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115 Cards in this Set
- Front
- Back
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Where does the nutriets go during absorption?
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The epithelial cells of the digestive tract, from there they go to the lymph and blood.
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What is the process of compaction?
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absorbing water and creating feces with all the indigestible nutrients.
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Explain mechanical digestion and its mechanisms.
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Physical breakdown of food to make smaller particles. Biting (chewing), churning action of the stomach and small intestine. Smaller particles expose more food surface to the digestive enzymes.
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Explain chemical digestion and its mechanisms. Why is it different than mechanical digestion?
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Hydrolysis reactions that breaks dietary macromolecules into monomers. Carried out by digestive enzymes made by saliva, stomach, pancreas, and small intestine.
It turns polysaccharides into monosaccharides. Proteins into amino acids. Fat into monoglycerides and fatty acids. Nucleic acids into nucleotides. |
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What kinds of nutrients can be used sometimes without being digested?
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vitamins, free amino acids, minerals, cholestrol and water
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What are the two anatomical subdivisions of the digestive system?
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the digestive tract (ALIMENTARY CANAL): 30 ft. muscular tube from mouth to anus, mouth-pharynx-small intestine-esophagus-stomach-large intestine
the gastrointestinal tract is the stomach and intestines. |
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What are the accessory organs of the digestive system?
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teeth, tongue, salivary glands, liver, gall bladder and pancreas
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Is the material in the digestive tract considered internal or external? When does it change?
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It is considered external until it is absorbed by the epithelial cells of the alimentary canal. "defacted food was never in the body"
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What is the basic structural plan of the digestive tract walls?
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MUCOSA- epithelium-lamina propria-muscularis mucosae
SUBMUCOSA MUSCULARIS EXTERNA- inner circular layer, outer longitudinal layer SEROSA- areolar tissue-mesothelium |
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What are the subdivisions of mucosa in the digestive tract wall?
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Epithelium-->lamina propria-->muscularis mucosae
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What are the subdivisions of submucosa in the digestive tract wall?
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There are none.
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What are the subdivisions of the muscularis externa?
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inner circular later--->outer longitudinal layer
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What are the subdivisions of the serosa in the digestive tract wall?
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areolar tissue--->mesothelium
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What does the mucosa line? what does it consist of? What does it have an abundance of?
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the lumen----epithelium, lamina propria, muscularis mucosa. It has an abundane of lymphocytes and lymphatic tissue
(MALT..mucosa associated lymphatic tissue) |
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Describe the inner epithelium.
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The inner epithelium of the gastrointestinal tract is SIMPLE COLUMNAR in most of digestive tract. STRATIFIED SQUAMOUS from mouth through espohagus and in the lower anal canal.
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Describe the lamina propria.
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It is a loose connective tissue layer.
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Describe the muscularis mucosae.
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The muscularis mucosae is a thin layer of smooth muscle. It makes the mucosa tense creating grooves and dents to increase surface area and the contact with food. (improves efficiency and digestion of food)
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Describe the submucosa. What does it do?
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The submucosa is a thicker layer of connective tissue. It contains blood vessels, a nerve plexus, lymphatic vessels, and sometimes a mucus secreting gland that dumps lubricating mucus into the lumen. (MALT EXTENDS INTO SOME PARTS OF THE SUBMUCOSA)
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Describe the muscularis externa. What is it made up of?
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It is made up of outer longitudinal layer and an innter circular layer. It is composed of two muscle layers.
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Describe the outer longitudinal layer.
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It is responsible for the motility that propels food through the tract.
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Describe the inner circular layer of the muscularis externa.
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the layer thickens to form valves (sphincters) which are responsible for what material passes through the tract.
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Descirbe the serosa. What does it do?
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The serosa is a thin layer of areolar tissue topped with a layer of simple squamous mesothelium tissue. It begins in the lower portion of the esophagus and ends just BEFORE THE RECTUM.
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What is adventitia?
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Adventitia is a fibrous connective tissue that binds and blends the pharynx, most of the esophagus, and rectum into the adjacent connective tissue of other organs. (SEROSA)
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What does the enteric nervous system do?
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it is a nervous system in the esophagus, stomach, and intestines that regulates digestive tract motility, secretion and blood flow. (has more neurons than the spinal cord). It functions INDEPENDENTLY OF THE CENTRAL NERVOUS SYSTEM
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What are the two networks of neurons that the enteric nervous system is composed of?
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Submucosal (Meisner) plexus and myenteric (Auerbach) plexus.
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What does the submucosal plexus do and what is another name for it?
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Meissner and it controls glandular secretion in the mucosa and controls movements of the muscularis mucosae.
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What does the myenteric plexus do and what is another name for it?
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Another name for the myenteric plexuc is Auerbach. it is parasympathetic ganglia and nerve fibers between the two layers of muscularis interna. controls peristalis and movements of the musc. int.
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what are mesenteries?
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sheets of connective tissue that loosely suspend stomach and intestines from the abdominal wall. allowing stomach to undergo strenuous contractions,allow freedom of movement, prevents intestines from becoming twisted, provides passage of nerves and blood vessels to supply tract, contain lymph nodes and vessels
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what are the cells of the gastric glands?
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regenerative, chief, parietal, and enterendocrine
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what do the chief cells do?
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secrete pepsinogen and gastric lipase and they are only in the gastric glands.
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what do the parietal cells do?
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secrete ghrelin (hunger), intrinsic factor, and hcl
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what do enterendocrine cells do?
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secrete hormones to regulate digestion
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what is gastric juice made up of?
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water, hcl, and pepsin
high concentration of HCl |
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How is H+ pumped into the gland?
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h+-k- ATPase pump
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____ uses ATP to pump H+ ___ and K+ ___
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antiporter, out, in
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What is HCO3- exchanged for in blood plasma? why?
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cl- (cloride shift). it forms hcl with H+. elevated hco3- forms alkaline tide which raises pH.
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Activates pepsin and lingual lipase, breaks up connective tissue (liquefies food to create chyme, converts fe3+ to fe2+, and destroys most ingested pathogens. What is this?
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HCl.
Fe2+ is used for hemoglobin synthesis |
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What are zymogens?
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PEPSIN....digestive enzymes secreted as inactive enzymes. activated by removing amino acids.
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Pepsinogen is a __________ secreted by chief cells.
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zymogen
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What removes the amino acids from pepsinogen to create pepsin, to digest proteins?
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HCl
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What is the autocatalytic effect?
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converts pepsinogen into pepsin
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What does pepsin do?
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breaks down larger peptide chains into smaller in the small intestine to be absorbed.
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The intrinsic factor is essential to the absorption of what?
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b12..which is needed to synthesize hemoglobin (prevents pernicious anemia)
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what lines the stomach and creates contractions?
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muscularis externa
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What does the muscularis externa do?
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creates rippling effect in the stomach to mix food with gastric juice. contractions become more intense at pyloric region.
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An antrum holds about ______, until a peristalic wave passes through the antrum (chamber) pushing about ______ into the duodenum at a time.
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30 ml chyme
3 mL chyme the small amount allows the duodenum to neutralize the stomach acid and digest little by little. |
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what happens if the duodenum is overfilled?
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it inhibits gastric motility.
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how long does a meal take to be emptied from the stomach?
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4 hours for a typical meal. less if it is mostly liquid, up to 6 hours for high fat meal
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what part of the medulla oblongata enables the muscle movements to vomit?
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THE EMETIC CENTER of the medulla enables vomiting contractions of the muscles.
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What is RETCHING and when does it occur?
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retching is thoracic expansion and abdominal contraction that creates a pressure difference dilating the esophagus. chyme enters the esophagus but comes back down. it occurs before vomiting.
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What is a peptic ulcer?
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pepsin and hcl erode the stomach wall.
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What are most ulcers caused by?
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acid resistant bacteria helicobacter pylori
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Gastric activity is divided into 3 phases...
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cephalic-stomach controlled by brain (stimulates gastric juice before food is even swallowed)
gastric-stomach controlled by itself (Stretches stomach and myenteric reflexes to stimulate secretion of gastric juices) 2/3 of gastric secretion occur here...also can increase pH of contents intestinal-stomach controlled by small intestine |
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What is gastric secretion stimulated by?
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ACh, histamine, gastrin
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Intestinal phase of gastric activity. Duodenum?
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Duodenum initially enables gastric secretion---but in the end inhibits
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What causes the enteroendocrine reflex?
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acids and semi digested fats in the duodenum triggers duodenum to send signals to the stomach (enteric nervous system) which then signals the medulla oblongata
this inhibits vagal (vagus nerve) nuclei (reduces vagal stimulation of the stomach) and STIMULATES PARASYMPATHETIC NEURONS to send signals |
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Chyme stimulates ______ to release ___________ which stimulate pancreas and gall bladder and suppress gastric secretion.
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Chyme stimulates duodenal enteroendocrine cells to release secretin and cholecystokinin which stimulate pancreas and gall bladder and suppress gastric secretion.
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What does the pyloric sphincter in the regulation of gastric functions?
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Limits the amount of chyme to enter duodenum to give it time to work on chyme
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Besides hormones and paracrine, what do the enterendocrine cells secrete?
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GIP (glucose dependent insulinotropic peptide) which stimulates insulin secretion to prepare small intestine for nutrients to be absorbed
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What is the body's largest gland?
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the liver. it secretes bile which helps with digestion
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What is an irregular opening in the lobes of the liver called? what exits and enters here? where does all these things travel through?
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porta hepatis. It is the point of entrance for the proper hepatic artery and the hepatic portal vein. point of exit for bile. All travel through the lesser omentum.
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what are the tiny cylinders that fill the liver called? what do they consist of? (4)
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hepatic lobules. Hepatic lobules consist of:
-a central vein -hepatocytes which surround central vein -hepatic sinusoids -hepatic macrophages (kupffer cells) |
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what do the hepatic macrophages (Kupffer cells) of the hepatic lobules in the liver do?
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they are phagocytic cells in the sinusoids that remove bacteria and debris from the BLOOD
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What do the hepatic sinusoids of the hepatic lobules in the liver do?
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The hepatic sinusoids are lined in fenestrated epithelium that seperate the hepatocytes from the blood cells.
House the microvilli from the hepatocytes. Allow plasma in the space between the endothelium and hepatocytes. Filters the blood which goes to the stomach and intestines. |
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What is another name for the hepatic macrophages in the hepatic lobules of the liver?
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Kupffer cells
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What do the hepatocytes do after a meal?
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absorb amino acids, glucose, vitamins, and iron and other nutrients for metabolic functioning
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What do hepatocytes remove?
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remove and degrade hormones, toxins, bile pigments and drugs
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What do hepatocyes secrete into the blood?
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ambumin, lipoproteins, clotting factors, angiotensinogen and others
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What do hepatocytes do between meals?
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break down glycogen and release glucose into the blood
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What are hepatic lobules seperated by?
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Stroma connective tissue
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What is the structure which the liver secretes bile into?
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the Bile canaliculi.
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Describe bile.
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yellow green liquid that contains cholesterol, minerals, fats, phospholipids, bile pigments and bile acids
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What is the primary bile pigment and where does it come from?
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bilirubin is the primary bile pigment that is made from the breakdown of hemoglobin.
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Why is feces brown?
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bilirubin is converted to urobilinogen from bacteria in the large intestine.
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What do bile acids (salts) do and where are they from?
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bile acids are steroids synthesized from cholesterol and they aid in FAT DIGESTION AND ABSORPTION with the help of lecithin (a phospholipid)
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How does bile get into the gallbladder?
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overflows the bile duct into the gallbladder
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____% of bile acids are reabsorbed in the ____ and returned to the _____ where _____ absorb and _____ them.
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80% of bile acids are reabsorbed by the ileum and returned to the liver where hepatocytes absorb and resecrete them.
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What is enterohepatic circulation?
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the route of secretion, absorption, resecretion of bile acids two or more times during a meal.
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what are gallstones composed of?
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cholestrol, calcium carbonate and bilirubin
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what is chloethiasis?
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the formation of gallstones is called CHLOETHIASIS. COMMON IN women over 40 because of excess cholesterol
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what does lithotripsy do?
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vibrates gallstones to break them down without surgery
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what is both an endocrine and exocrine gland?
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the pancreas
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what does the endocrine portion of the pancreas consist of and what does it do?
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pancreatic islets that secrete insulin and glucagon.
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what does the exocrine part of the pancreas do?
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it is 99% of the pancreas and it secretes gastric juices
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what is pancreatic juice made up of?
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water, enzymes, zygomes, bicarbonate
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_____ secretes _____ (pancreatic juice)
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acini secretes enzymes and zygomes
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_____ secretes _____ which buffers HCl before arriving to the stomach (pancreatic juice)
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ducts secrete bicarbonate
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what are the three pancreatic zygomes?
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trypsinogen...chymotrypsinogen..procarboxypeptidase
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what are other pancreatic enzymes? what do they do?
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pancreatic amylase- breaks down starch
pancreatic lipase-breaks down fat RNA AND DNA |
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what are the 3 substances responsible for the release of pancreatic juice and bile?
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ACh, cholecystokinin, and secretin
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what does ACh do for the release of pancreatic juice and bile?
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stimulates acini to secrete enzymes in cephalic phase. enzymes stay in acini and duct until chyme enters the duodenum.
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what does cholecystokinin do for the release of pancreatic juice and bile?
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it is secreted by the mucosa at the arrival of fats in the small intestine. it strongly stimulates gall bladder
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when is secretin released?
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it is released from the duodenum in response to acidic chyme arriving to the stomach. stimulates liver and pancreas to secrete more sodium bicarbonate.
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what is the longest part of the digestive system?
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the small intestine
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These glands produce bicarbonate-rich mucus, which neutralizes stomach acid.
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brunner glands
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This brush border enzyme will complete polypeptide digestion.
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carboxypeptidase
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Chemical digestion of food begins in the____________
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stomach
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Chemical digestion of carbohydrates begins in the __________
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mouth
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what is pepsin inactivated?
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inactivated with increased pH
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what is the position of the both jejunum and ileum?
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intraperitoneal
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where are brush border enzymes?
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they are in the plasma membrane of the microvilli. chyme must be in contact with them for digestion to occur. intestinal churning insures contact with the mucosa.
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when does amylase work best to break down carbs? pH
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pH 6.8-7. It is quickly broken down by stomach acid
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what pH does amylase stop working?
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less than 4.5. when reaching small intestine amylase converts to oligosaccharides and maltose within 10 mins
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what are the brush border enzymes? what happens when oligosaccharides and maltose come in contact with them?
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dextrinase, glucoamylase, maltase, sucrase, and lactase are the brush border enzymes.
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what delivers sugars to the liver?
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hepatic portal system
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what happens to lactose intolerant people?
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lactose arrives to the large intestine undigested which increases osmolarity of large intestine substances causing water retention, diarreha,
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Where do amino acids absorbed by the small intestine come from?
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dietary proteins, sloughed epithelial cells, digestive enzymes.
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what are enzymes that digest proteins called?
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proteases (peptidases)-
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what are aminopeptidase and dipeptidase? what is carboxypeptidase?
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aminopeptidase and dipeptidase are brush border enzymes. carboxypeptidase is a pancreatic secretion.
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what do brush border enzymes do?
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created free amino acids that are absorbed into the intestinal epithelial cells.
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what are lipase?
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fat digesting enzymes.
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what are micelles?
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minute droplets of bile made in the liver that can absorb free fatty acids, monoglycerides and other lipids. they pass down the bile duct to the duodenum where they do their absorption.
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where are free fatty acids and monoglycerides transported?
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the smooth er where they are resynthesized to triglycerides,
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what are fat soluble vitamins?
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e, d, c, k
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what are water soluble vitamins?
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b complex, and c,
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