A. ingestion
B. propulsion
C. segmentation
D. absorption
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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.
Therefore, the Correct Answer is B.
. 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.
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.
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.
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 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.
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 human excretory organ breaks down red blood cells and synthesizes urea?
A. lung
B. kidney
C. skin
D. liver
The Correct Answer is D.D) liver
- Correct: The liver is the human excretory organ that breaks down red blood cells and synthesizes urea. Red blood cells have a finite lifespan and are continually replaced by new cells produced in the bone marrow. When old or damaged red blood cells are removed from circulation, their components are broken down by macrophages, primarily in the spleen and liver. The liver plays a crucial role in this process by breaking down hemoglobin, the oxygen-carrying protein in red blood cells, into heme and globin. Heme is further broken down into bilirubin, which is excreted in bile and eventually eliminated from the body in feces. Additionally, the liver synthesizes urea as a waste product of protein metabolism, which is excreted by the kidneys in urine.
A) lung
- Incorrect: While the lungs play a role in the excretion of carbon dioxide during respiration, they are not involved in breaking down red blood cells or synthesizing urea.
B) kidney
- Incorrect: The kidneys are responsible for filtering blood to remove waste products and excess substances, such as urea, creatinine, and electrolytes, to produce urine. While the kidneys excrete urea synthesized by the liver, they do not break down red blood cells.
C) skin
- Incorrect: The skin is involved in excreting certain waste products, such as sweat (containing water, electrolytes, and small amounts of urea and other metabolic waste), but it does not break down red blood cells or synthesize urea.
Which of these is most associated with villi?
A. haustra
B. lacteals
C. bacterial flora
D. intestinal glands
The Correct Answer is B.b) lacteals
- Correct: Villi are small, finger-like projections that extend into the lumen of the small intestine, increasing its surface area for absorption. Lacteals are specialized lymphatic vessels located within the villi. They play a crucial role in the absorption of dietary fats and fat-soluble vitamins. Lacteals absorb digested fats and fat-soluble nutrients and transport them through the lymphatic system to the bloodstream.
a) haustra
- Incorrect: Haustra are pouches or sacculations formed by the longitudinal muscle of the colon. They are characteristic features of the large intestine, particularly the colon, and are not directly associated with villi.
c) bacterial flora
- Incorrect: Bacterial flora (microbiota) refers to the diverse population of microorganisms inhabiting the gastrointestinal tract. While they play important roles in digestion, nutrient absorption, and immune function, they are not specifically associated with villi. They primarily inhabit the large intestine, where they aid in the fermentation of undigested carbohydrates and the production of certain vitamins.
d) intestinal glands
- Incorrect: Intestinal glands, also known as crypts of Lieberkühn or intestinal crypts, are invaginations of the epithelium located between the villi in the mucosa of the small intestine. They contain stem cells that continuously divide to replace the epithelial cells lining the intestine. While they are anatomically close to villi, they are distinct structures responsible for epithelial cell renewal and secretion of intestinal juices, but they are not directly associated with villi.
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 of these ingredients in saliva is responsible for activating salivary amylase?
A. mucus
B. phosphate ions
C. chloride ions
D. urea
The Correct Answer is B.b) phosphate ions
- Correct: Phosphate ions are responsible for activating salivary amylase. Saliva contains salivary amylase (also known as alpha-amylase or ptyalin), which is an enzyme that catalyzes the hydrolysis of starch into maltose and other smaller carbohydrates. However, salivary amylase is only activated in the presence of certain ions, particularly phosphate ions. These ions help to stabilize the enzyme's structure and facilitate its enzymatic activity. Therefore, phosphate ions play a crucial role in the function of salivary amylase.
a) Mucus
- Incorrect: Mucus in saliva serves primarily as a lubricant and protective barrier for the oral mucosa and facilitates swallowing. It does not directly activate salivary amylase
c) Chloride ions
- Incorrect: Chloride ions are electrolytes present in saliva, but they do not directly activate salivary amylase. Instead, they help maintain the osmotic balance and pH of saliva.
d) Urea
- Incorrect: Urea is a waste product found in urine and is not directly involved in the activation of salivary amylase.