The outer layer of the GI tract is composed of connective tissue and a simple squamous epithelium. This tunic is called the tunica ______ and the simple squamous epithelium is called the ______.

Correct Answer: B

Rationale: The correct answer is B: serosa, visceral peritoneum. The outer layer of the GI tract is called the serosa, which is composed of connective tissue and a simple squamous epithelium known as the visceral peritoneum. The serosa helps to protect and support the GI tract. A: adventitia, visceral peritoneum - Adventitia is a dense connective tissue layer found in structures that are not intraperitoneal, whereas the visceral peritoneum is specific to the peritoneal cavity. C: serosa, parietal peritoneum - The parietal peritoneum is the outer layer of the peritoneum lining the abdominal cavity, not the outer layer of the GI tract. D: adventitia, parietal peritoneum - Similar to choice A, the parietal peritoneum is not part of the outer layer of the GI tract.

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: A

Rationale: The correct answer is A: plicae circulares; increase surface area. Plicae circulares are circular folds in the small intestine that increase surface area for nutrient absorption. They help in maximizing contact with digested food. Villi and microvilli are structures on the surface of the small intestine that further increase surface area for absorption but are not the folds themselves. Rugae are folds found in the stomach, not the small intestine.

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.