ANPS 2 Exam 3
Which cells in the small intestine's mucosa secrete mucus?
Goblet cells, which secrete mucus and are found in several areas of the digestive tract, are located on the villi of the small intestine.
What is the name of the permanent folds seen in the wall of the small intestine?
Plicae circulares or circular folds are permanent folds in the wall of the small intestine. The plicae circulares are folds of the submucosa and are oriented in a circular direction (hence the name circular folds) - they help to slow down the flow of chyme through the small intestine and increase the surface area - both of which will increase the efficiency of absorption in the small intestine.
The wall of the small intestine has three structural features that help to increase the surface area for absorption. What are these 3 features, and list them in the order of largest to smallest.
Plicae circulares, villi, microvilli The features of the wall of the small intestine that increase the surface area for absorption, listed largest to smallest, are plicae circulares, villi and microvilli.
Which sphincter controls the flow of chyme from the stomach to the small intestine?
Pyloric sphincter The thickened circular muscle at the junction of the pylorus of the stomach and the duodenum is called the pyloric sphincter. It controls the rate of gastric emptying, hence the name pyloric, a Greek word meaning gatekeeper.
Which sphincter prevents reflux of gastric contents into the esophagus?
The LES or lower esophageal sphincter is at the gastroesophageal junction (junction of stomach and esophagus). Even though no thickened circular muscle is present, a zone of increased pressure, called a physiological sphincter, functions like circular muscle. When constricted, the LES prevents reflux of gastric contents into the esophagus. This sphincter is also called the gastroesophageal sphincter.
Defecation requires:
relaxation of both anal sphincters. Defecation is the elimination of feces from the rectum and requires relaxation of both the involuntary internal anal sphincter (smooth muscle) and the voluntary external anal sphincter (skeletal muscle).
Which enzyme digests starch?
amylase Both salivary amylase (from salivary glands) and pancreatic amylase (from the pancreas) can digest starch and glycogen, which are polysaccharides. Poly = many; saccharides = sugars.
During which gastrointestinal phase does just the thought of food stimulate gastric secretions?
cephalic In the cephalic phase, just the sight, smell, taste or thought of food can initiate reflexes that cause salivation or the production of gastric juice and gastric contractions. Recall that "cephalic" is an anatomical term that means "head".
What does the pancreas secrete?
digestive enzymes The exocrine part of the pancrease secretes digestive enzymes that aid in the digestion of starches, fats and proteins. In addition, the pancreas secretes bicarbonate, an alkaline secretion that helps to neutralize the acidic chyme coming from the stomach.
Which of the following nutrients yield the highest amount of energy per gram when metabolized?
fats
What is digestion?
food is broken down into nutrient molecules small enough to be absorbed by the lining of the gastrointestinal tract The purpose of digestion is to break the food that we ingest into the individual nutrient molecules that are small enough to be absorbed by the epithelial cells that line the gastrointestinal tract. Digestion involves a series of steps in which enzymes secreted into the lumen of the gastrointestinal tract break down complex food molecules into their chemical building blocks.
During which phase does the presence of food in the stomach initiate reflexes that cause the production of gastric secretions and increase gastric motility?
gastric phase During the gastric phase, the meal is in the stomach and the presence of food initiates reflex production of gastric secretions and increased motility of the stomach muscularis.
Gluconeogenesis is the process in which ________.
glucose is formed from noncarbohydrate molecules
What is the correct sequence of steps as energy is extracted from glucose during cellular respiration?
glycolysis → acetyl CoA → citric acid cycle → electron transport chain Glycolysis produces pyruvic acid, which enters the mitochondrion. There, it is converted to acetyl CoA, which enters the citric acid cycle. Electron carriers bring electrons from the first three steps to the electron transport chain, and ATP is made.
Which hormone directs essentially all the events of the absorptive state?
insulin
Secretions from goblet cells do all of the following EXCEPT: A. regulate secretion of bile, bicarbonate ions and digestive enzymes B. lubricates intestinal contents for ease of movement C. protect intestinal mucosa from acid D. protect epithelium from digestion by proteases
regulate secretion of bile, bicarbonate ions and digestive enzymes Goblet cells secrete a mucus secretion which coats the surface of the epithelium to help protect it from the acidic chyme and from digestion by proteases. In the duodenum, there are also submucosal glands that secrete additional mucus for protection. The mucus secretion also helps lubricate the intestinal contents for ease of movement. While goblet cells are present in both the small intestinal and large intestinal epithelium, their numbers increase in the large intestine. CCK and secretin released from enteroendocrine cells regulate the release of bile, bicarbonate and digestive enzymes.
Which of the following processes takes place in the cytosol of a eukaryotic cell?
Glycolysis, the breakdown of glucose into two molecules of pyruvic acid, takes place in the cytosol, outside the mitochondria.
Which of the following molecules is broken down in cellular respiration, providing fuel for the cell? A. Glucose B. ATP C. Water D. O2
A. Glucose
Which major process involves removing nutrients and water from the lumen of the gastrointestinal tract and delivering them to the blood or lymph?
Absorption is the passage of digested end products (i.e nutrients) and water from the lumen of the gastrointestinal tract through the mucosal cells into blood or lymph. Recall that most nutrients are absorbed into blood capillaries, and travel to the liver for processing by way of the hepatic portal system. Most fats, however, are too large to be absorbed into blood capillaries and are absorbed into the larger lacteals. These lymph capillaries carry the fats all the way through the lymph system until the lymph joins the bloodstream at the junction of the internal jugular and subclavian veins (remember this from the lymphatic system?).
Which statement describes the citric acid cycle?
Acetyl CoA is broken down, producing carbon dioxide and a few molecules of ATP. When acetyl CoA enters the citric acid cycle, carbon molecules are broken down, releasing carbon dioxide and forming just a few molecules of ATP.
__________ refers to reactions in which small molecules are combined to build larger molecules.
Anabolism Anabolism is the general term for all reactions that build larger molecules or structures from smaller ones, such as the bonding together of amino acids to build proteins.
What is another name for serosa?
Another name for serosa is visceral peritoneum. Recall that many of the organs in the abdominal cavity are surrounded by the double layered peritoneal sac. The space in between the two layers is called the peritoneal cavity, the layer that covers the surface of an organ is called the visceral peritoneum (or serosa) and the layer which lines the wall of the abdominal cavity is the parietal peritoneum. You will see that some reflections of the peritoneum form other named structures such as the mesentery (which suspends the small intestine from the posterior abdominal wall), and the greater omentum (which is a fat filled peritoneal reflection suspended from the greater curvature of the stomach).
Which energy-rich molecule produced by cellular respiration directly powers cell work? A. Glucose B. ATP C. Water D. O2
B. ATP
Which compound results in the emulsification of fats?
Bile salts and lecithin from bile surround small fat droplets to keep them in solution. This process is called emulsification. Emulsification makes it easier for lipase to have access to and to digest the fats.
What is TRUE about salivation?
Both the parasympathetic and sympathetic branches of the autonomic nervous system can influence salivation. Parasympathetic signals from the brainstem (through cranial nerves VII and IX) cause an increase in watery and enzyme-rich secretions from the salivary glands. The sympathetic nervous system can cause the release of low volumes of a sticky, mucus-rich saliva, which tends to make the mouth feel dry. In addition, stronger activation of the sympathetic nervous system can inhibit salivation by constricting blood vessels that supply the salivary glands.
Which process generates the most ATP molecules (for each molecule of glucose)? A. Glycolysis B. Citric acid cycle C. Electron transport
C. Electron transport Most of the ATP generated during cellular respiration occurs during oxidative phosphorylation using the electron transport chain and the ATP synthase. This is generally accepted to be about 28 ATP molecules, but the number may vary depending on your textbook. The electron transport chain creates a proton (H+) gradient across the inner mitochondrial membrane using high energy electrons removed from food fuels, and the ATP synthase harnesses the energy of the proton gradient to synthesize ATP. As the protons (H+) flow back across the membrane through the ATP synthase, the synthase rotor spins, causing a high energy phosphate group to attach to ADP, forming ATP.
All of the following statements about gastrin are true EXCEPT: A. Peptides in the lumen of the stomach can cause gastrin release from enteroendocrine cells. B. Gastrin increases acid secretion in the stomach. C. Gastrin is released into the lumen of the stomach. D. Gastrin promotes gastric motility and secretions.
C. Gastrin is released into the lumen of the stomach. Gastrin is released from G cells, the enteroendocrine cells of the stomach. Recall that enteroendocrine cells release their hormones into the lamina propria so that they can enter the bloodstream. They DO NOT release the hormones into the lumen of the GI tract. If peptide hormones were released into the lumen of the stomach or the small intestine, they would be denatured by the acid in the stomach, and digested by the proteases in either organ.
What is the correct general equation for cellular respiration?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy Cellular respiration extracts energy from glucose (C6H12O6) to produce smaller energy packets (ATP).
CCK and secretin are released from
CCK and secretin are secreted from enteroendocrine cells of the small intestine when chyme containing fats or proteins (or acidic chyme) enters the small intestine.
Which of the GI hormones released from enteroendocrine cells stimulates the release of bile from the gall bladder and the secretion of digestive enzymes from the pancreas?
CCK or cholecystokinin is released from enteroendocrine cells of the duodenum when the cells detect fatty chyme in the lumen of the duodenum. CCK stimulates the gall bladder to contract and release bile, stimulates exocrine gland cells (acinar cells) in the pancreas to release digestive enzymes and relaxes the hepatopancreatic sphincter (Sphincter of Oddi) so that bile and pancreatic juices can enter the duodenum.
Which dietary component cannot be digested and absorbed by humans?
Cellulose is a polysaccharide found in fruits and vegetables and cannot be digested by humans. Cellulose makes up dietary fiber, which serves to increase the bulk of the stool and promotes timely movement through the colon. Animals such as cows (ruminants) that can digest cellulose do so because they harbor microbes (bacteria) that have the ability to digest the cellulose.
Pepsinogen, an inactive digestive enzyme, is secreted by the ________.
Cheif cells of the Stomach
The acidic environment in the stomach converts pepsinogen to pepsin. Which cells of the gastric glands produce pepsinogen?
Chief cells secrete the inactive enzyme pepsinogen which is converted to the active enzyme pepsin, by the acidic environment of the stomach. Pepsin is an enzyme that breaks proteins into smaller peptides and is most active at low pH such as pH 2.0 in the stomach. Pepsin can also activate more pepsinogen by cleaving off amino acids.
The presence of fat in the small intestine lumen causes enteroendocrine cells to release cholecystokinin (CCK) which stimulates all the following EXCEPT: A. gall bladder contraction B. release of digestive enzymes C. relaxation of hepatopancreatic sphincter D. stomach acid secretions
D. stomach acid secretions Cholecystokinin or CCK stimulates gall bladder contraction which releases bile, release of pancreatic enzymes by acinar cells and relaxation of the hepatopancreatic sphincter so that these secretions can enter the duodenum. The enteroendocrine cells that release CCK are stimulated to do so by the presence of fat and to a lesser extent, peptides in the lumen of the small intestine.
Which of the enteric nervous system neurotransmitters can slow intestinal motility, contract the gastrointestinal sphincters, and inhibit intestinal secretions?
Enkephalins are endogenous opiate peptides that slow intestinal motility, contract gastrointestinal sphincters and inhibit intestinal secretions. This is interesting because these are all things that can lead to constipation. You may have heard that opiate pain medicines can cause side effects such as constipation in your patients. Understanding how neurotransmitters affect different tissues will help you understand side effects of drugs that are prescribed for your patients.
Eating large quantities or excesses of any single type of nutrient is never harmful because nutrients are always beneficial.
False Excessive consumption of any nutrient can lead to various problems such as diabetes, obesity, coronary disease, or kidney stones. Counselling your patients on the recommended daily allowances of nutrients may help prevent disease or problems. A thorough understanding of the impact of various nutrients on the body will enable you to educate your patients on leading healthy and nutritionally balanced lives.
Which hormone is released from enteroendocrine cells in response to food (and especially proteins) in stomach and causes production of hydrochloric acid?
Gastrin is released from enteroendocrine cells in the mucosa of the stomach in response to the presence of food (and especially proteins) in the stomach. Gastrin increases hydrochloric acid (HCl) release from the parietal cells of the gastric glands.
What do parietal cells in the gastric glands secrete?
Hydrochloric acid and intrinsic factor are secreted from parietal cells of the gastric glands.
What is the role of bile?
It emulsifies fat The bile salts contained in bile emulsify fats, which means that they break the fat droplets into smaller droplets to make it easier for lipases to digest the fats.
Where is the pancreas located?
It extends between the duodenum and the spleen. The pancreas is a glandular organ with both exocrine and endocrine portions. It extends between the duodenum and the spleen.
What is TRUE about intrinsic factor?
It is required for the absorption of Vitamin B12 in the ileum. Intrinsic factor is released from parietal cells. The production of intrinsic factor is the most important function of the stomach. All of the other digestive functions of the stomach can be replaced by digestion that occurs in the small intestine. Intrinsic factor forms a complex with Vitamin B12 which allows it to be absorbed in the ileum. Vitamin B12 is required for the maturation of red blood cells, and its absence causes pernicious anemia. Vitamin B12 can be administerd by injection, so individuals can survive with minimal digestive problems even after total gastrectomy (stomach removal).
What is TRUE about pepsin?
It is secreted as the inactive form pepsinogen. Pepsin is secreted from chief cells as the inactive form pepsinogen. Once pepsinogen is released, it is converted to pepsin by the acidic environment of the stomach. Pepsin breaks down proteins into smaller peptides and some individual amino acids. Pepsin can also cleave amino acids off pepsinogen to activate more pepsin. Pepsin is most active at low pH, such as pH 2.0 in the lumen of the stomach.
What is the role of bicarbonate secreted into the duodenum?
It neutralizes acidic chyme coming from the stomach. The release of bicarbonate from the ducts of the pancreas and liver help to neutralize the acidic chyme coming from the stomach. This is necessary to help protect the epithelium of the small intestine (along with mucus secretions from the mucosa) and to adjust the pH of the lumenal environment to one that is more conducive to the activity of the pancreatic enzymes. Pancreatic enzymes work optimally in a neutral to slightly alkaline pH.
__________ are considered "bad" cholesterol; high blood levels are correlated with increased risk of cardiovascular disease.
LDLs LDLs are considered "bad" cholesterol because high levels are correlated with an increased risk of cardiovascular disease. The job of cholesterol-rich LDLs is to transport cholesterol to peripheral tissues, making it available to tissue cells to synthesize membranes or hormones, and to store it for later use.
Which enzyme breaks down fats into their chemical building blocks?
Lipase breaks down triglycerides into monoglycerides and free fatty acids. This process is made more efficient by the addition of bile, which emulsifies the fats.
Which type of food molecule provides components for cellular structures like plasma membranes, myelin sheaths, and steroid hormones?
Lipids
In what organelle would you find acetyl CoA formation, the citric acid cycle, and the electron transport chain?
Mitochondrion All of the steps of cellular respiration except glycolysis take place in the mitochondrion.
Most absorption of dietary nutrients occurs in the small intestine. Which breakdown products of digestion can cross the plasma membrane of small intestine epithelial cells by simple diffusion?
Monoglycerides and free fatty acids are nonpolar molecules that are lipid soluble and can be absorbed by intestinal epithelial cells by the process of simple diffusion.
Carbohydrates are digested into __________.
Monosaccharides Monosaccharides are simple sugars, the building blocks of complex carbohydrates such as starch or glycogen.
Where does most digestion and absorption of nutrients occur?
Most of the digestion and absorption of nutrients occurs in the small intestine. The stomach stores food and begins the digestion of proteins - hardly anything (alcohol and aspirin) is absorbed in the stomach. The pancreas secretes most digestive enzymes and the liver produces and secretes bile. The large intestine absorbs some water, but most digestion and absorption of nutrients occurs in the small intestine.
What protects the epithelium of the stomach from the damaging effects of acid and the enzyme pepsin?
Mucus secretions from the simple columnar epithelial cells and the mucus neck cells create a layer that protects the epithelium (and the rest of the stomach mucosa) from the damaging effects of hydrochloric acid and digestion by pepsin.
All of the following are structural modifications of the small intestine that increase surface area EXCEPT? (which one is NOT a structural modification of the small intestine?)
Rugae are a structural modification that allow expansion of the stomach wall, and are NOT found in the small intestine. Three structural modifications of the small intestine—circular folds, villi, and microvilli—amplify its absorptive surface enormously (by a factor of more than 600 times). The result is an intestinal surface area equal to about 200 square meters, the size of a singles tennis court!
What is TRUE about nervous control of salivation?
Salivation is controlled by cranial nerves VII (facial) and IX (glossopharyngeal). Salivation is primarily controlled by the facial nerve (CN VII) and the glossopharyngeal nerve (CN IX). These cranial nerves carry parasympathetic signals from the brainstem which cause an increase in watery and enzyme-rich secretions from the salivary glands. We haven't talked a lot about anatomy of the sympathetic nervous system in this course, but the cell bodies of the preganglionic sympathetic neurons that control salivary glands are located in the upper thoracic regions of the spinal cord gray matter. The preganglionic axons synapse in a sympathetic ganglion in the neck, and the postganglionic sympathetic axons then travel along blood vessels to reach their target cells in the salivary glands.
Which of the GI hormones released from enteroendocrine cells increases the secretion of bicarbonate from the pancreas and inhibits gastric secretions (in the stomach)?
Secretin Secretin is released from the enteroendocrine cells of the small intestine when acidic chyme is detected in the lumen. Secretin inhibits gastric secretions (from stomach) and increases the secretion of bicarbonate from the pancreas.
Which GI hormone is known as "nature's antacid"?
Secretin is known as "nature's antacid" because it stimulates the release of bicarbonate ions from duct cells in the pancreas in response to acidic chyme in the small intestine.
Secretions from the liver, gall bladder and pancreas are delivered to which organ?
Small intestine. Secretions from the liver, pancreas and gall bladder are delivered to the duodenum, the first part of the small intestine.
The pharynx contains skeletal muscle in its wall and is involved in
Swallowing The pharynx is a muscular tube that conveys food from the nasal and oral cavities to the esophagus. The pharynx has skeletal muscle in its walls and is involved in the process of swallowing - a voluntary propulsive mechanism that propels food into the esophagus.
Which of the following best describes the capillary wall structure found in the liver lobules?
The capillary walls have openings that allow large proteins and small cells to pass through. The capillaries in the lobules of the liver are of the sinusoidal type. Sinusoidal capillaries are the "leakiest" type of capillary. This means that the capillaries have large openings in their wall that allow large proteins and even blood cells to pass, permitting the liver to perform its functions.
What are liver cells called?
The cells of the liver that process nutrients and produce bile are called hepatocytes.
What do chief cells secrete?
The chief cells of the gastric gland secrete pepsinogen, the inactive form of the enzyme pepsin. The pepsinogen is converted to the active enzyme pepsin in the acidic environment of the stomach.
What structural modification of the small intestine slows the movement of chyme through the lumen?
The circular folds (also called plicae circulares) of the small intestine help slow the progress of food through the intestine so that it can be digested and absorbed more effectively. These folds also increase surface area and help mix chyme.
Which part of the small intestine is at greatest risk for acid damage?
The duodenum is the first section of the small intestine, so it receives the acidic chyme from the stomach. Because of this, it is the area of the small intestine most vulnerable to acid damage. Recall that the duodenum is the area of the small intestine that receives the digestive enzymes and bicarbonate secretions from the pancreas. The bicarbonate helps neutralize the acidic chyme coming from the stomach.
What is the function of the gall bladder?
The gall bladder stores and concentrates bile. The gallbladder is a storage sac for excess bile. Bile made in the liver travels to the small intestine via the bile ducts. If the small intestine doesn't need it, the bile travels into the gallbladder, where it awaits the signal from the duodenum that food is present. In the small intestine, bile helps to emulsify lipids, which means that it prevents them from aggregating into large clumps which they would normally do due to their hydrophobic nature. The presence of bile helps to separate the lipids from each other so that the lipases (enzymes that break down fats) can do their job.
What is the role of the gall bladder?
The gall bladder stores and concentrates bile. The hepatocytes of the liver produce bile almost continuously, and the bile travels from the liver through first the hepatic ducts and then the common bile duct. If the duodenum does not need bile (it is not ready to digest fats), the hepatopancreatic sphincter will be closed and bile will back up into the common bile duct to the cystic duct that leads to the gall bladder. Bile will be stored (and concentrated) until it is needed. In response to fatty chyme in the duodenum, enteroendocrine cells of the small intestine will secrete the hormone CCK (cholecystokinin), which does several things. CCK will cause contraction of the gall bladder so it releases its bile, stimulate secretion of digestive enzymes from the acinar cells of the exocrine pancreas, and will relax the hepatopancreatic sphincter to allow secretions from both the pancreatic duct and bile duct into the duodenum.
What is the name of the sphincter that controls whether digestive enzymes or bile can enter the duodenum?
The hepatopancreatic sphincter (also called Sphincter of Oddi) controls whether the secretions from the liver, gall bladder and pancreas can enter the duodenum. The GI hormone CCK causes relaxation of this sphincter.
Which sphincter prevents backwards flow (reflux) from the large intestine into the small intestine?
The ileocecal sphincter prevents reflux of chyme from the large intestine (cecum) to the small intestine (ileum).
Which part of the small intestine delivers chyme to the large intestine?
The ileum is the last part of the small intestine, which joins the first part of the large intestine, the cecum at the ileocecal junction.
What is the name of the structure that anchors the small intestine to the posterior abdominal wall?
The mesentery is a peritoneal reflection that suspends the small intestine from the posterior abdominal wall. Between the two layers of peritoneum that form the mesentery are collections of fat, and blood vessels, lymphatics and nerves that supply the wall of the small intestine.
Which layer of the stomach contains the gastric pits that secrete mucous, acid, and digestive enzymes?
The mucosa of the stomach contains the epithelial lining and the gastric pits, which extend down into the mucosa but do not penetrate the submucosa.
What is true about the muscularis externa in the esophagus?
The muscularis externa has skeletal muscle in the upper regions of the esophagus, and smooth muscle in the lower regions. The muscularis externa is made of skeletal muscle in the upper 1/3 of the esophagus, smooth muscle in the lower 1/3, and is mixed in the middle 1/3 of the esophagus. The pharynx, which is involved in swallowing, has skeletal muscle in its walls. The skeletal muscle in the upper portion of the esophagus allows the swallowing action to continue into the upper part of the esophagus.
What is TRUE regarding the characteristic features of the wall of the large intestine?
The outer layer of longitudinal smooth muscle is incomplete in the muscularis externa. In the muscularis externa of the large intestine, the outer longitudinal layer of smooth muscle is incomplete, which results in the formation of 3 longitudinal strips of smooth muscle that can be seen on the outer surface of the large intestine. This longitudinal strips are called the teniae coli.
Which of the following would be more likely to increase digestive system function?
The parasympathetic nervous system is known as the "Rest and Digest" system. It tends to support general housekeeping functions of the body organs, compared to the sympathetic nervous system which stimulates activity in organs needed in emergency situations (Fight & Fright).
Which statement describes the gastric phase of stomach (gastric) activity?
The presence of food in the lumen of the stomach increases gastrin secretion and gastric motility. The gastric phase of stomach or gastric activity begins when food enters the stomach. Distension (stretch) of the stomach wall and the presence of food chemicals in the lumen of the stomach increase gastric motility and gastric secretions. Gastric secretions include the release of the hormone gastrin into the blood (from enteroendocrine cells), release of acid (HCl) from parietal cells, and release of pepsinogen from chief cells.
Which area of the stomach empties into the small intestine?
The pylorus is the lowest part of the stomach. It attaches to and empties food into the small intestine via the pyloric sphincter.
Which is the largest lobe of the liver?
The right lobe is the largest lobe of the liver.
Where does the majority of digestion and absorption occur in the gastrointestinal tract?
The small intestine is responsible for the majority of chemical digestion and the absorption of nutrients.
Which organ of the digestive tract is the body's major digestive organ?
The small intestine is the major digestive organ because it is the site of the majority of enzymatic digestion and absorption of nutrients.
What is the name of the temporary folds in the wall of the stomach that allow the stomach to expand more than 10 times its size in order to accommodate large meals?
The temporary folds in the stomach are called rugae. They allow the stomach to expand greatly in size to accommodate large meals.
Which layers make up the mucosa of a GI tract organ?
The three layers of the mucosa are the epithelium, lamina propria, and muscularis mucosae. You will find that the features of these layers change in different organs of the GI tract.
The __________ is the serous membrane that covers most digestive organs.
The visceral peritoneum covers the external surfaces of most digestive organs and is continuous with the parietal peritoneum that lines the body wall.
From the esophagus to the anus, the walls of the alimentary canal have the same four basic tunics. The __________ is the outermost layer of the walls of the intraperitoneal organs.
The visceral peritoneum, or serosa, forms the outermost layer (tunic) along most of the alimentary canal. In the esophagus, which is located in the thoracic instead of the abdominopelvic cavity, the serosa is replaced by an adventitia (dense connective tissue). Retroperitoneal organs have both an adventitia (on the side facing the dorsal body wall) and a serosa (on the side facing the peritoneal cavity).
All of the following statement are true about enteroendocrine cells EXCEPT:
They release their products into the lumen of the GI tract. Enteroendocrine cells DO NOT release their contents into the lumen of the GI tract. If they did, the products, which are peptide hormones would be digested. Enteroendocrine cells release the GI hormones which help regulate digestion. Enteroendocrine cells "sense" the environment in the lumen of the GI tract, and when they detect the presence of food particles, fat, proteins or even acidic chyme, they release their contents. (Different enteroendocrine cells respond to different stimuli). Enteroendocrine cells release their hormones into the lamina propria where the hormones then enter the blood capillaries for circulation through the bloodstream.
All of the following statements correctly describe surface mucous cells in the epithelium of the stomach EXCEPT:
They secrete stomach acid (HCl) The stomach mucosa is exposed to some of the harshest conditions in the entire digestive tract, but the stomach epithelium protects the underlying layers by producing a mucosal barrier. The features of this mucosal barrier include a thick coating of bicarbonate rich mucus secreted by the surface epithelial cells, tight junctions between epithelial cells and quick replacement of damaged epithelial cells by rapidly dividing undifferentiated stem cells.
Which statement describes glycolysis?
This process splits glucose in half and produces 2 ATPs for each glucose. In glycolysis, glucose is split into two molecules of pyruvic acid. The released energy is stored in ATP and the electron carrier NADH.
Which statement describes the electron transport chain?
This process uses energy captured from electrons flowing to oxygen to produce most of the ATPs in cellular respiration. In the electron transport chain, electrons move from one electron carrier to another, eventually reaching oxygen. The released energy is used to make ATPs. Return to Assignment
What is the job of the esophagus?
To transmit food from the pharynx to the stomach. The esophagus transmits the food bolus from the pharynx to the stomach by the action of peristalsis, wave-like muscle contractions that propels the food bolus forward.
What are the finger-like projections of mucosa in the small intestine that help increase the surface area for absorption?
Villi (villus, singular) are the finger-like projections of mucosa that are covering the surface of the plicae circulares in the small intestine.
Which of the following is the primary physiological function of the large intestine?
Water absorption and feces elimination are the primary physiological functions of the large intestine. The large intestine also provides a transport route and a surface for healthful bacteria.
Salivation is controlled almost entirely by the nervous system. Which of the following stimuli would decrease salivation?
Yes, fear, sleep, fatigue and dehydration all decrease salivation by way of the sympathetic nervous system. Sympathetic nervous system activity can stimulate the release of low volumes of mucus-rich saliva, which makes the mouth feel dry. In addition, strong activation of the sympathetic nervous system inhibits salivation by constricting blood vessels to the salivary glands. Dehydration inhibits salivation because of low blood volume. Things that increase salivation are the thought, sight and smell of food, acidic substances, nausea & intestinal irritation, and the parasympathetic nervous system.
Which of the following constitute a portal triad?
a bile duct along with a portal venule and arteriole A bile duct along with a portal venule (branch of hepatic portal vein) and arteriole (branch of hepatic artery) constitute a portal triad. The blood vessels bring blood into to the hepatic lobule and the bile duct carries bile away from the lobule (on its way to the gall bladder or duodenum by way of the bile duct system).
Which of these best describes a lacteal?
a lymphatic vessel designed to help introduce fats to the blood Lacteals are lymphatic vessels located in the intestinal villi. Their ability to accept large materials makes them helpful in transporting large fat particles (called chylomicrons) into the lymph and eventually the bloodstream.
What are the two compounds that the screencast mentions that are the only two compounds absorbed from the stomach?
alcohol and asprin The screencast mentions that alcohol and aspirin are the only two compounds that are absorbed in the stomach. This statement is not 100% accurate. What is true is that while very few substances are absorbed in the stomach, certain lipid-soluble compounds such as aspirin, other non-steroidal anti-inflammatory drugs, and alcohol are among those that are. These substances can also cause gastric irritation and their overuse can result in gastritis and gastric ulcers.
Which of these structures is found in the stomach but nowhere else in the alimentary canal?
an oblique muscle layer All areas of the alimentary canal have a circular and a longitudinal layer of muscle. The stomach has an additional oblique layer of muscle for "wringing" itself while processing food.
In order for dietary nutrients to be absorbed by the epithelial cells of the small intestine, the nutrients must be broken down into their chemical building blocks, or monomers. Which one of the following is INCORRECTLY matched with its chemical monomer?
carbohydrates: amylase Carbohydrates are chains of individual monosaccharides. Amylase is the enzyme that breaks down starch and glycogen into smaller pieces called oligosaccharides and disaccharides. Brush border enzymes break oligo- and disaccharides into monosaccharides, which are the monomers or chemical building blocks of sugars. In the case of starch and glycogen, the individual monomer is glucose. Recall that starch and glycogen are polysaccharides (poly = many; saccharides = sugars). Starch is the storage form of glucose in plant tissues, and glycogen is the storage form of glucose in animal tissues.
Which of the following lists the sections of the large intestine in the correct order?
cecum, ascending colon, transverse colon, descending colon The sections of the large intestine are: cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal
What is the primary purpose of the small intestine?
chemical digestion and absorption of nutrients The small intestine finishes the chemical digestion process and is responsible for absorbing most of the nutrients and a large percentage of the water and electrolytes. The breakdown products of proteins and carbohydrates (amino acids and sugars) are absorbed by the blood capillaries that travel through the villi, while digestion products of fats are absorbed into the lacteals, which are the lymph capillaries in the villi.
Enteroendocrine cells of the small intestine secrete two GI hormones that are important in regulating the function of GI organs during digestion. What are these GI hormones?
cholecystokinin (CCK) and secretin The enteroendocrine cells of the small intestine secrete CCK and secretin. Recall that enteroendocrine cells are single cells in the epithelium of a GI tract organ that can "sense" the contents of the lumen. In the case of the small intestine, the enteroendocrine cells "sense" the acidic or fatty chyme (also with peptides) coming from the stomach, which stimulates the cells to secrete CCK and secretin.
Glycolysis is best defined as a catabolic reaction based upon the ________.
conversion of glucose into two molecules of pyruvic acid
Secretions from the liver, gall bladder and pancreas are delivered to which part of the small intestine?
duodenum Bile from the gall bladder and liver, and digestive enzymes and bicarbonate from the pancreas, enter the duodenum where the common bile duct and pancreatic duct join together at the hepatopancreatic ampulla. A sphincter called the hepatopancreatic sphincter, or Sphincter of Oddi, controls the delivery of secretions to the duodenum.
Which part of the small intestine receives secretions from the liver, gall bladder and pancreas?
duodenum Secretions from the liver, gall bladder and pancreas enter the first part of the small intestine, the duodenum through a duct controlled by the hepatopancreatic sphincter, which is also called the Sphincter of Oddi.
Which of the following food groups are considered good sources of complete proteins?
eggs, milk, yogurt, meat, and fish
What serves as the energy source for the proton pumps in oxidative phosphorylation?
electrons passing from transfer molecules to oxygen (Electron Transport Chain) As electrons move through the electron transport chain from transfer molecules to oxygen, energy is released and used to form an H+ (proton) gradient across the membrane.
What is the name of the enzyme embedded in the microvilli (brush border) of the small intestine epithelial cells that is responsible for activating pancreatic proteases?
enteropeptidase (enterokinase) Enteropeptidase (which used to be called enterokinase) is the enzyme that is embedded in the brush border of the small intestine epithelial cells. Brush border is another name for the microvilli which are found on the apical border of the epithelial cells. Recall that the microvilli are one specialization of the small intestine that help to increase the surface area for absorption. Enteropeptidase converts trypsinogen to trypsin, and then trypsin activates the other pancreatic proteases. Chymotrypsinogen is converted to chymotrypsin and procarboxypeptidase is converted to carboxypeptidase. Trypsin can also convert more trypsinogen to trypsin. Proteases are released as inactive molecules so that they don't start working until they are needed to digest proteins in the chyme. There are also other enzymes embedded in the brush border: Peptidases break dipeptides and tripeptides down further into individual amino acids and disaccharidases break disaccharides into monosaccharides.
What is the name of the large peritoneal fold that contains fat and hangs off the greater curvature of the stomach?
greater omentum A large flap or fold of peritoneum hangs from the greater curvature of the stomach and contains fat, blood vessels and lymphatics. It is the first thing that can be seen when the abdomen is opened from the anterior side, and can provide some protection for the abdominal organs.
Which vessel delivers nutrient-rich blood to the liver from the digestive tract?
hepatic portal vein All blood from the digestive organs as well as the spleen is delivered to the liver in the hepatic portal vein before being returned to the general circulation. Note that there is a big difference between the "hepatic vein" and the "hepatic portal vein". Sometimes the hepatic portal vein is just called the "portal vein", but it is NEVER called the "hepatic vein". The hepatic portal vein brings nutrient-rich (but oxygen-poor) blood TO the liver, the hepatic veins carry oxygen-poor and nutrient-poor blood AWAY FROM the liver. Return to Assignment
What is produced by enteroendocrine cells?
hormones Enteroendocrine cells secrete hormones into the blood capillaries in the lamina propria of the mucosa. The hormones travel through the bloodstream and influence digestive processes throughout the GI tract. Recall that hormones are released into the blood supply and can travel throughout the body to affect any cells that have receptors for that particular hormone. In lecture, you will learn about the peptide hormones secreted by enteroendocrine cells in the stomach and small intestine and how they affect other digestive organs.
What is produced by parietal cells?
hydrochloric acid and intrinsic factor Parietal cells produce intrinsic factor and hydrochloric acid which decreases the effective pH of the stomach lumen. Recall from lecture that the parietal cells don't exactly "secrete" acid. Instead, they use a proton pump to pump H+ (protons) out of the cell, and the H+ combines with Cl- (chloride ion) to form hydrochloric acid.
How are chylomicrons transported from the intestinal villi?
in lymph capillaries called lacteals Once the free fatty acids and monoglycerides of fat digestion are absorbed into small intestine epithelial cells, the smooth ER converts them back to triglycerides. The triglycerides are then combined with other compounds to form water-soluble lipoprotein droplets called chylomicrons. Chylomicrons leave the epithelial cell by exocytosis. They are too large to cross the basal lamina of a blood capillary, so enter the more permeable lacteals, and enter the lymphatic stream for distribution in the lymph. Eventually the chylomicrons are emptied into the venous blood supply (like the rest of the lymph at the junction of the subclavian and internal jugular veins). In the blood, the triglycerides of the chylomicrons are hydrolyzed to free fatty acids and glycerol. The fatty acids and glycerol can then pass through the capillary walls to be used by tissue cells for energy or stored as fats in adipose tissue.
What are the endocrine hormones that are released from the endocrine pancreas?
insulin and glucagon The two hormones released from the endocrine pancreas are insulin and glucagon. These hormones are released from clusters of endocrine cells in the pancreas that are called the Islets of Langerhans. They are related to controlling blood glucose levels in the absorptive and postabsorptive states.
Which one of the sphincters that control defecation (elimination of feces) are under involuntary control (i.e. are controlled by the autonomic nervous system)?
internal anal sphincter The internal anal sphincter is made of smooth muscle and is controlled by the autonomic nervous system. The external anal sphincter is made of skeletal muscle and is controlled by somatic motor nerves (voluntary).
During which phase in the control of the digestive system would bicarbonate and bile be stimulated?
intestinal phase Yes, the arrival of food (chyme) in the small intestine initiates a reflex that stimulates secretions of bicarbonate, digestive enzymes and bile. This phase also decreases gastric emptying (slows it down), in order to prevent too much acidic chyme from entering the small intestine at once, and to allow time for digestion to occur in the small intestine.
Bile salts break up the fat globule into smaller fat droplets. This role of bile salts is best described as ________.
lipid emulsification
In the enteric nervous system, a long reflexive pathway has an advantage over a short reflexive pathway in the fact that ________.
long reflexive pathways can be stimulated by things outside of the GI tract
How would you classify chewing food?
mechanical breakdown Chewing breaks apart and grinds food and mixes it with saliva. Another word for chewing is "mastication". In ANPS19, we learned that the muscles of mastication (chewing muscles) are innervated by cranial nerve V, the trigeminal nerve. Other places where mechanical breakdown of food occurs is in the stomach (by the churning action of the 3 smooth muscle layers), and in the small intestine (through the back and forth movement called segmentation).
What is the brush border?
microvilli on epithelial cells of the small intestine Brush border is another name for the microvilli that line the apical surface of the small intestine enterocytes, or absorptive epithelial cells. Recall that the microvilli greatly increase the surface area for absorption in the small intestine (along with villi and plicae circulares). In addition, there are important enzymes embedded in the plasma membrane that help to finish digestion of dietary nutrients. Enteropeptidase (enterokinase) activates the protease trypsin, and dipeptidases and disaccharidases break dipeptides into amino acids, and disaccharides into monosaccharides, respectively.
Which two organs or parts of the digestive system can participate in the mechanical breakdown of food?
mouth and stomach Both the mouth and the stomach are involved in the mechanical breakdown of food, through the processes of physical disruption. (The small intestine is also, even though its not mentioned in this presentation). In the mouth, the teeth and the tongue are involved in physically tearing and manipulating the food to break it into smaller pieces. In the stomach, the churning and mixing action of the smooth muscle in the organ wall act to pummel the food, which physically breaks it down into smaller pieces. Some chemical digestion also occurs in the mouth (salivary glands) and stomach (pepsin, HCl acid). The pharynx is involved in swallowing, the esophagus delivers the food to the stomach, and the small intestine is responsible for chemical digestion, some mechanical digestion (because of segmentation) and absorption of nutrients. The large intestine is primarily involved in the absorption of water and elimination of feces.
Which layer of the alimentary canal or gastrointestinal tract can include either a stratified squamous or simple columnar epithelium?
mucosa The inner lining of the mucosa is composed of columnar epithelium for most of the alimentary canal (GI tract), however in areas that experience more abrasive forces, the epithelium is stratified squamous (esophagus, oral cavity, and anus).
What are the four layers that make up the wall of an organ in the gastrointestinal tract? List the layers in order starting with the layer closest to the food in the lumen of the GI tract.
mucosa, submucosa, muscularis externa, serosa (adventitia) The four layers that make up the wall of a typical organ in the gastrointestinal tract are, starting from the lumen, mucosa, submucosa muscularis externa and serosa (or adventitia). The mucosa can further be divided into the epithelium, lamina propria, and muscularis mucosae.
Which layer of the alimentary canal is responsible for segmentation and peristalsis?
muscularis externa Contractions of the circular and longitudinal layers of the muscularis externa produce the effects of peristalsis and segmentation. In the stomach, an additional muscle layer adds a twisting action.
Which nervous plexus is located between the layers of the muscularis externa?
myenteric plexus Recall that the prefix "myo" refers to muscle. The myenteric plexus is the nerve plexus located between the muscle layers of the muscularis externa.
Salivary gland secretions (saliva) are released into the ______________________.
oral cavity The major or extrinsic salivary glands (paired parotid, submandibular and sublingual glands) lie just outside the oral cavity and secrete their saliva through ducts into the oral cavity. Smaller intrinsic salivary glands are scattered throughout the oral cavity mucosa and also secrete a small amount of saliva.
Which of the following mechanisms produces the most ATP during cellular respiration?
oxidative phosphorylation
What is the (approximate) pH of the stomach (in the lumen)?
pH=2.0 The juices in the lumen of the stomach create a very acidic environment. The pH of the stomach contents can range from ~1.5 to 3.5 due to the HCl produced by the parietal cells. While most proteins (like digestive enzymes) are denatured in an acidic environment, pepsin, the enzyme that is active in the stomach works best in an acidic environment, and in fact requires a low pH for its activation. The acidity in the stomach also helps digest food by denaturing proteins and breaking down cell walls of plant foods, and helps to kill many of the bacteria that may be ingested with food.
Most of the digestive enzymes are secreted by which organ?
pancreas Most digestive enzymes are secreted by the exocrine portion of the pancreas and are delivered to the first part of the small intestine through the pancreatic duct. These include proteases, lipases, amylase and nucleases. Many of these enzymes are secreted in their inactive form, so are also called zymogens.
Which organ supplies most of the enzymes used in digestion?
pancreas The exocrine part of the pancreas produces and secretes most of the digestive enzymes.
All of the following are examples of pancreatic proteases except:
pancreatic amylase Pancreatic proteases consist of trypsin, chymotrypsin, and carboxypeptidase. Pancreatic amylase is not a protease. It is an amylase, which is an enzyme that digests (breaks down) starch and glycogen into smaller pieces called oligosaccharides and disaccharides. The term "pancreatic" means that these enzymes are released from the pancreas. The pancreatic digestive enzymes are delivered to the duodenum by way of the hepatopancreatic sphincter when they are needed.
What is the process by which food is propelled from the pharynx to the stomach?
peristalsis in esophagus The esophagus is a long muscular tube that delivers food from the pharynx to the stomach by the process of peristalsis. Peristalsis involves alternating waves of contraction and relaxation of muscles in the organ walls. Its main effect is to squeeze food along the tract. Peristaltic waves are so powerful, that once swallowed, food and fluids will reach your stomach even if you stand on your head.
What is the function of hepatocytes?
process substances from the blood, produce bile The basic function of the liver is to remove and add components to the blood as it circulates through the lobules. This task can be divided into three categories: secretion, storage and detoxification. The liver secretes proteins involved in blood coagulation and bile, which aids in the digestion of fats. The liver stores absorbed products of digestion such as carbohydrates, fats, vitamins and iron. The liver also detoxifies the blood by modifying hormones, drugs and alcohol to make them less toxic and more easily eliminated from the body.
Which of the following functions is NOT correctly matched with its description?
propulsion: physical breakdown of ingested food in the GI tract
Secretions of the large intestine epithelium are primarily responsible for
protection of the epithelium The large intestine secretes an alkaline mucus that protects the intestinal mucosa from acid released by resident bacteria. Mucus also eases the passage of feces and protects the mucosa from mechanical damage.
What is the correct substrate for proteases?
proteins or peptides The substrates for proteases are proteins or peptides. Substrates are the compound that an enzyme acts on to create an end product. In the case of protein digestion, proteins or peptides are the substrates, the enzymes are proteases, and the products are smaller peptides or individual amino acids.
What are the three major nutrients the body needs to function normally?
proteins, carbohydrates and fats Our body functions most efficiently when we are able to eat a well balanced diet that includes 5 types of nutrients. Three of these, proteins, carbohydrates and fats are known as macronutrients because they make up most of what we eat. Vitamins and minerals are also necessary in our diet - they are known as micronutrients because they are required in much smaller quantities than the macronutrients.
All of the following are functions of the salivary glands EXCEPT:
secretion of bile There is no bile secreted by salivary glands. Bile is produced by hepatocytes in the liver and is stored and concentrated by the gall bladder. Bile aids in the digestion of fats by emulsifying fats so that lipases can digest them more effectively.
What is the epithelium in most of the large intestine?
simple columnar (with goblet cells) The lining of the large intestine is simple columnar epithelium with goblet cells. The simple columnar epithelium is typical of the stomach, small intestine and large intestine, organs where absorption and secretion are occurring. In the case of the large intestine, the absorptive cells absorb excess water and the goblet cells secrete mucus.
Where does the process of segmentation occur?
small intestine Several areas of the digestive tract are capable of peristalsis, which propels food onward, but only the small intestine undergoes segmentation, whose purpose is mixing food with enzymes and bringing it close to intestinal walls.
Where is most of the water absorbed from the GI tract?
small intestine The absorption of most of the electrolytes and water occurs in the small intestine. Some additional water is absorbed in the large intestine, during the formation of the stool (feces). If water is not reabsorbed, diarrhea will result (and can result in dehydration).
What causes heartburn?
stomach acids backs up into the esophagus, causing irritation Heartburn is the burning sensation that can occur when stomach acid backs up into the esophagus. Heartburn is most likely when a person has eaten or drunk to excess, and in conditions that force abdominal contents superiorly, such as extreme obesity, pregnancy or running.
Which type of epithelium lines the esophagus?
stratified squamous The epithelium in the esophagus is stratified squamous, the protective type of epithelium because of the undigested food that must pass through the lumen. Note that the stratified squamous epithelium in the esophagus is NOT keratinized, compared to the keratinized stratified squamous epithelium that covers the surface of the skin. The skin is on the exterior of the body, so requires more protection compared to the lining of the esophagus, which is in the interior of the body.
Which layer of the alimentary canal contains not only glands and blood vessels but also a nerve plexus that helps regulate digestive activity?
submucosa The submucosa layer contains blood and lymphatic vessels, lymphoid follicles, and the submucosal plexus of nerve fibers. In some GI tract organs, the submucosa also contains glands (i.e. the mucus-secreting duodenal glands in the duodenum).
Which structures are part of the enteric nervous system?
submucosal plexus and myenteric plexus There are two named networks of neurons and nerve fibers located in the wall of the GI tract that communicate widely with one another to regulate and coordinate digestive system activity. This system is made up of over 100 million neurons and is called the enteric nervous system. The submucosal nerve plexus is located in the submucosa and the myenteric nerve plexus lies between the circular and longitudinal muscle layers of the muscularis externa.
What are the 3 longitudinal bands of smooth muscle that can be seen from the external surface of the large intestine?
teniae coli The 3 longitudinal bands of smooth muscle seen on the outside of the large intestine are called teniae coli. The resting muscle tone of these smooth muscle bands puckers the wall of the large intestine into pocketlike sacs called haustra (singular: haustrum).
Which cranial nerve controls digestive system function and releases ACh as the neurotransmitter from its postganglionic neurons?
vagus Recall that the vagus nerve is called "the wanderer" because of its widespread influence: it provides parasympathetic innervation to visceral organs in the thoracic cavity and most of the gastrointestinal tract. The lower portions of the colon and other pelvic viscera get their parasympathetic innervation from sacral spinal levels S2, S3 and S4.
Which of the following is the primary physiological function of the large intestine?
water absorption and feces elimination Though most water is absorbed in the small intestine, the absorption of most remaining water and the elimination of feces are the primary physiological functions of the large intestine. The large intestine also provides a transport route and a surface for healthful bacteria.