Which of the following organs is supported by a layer of adventitia rather than serosa?

A. Short reflexes are provoked by nerves near the GI tract.

B. Short reflexes are mediated by the enteric nervous system.

C. Food that distends the stomach initiates long reflexes.

D. Long reflexes can be provoked by stimuli originating outside the GI tract.

c) Food that distends the stomach initiates long reflexes.

- False: This statement is false. Food that distends the stomach initiates short reflexes, not long reflexes. Short reflexes are local reflexes that are mediated by the enteric nervous system, which consists of a network of neurons within the walls of the digestive tract. When food stretches or distends the stomach, sensory neurons in the stomach wall detect this mechanical stimulus and initiate short reflexes that regulate local gastrointestinal functions, such as gastric motility and secretion.

A. muscles churn and mix the food with acids and enzymes

B. glands make 3 quarts of digestive juices each day

C. food leaves as a thick liquid called chyme

D. all of the above

d. all of the above

- Correct: All of the statements are true regarding the stomach:

a. muscles churn and mix the food with acids and enzymes: The stomach has muscular walls that contract and relax to mechanically churn and mix food with gastric juices, including hydrochloric acid and various enzymes (such as pepsin) that aid in the digestion of proteins.

b. glands make 3 quarts of digestive juices each day: The gastric glands in the lining of the stomach produce gastric juice, which contains hydrochloric acid, enzymes (such as pepsinogen), mucus, and intrinsic factor. These glands collectively secrete about 2 to 3 liters (quarts) of gastric juice per day.

c. food leaves as a thick liquid called chyme: After mixing with gastric juices and undergoing partial digestion in the stomach, food is transformed into a semi-liquid mixture called chyme. Chyme is then gradually released from the stomach into the small intestine for further digestion and absorption.

Therefore, all of the statements accurately describe processes that occur in the stomach.

A. manufacturing red blood cells

B. producing chemical compounds known as auxins

C. storing the carbohydrate reserve glycogen

D. synthesizing the hormone insulin

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.

A. secreting mucus

B. buffering acidic chyme

C. activating pepsin

D. preventing bacteria from entering the bloodstream

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.

A. lung

B. kidney

C. skin

D. liver

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.

A. fundus and body

B. cardia and fundus

C. body and pylorus

D. body

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.

A. ingestion

B. mechanical digestion

C. chemical digestion

D. all of the above

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.

A. digestive fluids

B. enzymes

C. mucous membranes

D. smooth muscles

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.

A. pancreas, liver, and gallbladder

B. esophagus, stomach, and intestines

C. colon, rectum, and anus

D. mouth, esophagus, and stomach

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.

A. Both the internal and the skin temperatures reach 40ºC.

B. Both the internal and the skin temperatures increase by about 7ºC.

C. The skin temperature decreases to about 30ºC.

D. The internal temperature increases by about 1ºC.

D) The internal temperature increases by about 1ºC.

- Correct: As environmental temperature increases from 20ºC to 30ºC, the body's internal temperature tends to increase slightly. This is due to the body's thermoregulatory mechanisms, which work to maintain a relatively constant internal temperature (around 37ºC or 98.6ºF) despite fluctuations in environmental temperature. When the environmental temperature rises, the body responds by increasing blood flow to the skin and by initiating mechanisms such as sweating to dissipate heat and maintain thermal equilibrium. However, the increase in environmental temperature may result in a slight increase in internal temperature, typically by about 1ºC, as the body works to dissipate excess heat.

A) Both the internal and the skin temperatures reach 40ºC.

- Incorrect: A 10ºC increase in environmental temperature from 20ºC to 30ºC is not likely to cause both internal and skin temperatures to reach 40ºC. Such a significant increase would likely lead to heatstroke or hyperthermia, which can be life-threatening.

B) Both the internal and the skin temperatures increase by about 7ºC.

- Incorrect: A 10ºC increase in environmental temperature is not likely to cause both internal and skin temperatures to increase by about 7ºC. Such a large increase in temperature would be excessive and would likely lead to severe heat-related illnesses.

C) The skin temperature decreases to about 30ºC.

- Incorrect: In response to an increase in environmental temperature, the body typically increases blood flow to the skin and initiates mechanisms such as sweating to dissipate heat. This would not result in a decrease in skin temperature to match the environmental temperature of 30ºC.