A. esophageal hiatus
B. cardiac orifice
C. upper esophageal sphincter
D. lower esophageal sphincter
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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.
Therefore, the Correct Answer is A.
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.
In which part of the alimentary canal does most digestion occur?
A. stomach
B. proximal small intestine
C. distal small intestine
D. ascending colon
The Correct Answer is B.b) proximal small intestine
- Correct: Most digestion occurs in the proximal small intestine, specifically in the duodenum. The duodenum receives chyme from the stomach and plays a crucial role in digestion by mixing the chyme with digestive enzymes and bile. Digestive enzymes from the pancreas, including amylase, lipase, and proteases, break down carbohydrates, fats, and proteins, respectively, in the duodenum. Bile, produced by the liver and stored in the gallbladder, emulsifies fats to aid in their digestion and absorption.
a) stomach
- Incorrect: While digestion begins in the stomach, where proteins are broken down by pepsin and fats are emulsified to some extent by gastric lipase, the majority of digestion occurs in the small intestine, particularly in the duodenum.
c) distal small intestine
- Incorrect: The distal small intestine, including the jejunum and ileum, is primarily involved in nutrient absorption rather than digestion. Although some digestion continues in these regions, the majority of digestive processes have already occurred in the proximal small intestine.
d) ascending colon
- Incorrect: The ascending colon is part of the large intestine and is not directly involved in digestion. Its main function is to absorb water and electrolytes from the indigestible residue of food (feces) before it is excreted from the body.
. Parietal cells secrete ________.
A. gastrin
B. hydrochloric acid
C. pepsin
D. pepsinogen
The Correct Answer is B.b) hydrochloric acid
- Correct: Parietal cells, also known as oxyntic cells, secrete hydrochloric acid (HCl) into the stomach lumen. HCl plays a critical role in the digestive process by creating an acidic environment necessary for the activation of pepsinogen to pepsin and for the breakdown of food proteins. Parietal cells also secrete intrinsic factor, which is essential for the absorption of vitamin B12 in the small intestine.
a) gastrin
- Incorrect: Gastrin is a hormone secreted by G cells in the gastric glands of the stomach. It stimulates the secretion of gastric acid (HCl) by parietal cells and promotes gastric motility and emptying.
c) pepsin
- Incorrect: Pepsin is an enzyme that digests proteins by breaking them down into smaller peptides. Pepsin is formed from the precursor molecule pepsinogen, which is secreted by chief cells in the gastric glands. Parietal cells do not directly secrete pepsin.
d) pepsinogen
- Incorrect: Pepsinogen is the inactive precursor of pepsin. It is secreted by chief cells in the gastric glands of the stomach. Pepsinogen is activated to pepsin by the acidic environment created by hydrochloric acid secreted by parietal cells.
Pancreatic juice ________.
A. deactivates bile.
B. is secreted by pancreatic islet cells.
C. buffers chyme.
D. is released into the cystic duct.
The Correct Answer is C.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.
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 these cells secrete hormones?
A. parietal cells
B. mucous neck cells
C. enteroendocrine cells
D. chief cells
The Correct Answer is C.c) enteroendocrine cells
- Correct: Enteroendocrine cells are specialized cells located in the epithelium of the gastrointestinal tract that secrete hormones. These hormones play various roles in the regulation of digestion, nutrient absorption, and other physiological processes. Examples of hormones secreted by enteroendocrine cells include gastrin, secretin, cholecystokinin (CCK), and ghrelin.
a) parietal cells
- Incorrect: Parietal cells are found in the gastric glands of the stomach and secrete hydrochloric acid (HCl) and intrinsic factor, but they do not secrete hormones.
b) mucous neck cells
- Incorrect: Mucous neck cells are found in the gastric glands of the stomach and secrete mucus, which helps protect the stomach lining from the acidic environment, but they do not secrete hormones.
d) chief cells
- Incorrect: Chief cells are found in the gastric glands of the stomach and secrete pepsinogen, the precursor to the enzyme pepsin, which plays a role in protein digestion. Chief cells do not secrete hormones.
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.
A disorder of the digestive system that can cause severe dehydration is known as
A. appendicitis
B. gallstones
C. constipation
D. diarrhea
The Correct Answer is D.D) diarrhea
- Correct: Diarrhea is a disorder of the digestive system that can cause severe dehydration. Diarrhea is characterized by frequent, loose, or watery bowel movements, often accompanied by abdominal cramps, bloating, and urgency. It occurs when the intestines fail to properly absorb water or when excess fluid is secreted into the intestines. Diarrhea can lead to significant fluid loss and electrolyte imbalance, resulting in dehydration, particularly if not promptly treated by replenishing lost fluids and electrolytes.
A) appendicitis
- Incorrect: Appendicitis is inflammation of the appendix, a small pouch located near the junction of the small and large intestines. While appendicitis can cause symptoms such as abdominal pain, fever, and vomiting, it is not directly associated with dehydration.
B) gallstones
- Incorrect: Gallstones are hardened deposits that form in the gallbladder and can cause symptoms such as abdominal pain, nausea, and jaundice. While gallstones can lead to complications such as obstruction of the bile duct, they are not directly associated with dehydration.
C) constipation
- Incorrect: Constipation refers to infrequent bowel movements or difficulty passing stool, often characterized by hard, dry stools that are difficult to pass. While severe constipation can cause discomfort and complications such as fecal impaction, it is not directly associated with dehydration.
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.
Which of these statements about bile is true?
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.
The Correct Answer is D.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.