A male infant, who was normal for the first three weeks of life, develops projectile vomiting after feeding. The likely diagnosis is:

Correct Answer: D

Rationale: The correct answer is D, congenital pyloric stenosis. This condition typically presents in male infants around 3-6 weeks of age with projectile vomiting due to hypertrophy of the pyloric muscle, leading to obstruction at the pylorus. This causes the infant to forcefully vomit shortly after feeding. Meckel's diverticulum (A) presents with painless rectal bleeding. Esophageal atresia (B) presents with drooling and choking with feeding. Congenital diaphragmatic hernia (C) presents with respiratory distress and scaphoid abdomen due to herniation of abdominal organs into the chest cavity.

Correct Answer: B

Rationale: The correct answer is B because HCl secretion is primarily carried out by parietal cells in the stomach lining. Parietal cells contain proton pumps that actively secrete HCl to aid in digestion. Chief cells secrete pepsinogen, not HCl (A is incorrect). Gastrin actually stimulates HCl secretion, so it doesn't inhibit it (C is incorrect). Acetylcholine (Ach) is a neurotransmitter that can stimulate, not inhibit, HCl secretion (D is incorrect). Therefore, option B is the correct choice based on the roles of parietal cells in HCl secretion.

Correct Answer: D

Rationale: The correct answer is D because none of the statements are true. A is incorrect because fat-soluble vitamins are incorporated into chylomicrons before absorption. B is incorrect because triglycerides are resynthesized in the intestinal cell but packaged into chylomicrons, not directly exported. C is incorrect because pancreatic lipase functions best at a pH of around 7-8, not 3. So, the correct answer is D as all the other choices are incorrect.

Correct Answer: C

Rationale: The correct answer is C: Bile. Bile is not a component of gastric juice; it is produced by the liver and stored in the gallbladder to aid in digestion in the small intestine. Pepsinogen, hydrochloric acid, and mucus are all components of gastric juice. Pepsinogen is the inactive form of pepsin, an enzyme that breaks down proteins. Hydrochloric acid helps in the digestion of food and kills bacteria. Mucus protects the stomach lining from the acidic environment.

Correct Answer: C

Rationale: The correct answer is C, absent bowel sounds. Absence of bowel sounds may indicate a serious issue requiring further assessment. Normal bowel sounds include soft gurgles and clicks, so choices A, B, and D are variations of normal findings and do not necessarily indicate a need for further assessment. Absent bowel sounds could indicate bowel obstruction, peritonitis, or ischemia, warranting a focused abdominal assessment to determine the underlying cause.