Which of these is the most abundant type of muscle in the digestive tract?

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: 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.

Correct Answer: B

Rationale: The correct answer is B: Control centers in the medulla oblongata. The myenteric plexus is part of the enteric nervous system located in the gastrointestinal tract, involved in regulating gut motility. Sensory neurons (A), motor neurons (C), and synapses (D) are essential components of the myenteric plexus, responsible for sensing stimuli, transmitting signals, and coordinating muscle contractions in the gut. Control centers in the medulla oblongata are part of the central nervous system, not directly related to the myenteric plexus functions. Thus, choice B is incorrect in the context of the components of the myenteric plexus.

Correct Answer: C

Rationale: The correct answer is C (6 liters) because the average daily amount of fluid that passes through the pylorus in a healthy adult is approximately 5-7 liters. This is based on the normal daily volume of gastric juice secretion and other fluids entering the duodenum. Choice A (2 liters) is too low and would not be sufficient for normal bodily functions. Choice B (9 liters) is too high and would lead to excessive fluid loss. Choice D (8 liters) is also too high and would not align with the typical physiological range. Therefore, C is the most accurate option based on the known physiology of the digestive system.