During gastric emptying, chyme is released into the duodenum through the .

Correct Answer: D

Rationale: The correct answer is D: pyloric sphincter. The pyloric sphincter is a ring of muscle at the junction between the stomach and the duodenum. It controls the release of chyme into the small intestine. The sphincter opens and closes to regulate the flow of partially digested food from the stomach into the duodenum for further digestion and absorption. A: esophageal hiatus is incorrect as it is the opening in the diaphragm through which the esophagus passes. B: pyloric antrum is incorrect as it is the lower part of the stomach that connects to the pyloric canal. C: pyloric canal is incorrect as it is the part of the stomach leading to the pyloric sphincter, not the opening into the duodenum.

Correct Answer: B

Rationale: The correct answer is B: smooth muscle. Smooth muscle is the most abundant type of muscle in the digestive tract due to its involuntary nature and the ability to maintain sustained contractions for digestion and movement of food. Skeletal muscle (A) is not found in the digestive tract. Cardiac muscle (C) is specific to the heart and not present in the digestive tract. Fibrous muscle (D) is not a recognized type of muscle tissue. Smooth muscle is the most suitable choice as it aligns with the functions and characteristics of muscle in the digestive system.

Correct Answer: C

Rationale: The correct answer is C: gallbladder. Bile is produced by the liver and stored in the gallbladder. When we eat, the gallbladder releases bile into the small intestine to aid in the digestion of fats. The pancreas produces digestive enzymes, not bile (A). The liver produces bile but does not store it (B). The small intestine is where bile is released, not stored (D). Therefore, the gallbladder is the correct location for bile storage.

Correct Answer: B

Rationale: Water is absorbed in the stomach through a process called osmosis, where water molecules pass through the stomach lining into the bloodstream. Vitamins are primarily absorbed in the small intestine, while carbohydrates and proteins are broken down in the stomach but absorbed in the small intestine. Water is the only substance among the choices that undergoes absorption directly in the stomach due to its small molecular size and the body's constant need for hydration.

Correct Answer: B

Rationale: The main function of the gallbladder is to store bile produced by the liver and concentrate it. When we eat, the gallbladder releases bile into the small intestine to help with the digestion of fats. Storing bile allows for a controlled release when needed. Choice A is incorrect because bile is produced by the liver, not the gallbladder. Choice C is incorrect as digestive enzymes are mainly produced by the pancreas. Choice D is incorrect as nutrient absorption primarily occurs in the small intestine, not the gallbladder.