A filling defect on a barium examination of the gastrointestinal tract means:

Correct Answer: B

Rationale: The correct answer is B because a filling defect on a barium examination indicates that something is protruding into the lumen, displacing the barium. This means there is an abnormality or mass present that prevents the barium from flowing uniformly. Choice A is incorrect because a filling defect does not necessarily indicate local dilation or outpouching. Choice C is incorrect because it combines both A and B, which is not always the case. Choice D is incorrect as there is indeed something causing the barium to be displaced in the lumen.

Correct Answer: D

Rationale: The correct answer is D: Amylase. Gastric secretion does not contain amylase. Amylase is an enzyme produced by the pancreas and salivary glands to break down carbohydrates. In the stomach, gastric secretions mainly consist of hydrochloric acid (HCl) for digestion, intrinsic factor (IF) for vitamin B12 absorption, and mucous to protect the stomach lining. Therefore, amylase is not a component of gastric secretion.

Correct Answer: C

Rationale: The correct answer is C because during swallowing, the swallowing center in the medulla oblongata inhibits the medullary respiratory center to prevent aspiration. This coordination ensures that breathing is temporarily halted to prevent food or liquid from entering the airway. Choices A, B, and D are incorrect because not all processes of deglutition are under voluntary control, the vocal folds actually close to protect the airway during swallowing, and the movement of the food bolus down the esophagus is facilitated by peristalsis rather than gravity.

Correct Answer: B

Rationale: The correct answer is B: Break down proteins. Hydrochloric acid in the stomach helps to activate pepsin, an enzyme that breaks down proteins into smaller peptides. This process is essential for proper digestion of proteins. Choice A is incorrect because carbohydrates are broken down by amylase enzymes in the mouth and small intestine. Choice C is incorrect because emulsification of fats occurs in the small intestine with the help of bile. Choice D is incorrect as hydrochloric acid plays a significant role in the digestion of proteins in the stomach.

Correct Answer: A

Rationale: The correct answer is A: a creamy paste called chyme. After food enters the stomach, it gets mixed with gastric juices and enzymes, forming a semi-liquid substance known as chyme. This chyme is then slowly released into the small intestine for further digestion and absorption of nutrients. Option B is incorrect as food is not rolled into a bolus in the stomach but rather churned into chyme. Option C is incorrect as pepsin, an enzyme for protein digestion, is already present in the stomach and starts working on digesting proteins before the food leaves the stomach. Option D is incorrect as chyme is the accurate description of the partially digested food leaving the stomach.