A. lung
B. kidney
C. skin
D. liver
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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.
Therefore, the Correct Answer is D.
. 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.
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.
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.
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.
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.
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 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 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.
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.
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.