Stretch of stomach lining, protein, increased(or alkalinic) pH
3 chemicals released in gastric stage in response to triggers of stretch, protein, increased pH, and their effect?
Histamine, ACh, gastrin-each stimulate gastric juice secretion.
Begins when PNS inhibits somatostatin secretion which releases gastrin -stimulating gastric glands- thro thought, smell, sight & taste.
Explain the alkalinic tide.
For the stomach to produce hydrochloric acid, H+ ions are removed from the blood. The same # of alkalinic HCO3 is released into the blood. After a meal, blood HCO3 increases & urine excretes excess.
Gastric phase starts..
When food enters the stomach.
How does hormone cholecystokinen effect somach motility and what triggers it?
(CCK) Decreases gastric motility. Triggered by fats/proteins in SI.
Most nutrients are absorbed in
The small intestine.
What type of food moves quickest thro stomach?
Liquids, foods high in protein, carbs.
What type of food moves slowly thro the stomach?
Solids: fatty foods.
What stimulates the hormone gastrin?
PNS impulses inhibit somatostatin and stimulate certain stomach cells in the pyloric region to release the hormone gastrin, which increases secretory activity of gastric glands.
Which hormone is triggered by low or acidic pH? and what is its effect?
Secretin. It is released into the blood from the duodenal mucous membrane in response to acidic chyme in SI. It stimulates pancreas to release PJ high in HCO3.
Describe enterogastric reflex.
Starts in sm intestine(intero), ends in stomach(gastric). Chyme fills duodenum. Stretch receptors slow PNS impulse. As a result, peristalsis is inhibited, slowing intestinal filling and regulating how fast chyme leaves the stomach.
What is the result of secretin release and why is it important?
Secretin stimulates the release of PJ which is rich in bicarbs. The bicarbonate ions neutralize(alkaline) the acidic chyme so that the action of digestive enzymes can function.
Function of pancreatic amylase:
Splits carbs into dissacharides.
Function of pancreatic trypsin, chymotrypsin, carboxypeptidase:
Function of pancreatic nucleases:
Breaks nucleic acids into nucleotides.
Function of pancreatic lipase:
Breaks tryglycerides into fatty acids & monoglycerides.
Pancreatic juices digest:
Carbs, fats, proteins, nucleic acids.
The 6 major pancreatic enzymes found in pancreatic juice:
The function of zymogen granules?
Stores proteolytic(protein-splitting) enzymes, which are secreted in inactive forms & activated by enterokinase, after they reach the sm intestine.
Actions of trypsin:
Turns: chymotrypsinogen to chymotrypsin
:procarboxypeptidase to carboxypeptidase.
Function of enterokinase and where the action happens?
Activates trypsinogen to trypsin- which in turn activates chymotrypsin and carboxypeptidase.All are protein-splitting enzymes secreted in inactive forms from the pancreas' zymogen granules into SI where they encounter enterokinase.
The 2 hormones that control pancreas secretion, their triggers and their effects:
Secretin: Triggered by acidic chyme in duodenum. Stimulates pancreatic secretion high in bicarbonate ions to neutralize acid in duodenum.
Cholycystokinin(CCK): Triggered by proteins and fats in duodenum and stimulates a pancreatic juice high in digestive enzymes.
2 actions of bicarb important to DS:
1)Alkalinic(high in bicarbs, low in H+) pancreatic juice provides the alkalinic environment needed for the actions of digestive enzymes.
2)An alkaline environment in SI blocks pepsin action and damage to duodenum.
Pancreatic juice contains enzymes that digest:
Carbs, fats, proteins, and nucleic acid.
One fatty acid bound to glycerol.
Largest internal organ and what it does:
Liver; much metabolic activity, most importantly protein. Stores many substances including iron, vits A, D, B12. Detoxifies. Role in digestion is to secrete bile.
Path of bile from bili canaliculus to SI, naming all vessels and sphincters.
Bile canaliculi, bile ductile, L or R hepatic duct, common hepatic duct, bile duct, hepatopancreatic sphincter.
What is the main digestive function of the liver?
To secrete bile.
What function does bile perform?
Bile salts break down fats. Lack of bile salts results in poor lipid reabsorption & vit deficiencies.
Bile salts breaking fat globules into fat droplets! :0! Droplets can then mix with water and be digested more effectively.
The function of Kupferr cells and where they are located?
Large cells in the lining of hepatic sinusoids that remove most of bacteria from the blood by phagocytosis.
What is the function of the gall bladder?
Stores bile, concentrates bile by reabsorbing water, contracts to release bile.
What are gallstones and how do they form?
Bile becomes concentrated in gallbladder d/t water and electrolyte reabsorption. If cholesterol is separated from bile composition, it forms gallstones.
7 main functions of liver:
4)Glycogen and vitamin storage
7)Secretion of bile
Carb metabolism by liver helps maintain:
Lipid metabolism by liver produces:
Fats which are transported to adipose tissue for storage.
Protein metabolism by liver is:
Most vital function. Forms urea, clotting factors and more.
Liver storage includes
Many substances including glycogen, iron, vits A, D, B12, & blood.
Liver blood filtering removes:
Damaged red blood cells and foreign substances by phagocytotic Kupferr cells.
What effect does CCK have on the gallbladder?
Contraction, & release of bile/opens the sphincter of Oddi.
What is the hormone CCK released in response to?
Proteins and fats in the SI.
What effect does CCK have on the pancreas?
Stimulates pancreatic enzyme secretion of fluid with high digestive enzyme.
What causes the hepatopancreatic sphincter(sphincter of Oddi) to open?
3 general areas of the small intestine(SI)?
Duodenum, jejunum, ileum.
Main digestive function of SI?
To absorb the products of digestion.
How is the mucosa of the SI specialized to support it's function?
Increased surface layer due to plicae circularis of mucosa, villa, an microvilla.
How does each speciliazed structure of SI support absorption?
Mucous is secreted, causing surface area to flow together and be increased; hairs of villa/microvilla also increase surface area.
List the major enzymes embedded in the membranes of the microvilla of the SI?
Peptidases: split peptides
Sucrase, maltese, lactase: split to monosaccharides
Intestinal lipase: splits fat into fatty acids&glycerol
The double layered fold of peritoneum that suspends the jejunum and ileum from the abdominal wall. Also supports cardiovascular system to intestinal wall.
What is peristaltic rush?
Overdistended or irritated SI wall causes a strong peristaltic rush to pass along the length of the tube, sweeping contents into LI so quickly that water, electrolytes, & nutrients are not absorbed, ie: diarrhea!
Intestinal villi are:
Tiny projection of mucous membrane in SI, increasing SI surface area & thus absorption.
Intestinal microvilli are:
Tiny brush-like extensions of intestinal villa that continue to increase area/reabsorption!
Plicae circularis are:
Circular folds of mucosa in the lining of the SI and increase the surface area for absorption.
The 2 main functions of the large intestine?
1) Absorb water and electrolytes
2) Form & store feces
How is the mucosa of the LI specialized to support it's function?
No plicae circularis & no villa, but has goblet cells which secrete mucous.
2 major changes in the gross anatomy of LI compared to rest of alimentary canal:
1)Tenia coli: Longitudinal fibers in 3 distinct bands that extend the length of the colon.
2)Haustra: When the bands exert tension lengthwise on the wall, a series of pouches(haustra) are created.
Define mass movements.
Peristaltic wave in the LI happen only 2 to 3 tmes daily, compared to those of the SI that occur frequently. These waves in the LI produce mass movements in which a large section of wall constricts vigorously, forcing contents down LI.
Describe the defecation reflex.
As the rectum walls extend, the defecation reflex is triggered, which in turn triggers peristaltic waves in the descending colon. The internal involuntary sphincter relaxes. Abdominal muscles increase pressure on the rectum. The external sphincter muscle is signaled to relax.
The 4 main parts of LI?
Describe the appendix?
Near the opening of the LI, hangs a narrow tube w a closed end. Contains lymphatic tissue, but has no known digestive function.
Enterokinase is secreted by:
The mucosa of the SI.
The first action of the PNS in digestion?
To inhibit somatostatin secretion by parietal cells so that gastrin flows uninhibited.
The hormone histamine is released by? and what is it's effect?
PNS impulses AND gastrin promote release of histamine from mucous cells, stimulating more gastric secretion.
A substance that acts as a catalyst to bring about a specific biochemical reaction.
Breaks down toxins.
Liver secretes___ and why is it important?
Bile, which contain bile salts to break down fats.
Function of gallbladder besides storage?
Reabsorbs water and electrolytes and concentrates bile. Cholesterol normally remains in bile solution.
Water, bile salts, bile pigments, cholesterol & electrolytes.
What bile substance is most abundant and what does it do?
Bile salts; they are the only bile substance with a digestive function.
What do hepatic cells use to produce bile salts?
Cholesterol! which has no special function in bile or digestion. Altho in releasing bile salts, hepatic cells also release some cholesterol into bile.
What purpose do the goblet cells of the LI serve?
Alkalines the LI contents, assists to form feces, protects intestinal wall against abrasion.