Chapter 9: The Digestive System

B (The question is basically asking us to identify the structure that lies between the stomach and the small intestine. This is the pyloric sphincter; the presentation given in the question is a classic example of what is called pyloric stenosis, in which the pyloric sphincter is thickened and cannot relax to permit chyme through. The cardiac sphincter, choice A, lies between the esophagus and the stomach. The ileocecal valve, choice C, lies between the ileum of the small intestine and the cecum of the large intestine. The internal anal sphincter, choice D, lies at the end of the rectum.)

A two-week old male infant is brought to the emergency room. His mother reports that he has been unable to keep any milk down; shortly after he nurses, he has sudden projectile vomiting. During exam, an olive-shaped mass can be felt in his upper abdomen. It is determined that there is a constriction in the digestive system that prevents food from reaching the small intestine from the stomach. What structure is most likely the site of the problem? A.) Cardiac sphincter B.) Pyloric sphincter C.) Ileocecal valve D.) Internal anal sphincter

liver (via the hepatic portal circulation)

Absorbed molecules by the small intestine are transported to what organ?

liver, gallbladder, duodenum

Bile is produced in the _______ and travels down bile ducts where it may be stored in the _______ or secreted into the _______.

cholesterol

Bile salts are derived from _______ and have both hydrophobic and hydrophilic regions, allowing them to serve as a bridge between aqueous and lipid environments.

conjugated

Bilirubin, from the breakdown of hemoglobin, travels to the liver where it is _______ (attached to a protein) and secreted into bile for excretion.

aminopeptidase, dipeptidase

Brush-border peptidases include ______, which removes the N-terminal amino acid from a peptide, and ______, which cleaves the peptide bonds of dipeptides to release free amino acids.

saliva, salivary glands

Chemical digestion in the oral cavity relies on enzymes from ______ produced by the three pairs of ______ ______. This also aids mechanical digestion by moistening and lubricating food.

peristalsis

Enteric neurons are present in the walls of the alimentary canal and trigger ______, or rhythmic contractions of the gut tube, in order to move materials through the system.

lower esophageal (cardiac) sphincter

Food enters the stomach through a muscular ring known as the ______ ______ ______, which relaxes and opens as a bolus approaches the stomach.

bolus

Food is formed into a(n) ______ by the tongue, which is then forced back to the pharynx and swallowed.

epiglottis

Food is prevented from entering the larynx during swallowing by the ______, a cartilaginous structure that folds down to cover the laryngeal inlet. Failure of this mechanism can lead to aspiration of food and choking.

pyloric sphincter

Food leaves the stomach through the ______ ______ and enters the duodenum.

vitamin K, biotin (vitamin B₇)

Gut bacteria produce ______ ______, which is essential for the production of clotting factors, and ______, which is a coenzyme for many metabolic enzymes.

bilirubin, jaundice

If the liver is unable to process or excrete ______ (from liver damage, excessive red blood cell destruction, or blockage of bile ducts), _______ or yellowing of the skin may occur.

mastication, enzymatic

In the oral cavity, ______ (chewing) starts the mechanical digestion of food. This helps to increase the surface area-to-volume ratio of the food, allowing for more surface area for ______ digestion as it passes through the gut tube. It also moderates the size of food particles entering the lumen of the alimentary canal; food particles that are too large create an obstructive risk in the tract.

salivary amylase (also known as ptyalin), lipase

In the oral cavity, ______ ______ is capable of hydrolyzing starch into smaller sugars (maltose and dextrins), while _______ catalyzes the hydrolysis of lipids to start the chemical digestion of food.

bile salts

In the small intestine, ______ ______emulsify fats and cholesterol into micelles. These micelles increase the surface area of the fats, increasing the rate at which pancreatic lipase can act.

methane gas, osmotic

Lack of a particular disaccharidase causes an inability to break down the corresponding disaccharide. Then bacteria in the intestines are able to hydrolyze that disaccharide, producing ______ ______ as a byproduct. In addition, undigested disaccharides can have a(n) ______ effect, pulling water into the stool and causing stool and diarrhea. This explains why people who are lactose intolerant have symptoms of bloating, flatulence, and possibly diarrhea after ingesting diary products.

salivary glands, pancreas, liver, gallbladder

List the accessory organs of digestion, which provide the enzymes and lubrication necessary to aid the digestion of food.

trypsin, chymotrypsin, carboxypeptidases (A and B)

List three pancreatic peptidases found in pancreatic juices that are released as zymogens, but once activated are responsible for protein digestion.

bicarbonate

Mucous cells produces a(n) ______-rich mucus to protect the stomach.

glucagon (secreted by the pancreas), ghrelin (secreted by the stomach and pancreas)

Multiple hormones regulate feeding behavior. List two that promote hunger.

leptin, cholecystokinin

Multiple hormones regulate feeding behavior. List two that promote satiety.

aldosterone, ADH (antidiuretic hormone, vasopressin)

Multiple hormones regulate feeding behavior. List two that promote thirst.

mucus (Disruption of mucus production within the stomach leaves the mucosa of the stomach unprotected, and irritation results. This irritation can be in the form of gastritis, inflammation of the mucosa of the stomach, or gastric ulcers, deep wounds in the surface of the stomach.)

Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen, and aspirin, are very common drugs. However, these drugs are not without side effects. What stomach secretion is disrupted and can cause gastritis or gastric ulcers?

pancreatic duct (Like all exocrine cells, acinar cells secrete their products into ducts.)

Pancreatic juices are transferred to the duodenum via the _______ _______ that runs along the middle of the pancreas.

pancreatic enzymes

Pancreatitis, or inflammation of the pancreas, is usually caused by gallstones or excessive consumption of alcohol. Regardless of the cause, pancreatitis results from premature activation of ______ ______ and autodigestion of the pancreatic tissue.

zymogen

Pepsinogen secreted by chief cells is the inactive ______ form of pepsin, a proteolytic enzyme.

smooth

Peristalsis refers to the rhythmic contraction of ______ muscle (such as that found at the bottom third of the esophagus) that propels food toward the stomach.

decreases, increases, increases

Secretin (DECREASES / INCREASES) HCl secretion from parietal cells, (DECREASES / INCREASES) bicarbonate secretion from the pancreas, and (DECREASES / INCREASES) the release of pancreatic enzymes into the duodenum.

enterogastrone

Secretin is a(n) _______, a hormone that slows motility through the digestive tract. Slowing of motility allows increased time for digestive enzymes to act on chyme, especially fats.

secondary active transport, facilitated diffusion, facilitated diffusion (which is possible because the blood always has a lower concentration of monosaccharides and amino acids than the epithelial cells)

Simple sugars, such as glucose, fructose, and galactose, and amino acids are absorbed by ______ ______ ______ and ______ ______ into the epithelial cells lining the small intestine, as shown in the figure. Then these substances move across the epithelial cells into the intestinal capillaries by ______ ______.

B (Starch is hydrolyzed to maltose by two enzymes: salivary amylase (secreted by the salivary glands) in the mouth and pancreatic amylase (secreted by the pancreas) in the duodenum. Brush-border disaccharidases can further break down maltose, but do not break down starch.)

Starch is hydrolyzed into maltose by enzymes from the: I. salivary glands. II. brush border. III. pancreas. A.) I only B.) I and III only C.) II and III only D.) I, II, and III

chylomicrons, lacteals, thoracic duct

Summary of Lipid Absorption: Larger triglycerides and esterified cholesterol molecules are packaged into _______. Rather than entering the bloodstream, they enter the lymphatic circulation through ______, small vessels that form the beginning of the lymphatic system. These vessels converge and enter the venous circulation through the ______ ______ in the base of the neck, which empties into the left subclavian vein.

upper esophageal sphincter

Swallowing is initiated in the skeletal muscles of the oropharynx, which constitute the ______ ______ ______--a barrier between the esophagus and the pharynx that intermittently opens and closes to allow passage of contents during various physiological events.

alimentary canal, sphincters

The ______ ______ runs from the mouth to the anus and is sectioned off by ______, or circular smooth muscles around the passage that can contract to allow compartmentalization of function (e.g. digestion, absorption).

pyloric, gastrin

The ______ glands contain G-cells that secrete ______, a peptide hormone that induces the parietal cells in the stomach to secrete more HCl and signals the stomach to contract, mixing its contents.

stomach

The ______ is a highly muscular organ located in the upper left quadrant of the abdominal cavity under the diaphragm with a capacity of approximately two liters.

esophagus

The ______ is a muscular tube that propels food from the pharynx to the stomach using peristalsis.

liver

The ______ is located in the upper right quadrant of the abdomen. Its functions include processing of nutrients (glycogenesis, glycogenolysis, storage and mobilization of fats, gluconeogenesis), production of urea, detoxification of chemicals, production of bile, and synthesis of albumin and clotting factors.

gallbladder

The ______ is located just beneath the liver and both stores and concentrates bile.

pharynx

The ______ is the cavity that leads from the mouth and posterior nasal cavity to both the esophagus and larynx.

rectum

The ______ serves as a storage site for feces, which are then excreted through the anus. This consists of indigestible material, water, bacteria (E.coli and others), and certain digestive secretions that are not reabsorbed (enzymes and some bile).

appendix (Inflammation of the appendix, or appendicitis, is a surgical emergency; in fact, it is the most common reason for an unscheduled surgery in the United States.)

The _______ is a small fingerlike projection that connects to the large intestine at the cecum. It was once thought to be vestigial, although recent evidence suggests that it may have a role in warding off certain bacterial infections and repopulating the large intestine with normal flora after episodes of diarrhea.

enteric

The _______ nervous system is a collection of one hundred million neurons that govern the function of the gastrointestinal system.

endoderm (As outgrowths of the gut tube, the accessory organs of digestion arise from embryonic endoderm.)

The accessory organs of digestion (liver, gallbladder, pancreas) originate from which primary germ layer?

up (Secretions from all of the glands of the digestive system are increased and peristalsis is promoted. In contrast, the enteric nervous system is downregulated by the sympathetic nervous system and peristalsis is slowed.)

The activity of the enteric nervous system is (DOWN / UP)-regulated by the parasympathetic nervous system.

pyloric

The antrum and pylorus of the stomach contain mostly ______ glands.

A (The top third of the esophagus is composed of skeletal muscle, the bottom third is composed of smooth muscle, and the middle third is a mix of both.)

The bottom third of the esophagus is composed of: A.) smooth muscle. B.) skeletal muscle. C.) cardiac muscle. D.) Both A and B

C (The top third of the esophagus is composed of skeletal muscle, the bottom third is composed of smooth muscle, and the middle third is a mix of both. In terms of nervous control, this means the bottom of the esophagus is under autonomic (involuntary) nervous control, making choice C the correct respond. In contrast, the top of the esophagus is under somatic (voluntary) motor control.)

The bottom third of the esophagus is under control by the ______ nervous system. A.) central B.) somatic C.) autonomic D.) Both B and C

ileocecal valve, appendix

The cecum is an outpocketing of the large intestine that accepts fluid from the small intestine through the ______ ______ and is the site of attachment of the _______.

ascending, transverse, descending, sigmoid

The colon is divided into the ______, ______, ______, and ______ colons. Its main function is to absorb water and salts (such as sodium chloride) from the undigested material left over from the small intestine.

somatic (voluntary; not to be confused with the internal sphincter which is under autonomic control)

The external anal sphincter is under ______ control

gastric

The fundus and body of the stomach contain mostly ______ glands.

vagus nerve

The gastric glands of the stomach respond to signals from the ______ ______ of the parasympathetic nervous system, which is activated by the brain in response to the sight, taste, and smell of food.

autonomic (involuntary; not to be confused with the external sphincter which is under somatic control)

The internal anal sphincter is under ______ control.

lesser curvature, greater curvature

The internal curvature of the stomach is called the ______ ______ (red); the external curvature is called the ______ ______ (blue).

cecum, colon, rectum

The large intestine is divided into three major sections: the _______, the _______, and the _______.

B (The duodenum is primarily involved in digestion, choice A. The jejunum and ileum are involved in the absorption of nutrients, choice C. Protein synthesis, choice D, occurs in many organs but largely the liver. The large intestine primarily absorbs water, making choice B the correct response.)

The large intestine is primarily concerned with... A.) Digestion B.) Absorption of water C.) Absorption of nutrients D.) Synthesis of protein

rugae

The lining of the stomach is thrown into folds called ______.

urea

The liver detoxifies both endogenous and exogenous compounds. For example, it modifies ammonia, a toxic waste product of amino acid metabolism to _______, which can be excreted by the kidneys. It also detoxifies and metabolizes alcohol and medications.

albumin, clotting factors

The liver is responsible for the synthesis of ______, a protein that maintains plasma oncotic pressure and also serves as a carrier for many drugs and hormones, as well as ______ ______ used during blood coagulation.

gluconeogenesis, lipoproteins

The liver mobilizes stored energy by producing glucose for the rest of the body through glycogenolysis and _______ while also mobilizing fats in _______.

hepatic portal vein

The liver receives all blood draining from the abdominal portion of the digestive tract through the ______ ______ ______. This nutrient-rich blood can be processed by the liver before draining into the inferior vena cava on its way to the right side of the heart.

glycogen, triacylglycerols

The liver takes up excess sugar from blood flowing through the hepatic portal vein to create ______ and stores fats as ______.

bilirubin

The major pigment in bile is ______, which is a byproduct of the breakdown of hemoglobin.

chyme

The mechanical and chemical digestion of solid food in the stomach results in an acidic, semifluid mixture known as _______.

bile, micelles, lipase

The mechanical digestion of fats depends on _______, which gets the fats into the solution and increases their surface area by placing them in ______. Then chemical digestion of lipids is achieved by _______, which hydrolyzes the ester bonds holding them together.

capillary bed, lacteal

The middle of each villus contains both a(n) ______ ______ for the absorption of water-soluble nutrients (monosaccharides, amino acids, small fatty acids, water-soluble vitamins) and a(n) ______ for the transport of fats, cholesterol, and fat-soluble vitamins into the lymphatic system.

duodenal papillae

The pancreatic duct empties into the duodenum through the major (red)and minor (blue) ______ ______.

nasopharynx, oropharynx, laryngopharynx

The pharynx can be divided into three parts: the ______ (behind the nasal cavity), the ______ (at the back of the mouth), and the ______ (above the vocal cords).

villi, microvilli

The small intestine is lined with _______ (small fingerlike projections from the epithelial lining), which are covered with _______, increasing the surface area available for absorption.

duodenum, jejunum, ileum

The small intestine is quite long, up to seven meters. It consists of three segments: the ______, the ______, and the ______.

fundus, body, antrum, pylorus

The stomach can be divided into four main anatomical divisions: the ______ (1) and ______ (2), which contain mostly gastric glands, and the ______ (3) and ______ (4), which contain mostly pyloric glands.

B (The top third of the esophagus is composed of skeletal muscle, the bottom third is composed of smooth muscle, and the middle third is a mix of both.)

The top third of the esophagus is composed of: A.) smooth muscle. B.) skeletal muscle. C.) cardiac muscle. D.) Both A and B

B (The top third of the esophagus is composed of skeletal muscle, the bottom third is composed of smooth muscle, and the middle third is a mix of both. In terms of nervous control, this means the top of the esophagus is under somatic (voluntary) motor control, making choice B the correct response. While the bottom--and most of the gastrointestinal tract, for that matter--is under autonomic (involuntary) nervous control.)

The top third of the esophagus is under control by the ______ nervous system. A.) central B.) somatic C.) autonomic D.) Both B and C

B (The first graph shows maximal activity at a very acidic pH, implying that this is an enzyme acting in the stomach. The second graph shows maximal activity around pH 8.5, implying that this is an enzyme acting in the duodenum. The only choice that matches the first graph with a stomach enzyme (pepsin) and the second with a duodenal enzyme (carboxy-peptidase) is choice B.)

The two graphs show the relative activities of two enzymes in solution of varying pH. Which of the following choices correctly identifies the two enzyme? A.) 1 = chymotrypsin; 2 = pepsin B.) 1 = pepsin; 2 = carboxypeptidase B C.) 1 = lactase; 2 = aminopeptidase D.) 1 = enteropeptidase; 2 = amylase

oral cavity (mouth), pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus

Trace the path of food though the body, starting with ingestion and ending with excretion of feces.

True (Because pepsin is activated by the acidic environment of hydrogen ions in the stomach, it follows that pepsin is most active at a pH of 2. This is a unique characteristic among human enzymes, as most human enzymes are most active at physiological pH.)

True of False: Pepsin is most active at a low pH.

False (Salivary glands are an exception because they are innervated by the sympathetic nervous system. Otherwise, all glands (especially those in the digestive tract) are innervated by the parasympathetic nervous system.)

True or False: All of the glands of the body are innervated by the parasympathetic nervous system.

False (Bile salts are not enzymes and therefore do not directly perform chemical digestion (the enzymatic cleavage of chemical bonds). However, bile salts serve an important role in the mechanical digestion of fats and ultimately facilitate the chemical digestion of lipids.)

True or False: Bile salts act as enzymes.

True (Celiac disease results from an immune reaction against gluten, a protein found in grains, especially wheat. In this condition, the immune system develops antibodies against certain components of gluten. These antibodies then cross-react with elements of the small intestine, causing damage to the mucosa. This results in diarrhea and discomfort. Sometimes, this condition also results in malabsorptive syndromes, including the inability to absorb fat and fat-soluble vitamins. Contrary to popular belief, celiac disease and gluten sensitivity are immune responses,but are not true allergies.)

True or False: Celiac disease and gluten sensitivity are immune responses but are not true allergies.

True (This contrasts carbohydrates, which must be broken down into monosaccharides for absorption.)

True or False: Di- and tripeptides can be absorbed across the small intestine wall.

True (This is because fat-soluble vitamins (A, D, E, K) dissolve directly into chylomicrons to enter the body. In contrast, the water-soluble vitamins (B complex and C) are absorbed along with water, amino acids, and carbohydrates, across the endothelial cells of the small intestine, passing directly into the plasma.)

True or False: Failure to digest and absorb fat properly may lead to deficiencies of vitamin A, D, E, or K but does not affect B complex and C vitamins.

True (Thus, digestion that occurs prior to the entrance of the bolus into the stomach is minimal compared to the digestion that occurs in the stomach and small intestine.)

True or False: No mechanical or chemical digestion takes place in the esophagus, except for the continued enzymatic activity initiated in the mouth by salivary enzymes.

True (One is active in the mouth and the other in the small intestine, but both function to digest carbohydrates.)

True or False: Salivary amylase and pancreatic amylase have the same function.

True (These fatty acids do not require transporters because they are nonpolar, so they can easily traverse the cellular membrane. Larger fats, glycerol, and cholesterol move separately into the intestinal cells but then reform into triglycerides.)

True or False: The absorption of small fatty acids in the small intestine follows the same process as carbohydrates and amino acid by diffusing directly into the intestinal capillaries.

False (The alimentary canal is the whole passage along which food passes through the body from mouth to anus. This is technically "outside" the body, as it is outside the cell borders. It is the site of extracellular digestion.)

True or False: The alimentary canal is the site of intracellular digestion.

False (The duodenum is responsible for the majority of chemical digestion and has some minor involvement in absorption. Most of the absorption in the small intestine actually takes place in the jejunum and ileum.)

True or False: The duodenum segment of the small intestine is responsible for the majority of absorption.

False (This system can function independently of the brain and spinal cord, although it is heavily regulated by the autonomic nervous system.)

True or False: The enteric nervous system cannot function independently of the brain AND spinal cord.

False (The large intestine has a larger diameter but shorter length than the small intestine.)

True or False: The large intestine is longer than the small intestine.

False (In addition to nutrients, the small intestine also absorbs water. Much of the water in chyme is actually the result of secretions. The average person may consume up to two liters of fluid per day, but secretions into the upper gastrointestinal tract may total up to seven liters of fluid per day. In order to maintain proper fluid levels within the body, much of this fluid must be reabsorbed by osmosis. As solutes are absorbed into the bloodstream, water is drawn with it, eventually reaching the capillaries.)

True or False: The small intestine is not involved in water absorption.

True (There are a few substances that are absorbed directly from the stomach, such as alcohol and aspirin, but the stomach is mainly an organ of digestion. The mechanical and digestive activities of the stomach actually maximize the absorption of nutrients in the small intestine by increasing the surface area of food particles.)

True or False: The stomach is primarily an organ of digestion.

emesis

Under normal circumstances, peristalsis proceeds down the digestive tract. However, certain conditions, such as exposure to chemicals, infectious agents, physical stimulation in the posterior pharynx, and even cognitive stimulation, can lead to reversal of peristalsis in the process of ______ (vomiting).

biliary tree

Upon release of cholecystokinin (CCK), the gallbladder contracts and pushes bile into the ______ ______. The bile duct system merges with the pancreatic duct before emptying into the duodenum.

small intestine (While the large intestine's main function is to absorb water, the small intestine actually absorbs a much larger volume of water. Thus, massive volumes of watery diarrhea are more likely to arise from infections in the small intestine than the large intestine.)

Vibrio cholera causes a severe infection in the intestines, leading to massive volumes of watery diarrhea--up to 20 liters per day. Given these symptoms, does cholera likely impact the small intestine or the large intestine?

lower esophageal sphincter, heartburn

Weakness in the ______ ______ ______ is a key feature of gastroesophageal reflux disease (GERD). As food and acid reflux down the esophagus, they irritate the less-protected mucosa, stimulating pain receptors. These receptors localize pain poorly, so a general burning sensation is felt in the lower chest lead to the classic symptom of ______ after eating.

bile salts (amphipathic molecules derived from cholesterol that emulsify fats), pigments (especially bilirubin from the breakdown of hemoglobin), cholesterol

What are the main components of bile?

parotid, submandibular, sublingual (NOTE that other microscopic salivary glands are scattered throughout the upper digestive system)

What are the three pairs of major salivary glands?

Brush-border enzymes (disaccharidases like maltase, isomaltase, lactase, and sucrase; peptidases including dipeptidase)

What class of enzymes are secreted in response to the presence of chyme in the duodenum?

Cholecystokinin (CCK)

What enzyme is secreted in response to the entry of amino acids and fat from chyme into the duodenum?

Acinar cells

What exocrine cells in the pancreas produce pancreatic juices that contain bicarbonate, pancreatic amylase, pancreatic peptidases (trypsinogen, chymotrypsinogen, carboxypeptidase A and B), and pancreatic lipase?

D (Pancreatic enzymes are active in the duodenum and work best at pH 8.5, making D the correct response. A pH of 2, choice A, is ideal for enzymes active in the stomach such as pepsin. Choice C, pH 7.4, is equal to physiological pH making it effective for the functioning of many enzymes.)

What pH would you expect pancreatic enzymes to be most active? A.) 2.0 B.) 5.0 C.) 7.4 D.) 8.5

G-cells (pyloric glands)

What secretory cell of the stomach secretes gastrin, a peptide hormone?

Parietal cells

What secretory cell of the stomach secretes hydrochloric acid which kills microbes, denatures proteins, and converts pepsinogen into pepsin?

Parietal cells

What secretory cell of the stomach secretes intrinsic factor which is required for normal absorption of vitamin B₁₂?

Chief cells

What secretory cell of the stomach secretes pepsinogen (the inactive zymogen of pepsin)?

Mucous cells

What secretory cell produces the bicarbonate-rich mucus that protects the muscular wall of the stomach from its harshly acidic (pH=2) and proteolytic environment?

D (Lipase is involved in the digestion of fats, but its function is not to emulsify fats--this is the job of bile. Rather, lipase chemically digests fats in the duodenum, allowing them to be brought into duodenal cells and packaged into chylomicrons. The other associations given here are all correct.)

Which of the following INCORRECTLY pairs a digestive hormone with its function? A.) Trypsin--hydrolyzes specific peptide bonds B.) Lactase--hydrolyzes lactose to glucose and galactose C.) Pancreatic amylase--hydrolyzes starch to maltose D.) Lipase--emulsifies fats

C (Protein digestion begins in the stomach, where pepsin (secreted as pepsinogen) hydrolyzes specific peptide bonds. Protein digestion continues in the small intestine as trypsin (secreted as trypsinogen), chymotrypsin (secreted as chymotrypsinogen), carboxypeptidases A and B (secreted as pro-carboxypeptidases A and B), aminopeptidase, and dipeptidases hydrolyze specific parts of the peptide. No proteins digestion occurs in the mouth or large intestine.)

Which of the following correctly lists two organs in which proteins are digested? A.) Mouth and stomach B.) Stomach and large intestine C.) Stomach and small intestine D.) Small intestine and large intestine

B (The salivary glands, like all glands of the digestive tract, are innervated by the parasympathetic nervous system. The presence of food in the oral cavity triggers a neural circuit that ultimately leads to increased parasympathetic stimulation of these glands. Salivation can also be triggered by signals that food is near, such as smell or sight, making choice B the correct response.)

Which of the following innervates the salivary glands by the parasympathetic nervous system? I. Smell of food II. Presence of food in the oral cavity III. Stress A.) II only B.) I and II only C.) II and III only D.) I, II, and III

C (Elevated bilirubin implies blockage to bile flow, increased production of bilirubin (from massive hemoglobin release), or an inability of the liver to produce bile. If the bile duct were occluded, as in choice A, then the bile would not be able to flow into the digestive tract and would build up, increasing bilirubin levels in the blood. If many red blood cells were lysed, as in choice B, then bilirubin levels would rise in accordance with the increased hemoglobin release. If liver failure occurred, as in choice D, then it would be unable to produce bile, and bilirubin would again build up. Choice C refers to a pathology in the stomach--the key word given here is rugae, which are the folds in the stomach wall. Lack of gastric function would have no effect on bilirubin levels, making this the correct choice.)

Which of the following would NOT likely lead to elevated levels of bilirubin in the blood? A.) Cholangiocarcinoma, a cancer of the bile ducts that can ultimately lead to full occlusion of the duct lumen B.) Autoimmune hemolytic anemia, a disease in which the red blood cells are attacked by antibodies and are lysed C.) Menetrier's disease, in which rugae thicken and overlying glands lose secretory ability D.) Acetaminophen (Tylenol) overdoes, in which the accumulation of toxic metabolites can cause rapid liver failure

small intestine (The colon primarily concentrates the remaining material to form feces. Too little or too much water absorption in the intestine or colon can cause diarrhea or constipation, respectively.)

Which organ absorbs more water: the small intestine or colon?

C (Stone formation is nothing more than precipitation of a solid once its concentration has reached the Ksp of the compound. This is particularly common in the gallbladder because bile is concentrated here. This painful conditions causes inflammation of the gallbladder. The stones may also travel into the bile ducts and get stuck in the biliary tree. In some cases, stones can get caught just before entering the duodenum, resulting in blockage of not only the biliary tree, but the pancreatic duct as well, causing pancreatitis.)

Which organ would you expect to be a common site of cholesterol or bilirubin stone formation? A.) Pancreas B.) Liver C.) Gallbladder D.) Duodenum

intestinal capillaries (Simple sugars and amino acids are absorbed by secondary active transport and facilitated diffusion into the epithelial cells lining the small intestine. Then, these substances move across the epithelial cells into the intestinal capillaries. Blood is constantly passing by the epithelial cells in the capillaries, carrying the carbohydrate and amino acid molecules away from the epithelial cells. This creates a concentration gradient such that the blood always has a LOWER concentration of monosaccharides and amino acids than inside the epithelial cells. Thus, simple carbohydrates and amino acids DIFFUSE from epithelial cells into the capillaries.)

Which would you expect to have a lower concentration of monosaccharides and amino acids: epithelial cells lining the small intestine or intestinal capillaries?

viscosity (This explains why "dry mouth" and even a tacky sensation in the mouth occurs during a fight-or-flight response.)

While the parasympathetic nervous system is responsible for promoting salivation, the sympathetic nervous system has some input into the glands as well. The SNS increases the ______ of saliva.

pancreatic lipase

Without bile, fats would spontaneously separate out of the aqueous mixture in the duodenum and would not be accessible to ______ _______, which is water soluble.

pancreas (The excess gastrin leads to excessive HCl production by parietal cells. Not surprisingly, one of the most common signs of Zollinger-Ellison syndrome is the presence of intractable ulcer disease.)

Zollinger-Ellison syndrome is a rare disease resulting from a gastrin-secreting tumor usually found in what organ?

Pancreatic juices

______ ______ are a complex mixture of several enzymes that digest all three types of nutrients (carbohydrates, fats, and proteins) in a bicarbonate-rich alkaline solution. This bicarbonate helps to neutralize acidic chyme, as well as provide an ideal working environment for each of the digestive enzymes, which are most active around pH 8.5.

Bile ducts

______ ______ connect the liver with both the gallbladder and small intestine.

Gastric juice

______ ______ is a combination of secretions from the chief cells (pepsinogen) and parietal cells (hydrochloric acid).

Intrinsic factor

______ ______ is a glycoprotein involved in the proper absorption of vitamin B₁₂. Parietal cells secrete this product in addition to HCl.

Enteropeptidase (formerly called enterokinase)

______ activates trypsinogen (from trypsin) and procarboxypeptidases A and B, initiating an activation cascade.

Extracellular

______ digestion describes the process by which nutrients are obtained from food and occurs within the lumen of the alimentary canal.

Intracellular

______ digestion involves the oxidation of glucose and fatty acids to make energy as a part of metabolism.

Chemical

______ digestion is the enzymatic cleavage of chemical bonds, such as the peptide bonds of proteins or the glycosidic bonds of starches.

Mechanical

______ digestion is the physical breakdown of large food particles into smaller food particles.

Digestion

______ involves the breakdown of food into its constituent organic molecules: starches and other carbohydrates into monosaccharides, lipids (fats) into free fatty acids and glycerol, and proteins into amino acids; it can be subdivided into mechanical and chemical processes.

Absorption

______ involves the transport of products of digestion from the digestive tract into the circulatory system for distribution to the body's tissues and cells.

hydrogen, hydrochloric acid

______ ions in the stomach, secreted by parietal cells as ______ ______, cleave pepsinogen to pepsin.

Cholecystokinin (CCK)

______ is a peptide hormone that stimulates bile release from the gallbladder, release of pancreatic juices, and satiety.

Brush-border enzymes

______-______ ______ are present on the luminal surface of cells lining the duodenum and break down dimers and trimers of biomolecules into absorbable monomers.

Disaccharidases

_______ are brush-border enzymes that break down maltose, isomaltose, lactose, and sucrose into monosaccharides.

Pepsin

_______ is an enzyme that partially digests proteins by cleaving peptide bonds near aromatic amino acids, resulting in short peptide fragments.

Secretin

_______ stimulates the release of pancreatic juices into the digestive tract and slows motility.