. Parietal cells secrete ________.

A. esophagus

B. stomach

C. small intestine

D. large intestine

a) esophagus

- Correct: The esophagus is supported by a layer of adventitia rather than serosa. The adventitia is a connective tissue layer that covers organs and structures that are not located within the peritoneal cavity. In the case of the esophagus, it lies behind the trachea and heart and passes through the diaphragm before connecting to the stomach. Since it is located outside the peritoneal cavity, it is covered by adventitia instead of serosa, which is the visceral peritoneum that covers organs within the abdominal cavity.

b) stomach

- Incorrect: The stomach is supported by a layer of serosa, which is the visceral peritoneum covering organs within the abdominal cavity.

c) small intestine

- Incorrect: The small intestine is supported by a layer of serosa, which is the visceral peritoneum covering organs within the abdominal cavity.

d) large intestine

- Incorrect: The large intestine is supported by a layer of serosa, which is the visceral peritoneum covering organs within the abdominal cavity.

A. mouth

B. salivary glands

C. pancreas

D. liver

a) mouth

- Correct: The mouth is not considered an accessory digestive structure; it is an integral part of the alimentary canal (digestive tract). The mouth is where the process of digestion begins, as food is ingested, chewed, and mixed with saliva. Saliva, produced by the salivary glands, contains enzymes (such as amylase) that initiate the breakdown of carbohydrates. Once food is sufficiently broken down in the mouth, it is formed into a bolus and swallowed, entering the esophagus and continuing its journey through the digestive system.

b) salivary glands

- Incorrect: Salivary glands are accessory digestive structures that secrete saliva into the mouth. Saliva contains enzymes and lubricants that aid in the mechanical and chemical digestion of food.

c) pancreas

- Incorrect: The pancreas is an accessory digestive structure that plays a crucial role in digestion by producing and secreting digestive enzymes into the small intestine. These enzymes aid in the breakdown of carbohydrates, proteins, and fats.

d) liver

- Incorrect: The liver is also an accessory digestive structure that contributes to digestion by producing bile, which is stored in the gallbladder and released into the small intestine to aid in the emulsification and digestion of fats. Additionally, the liver plays a role in processing nutrients absorbed from the small intestine and regulating glucose metabolism.

A. digestive fluids

B. enzymes

C. mucous membranes

D. smooth muscles

d. smooth muscles

- Correct: Smooth muscles are responsible for moving food through the digestive system via a process called peristalsis. Peristalsis involves rhythmic contractions and relaxations of the smooth muscle layers in the walls of the digestive organs, such as the esophagus, stomach, and intestines. These coordinated muscle movements propel food forward along the digestive tract, allowing for mechanical digestion, mixing with digestive fluids, and absorption of nutrients.

a. digestive fluids

- Incorrect: Digestive fluids, such as saliva, gastric juice, bile, and pancreatic enzymes, play crucial roles in the digestion and breakdown of food into smaller molecules. However, they do not directly move food through the digestive system.

b. enzymes

- Incorrect: Enzymes are biological catalysts that facilitate chemical reactions involved in the breakdown of food molecules into smaller, absorbable components. While enzymes aid in digestion, they do not themselves move food through the digestive system.

c. mucous membranes

- Incorrect: Mucous membranes line the inner surfaces of the digestive tract and secrete mucus, which lubricates and protects the epithelial cells from mechanical damage and chemical irritation. While mucous membranes are important for maintaining the health of the digestive tract, they do not actively move food through the digestive system.

A. falciform ligament

B. mesocolon

C. parietal peritoneum

D. visceral peritoneum

d) visceral peritoneum

- Correct: The visceral peritoneum covers the stomach. The peritoneum is a serous membrane that lines the abdominal cavity and covers most of the abdominal organs. The portion of the peritoneum that directly covers the surface of an organ is called the visceral peritoneum. In the case of the stomach, the visceral peritoneum covers its outer surface, providing a protective and lubricating layer.

a) falciform ligament

- Incorrect: The falciform ligament is a fold of peritoneum that attaches the liver to the anterior abdominal wall and diaphragm. It does not cover the stomach.

b) mesocolon

- Incorrect: The mesocolon is a fold of peritoneum that attaches the colon to the posterior abdominal wall. It does not cover the stomach.

c) parietal peritoneum

- Incorrect: The parietal peritoneum lines the abdominal cavity but does not cover individual organs. It forms the outer layer of the peritoneum and is not directly associated with covering the stomach.

A. deactivates bile.

B. is secreted by pancreatic islet cells.

C. buffers chyme.

D. is released into the cystic duct.

c) buffers chyme.

- Correct: Pancreatic juice contains bicarbonate ions, which act as buffers to neutralize the acidic chyme entering the duodenum from the stomach. This neutralization is essential for maintaining the optimal pH for the activity of digestive enzymes in the small intestine.

a) deactivates bile.

- Incorrect: Pancreatic juice does not deactivate bile. Bile is not deactivated in the digestive process; instead, it aids in the emulsification and digestion of fats in the small intestine.

b) is secreted by pancreatic islet cells.

- Incorrect: Pancreatic juice is secreted by exocrine cells called pancreatic acinar cells, not by pancreatic islet cells. Pancreatic islet cells secrete hormones such as insulin and glucagon, which regulate blood glucose levels.

d) is released into the cystic duct.

- Incorrect: Pancreatic juice is released into the duodenum through the pancreatic duct, not the cystic duct. The cystic duct connects the gallbladder to the common bile duct, allowing bile to be released into the duodenum when needed for digestion.

A. esophageal hiatus

B. cardiac orifice

C. upper esophageal sphincter

D. lower esophageal sphincter

a) esophageal hiatus

- Correct: The structure located where the esophagus penetrates the diaphragm is called the esophageal hiatus. The esophagus passes through an opening in the diaphragm known as the esophageal hiatus as it descends from the thoracic cavity into the abdominal cavity. This hiatus allows the esophagus to connect the pharynx to the stomach.

b) cardiac orifice

- Incorrect: The cardiac orifice is the opening of the stomach into the esophagus. It is located at the superior portion of the stomach and is surrounded by the lower esophageal sphincter. It is not located where the esophagus penetrates the diaphragm.

c) upper esophageal sphincter

- Incorrect: The upper esophageal sphincter is a muscular ring located at the upper end of the esophagus, where it meets the pharynx. It controls the passage of food from the pharynx into the esophagus but is not located where the esophagus penetrates the diaphragm.

d) lower esophageal sphincter

- Incorrect: The lower esophageal sphincter (LES), also known as the cardiac sphincter, is a muscular ring located at the lower end of the esophagus, where it meets the stomach. It controls the passage of food from the esophagus into the stomach but is not located where the esophagus penetrates the diaphragm.

A. the intestines into the bladder

B. the blood into the organs

C. the intestines into the bloodstream

D. the mouth into the stomach

c. the intestines into the bloodstream

- Correct: During the process of absorption, nutrients from food pass from the intestines into the bloodstream. After food is broken down into its constituent nutrients through digestion in the stomach and small intestine, these nutrients are absorbed across the lining of the small intestine into the bloodstream. The small intestine is highly specialized for absorption, with villi and microvilli increasing the surface area available for nutrient absorption. Once absorbed into the bloodstream, nutrients are transported to various organs and tissues throughout the body to provide energy, support growth and repair, and maintain overall health.

a. the intestines into the bladder

- Incorrect: The bladder is part of the urinary system and is responsible for storing urine produced by the kidneys. Absorption of nutrients does not involve passage into the bladder.

b. the blood into the organs

- Incorrect: While nutrients absorbed into the bloodstream are indeed transported to various organs and tissues throughout the body, absorption itself occurs in the intestines, not directly from the blood into the organs.

d. the mouth into the stomach

- Incorrect: The mouth and stomach are primarily involved in the initial stages of digestion, including mechanical breakdown of food and the initiation of chemical digestion of carbohydrates and proteins. Absorption of nutrients occurs primarily in the small intestine, not from the mouth into the stomach.

A. nutrients

B. amylase

C. saliva

D. sphincters

a. nutrients

- Correct: The digestive system breaks down food into nutrients. These nutrients include carbohydrates, proteins, fats, vitamins, minerals, and water, which are essential for various physiological functions in the body. Once broken down into nutrients through mechanical and chemical digestion, these substances are absorbed by the intestines and transported via the bloodstream to cells throughout the body for energy production, growth, repair, and other metabolic processes.

b. amylase

- Incorrect: Amylase is an enzyme involved in the digestion of carbohydrates. It is produced by salivary glands in the mouth and by the pancreas and helps break down complex carbohydrates into simpler sugars. While amylase is an important component of the digestive process, it is not the end product of digestion.

c. saliva

- Incorrect: Saliva is a fluid secreted by salivary glands in the mouth. It contains water, electrolytes, mucus, and enzymes such as amylase. Saliva helps moisten food, initiate the digestion of carbohydrates, and facilitate swallowing, but it is not the end product of digestion.

d. sphincters

- Incorrect: Sphincters are ring-like muscles that control the movement of materials through various parts of the digestive tract by opening and closing. While sphincters play a crucial role in regulating the flow of food and waste through the digestive system, they are not the end products of digestion.

A. esophagus

B. stomach

C. duodenum

D. oral cavity

D. oral cavity

- Correct: Chemical digestion of carbohydrates begins in the oral cavity. Salivary glands in the mouth secrete saliva, which contains an enzyme called amylase. Amylase breaks down complex carbohydrates (such as starch) into simpler sugars (such as maltose) through hydrolysis. This process initiates the digestion of carbohydrates before the food bolus reaches the stomach or small intestine.

A. esophagus

- Incorrect: The esophagus is primarily involved in the propulsion of food from the mouth to the stomach through peristaltic contractions. It does not play a significant role in the chemical digestion of carbohydrates.

B. stomach

- Incorrect: While the stomach plays a role in the digestion of proteins through the action of gastric juices containing pepsin and hydrochloric acid, it does not contribute significantly to the digestion of carbohydrates. In fact, the acidic environment of the stomach may temporarily inhibit the activity of salivary amylase.

C. duodenum

- Incorrect: The duodenum is the first part of the small intestine where the majority of chemical digestion occurs. While the duodenum receives pancreatic enzymes and bile that aid in the digestion of carbohydrates, proteins, and fats, the initial chemical digestion of carbohydrates primarily occurs in the oral cavity with the action of salivary amylase.

A. ascending colon

B. stomach

C. jejunum

D. ileum

C. jejunum

- Correct: Most of the nutrient absorption along the alimentary canal occurs in the jejunum, which is the middle segment of the small intestine. The jejunum has a highly folded inner surface covered with finger-like projections called villi and even smaller microvilli. These structures greatly increase the surface area available for absorption. The epithelial cells lining the villi contain numerous transport proteins and enzymes responsible for absorbing nutrients such as carbohydrates, proteins, fats, vitamins, and minerals into the bloodstream for distribution to the body's cells.

A. ascending colon

- Incorrect: The ascending colon is part of the large intestine (colon) where water and electrolytes are primarily absorbed, but it is not a major site of nutrient absorption.

B. stomach

- Incorrect: While some substances, such as water, electrolytes, alcohol, and certain drugs, can be absorbed in small amounts in the stomach, the stomach is not a major site of nutrient absorption. Its main function is to begin the digestion of proteins and store food temporarily.

D. ileum

- Incorrect: The ileum is the final segment of the small intestine, and while it does participate in nutrient absorption, the majority of nutrient absorption occurs in the jejunum, which precedes the ileum along the alimentary canal. The ileum primarily absorbs bile salts, vitamin B12, and some remaining nutrients not absorbed in the jejunum.