9. GI system Flashcards
Digestion vs absorption
breakdown of food into organic molec (ex: starches and carbs to monosaccharides, proteins to amino acids) vs transporting food from GI tract to circulatory system
Mechanical digestion vs chemical digestion. Intracellular digestion vs extracellular digestion
physical break down of food (mastication) vs enzymatic cleavage of bonds in food (saliva/salivary glands). oxidation of glucose and fatty acids for energy vs obtaining nutrients from food in alimentary canal
Name parts of alimentary canal; how are they sectioned off?
mouth/oral cavity, pharynx, esophagus, stomach, small intestine, large intestine/colon, rectum, anus; sphincters
What is peristalsis? Which nervous system is responsible for this?
Contractions that move food throughout digestive tract. Parasympathetic nervous system (remember “rest and digest”), specifically enteric nervous system
What is salivary amylase and lipase?
Enzyme in saliva that hydrolyzes starch into smaller sugars; aka ptyalin. Lipase hydrolyzes lipids
What are the 3 parts of the pharynx? (Use prefixes to determine their location)
nasopharynx, oropharynx, laryngopharynx (above vocal cords)
Describe roles of upper vs lower esophageal sphincter vs cardiac sphincter
swallows food (it’s made of skeletal muscle), involves oropharynx vs relaxes and opens passage for food vs prevents reflux of stomach contents into esophagus
4 main divisions of stomach; know lesser and greater curvature; know rugae
fundus and body (contain gastric glands), antrum and pylorus (contain pyloric glands that contain G-cells that secrete gastrin to induce parietal cells to release HCl). Lesser = inner curvature, greater = outer curvature. Folds w/in stomach wall
Describe 3 cells produced in stomach
parietal cells release HCl (it converts inactive pepsinogen to active pepsin for hydrolysis of proteins) and intrinsic factor (IF) to scavenge vitamin B-12 and chaperone it to ileum for absorption; chief cells release pepsinogen; mucus cells release mucus to coat stomach and prevent gastric ulcers
Describe biliary tree
- Bile production in liver from cholesterol. 2. bile moves thru common hepatic duct. 3. bile moves thru cystic duct 4. bile hangs out in gallbladder until cholecystokinin (CCK) tells gallbladder to contract bile out 5. bile moves thru common bile duct 6. bile moves to duodenum where bile salts emulsify fats 7. bile moves to ileum where bile salts and fats = absorbed 8. bile salts circulate back to liver and redo the process
What are the functions of the liver?
storage of carbs, fats and proteins, detoxification, bile production via cholesterol, converting ammonia to urea, albumin synthesis, metabolism (ana/catabolism), DESTRUCTION OF ERYTHROCYTES
Name and describe the 3 sections of small intestines vs Name sections of large intestines
duodenum (where most digestion occurs), jejunum (where most absorption occurs), ileum (where important absorption occurs) vs cecum, appendix, ascending colon, transverse colon, descending colon, sigmoid colon
Name 3 organs and 1 types of enzyme duodenum involves with
stomach (chyme, HCl), liver/gallbladder (bile salts and pigment), pancreas (enzymes), brush border enzymes (sucrase, lactase, isomaltase, aminonpeptidase and dipeptidase)
Hepatic portal vein vs proper hepatic artery vs hepatic vein vs common hepatic duct; know portal triad
Carries blood containing nutrients and toxins from GI to liver before going to IVC vs supplies arterial O2 rich RBCs from aorta to liver vs takes de-O2 and nutrient poor blood from liver to IVC vs transports bile out of liver
Portal triad: hepatic portal vein, hepatic artery and bile duct
Know hepatic lobules
hepatocytes surrounded by 6 units of portal triads like a hexagon; all blood = collected in central vein to hepatic vein
Describe exocrine pancreas
Acinar cells enzymes to duodenum. Secretin tells acinar cells to release HCO3- to neutralize gastric acid (HCl); amylase to break down starch into smaller carbs; lipase to break down lipids to free fatty acids + monoglycerides + diglycerides + glycerol; proteolytic enzymes like trypsinogen, chymotrypsinogen, procarboxypeptidase A&B (trypsinogen becomes trypsin via enteropeptidase, chymotrypsinogen becomes chymotrypsin via trypsin)
Describe endocrine pancreas
Releases hormones to blood stream. Releases alpha islet cells to release glucagon to convert glycogen to glucose, beta islet cells to release insulin to convert glucose to glycogen, delta islets cells to inhibit alpha and beta islet cells
What does colon absorb? What else can it do?
Water; absorb too much water –> constipation, absorb too little water –> diarrhea. Inorganic ions like Na+. Normal flora can produce vit K
What do rectum and anus do?
Rectum stores stool. Anus has 2 sphincters: internal anal (smooth muscle –> involuntary control) and external anal (skeletal –> voluntary control)
Bilirubin vs albumin
Major pigment in bile, the byproduct of hemoglobin breakdown. It goes to the liver to be conjugated (attach to protein) and secreted into bile for excretion. If liver can’t process or excrete bilirubin —> jaundice vs Major liver protein that prevents fluid from leaking into other tissues. Low albumin means you have a liver or kidney problem
What happens when RBCs are lysed?
Hemoglobin is released —> bilirubin levels inc
Ghrelin vs leptin and CCK vs gastrin
Promotes sensation of hunger —> inc feeding behavior vs promotes satiety —> dec feeding behavior vs inc acid production and gastric motility, no relation to feeding behavior
Components of bile
Bile salts, bilirubin, cholesterol
List pancreatic peptidases and their main function
Trypsinogen, chymotrypsinogen, carboxypeptidase A and B, pancreatic lipase. Protein digestion and pancreatic lipase digests fats (not emulsify)
Pepsin digests proteins in the stomach
What converts procarboxypeptidase A and B to carboxypeptidase A and B?
Enteropeptidase
What do aminopeptidase vs dipeptidase do?
Hydrolyzes at amino end vs hydrolyzes pairs of aa
Examples of fat soluble vs water soluble vitamins. Where are vitamins absorbed?
ADEK vs BC. Absorbed in small intestines
Do fat soluble cmpds reach the liver thru portal vein?
Nope they don’t drain to liver at all. They meet in lacteals which form into thoracic duct which drains to the left subclavian vein
Thrombopoietin
Secreted by liver and kidney to stimulate development of thrombocytes/platelets
What does the spleen do?
Blood storage and activation of B cells that later turn into plasma cells for adaptive immunity and destruction of damaged B cells, destruction of damaged or old RBCs, filters blood to help immune system
Goblet cells vs enterochromaffin-like (ECL) cells
Secreted thick mucous layer to prevent auto digestion of stomach wall caused by enzymes like pepsin vs secrete histamine to promote acidification of gastric lumen
Distention of stomach causes GI cells to secrete?
Gastrin
Does sympathetic nervous system affect esophageal peristalsis?
No b/c you need to swallow saliva even if you’re not eating or drinking; but it generally dec most GI activity
Why do small intestines have microvilli?
To provide more additional surface area for nutrient absorption
Gastrocolic reflex
presence of food in stomach tells colon to get ready; ENTERIC SYSTEM CONTROLS THIS
What’s the main function of the pH of stomach?
To break down proteins for digestion (stomach enzymes including proteases = able to w/stand the stomach pH)
