A. About 500 mL is secreted daily.
B. Its main function is the denaturation of proteins.
C. It is synthesized in the gallbladder.
D. Bile salts are recycled.
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d) Bile salts are recycled.
- Correct: Bile salts are recycled in the enterohepatic circulation. After aiding in the digestion and absorption of fats in the small intestine, bile salts are reabsorbed in the terminal ileum and transported back to the liver via the portal vein. Once in the liver, they are re-secreted into bile, allowing for their reuse in subsequent digestive processes. This recycling of bile salts is an important mechanism for conserving these critical components of bile.
a) About 500 mL is secreted daily.
- Incorrect: The daily secretion of bile by the liver is approximately 600-1000 mL, not 500 mL. Bile is continuously produced by hepatocytes (liver cells) and stored and concentrated in the gallbladder until it is released into the small intestine to aid in fat digestion.
b) Its main function is the denaturation of proteins.
- Incorrect: The main function of bile is not the denaturation of proteins. Bile aids in the emulsification and digestion of fats by breaking them down into smaller droplets, increasing the surface area for the action of pancreatic lipase and facilitating the absorption of lipids and fat-soluble vitamins.
c) It is synthesized in the gallbladder.
- Incorrect: Bile is not synthesized in the gallbladder. It is produced by hepatocytes (liver cells) in the liver and then stored and concentrated in the gallbladder until needed for digestion.
Therefore, the Correct Answer is D.
Chemical digestion of carbohydrates begins in the
A. esophagus
B. stomach
C. duodenum
D. oral cavity
The Correct Answer is D.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.
Where does the majority of chemical digestion in the stomach occur?
A. fundus and body
B. cardia and fundus
C. body and pylorus
D. body
The Correct Answer is A.a) fundus and body
- Correct: The majority of chemical digestion in the stomach occurs in the fundus and body regions. These regions contain gastric glands that secrete hydrochloric acid (HCl), pepsinogen, and mucus. Hydrochloric acid creates an acidic environment necessary for the activation of pepsinogen to pepsin, which is responsible for the digestion of proteins. Additionally, the stomach churns and mixes food with gastric juices in the fundus and body, facilitating the breakdown of food particles and the mixing of digestive enzymes with the food bolus.
b) cardia and fundus
- Incorrect: While the fundus region is involved in chemical digestion due to the presence of gastric glands, the cardia region primarily serves as the entry point of the esophagus into the stomach and does not significantly contribute to chemical digestion.
c) body and pylorus
- Incorrect: While the body region of the stomach is involved in chemical digestion, the pylorus region is primarily responsible for regulating the passage of partially digested food (chyme) into the small intestine through the pyloric sphincter. The pylorus region does not contribute significantly to chemical digestion.
d) body
- Incorrect: While the body region of the stomach is involved in chemical digestion, the majority of chemical digestion occurs in both the fundus and body regions. The body region alone does not represent the entirety of where chemical digestion occurs in the stomach.
Which of these processes occurs in the mouth?
A. ingestion
B. mechanical digestion
C. chemical digestion
D. all of the above
The Correct Answer is D.d) all of the above
- Correct: All of the listed processes occur in the mouth:
a) Ingestion: The mouth is the entry point for food into the digestive system. Ingestion refers to the act of taking food or drink into the mouth.
b) Mechanical digestion: Mechanical digestion involves the physical breakdown of food into smaller pieces through actions such as chewing and mixing with saliva. In the mouth, the teeth tear and grind food into smaller particles, which increases the surface area for chemical digestion.
c) Chemical digestion: Chemical digestion involves the breakdown of food into smaller molecules by enzymes and other chemicals. In the mouth, salivary glands secrete saliva, which contains the enzyme amylase. Amylase begins the chemical breakdown of carbohydrates, converting starches into simpler sugars such as maltose.
Therefore, all of the processes listed—ingestion, mechanical digestion, and chemical digestion—occur in the mouth during the initial stages of digestion.
Most of the nutrient absorption along the alimentary canal occurs in the
A. ascending colon
B. stomach
C. jejunum
D. ileum
The Correct Answer is C.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.
What is the role of the small intestine’s MALT?
A. secreting mucus
B. buffering acidic chyme
C. activating pepsin
D. preventing bacteria from entering the bloodstream
The Correct Answer is B.b) buffering acidic chyme
- Correct: MALT (Mucosa-Associated Lymphoid Tissue) in the small intestine plays a role in buffering acidic chyme. MALT contains immune cells, such as lymphocytes and plasma cells, that help protect the intestinal mucosa from pathogens and foreign substances. Additionally, MALT helps regulate the pH of the intestinal contents by neutralizing acidic chyme, which is important for optimal enzymatic activity and absorption in the small intestine.
a) secreting mucus
- Incorrect: The secretion of mucus is primarily the role of goblet cells, which are scattered throughout the epithelium of the small intestine. Mucus serves to lubricate and protect the intestinal epithelium from mechanical damage and chemical irritation.
c) activating pepsin
- Incorrect: Pepsin is an enzyme involved in protein digestion, and its activation primarily occurs in the stomach under acidic conditions. It is produced as pepsinogen by chief cells in the gastric glands and is activated by hydrochloric acid (HCl) secreted by parietal cells.
d) preventing bacteria from entering the bloodstream
- Incorrect: While MALT helps protect the intestinal mucosa from pathogens and foreign substances, its primary role is not to prevent bacteria from entering the bloodstream. Instead, MALT functions in the local immune defense of the mucosal surface of the intestine, including the initiation of immune responses against pathogens encountered in the gastrointestinal tract.
Which of these processes occurs throughout most of the alimentary canal?
A. ingestion
B. propulsion
C. segmentation
D. absorption
The Correct Answer is B.b) propulsion
- Correct: Propulsion is the movement of food along the length of the alimentary canal, from the mouth to the anus. This process occurs throughout most of the alimentary canal and includes both swallowing (deglutition) and peristalsis. Swallowing moves food from the mouth to the esophagus, while peristalsis involves rhythmic contractions and relaxations of smooth muscles in the walls of the digestive organs, pushing food forward through the esophagus, stomach, and intestines.
a) Ingestion: Ingestion refers to the intake of food into the mouth, which occurs at the beginning of the alimentary canal.
c) Segmentation: Segmentation involves the mixing and churning of food within certain regions of the digestive tract, particularly the small intestine. It does not occur throughout most of the alimentary canal but rather in specific areas where mechanical digestion and absorption are optimized.
d) Absorption: Absorption is the process by which nutrients and water are taken up from the digestive tract into the bloodstream or lymphatic system. While absorption occurs primarily in the small intestine, it also occurs in other parts of the alimentary canal, particularly in the large intestine, but it is not a continuous process throughout most of the alimentary canal like propulsion.
Which of the following membranes covers the stomach?
A. falciform ligament
B. mesocolon
C. parietal peritoneum
D. visceral peritoneum
The Correct Answer is D.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.
The pancreas, liver, and gallbladder help digestion in these ways, respectively:
A. making enzymes; making bile and processing nutrients; and storing bile
B. producing saliva; digesting carbohydrates; and eliminating waste
C. producing hormones; producing enzymes; and eliminating waste
D. making acids; producing digestive juices; and storing enzymes
The Correct Answer is A.a. making enzymes; making bile and processing nutrients; and storing bile
- Correct: The pancreas, liver, and gallbladder help digestion in the following ways:
1. The pancreas produces and secretes digestive enzymes into the small intestine to aid in the breakdown of carbohydrates, proteins, and fats. These enzymes include amylase (for carbohydrates), proteases (for proteins), and lipases (for fats).
2. The liver produces bile, a digestive fluid that emulsifies fats by breaking them down into smaller droplets, which increases the surface area for enzymes to act upon. The liver also processes nutrients absorbed from the small intestine, including carbohydrates, proteins, and fats.
3. The gallbladder stores and concentrates bile produced by the liver. When needed for digestion, the gallbladder releases bile into the small intestine via the common bile duct to aid in the emulsification and digestion of fats.
Therefore, option a accurately describes the roles of the pancreas, liver, and gallbladder in digestion.
Your digestive system works on the foods you eat for about:
A. 5 hours
B. 10 hours
C. 15 hours
D. 20 hours
The Correct Answer is B.The digestive system typically works on the foods you eat for about 10 hours. The entire process of digestion, from the moment food enters the mouth until waste is eliminated from the body, generally takes around 24 to 72 hours. However, the actual time it takes for food to move through the digestive tract and be fully digested varies depending on factors such as the type of food consumed, individual metabolism, and overall gastrointestinal health. On average, food spends approximately 4 to 6 hours in the stomach and small intestine, and another 12 to 36 hours in the large intestine before being eliminated as waste. Therefore, the total time for digestion and elimination is typically around 24 to 72 hours.
Which of the following organs is supported by a layer of adventitia rather than serosa?
A. esophagus
B. stomach
C. small intestine
D. large intestine
The Correct Answer is A.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.