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A&P 2
Digestive system
| Question | Answer |
|---|---|
| secretions or enzyme of salivary glands | salivary amylase (ptyalin) |
| function of salivary amylase | digestion of carbohydrates |
| secretions or enzymes of stomach | pepsinogen (chief), prorennin (chief), gastric lipase (chief), HCl (parietal), intrinsic factor (parietal) |
| where are chief and parietal cells more predominant | throughout fundus and body |
| chief cells vs parietal cells | chief cells- enzymes parietal cells- secretory cells |
| functions of pepsinogen | -When it encounters HCl and pepsin in the lumen of the stomach, it is converted into more pepsin -Pepsin is a protease (enzyme that digests proteins into amino acids). |
| functions of prorennin | - when activated by HCl in the lumen, becomes rennin - Rennin causes milk to curdle- helps retain milk in the stomach so it can be digested - produced by children up to the age of 2 |
| why doesn't prorennin function well in adult stomach | adult stomach is too acidic |
| function of gastric lipase | - produced in small quantities and may initiate the digestion of milkfat - Also primarily effective in children |
| functions of HCl | provides enzyme converting environment (pepsinogen --> pepsin, prorennin --> rennin) |
| functions of intrinsic factor | needed for absorption of vitamin B12 |
| secretions or enzyme of small intestine (brush border enzymes): inserted into plasma membrane to aid digestion | amylase, nuclease, protease, enterokinase |
| functions of amylase | breaks down carbohydrates |
| functions of nuclease | breaks down nucleic acids (DNA and RNA) |
| functions of protease | breaks down proteins |
| functions of enterokinase | converts trypsinogen (produced by pancreas) to trypsin (protein digesting enzyme) |
| secretions of enzyme of pancreas (acinar cells) that release into duodenum of small intestine | amylase, lipase, nuclease, trypsinogen |
| functions of lipase | break down fats |
| secretions or enzyme of liver and gallbladder that release into duodenum of small intestine | bile |
| what is bile a solution of | solution of: 1. bile salts (emulsify fat to make it easer for lipase to digest, combine with products of fat digestion to form micelle) 2. bile pigments (bilirubin/verdin from degradation of hemoglobin 3. cholesterol 4. bicarbonate 4. bicarbonate |
| what does micelle do | - The core of the micelle transports cholesterol and other lipids and the fat-soluble vitamins, A, D, K, E - transport is up to but not through the cell membrane of the microvilli |
| 4 layers of digestive organ wall | mucosa, submucosa, muscularis externa, serosa/adventitia |
| mucosa | - mucous membrane lining - either stratified squamous (openings/exits) or simple columnar (stomach through rectum) - middle lamina propria is areolar CT - outer muscularis mucosa is smooth muscle - produces mucus |
| submucosa | - blood and lymphatic vessels for transport of absorbed nutrients - glandes secret digestive enzymes |
| what are the glands of the submucosa supplied by | submucosal (Meissner's plexus) |
| muscularis externa | - 2 layers of smooth muscle (circular/longitudinal) - responsible for peristalsis innervated by myenteric plexus |
| serosa/adventita | - esophagus is adventitia - abdominal + pelvic cavities: organs wrapped in peritoneum, visceral peritoneum is the serosa |
| mesentary | double layer of peritoneum that extends to organs from body wall, anchors blood and lymphatic vessels, stores fat |
| 3 sets of salivary glands | parotid: high amylase content, submandibular: mucus + small amylase content, sublingual: mucus + smallest amylase content |
| mumps is the viral infection of this gland | parotid salivary glands |
| functions of saliva | facilitate taste, carb digestion, lubricate food, protect from microbes |
| voluntary phase of deglutition (swallowing) | buccal phase: generate bolus which is moved to back of tongue |
| involuntary phase of deglutition | - pharyngeal phase: food enters pharynx, reflexes close all other openings, peristalsis begins - esophageal phase: food travels down esophagus |
| true or false: during pharyngeal phase the epiglottis folds back to block trachea | true |
| esophagus | - mucosa is stratified squamous - mucosa externa is still 2 layers but upper 1/3 is skeletal muscle and lower 2/3 is smooth muscle - has adventitia not serosa |
| gastroesophageal sphincter | - where esophagus and stomach meet - normally closed , relaxes by approaching peristaltic wave - allow food in stomach region known as cardia - prevents regugitation |
| stomach | - mucosa is simple columnar, has gastric pits - mucosa + submucosa fold into rugae - muscularis externa has 3 layers (3rd is oblique) - divided into cardia, fundus, body, pylorus - separates from small intestine by pyloric sphincter |
| gastric pits | depressions in mucosa that have gastric glands. composed of 4 different cells that generate different secretions |
| different cells have gastric pits | - neck cells produce mucus - chief cells (pepsinogen, prorennin, gastric lipase) - parietal cells secrete HCl and Intrinsic factor |
| mixture of secretions is | gastric juice |
| enteroendocrine (G) cells in pyloric region | generate gastrin, stimulates production of more gastric juice |
| control of stomach secretions | - cephalic phase: impulses stimulate G cells to secrete gastrin - gastric phase: more gastrin produced - intestinal phase: chyme causes SI to secrete enterogastrones + initiate enterogastric reflex, which both inhibit movements + secretions |
| ulcers | sore that develop in linings of stomach, caused by helicobacter pylori or overuse of NSAIDS |
| small intestine | - have plicae circulares: deep folds of mucosa + submucosa, makes chyme spiral - has villi: fingerlike projections from mucosa, each villus has central lacteal, surface area for nutrient absorption - have microvilli, generate brush border enzymes |
| water, mucus, lysozyme produced by _______ found between villi | crypts of Lieberkühn (intestinal crypts) |
| sections of small intestine | - duodenum: contains brunners glands- secrete mucus and bicarbonate - jejunum: most villi and largest plicae circulares - ileum: has peyers patches- clusters of lymph nodules- prevent bacteria from getting in wall |
| small intestine separated from large intestine by | ileocecal valve |
| segmentation | alternating movement of smooth muscle, mixes and moves chyme forward few cm at a time |
| secretions of lobular ducts (pancreas) | bicarbonate, water |
| liver | - 4 lobes organized into lobules, each lobule has hepatocytes - secretes bile |
| gallbladder | - storage + concentration of bile |
| ductile system of gallbladder | - gallbladder release bile out of its cystic duct - hepatic duct comes out of liver with bile - cystic + hepatic ducts = bile duct - bile + pancreatic ducts merge. sphincter of Oddi allow bile and pancreatic enzymes to enter duodenum |
| absorption of carbohydrates and amino acids | - actively transported by Na symporters into absorptive columnar cells on surface of villi, diffuse into capillary |
| absorption of fatty acids | - diffuse as micelles to columnar cells - diffuse into cells, reconverted to fat inside - coated with proteins: chylomicrons - exit cells, enter lacteal to be carried to venous blood by thoracic duct |
| true or false: in blood, fats hydrolyzed into fatty acids and glycerol | true |
| absorption of vitamins | - fat soluble (A,D,E,K) diffuse with micelles, stored in liver - water soluble (B,C): vitamin B12 bound by intrinsic factor, other vitamins absorbed via diffusion |
| absorption of electrolytes | - positive ions: via active transports (except Ca- needs PTH and vitamin D) - negative ions: attracted by electrical gradient |
| absorption of water | osmosis |
| large intestine | - mix and move waste - fermentation- reduce bulk of waste material - absorbs remaining water - mass movements occur 2-3 times/day, once feces in rectum, starts defecation reflex |
| special modifications of large intestine | - longitudinal muscle has 3 thick bands- teniae coli - due to tension on wall haustra develop - fat filled epiploic appendages attached to serosa for energy storage - ascending + transverse colon- vagus, descending + sigmoid- pelvic splanchnic |
| anal canal | - lined with stratified squamous - mucosa folded into anal columns- contains artery and veins- hemorrhoids: when veins become varicose - internal anal sphincter: smooth muscle - external anal sphincter: skeletal muscle |
| defecation reflex | - involuntary reflex from stretch of rectum, relaxation of internal sphincter expel feces - voluntary relaxation of external sphincter = defecation |
| absorption phase | - glucose delivered to liver, is main energy source for ATP. 10% converted to glycogen, 40% converted to triglycerides - amino acids absorbed into villi, delivered to liver - fatty acids absorb into lacteal, empties into blood, delivered to adipose |
| control of absorption phase | - via insulin produced by beta cells in islets of Langerhans (pancreas) - stimulus: high glucose levels - effects: increase transport of glucose out of blood, into body, increase ATP production, inhibits activity that increases glucose |
| post absorption phase | - blood levels of nutrients fall - fat is now energy source, not glucose - lipolysis, supply energy to tissues (not brain) - use of fatty acids = ketogenesis - liver converts glycogen --> glucose (glycogenolysis) for brain - gluconeogenesis by liver |
| lipolysis | fat hydrolyzed to fatty acids |
| control of post absorption | - via glucagon produced by alpha cells in islets - does opposite of insulin by increasing glucose levels - low glucose levels + stress = hypothalamus sends impulses to adrenal medulla, release epinephrine |
| prolonged fasting/rapid declines of glucose | - brain begins using ketone bodes - low sugar = hypothalamus produces: glucocorticoids (cortisol) - do opposite of insulin and increase glucose levels, growth hormone- protein synthesis/lipolysis/gluconeogenesis to increase glucose levels |
| thyroid hormones, T4, T3 | - increase metabolic rate and heat production - increase rate of protein synthesis to increase growth and development |
Created by:
katiew0