The cardiac or lower gastroesophageal sphincter is composed of ______ muscle and prevents chyme from moving into the

Correct Answer: A

Rationale: The correct answer is A: smooth; esophagus. The cardiac sphincter is made of smooth muscle because smooth muscles are involuntary and control the movement of food from the esophagus into the stomach. Skeletal muscles are under voluntary control and are not found in sphincters. Choices C and D are incorrect because the duodenum is part of the small intestine and not relevant to the cardiac sphincter's function.

Correct Answer: C

Rationale: The correct answer is C: bicarbonate ions. Pancreatic juice is alkaline to neutralize the acidic chyme entering the small intestine from the stomach. Bicarbonate ions are secreted by pancreatic duct cells and play a major role in maintaining the pH balance. Mucus (choice A) is produced by goblet cells and helps protect the lining of the digestive tract but is not a major component of pancreatic juice. Trypsinogen, chymotrypsinogen, and procarboxypeptidase (choice B) are pancreatic enzymes, not the major component of the aqueous component. Secretin (choice D) is a hormone that stimulates the pancreas to release bicarbonate ions but is not a component of pancreatic juice itself.

Correct Answer: A

Rationale: The correct answer is A: chylomicron. After absorption, free fatty acids and glycerol are recombined in the epithelial cell to form triglycerides. These triglycerides are then packaged with proteins to form chylomicrons, which are lipoprotein particles that transport dietary fats through the lymphatic system and bloodstream. Chylomicrons are essential for the absorption of dietary fats and fat-soluble vitamins. Summary: - B: Micelle is incorrect because micelles are formed in the lumen of the small intestine to aid in the absorption of lipids but do not involve recombination of fatty acids and glycerol. - C: Lipoprotein is incorrect because while chylomicrons are a type of lipoprotein, the specific process described in the question is not about general lipoprotein formation. - D: Fatty droplet is incorrect as it does not involve the recombination and protein coating process described in the question.

Correct Answer: B

Rationale: The correct answer is B because the colonic microbiota performs multiple essential functions such as aiding in digestion, producing vitamins, regulating immune function, and maintaining gut barrier integrity. Option A is incorrect as it focuses on dietary fiber intake rather than the microbiota's functions. Option C is incorrect because while acetate, propionate, and butyrate are important organic acids produced, they are not the only ones. Option D is incorrect as the microbiota's establishment of an 'acetate buffer' does not necessarily suppress the growth of all pathogenic bacteria.

Correct Answer: D

Rationale: The correct answer is D because the hypothalamus acts as the body's thermostat and controls temperature regulation. When the body detects an infection or other triggers, the hypothalamus resets the temperature set point higher, causing a fever response to help fight off the infection. Choices A, B, and C are incorrect because while an infection can trigger a fever response, it is the hypothalamus that ultimately controls and initiates the response by resetting the temperature set point, not a local widening of blood vessels or activation of the complement system.