Chapter 22 The Digestive System
Name one organ of the alimentary canal found in the thorax. Name three organs located in the abdominal cavity.
The esophagus is found in the thorax. Three alimentary canal organs found in the abdominal cavity include the stomach, small intestine, and large intestine.
What is the usual site of ingestion?
The usual site of ingestion in a healthy person is the mouth.
Which essential digestive activity actually moves nutrients from the outside to the inside of the body?
The process of absorption moves nu¬trients into the body.
When sensors in the GI tract are stimulated, they respond via reflexes. What types of digestive activity may be put into motion via those reflexes?
Reflexes associated with the GI tract promote muscle contraction and secretion of digestive juices or hormones
The term ”gut brain” does not really mean there is a brain in the digestive system. What does it refer to?
The term "gut brain" refers to the enteric nervous system or web of neurons closely associated with the digestive organs.
How does the location of the visceral peritoneum differ from that of the parietal peritoneum?
The visceral peritoneum is the outermost layer of the digestive organ; the parietal peritoneum is the serous membrane covering the wall of the abdominal cavity.
Of the following organs, which is/are retroperitoneal? Stomach, pancreas, liver.
The pan¬creas is retroperitoneal
What name is given to the nervous portion of the splanchnic circulation?
The hepatic portal circulation is the venous portion of the splanchnic circulation.
Name the layers of the alimentary canal from the inside out.
From deep to superficial the lay¬ers of the alimentary canal are the mucosa, submucosa, muscularis ex¬terna, and serosa.
Jerry has been given a drug that inhibits parasympathetic stimulation of his digestive tract. Should he” eat hearty” or temporarily refrain from eating, and why?
He should temporarily refrain from eating because the parasympathetic nervous system oversees digestive activities.
How does the vestibule of the mouth differ from the oral cavity proper?
The vestibule is the region between the cheek and the teeth. The oral cavity proper is the area enclosed by the teeth.
What structure forms the roof of the mouth?
The palate forms the roof of the mouth. The hard palate supported by bone is anterior to the soft palate (no bony support).
Besides preparing food for swallowing, the tongue has another role. What is it?
The tongue is important for speech, partic¬ularly for uttering consonants, and taste.
What is the importance of the serous portion of saliva?
The serous portion of saliva is rich in salivary amylase, an enzyme that chemically breaks down starch. Additionally, the serous portion of saliva helps to hydrate the foodstuffs and helps provide protection against microorganisms.
Name four antimicrobial substances found in saliva.
Antimicrobial substances found in saliva include lysozyme, defensins, a cyanide compound, and IgA antibodies.
Seven-year-old Tina ran to her daddy to show him our lower central incisor which she had wiggled until it” fell out.” is this a primary or secondary tooth? What name is given to teat that (according to Tina) ball out?
Tina's "show and tell" tooth is a primary tooth, also called a deciduous tooth.
What tooth substance is harder than bone? Which tooth part includes nervous tissue and blood vessels?
Enamel is harder than bone. Pulp consists of nervous tissue and blood vessels.
Which teeth are the “ grinders”?
The molars are grinding teeth.
To what to organ systems does the pharynx belong?
The pharynx is part of the digestive and respiratory systems.
How is the muscular is externa of the esophagus unique in the body?
The esophageal mucularis externa undergoes a transformation along its length from skeletal muscle superiorly to smooth muscle near the stomach.
What is the functional significance of the epithelial change seen at the esophagus stomach-junction?
The esophagus is merely a chute for food passage and is subjected to a good deal of abrasion, which a strati¬fied squamous epithelium can withstand. The stomach mucosa is a secre¬tory mucosa served well by a simple columnar epithelium.
What role does the tongue play in swallowing?
The tongue mixes the chewed food with saliva and compacts the food into a bolus.
How are the respiratory passages blocked during swallowing?
During swallowing the larynx rises and the epiglottis covers its lumen so that foodstuffs are diverted into the esophagus posteriorly.
What structural modification of the stomach wall underlies the stomach’s ability to mechanically digest food?
The stomach has three layers of smooth muscle-s-longitudinal, circular, and oblique. Addition of the oblique layer allows the stomach to pummel food in addition to its peristaltic movements.
Two substances secreted by cells of the gastric glands are needed to produce the active protein digesting enzyme pepsin. What are these substances and what cells secrete them?
The chief cells produce pepsinogen, which is the inactive pepsin enzyme, and the parietal cells se¬crete HCl needed to activate pepsinogen.
What protective substances or activities make up the so-called mucosal barrier?
The mucosal barrier consists of the thick alkaline mucus secreted by the mucous cells, the fact that the epithelial cells of the mucosa are joined by tight junctions, and the quick replacement of dead or dying cells by stem cells.
Name the three phases of gastric secretion.
The three phases of gastric secretion are the cephalic, gastric, and intestinal phases.
How does the presence of food in the small intestine inhibit gastric secretion and motility?
The presence of food in the duodenum inhibits gastric activity by triggering the enterogastric reflex and the secretion of certain enterogastrones (hor¬mones).
How does the pH of venous blood leaving the stomach change during a meal?
Venous blood leaving the stomach during a meal becomes more alkaline due to the alkaline tide occurring during HCl secretion.
What common advantage do circular folds, villi, and microvillus provide to the digestive process? Which of these modifications causes chyme, to spiral through the lumen and slows its passage?
All of these modifications increase the surface area of the small in¬testine. The circular folds force the chyme to spiral through the lumen
What are brush border enzymes?
Brush border enzymes are enzymes associated with the microvilli of the small intestine mucosal cells.
What is a lacteal and what is its function?
A lacteal is a blind -ended lymphatic capillary that picks up lymph (fluid and proteins leaked from the blood¬stream), which is then returned to the blood.
Name three secretory products that help to protect the intestinal mucosa from bacterial damage.
19A, HCl, defensins, and lysozyme protect the intestinal cells from bacterial damage.
what is a portal triad?
A portal triad is a region at the corner of a hepatic lobule that contains a branch of the hepatic portal vein, a branch of the hepatic artery, and a bile duct.
What is the importance of the enterohepatic circulation?
The enterohepatic circulation is an important recycling mechanism for retaining bile salts needed for fat absorption.
What is the role of the Kupffer cells of the liver?
Kupffer cells are macrophages that rid the blood of bacteria and dead cells.
What is contained in zymogen granules?
Zymogen granules contain digestive enzymes.
Maryanne has pancreatitis and her pancreas is swollen and temporarily unable to produce pancreatic juice. What type of foodstuffs will probably not be digested until she recovers?
The pancreas is the only impor¬tant source of lipases, so fats will probably not be digested or absorbed duringher illness.
What is the functional difference between pancreatic acini and islets?
Pancreatic acini produce the exocrine products of the pancreas (digestive enzymes and bicarbonate-rich juice). The islets produce pancreatic hormones, most importantly insulin and glucagon.
What is the makeup of the fluid in the pancreatic duct? In the cystic duct? In the bile duct?
Fluid in the pancreatic duct is bicarbonate-rich, enzyme-rich pancre¬atic juice. Fluid in the cystic and bile ducts is bile.
What stimulates CCK release and what are its effects on the digestive process?
CCK is secreted in response to the entry of chyme rich in protein and fat into the duode¬num. It causes the pancreatic acini to secrete digestive enzymes and stimulates the gallbladder to contract.
Distention of the stomach and duodenal walls have different effects on stomach secretory activity. What are these effects?
Distension of stomach walls enhances stomach secretory activity. Distension of the walls of the small intestine reduces stomach secretory activity (to give the small intestine time to carry out its digestive and absorptive activities).
Which is more important in moving food along the small intestine- peristalsis or segmentation?
Segmentation is more important for moving food along the small intestine.
What is the MMC and why is it important?
MMC is the migrating motility complex, a pattern of peristalsis seen in the small intestine that moves the last remnants of a meal plus bacteria and other debris into the large intestine. MMC is important to prevent the over¬growth of bacteria in the small intestine.
What propulsive movements are unique to the large intestine?
Mass movements are unique to the large intestine. They are long, slow, powerful contractions that move over large areas of the colon three or fourtimes a day, forcing the contents toward the rectum.
What is the result of stimulation of stretch receptors in the rectal walls?
Activation of stretch receptors in the rectal wall initiates the defecation reflex.
In what ways are enteric bacteria important to our nutrition?
Enteric bacteria synthesize B vitamins and most of the vitamin K the liver needs to synthesize clotting proteins.
What type of chemical reaction is the basis of all enzymatic food digestion?
All food digestion depends on hydrolysis reactions
Fill in the blank: amylase is to starch as______ is to fats.
Amylase is to starch as lipase is to fats
What is the role of bile salts in the digestive process? In absorption?
Bile salts emulsify fats so that they can be acted on efficiently by lipase enzymes, and form micelles that aid fat absorption.