A. nutrients
B. amylase
C. saliva
D. sphincters
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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.
Therefore, the Correct Answer is A.
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 the following stimuli activates sensors in the walls of digestive organs?
A. breakdown products of digestion
B. distension
C. pH of chyme
D. all of the above
The Correct Answer is D.d) all of the above
- Correct: All of the listed stimuli activate sensors in the walls of digestive organs:
a) Breakdown products of digestion: The presence of breakdown products, such as nutrients and smaller molecules resulting from digestion, can activate sensors in the walls of digestive organs. These sensors help regulate various digestive processes and signal the release of digestive enzymes and hormones.
b) Distension: Distension, or stretching of the walls of the digestive organs, is a stimulus that activates sensors. It occurs as the volume of the digestive tract increases due to the presence of ingested food, and it triggers reflexes that coordinate muscular contractions for propulsion and mixing.
c) pH of chyme: The pH of the chyme (the semi-liquid mixture of food and digestive juices in the stomach and small intestine) is another stimulus that activates sensors. Changes in pH can signal the need for adjustments in the secretion of digestive enzymes and the regulation of gastric and intestinal functions.
Therefore, all of the mentioned stimuli play a role in activating sensors and regulating digestive processes in response to the specific conditions within the digestive organs.
The alimentary canal, or digestive tract, is made up of the:
A. pancreas, liver, and gallbladder
B. esophagus, stomach, and intestines
C. colon, rectum, and anus
D. mouth, esophagus, and stomach
The Correct Answer is B.b. esophagus, stomach, and intestines
- Correct: The alimentary canal, or digestive tract, is made up of the esophagus, stomach, and intestines (both small and large). These organs form a continuous tube that extends from the mouth to the anus and is responsible for the digestion and absorption of food and the elimination of waste. The esophagus transports food from the mouth to the stomach through peristaltic contractions, while the stomach and intestines further digest food and absorb nutrients.
a. pancreas, liver, and gallbladder
- Incorrect: While the pancreas, liver, and gallbladder are important accessory organs that produce digestive enzymes and substances involved in digestion (such as bile), they are not part of the alimentary canal itself. Instead, they secrete their products into the alimentary canal to aid in digestion.
c. colon, rectum, and anus
- Incorrect: The colon, rectum, and anus are parts of the large intestine, which is a component of the alimentary canal. However, the alimentary canal is not solely composed of these organs; it also includes the esophagus, stomach, and small intestine.
d. mouth, esophagus, and stomach
- Incorrect: While the mouth, esophagus, and stomach are indeed part of the alimentary canal, they do not represent the entirety of it. The alimentary canal includes additional organs such as the small and large intestines, which are also involved in the digestion and absorption of food.
During gastric emptying, chyme is released into the duodenum through the ________.
A. esophageal hiatus
B. pyloric antrum
C. pyloric canal
D. pyloric sphincter
The Correct Answer is C.c) pyloric sphincter
- Correct: During gastric emptying, chyme (partially digested food) is released from the stomach into the duodenum through the pyloric sphincter. The pyloric sphincter is a muscular valve located at the junction between the stomach and the duodenum. It regulates the passage of chyme from the stomach into the small intestine, allowing for controlled release and preventing backflow of intestinal contents into the stomach.
a) pyloric antrum
- Incorrect: The pyloric antrum is the lower portion of the stomach that leads into the pyloric canal. It is involved in mixing and churning food, but it does not regulate the release of chyme into the duodenum.
b) pyloric canal
- Incorrect: The pyloric canal is the narrow portion of the stomach that connects the pyloric antrum to the pyloric sphincter. It is involved in directing chyme toward the pyloric sphincter for release into the duodenum, but it is not the site of chyme release itself.
The esophageal hiatus is an opening in the diaphragm through which the esophagus passes as it descends from the thoracic cavity into the abdominal cavity. It is not directly involved in gastric emptying.
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 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.
Where does the chemical digestion of starch begin?
A. mouth
B. esophagus
C. stomach
D. small intestine
The Correct Answer is A.a) mouth
- Correct: The chemical digestion of starch begins in the mouth. Salivary amylase, an enzyme secreted by the salivary glands, initiates the breakdown of starch molecules into maltose and other smaller carbohydrate molecules. This process begins as soon as food enters the mouth and continues as it is mixed with saliva during chewing and swallowing.
b) esophagus
- Incorrect: The esophagus is not directly involved in the chemical digestion of starch. It serves primarily as a conduit for the passage of food from the mouth to the stomach via peristaltic contractions.
c) stomach
- Incorrect: While some minor digestion may occur in the stomach due to the presence of salivary amylase from swallowed saliva, the stomach is not the primary site of starch digestion. Its acidic environment inhibits the activity of salivary amylase, so significant starch digestion does not occur there.
d) small intestine
- Incorrect: Starch digestion continues in the small intestine, primarily in the duodenum, but it does not begin there. Enzymes such as pancreatic amylase and brush border enzymes further break down starch into simpler sugars in the small intestine.
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.
Which of these statements about the pharynx is true?
A. It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.
B. The oropharynx is continuous superiorly with the nasopharynx.
C. The nasopharynx is involved in digestion.
D. The laryngopharynx is composed partially of cartilage.
The Correct Answer is D.d) The laryngopharynx is composed partially of cartilage.
- True: The statement that the laryngopharynx is composed partially of cartilage is true. The pharynx, commonly known as the throat, is a muscular tube that extends from the base of the skull to the level of the sixth cervical vertebra. It serves as a passageway for both air and food. The pharynx is divided into three regions: the nasopharynx, oropharynx, and laryngopharynx.
a) It extends from the nasal and oral cavities superiorly to the esophagus anteriorly.
- False: The pharynx extends from the nasal and oral cavities superiorly to the esophagus and larynx inferiorly, not anteriorly.
b) The oropharynx is continuous superiorly with the nasopharynx.
- False: The oropharynx is continuous inferiorly with the oral cavity, not superiorly with the nasopharynx. The nasopharynx is continuous superiorly with the nasal cavity.
c) The nasopharynx is involved in digestion.
- False: The nasopharynx is primarily involved in respiration and the passage of air. It contains the openings of the auditory tubes and tonsils but is not directly involved in digestion.
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.