulates in renal proximal tubular cells and cochlear hair cells, causing dose-dependent nephrotoxicity and irreversible ototoxicity.

Question 146: The Hering-Breuer reflex is mediated by which receptors?

Peripheral chemoreceptors in the carotid body
Pulmonary stretch receptors (slowly adapting) (Correct answer)
J-receptors
Central chemoreceptors

Correct answer: Pulmonary stretch receptors (slowly adapting)

The Hering-Breuer reflex is triggered by slowly adapting pulmonary stretch receptors that signal the brain to stop inspiration when lungs are over-inflated.

Question 147: Which scoring system is used to assess the severity of acute pancreatitis at 48 hours?

Ranson's criteria (Correct answer)
MELD score
Child-Pugh score
APACHE II score

Correct answer: Ranson's criteria

Ranson's criteria evaluate 5 parameters at admission and 6 more at 48 hours; a score ≥3 indicates severe pancreatitis with increased morbidity and mortality.

Question 148: What pulmonary function test is the most effective at predicting postoperative performance when lobectomy is being considered?

Quantitative radionucleotide perfusion scanning
Plain chest roentgenogram
Predicted postoperative forced expiratory volume (FEV) in 1 second (FEV1) (Correct answer)
Gas exchange functions, such as DLCO (diffusion of carbon monoxide in the lung)

Correct answer: Predicted postoperative forced expiratory volume (FEV) in 1 second (FEV1)

When considering a lobectomy, accurately predicting the patient's postoperative pulmonary function is critical for assessing surgical candidacy and minimizing complications. The predicted postoperative forced expiratory volume in 1 second (ppoFEV1) is the most effective and widely accepted pulmonary function test for this purpose. It provides a reliable estimate of the remaining lung function after resection, guiding surgical decisions.

Question 149: Which hepatitis virus is transmitted via the fecal-oral route and does NOT cause chronic infection?

Hepatitis A (Correct answer)
Hepatitis D
Hepatitis C
Hepatitis B

Correct answer: Hepatitis A

Hepatitis A virus is transmitted fecal-orally and causes only acute self-limiting infection, never leading to chronic hepatitis or carrier state.

Question 150: The saphenous nerve is a branch of which nerve?

Sciatic nerve
Common peroneal nerve
Obturator nerve
Femoral nerve (Correct answer)

Correct answer: Femoral nerve

The saphenous nerve is the longest branch of the femoral nerve and supplies sensation to the medial leg and foot.

MBBS (Bachelor of Medicine and Bachelor of Surgery) Professional Examination

The MBBS Professional Examinations assess medical students' knowledge across pre-clinical and para-clinical subjects including Physiology, Pharmacology, and Microbiology, aligned with India's National Medical Commission (NMC) CBME curriculum standards.

150

Questions

180 min

Time Limit

50%

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