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84 Cards in this Set
- Front
- Back
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What controls the rate of parastatic waves of the stomach when digesting food
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pacemaker cells in the longitudinal smooth mm layer. They undergo
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What are the relative rates of emptying from the stomach for the following food types: carbohydrates, fats and proteins
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Carbohydrates rapidly
Fats slowly Proteins intermediate rate |
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What pattern does the motion of the small intestines make after a meal (to facilitate absorption)
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stationary contraction followed by relaxation of intestinal segments. chyme moves back and forth.
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What controls the movement of chyme in the small intestines
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pacemaker cells in the longitudinal smooth mm layer
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Following absorptions what motion does the small intestines make
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a pattern of peristaltic activity = migrating motility complex. These are initiated in the duodenum.
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About how long does it take food to move from the duodenum to the lieum
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about 2 hours
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What controls the patters of contractile activity in the small intestines
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enteric nervous system
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What controls the migrating motility complex in the small intestines
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Hormones
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Describe mixing of chyme in the Colon
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Haustral contractions are triggered by distention of the smooth mm. This produces a segmental motion. It is very slow allowing bacteria to grow and multiply.
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What effect does fiber in the diet have on the colon
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Increase strength of colon contractions and softens stool.
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What triggers the neural mediated defecation reflex
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Sudden distention of walls of rectum
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What is the main function of the deep myenteric plexus (Auerbach's plexus)
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control motility of the GI tract
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What is the main function of the superficial submucosal plexus (Meissner's Plexus)
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gland regulation
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What portion of the nervous system primarily controls the patterns of segmentation and peristalsis of the GI tract
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mainly automatic - includes local, short reflex arcs btw enteric neurons and the same or different plexuses or organs
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What embryological structure is the enteric nervous system derived from
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Neural crest cells
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How is the enteric nervous system connected to the CNS
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via afferent visceral fibers, sympathetic nervous system and parasympathetic nervous system
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What general effects does the parasympathetic system have on the GI tract
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enhances secretory and mobility activity
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What general effects does the sympathetic system have on the GI tract
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inhibits digestive activities
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What are the 3 phases of neural regulation of the GI tract
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cephalic, gastric and intestinal
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Explain the cephalic phase of digestion
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sight, smell, taste, chewing and emotions stimulate receptors in the head. Efferent n activate nerves in GI n plexus - affect secretory and contractile activities
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Explain the gastric phase of digestion
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initiated by stretch and chemoreceptors in stomach. Increases gastric secretions and motility
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Explain the intestinal phase of digestion
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initiated by stimuli in intestinal tract - distention, acidity, osmolarity & various digestive products. Begins with stimulation of gastrin and motility. As duodenum distends with chyme - inhibitory signals dec stomach activity and prolong emptying time to allow for digestion.
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Describe hormone secretion in the GI tract
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chyme comes in contact with one side of endocrine cells (lumenal side) - stimulates secretion of hormones on opposite side (communication w/blood)
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How do Gi hormones regulate luminal environment
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via feedback control system
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T or F each GI hormone affects only one type of target cell
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F - each hormone affects more than one type of target cell.
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What cranial nerves trigger salivary secretions
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CN VII and IX
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How does systemic nervous system affect salivary secretion
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Triggers secretion of thick mucous-rich saliva or inhibits salivary release completely
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What is saliva's main "ingredient"
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Water - 97-99%
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What is the pH of saliva
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6.7 to 7.0
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What electrolytes are found in saliva
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Na, K, Cl, HPO4, HCO3
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What is the main enzyme found in saliva
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amylase
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Where is gastrin produced
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The stomach
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What are Gastrin's target organs?
What does it stimulate? |
Target organ 1 - stomach, stimulates gastric glands and secretion of HCl and gastric juices.
Target organ 2 - stimulates stomach emptying. |
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What stimulates Gastrin's release
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1. Peptieds/Amino acids in the stomach --> stimulate gastric glands to produce HCl and gastric juicse
2. Ach (PNS) --> gastrin released It is inhibited by GIP |
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Where is somatostatin produced and what stimulates this production
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in the stomach and doudenum in response to food in the stomach
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What effect does somatostatin have on the stomach
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it inhibits all secretions, motility and emptying
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What effect does somatostatin have on the pancreas
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It inhibits the section of insulin and glucagon
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What effect does somatostatin have on the gallbladder
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it inhibits its contraction and bile release
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Where is CCK produced and what stimulates its production
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CCK is produced by the duodenal mucosa and production is stimulated by fatty acids and peptides entering the duodenum
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What are CCK's target organs and what effects does it have at these organs
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Pancreas - stimulates acinar cells to produce pancreatic enzymes
Gall bladder - stimulates contraction and bile release |
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Where secretin produced and what stimulates its production
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It is produced by S-cells in the duodenum in response to acidic chyme in the duodenum
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What are secretin's target organs and what effect does it have on these organs
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Pancreas (duct cells) - secrete bicarb ions
Liver - secrete bile & bicarb ions |
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Where gastric inhibitory peptide (GIP) produced and what stimulates its production
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GIP is produced by K-cells in the duodenum in response to the glucose and fatty acids in the duodenum
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What are secretin's target organs and what effect does it have on these organs
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Liver - secretion of bile/bicarb
Pancreas - secretion of bicarb |
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What gives saliva its sticky and viscous texture
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a glycoprotein called mucin
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What is the mucosal antibody found in saliva
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IgA
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What is in gastric juice
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HCl
Pepsin Intrinsic factor mucus |
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What is pepsin and where does it come from
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enzyme that hydrolyzes proteins into small peptides. It is secreted by chief cells as pepsinogen --> 1st activated by HCl to pepsin then pepsin itself.
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What do parietal cells produce
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Intrinsic factor
HCl |
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What roles does HCl have in digestion
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denature proteins
activates pepsinogen to pepsin anti-bacterial stimulates duodenum to secrete hormones the increase bile and pancreatic juice producion increase B12 absorption |
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What stimulates parietal cells
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Ach, gastrin, histamine during a meal (esp high protein)
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What role does intestinal juice play in digestion
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neutralize acidic chyme, maintain fluidity of chyme carrier for some nutrients from chyme
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What do Duodenal (Brunner's) glands secrete
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alkaline mucous into duodenum - helps neutralize chyme
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what do goblet cells secrete
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mucous
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What do paneth cells secrete
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antibacterial lysozymes, they are located deep in the crypts of Liberkuhn
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What are brush border enzymes
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Mostly disaccharidases and peptidases that complete carb and protein digestion
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What is enterokinase
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a proteolytic enzyme produced in the crypts of Liberkuhn in the duodenum. It activates typsinogen to trypsin
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What pancreatic enzymes are released in an inactive form
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Trypsinogen
Procarboxypeptidase Chymotrypsinogen |
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What pancreatic enzymes are released in their active from
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Amylase
Lipase Nuclease |
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What general pH are pancreatic juices and what creates this pH
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Alkaline due to bicarbo released by pancreatic epithelial cells
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What is in Bile
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bile salts, lecithin, bicarbonate ions, cholesterol, bile pigments, trace metals.
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What do bile salts due
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help solubilize fat in duodenum
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What does lecithin due
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a phospholipid that helps solubilize fat
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Why is cholesterol in the bile
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it was removed by the liver from the blood to be excreted
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What physically regulates the flow of bile into the duodenum
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Sphincter of oddi - btw meals is closed; it is relaxed by the secretion of CCK. CCK also causes contraction of the gall bladder hence release of bile into duodenum.
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What are the main secretions in the colon
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mucus, fluid containing bicarb and K ions; no digestive enzymes
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What triggers goblet cells to release mucous
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stretching of the lumen
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What health role do bacteria play in the colon, what effect do they have on the pH
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Metabolize vitamins and fiber. They create acidic bi-products which are counteracted by bicarb that defuses into the lumen
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How is water absorbed in the colon
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Water is absorbed with Na and K is secreted into the colon
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What does Amylase do
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breaks down starches
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What is absorbed in the stomach
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lipid soluble drugs like aspirin and alcohol
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How are monosaccharides absorbed
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via secondary active transport coupled with Na, except fructose - facilitated diffusion
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How are fats digested and absorbed
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Broken down by pancreatic lipase --> form micelles w/ bile salts -->diffuse btw microvilli, diffuse across membrane --> FAs and monglycerides --> TAG --> TAG + phospholipids + cholesterol --> chylomicrons --> lacteals --> venous blood
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How are proteins digested and absorbed
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Broken down by proteases --> active transport out of lumen coupled with Na
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How are fat soluble vitamins absorbed. What are they
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ADEK - via micelles/ passive diffusion
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How is Na absorbed in the sm intestines
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active absorption with glucose and aas, co-transported w/Cl or exchanged fro H+
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How is Cl absorbed in the sm intestines
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co-transported w/Na or in exchange for HCO3
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How is K absorbed in the sm intestines
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simple diffusion
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How is Ionic Iron absorbed in the sm intestines
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active transport into mucosal cells, binds to ferritin (stored) --> when needed moves into blood and binds to transferrin
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How is Ca absorbed in the sm intestines
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Actively absorbed and transported via calcium-binding protein (made in mucousa w/Vit D as cofactor)
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How does liver blood flow in response to the sinusoid
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blood flows from the portal vein and hepatic artery to the central vein
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What do RBCs become when broken down in the spleen
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globin and heme. Globin is broken down. Heme ring is opened --> belverdin -bilverdin reductase->bilirubin --> transported to liver on albumin
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What is hepcidin
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A protein made in the liver that is created in response to high iron in the body. It travels to sm intestines and inhibits iron absorption. Can also inhibit ferroportin (transport protein that helps transport iron out of cells)
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What do hepatocytes store
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glucose, glycogen, fat soluble vitamins and vit B12
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