A. small intestine
B. esophagus
C. stomach
D. large intestine
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C. stomach
- Correct: The stomach has three layers of smooth muscle in its muscularis externa, which is the muscular layer of the gastrointestinal tract responsible for peristalsis and mixing of food. These muscle layers are arranged in longitudinal, circular, and oblique orientations, allowing for the mechanical processing of ingested food and the propulsion of food through the digestive tract. This muscular arrangement contributes to the stomach's ability to churn and mix food with gastric juices during digestion.
A. small intestine
- Incorrect: While the small intestine does have smooth muscle in its muscularis externa, it typically has two layers of smooth muscle: an inner circular layer and an outer longitudinal layer.
B. esophagus
- Incorrect: The esophagus also has smooth muscle in its muscularis externa, but it typically has two layers of smooth muscle: an inner circular layer and an outer longitudinal layer.
D. large intestine
- Incorrect: The large intestine, like the small intestine, typically has two layers of smooth muscle in its muscularis externa: an inner circular layer and an outer longitudinal layer.
Therefore, the Correct Answer is C.
Which phase of deglutition involves contraction of the longitudinal muscle layer of the muscularis?
A. voluntary phase
B. buccal phase
C. pharyngeal phase
D. esophageal phase
The Correct Answer is A.a) voluntary phase
- Correct: The voluntary phase of deglutition (swallowing) involves the initial voluntary movement of food from the mouth into the pharynx. During this phase, the tongue pushes the food bolus backward toward the oropharynx. Contraction of the longitudinal muscle layer of the muscularis propels the food bolus into the pharynx, which is part of the voluntary control of swallowing.
b) buccal phase
- Incorrect: The buccal phase of deglutition involves the initial formation of the food bolus and its movement toward the oropharynx by the coordinated action of the tongue and muscles of the cheeks. It does not involve contraction of the longitudinal muscle layer of the muscularis.
c) pharyngeal phase
- Incorrect: The pharyngeal phase of deglutition is involuntary and occurs when the food bolus reaches the pharynx. It involves the sequential contraction of muscles in the pharyngeal wall to propel the food bolus downward toward the esophagus. The contraction of the longitudinal muscle layer of the muscularis is not a significant component of the pharyngeal phase.
d) esophageal phase
- Incorrect: The esophageal phase of deglutition involves the passage of the food bolus through the esophagus and into the stomach. Peristaltic waves of contraction and relaxation of the muscularis propels the food bolus along the length of the esophagus. The contraction of the longitudinal muscle layer of the muscularis primarily occurs during the voluntary phase of deglutition, not the esophageal phase.
Which structure is located where the esophagus penetrates the diaphragm?
A. esophageal hiatus
B. cardiac orifice
C. upper esophageal sphincter
D. lower esophageal sphincter
The Correct Answer is A.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.
Which of the following organs has 3 layers of smooth muscle in its muscularis externa?
A. small intestine
B. esophagus
C. stomach
D. large intestine
The Correct Answer is C.C. stomach
- Correct: The stomach has three layers of smooth muscle in its muscularis externa, which is the muscular layer of the gastrointestinal tract responsible for peristalsis and mixing of food. These muscle layers are arranged in longitudinal, circular, and oblique orientations, allowing for the mechanical processing of ingested food and the propulsion of food through the digestive tract. This muscular arrangement contributes to the stomach's ability to churn and mix food with gastric juices during digestion.
A. small intestine
- Incorrect: While the small intestine does have smooth muscle in its muscularis externa, it typically has two layers of smooth muscle: an inner circular layer and an outer longitudinal layer.
B. esophagus
- Incorrect: The esophagus also has smooth muscle in its muscularis externa, but it typically has two layers of smooth muscle: an inner circular layer and an outer longitudinal layer.
D. large intestine
- Incorrect: The large intestine, like the small intestine, typically has two layers of smooth muscle in its muscularis externa: an inner circular layer and an outer longitudinal layer.
Which is a function of the liver in human adults?
A. manufacturing red blood cells
B. producing chemical compounds known as auxins
C. storing the carbohydrate reserve glycogen
D. synthesizing the hormone insulin
The Correct Answer is C.C) storing the carbohydrate reserve glycogen
- Correct: One of the functions of the liver in human adults is storing the carbohydrate reserve glycogen. Glycogen is a polysaccharide that serves as a storage form of glucose in the body. When blood glucose levels are high, such as after a meal, the liver takes up excess glucose and converts it into glycogen for storage. When blood glucose levels drop, such as between meals or during fasting, the liver breaks down glycogen and releases glucose into the bloodstream to maintain blood sugar levels within a normal range.
A) manufacturing red blood cells
- Incorrect: The primary site of red blood cell production (erythropoiesis) in adults is the bone marrow, not the liver. While the liver is involved in the production of blood proteins and components, such as albumin, clotting factors, and plasma proteins, it is not responsible for manufacturing red blood cells.
B) producing chemical compounds known as auxins
- Incorrect: Auxins are a class of plant hormones involved in various physiological processes, such as cell elongation, apical dominance, and root development. They are not produced by the liver in human adults.
D) synthesizing the hormone insulin
- Incorrect: Insulin is a hormone produced by the pancreas, not the liver. Insulin plays a crucial role in regulating blood sugar levels by facilitating the uptake of glucose into cells for energy production or storage. While the liver responds to insulin by regulating glucose metabolism and storage, it does not synthesize insulin itself.
Which part of the large intestine attaches to the appendix?
A. cecum
B. ascending colon
C. transverse colon
D. descending colon
The Correct Answer is A.Cecum attaches to the appendix
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.
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.
These move food through the digestive system:
A. digestive fluids
B. enzymes
C. mucous membranes
D. smooth muscles
The Correct Answer is D.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.
Which of these is involved in the chemical digestion of protein?
A. pancreatic amylase
B. trypsin
C. sucrase
D. pancreatic nuclease
The Correct Answer is B.b) trypsin
- Correct: Trypsin is an enzyme involved in the chemical digestion of protein. It is secreted as trypsinogen by the pancreas and activated to its active form, trypsin, by enterokinase in the duodenum. Trypsin breaks down proteins into smaller peptides by cleaving peptide bonds between specific amino acids.
a) pancreatic amylase
- Incorrect: Pancreatic amylase is an enzyme involved in the digestion of carbohydrates (starches). It breaks down starch molecules into maltose and other simpler sugars.
c) sucrase
- Incorrect: Sucrase is an enzyme involved in the digestion of disaccharide sugars, specifically sucrose. It catalyzes the hydrolysis of sucrose into its constituent monosaccharides, glucose, and fructose.
d) pancreatic nuclease
- Incorrect: Pancreatic nuclease is an enzyme involved in the digestion of nucleic acids (DNA and RNA). It breaks down nucleic acid molecules into their component nucleotides.