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Chapter 25 - The Digestive System
Terms in this set (120)
Name the major organs of the digestive system.
Mouth, Pharynx, Esophagus, Stomach, Small Intestine, Large Intestine, and Rectum
Name the accessory organs of the digestive system.
Liver, Gallbladder, Pancreas, and Salivary Glands
Where does the process of digestion begin?
What tools are found in the mouth?
Teeth, tongue, and jaw
What happens to food with chewing?
Food is broken down between the teeth and mixed with saliva
What is a digestive fluid?
What secrete saliva into the oral cavity?
What is the function of saliva?
Moistens food and tissues in the oral space, facilitates chewing and ingestion, and aids digestion of starches
What facilitates the passage of food bolus into the esophagus?
What is located between the pharynx and stomach?
Besides saliva, what else do salivary glands release?
Mucus for lubrication, antimicrobial agents, and amylase to digest starch
What covers respiratory tract during swallowing?
What is located at the end of the esophagus?
Lower esophageal sphincter (LES)
How does propulsion of food occur?
What is made up of contractions that occur behind the bolus of food and relaxation occurs ahead of the bolus of food?
Name the functions of the stomach.
Store food, initiate digestion of proteins, kill bacteria with the strong acidity, and make chyme
Name the major parts of the stomach
Fundus, body, and pyloric region
What is located in the pyloric region?
What is material passed from the stomach to the small intestine called?
What is located from the pyloric sphincter to the ileocecal valve?
How long is the small intestine?
How big is the diameter of the small intestine compared to the large intestine?
Where does 90% of digestion and absorption of food occur?
What is the major function of the small intestine?
Absorption of nutrients and minerals from food
Name the three regions of the small intestine
Duodenum, jejunum, and ileum
In what part of the small intestine does the absorption of carbohydrates, lipids, amino acids, calcium, and iron occur?
Duodenum and jejunum
In what part of the small intestine does the absorption of bile salts, vitamin B12, and water electrolytes occur?
What increase the area of absorption in the small intestine?
Villi and microvilli
What are found in the core of villi?
Blood capillaries and lymphatic vessels
Where do monosaccharides and amino acids go after they are absorbed?
Where do fats go after they are absorbed?
What cells are found in the walls of the small intestine?
Columnar epithelial cells
What is located between the ileocecal valve and the anus?
Name the parts of the large intestine
Ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anal canal
What cells are found in the large intestine?
Columnar epithelial cells, goblet cells, scattered lymphocytes, and lymphatic nodules
What organ contains no villi?
What organ is involved in absorption of water, electrolytes, and vitamins?
What organ contains bacteria that have a number of functions?
What organ is in charge of absorbing vitamins B and K?
What organ produces small fatty acids that are used as energy by GI epithelial cells?
What organ helps breakdown indigestible molecules?
What organ is connected to the gallbladder via the bile duct and then to the small intestine?
What organ contains sinusoidal capillaries which are permeable to most substances?
What circulation is from the liver via bile duct to the small intestine and then from small intestine back through portal vein to liver?
Name the major functions of the liver
Production and secretion of bile
Detoxification of blood
Secretion and storage of glucose
Production of albumin
What clears substances via the bile duct in similar manner to the way the kidney clears substances in the nephron?
What are the components of bile?
Bile pigment (bilirubin)
What component of bile removes hemoglobin breakdown products?
Bilirubin (bile pigment)
What component of bile aids in fat absorption?
What organ stores bile?
What controls the bile entering the gallbladder?
Sphincter of Odiid
What function of the pancreas involves secretion into blood?
What is secreted by the endocrine side of the pancreas?
Insulin and glucagon
What function of the pancreas involves secretion into the GI system?
What does pancreatic juice contain?
Water, bicarbonate, amylase, trypsin, and lipase
What part of the pancreatic juice digests starch?
What part of the pancreatic juice digests protein?
What part of the pancreatic juice digests fatty acids?
What are the three phases of digestion?
Cephalic, gastric, and intestinal
Which digestion phase occurs before food enters the stomach especially while it is being eaten?
What digestion phase results from the sight, smell, thought, or taste of food?
What digestion phase utilizes the rule: the greater the appetite, the more intense the stimulation?
Where do neurogenic signals that initiate the cephalic phase of gastric secretion originate?
From the cerebral cortex and in the appetite centers of the amygdala and hypothalamus
How are neurogenic signals in the cephalic phase transmitted?
Through the dorsal motor nuclei of the vagi and then through the vagus nerve to the stomach
What digestion phase normally accounts for about 20% of the gastric secretions that are associated with eating a meal?
Since the enhanced secretory activity is brought on by the thought or sight of food, what kind of reflex is the cephalic phase?
A conditioned reflex so it only occurs when we like or want food
When one's appetite is depressed what is inhibited?
The cephalic reflex
What digestion phase causes an increase in HCl (hydrochloric acid) in the stomach?
What else does the cephalic phase influence?
An influence on G cells to increase gastrin circulation
Cephalic Phase Step #1: What stimulates the cerebral cortex during the cephalic phase?
Thinking of food (sight or smell)
Cephalic Phase Step #2: What does the cerebral cortex do after stimulated in the cephalic phase?
Sends messages to the hypothalamus, the medulla, and the parasympathetic nervous system via the vagus nerve and to the stomach via the gastric glands in the walls of the fundus and the body of stomach
Cephalic Phase Step #3: What do the gastric glands do?
Cephalic Phase Step #4: What happens when food enters the stomach?
The stomach stretches and activates stretch receptors
Cephalic Phase Step #5: What do the stretch receptors do?
Send a message to the medulla and then back to the stomach via the vagus nerve
Cephalic Phase Step #6: What do the gastric glands so?
Secrete more gastric juice
Cephalic Phase Step #7: What directly activate G cells (enteroendocrine cells) that are located in the pyloric region of the stomach to secrete gastrin and in turn stimulate the gastric glands to secrete gastric juice?
Chemical stimuli (partially digested proteins and caffeine)
What digestion phase is a period in which swallowed food and semi-digested protein (peptides and amino acids) activate gastric activity?
Which digestion phase does two-thirds of gastric secretion occur?
What two ways does ingested food stimulate gastric activity?
By stretching the stomach and by raising the pH of its contents
Stretching of the stomach activates what two reflexes?
A short reflex that is mediated through the myenteric nerve plexus and a long reflex that is mediated through the vagus nerves and brainstem
What digestion phase occurs in the duodenum as a response to the arriving chyme?
What digestion phase moderates gastric activity via hormones and nervous reflexes?
What part of the digestive system initially enhances gastric secretion but soon inhibits it?
What accentuates vagal reflexes that stimulate the stomach?
Stretching of the duodenum
What in the chyme stimulate the G cells of the duodenum to secrete more gastrin which further stimulates the stomach?
Peptides and amino acids
What in the duodenum trigger the enterogastric reflex?
Acid and semi-digested fats
What sends inhibitory signals to the stomach by way of the enteric nervous system while also sending signals to the medulla that inhibit the vagal nuclei?
The duodenum sending inhibitory signals to stomach and signals to the medulla causes what?
Reduces vagal stimulation of the stomach and stimulates sympathetic neurons that send inhibitory signals to the stomach
What organ runs from the appendix to the anus and frames the small intestine on three sides?
Despite its being about one half as long as the small intestine, why is it called the large intestine?
Because it is more than twice the diameter of the small intestine about 3 inches
What are the four main regions of the large intestine?
Cecum, colon, rectum, and anus
What is located at the opening between the ileum and the large intestine?
What controls the flow of chyme from the small intestine to the large intestine?
What is divided into three stages based on whether the stomach is being controlled by the brain, by itself, or by the small intestine?
What digestion phase occurs when the vagus nerve stimulates gastric secretion and motility just with sight, smell, taste, or thought of food?
What digestion phase makes up 2/3s of gastric secretion and is activated by presence of food or semi digested protein?
When does the gastric phase start?
By stretch or by an increase in pH
During what digestive phase does multiple chemicals/neurotransmitters stimulate the release of hydrochloric acid?
What digestive phase occurs when the duodenum responds to the arriving chyme and moderates gastric activity through hormones and nervous reflexes?
What occurs first in the intestinal phase?
Gastric activity increases and if duodenum is stretched or amino acids in chyme cause gastrin release
What occurs second in the intestinal phase?
The enterogastric reflex of the duodenum inhibits stomach activity and is caused by acid and semi digested fasts in duodenum
What occurs third in the intestinal phase?
Chyme stimulates duodenal cells to release secretin, cholecystokinin (CCK), and gastric inhibitory peptide
What do secretin, cholecystokinin (CCK), and gastric inhibitory peptide do?
They suppress gastric secretion and motility which gives the duodenum time to work on the chyme it has already received before being loaded with more
Where does absorption of the majority of nutrients take place?
Where is iron absorbed?
Where are vitamin B12 and bile salts absorbed?
Where and how are water and lipids absorbed?
By passive diffusion throughout the small intestine
What is a part of the GI tract between the stomach and large intestine where much of the digestion of food takes place?
What is the primary function of the small intestine?
The absorption of nutrients and minerals found in food
Where do digested nutrients go?
They pass into the blood vessels in the wall of the intestine through a process of diffusion
What is lined with simple columnar epithelial tissue?
Inner wall or mucosa of the small intestine
What is the mucosa of the small intestine covered in that are permanent features in the wall of the organ?
What are non permanent features that allow for distention and contraction?
Name the structures of the small intestine that increase the amount of surface area available for the absorption of nutrients?
Plicae circulares, villi, and microvilli
What contain a network of capillaries and fine lymphatic vessels called lacteals close to its surface?
What transport nutrients from the lumen of the intestine into these capillaries and lacteals?
Epithelial cells of the villi
What do capillaries absorb?
Amino acids and carbohydrates
What do lacteals (lymphatic vessels) absorb?
Where are the absorbed nutrients transported?
Via the blood vessels absorbed substances are transported to different organs of the body where they are used to build complex substances such as the proteins required by the body
What happens to the undigested and unabsorbed food?
Passes into the large intestine
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