3.3 Gastric enteroendocrine Flashcards
what does secretion of gastrin do
- Inc HCl secretion care0 8 3 activators
- Stimulates gastric emptying (minor effect)
- Stimulates parietal cell maturation
- Stimulates chief cells to secrete pepsinogen
- INC intestine muscle contraction
- Relaxes ileocecal valy and stimulates mass movements
what does secretion of histamine do
- secreted from enterochromaffin cells
- inc parietal cells HCl release (one of the 3 thigns needed to activates secretion of HCl)
what does secretion of serotonin do
- from enterochromaffin like cells
- inc contraction of stomach muscle
(makes 90% of total body serotonin, SSRI)
what does release of Somatostatin do
- inhibits secretion from stomach and pancreas
- inhibts small intestine absorption
- inhibits gall bladder and liver release of bile
describe the regulation of gastric secretion
- neural & hormonal mechansims that alter secretions
- Stimulatory and Inhibitory events occur in phases
- Cephalic (reflex) phase: few min prior to food entry (short)
- Gastric phase: food entering stomach t0 3-4 hours later
- intestinal phase: brief sitmulatory effect as partially digested food enters duodenum, followed by inhibitory effects
describe the Cephalic Phase of gastric digestion
- starts with sight, smell, taste or thgouht of food
- > CNS sends impulse via CNX
- Stim mucous cells -> muscus, Chief cells -> pepsinogen, Parietal cells -> HCl, and G cells to make Gastrin
describe the Hastric phase of gastric secretion
- can be triggered by
- psrtially digested proteins, caffeine, inc in pH
- acts on G cells to secrete gastrin which encourages all the stomach actions
- Chemo and stretch receptors
- trigger mucous, chief, parietal and G cells
- psrtially digested proteins, caffeine, inc in pH
describe the intestinal phase of gastric secretion
- decreased pH (more acidic) or prescence of lipids and carbs caues release of secretin, GIP and CCK -> goes in blood stream and inhibits chief and parietal cells, and peristalsis
- duodenal stretch & chemoreceptors act via enterogastic reflax and inhibt myenteric plexus
describe the gross anatomy of the small intestine
* major organ of digestion and absorption
- diameter: 2.5-4cm
- Duodenum: 25cm, jejunum (upper left) 2.5m, ileum (lower right) 3.5 m
what surface modifcation are made to the SI to increase SA
- need inc SA for nutrient abs
- circular fold (plicae circulares) ~1 cm deep (ones you can see)
- villi 1mm high (on folds make it look fuzzy)
- microvilli ~100-2000nm high
- total SA of SI = 200m2
describe the structure of the intestinal mucosa
- Absorptive cells (simple columnar epithelium)
goblet cells and enteroendocrine cells in epithelium
- lacteal running thi middle
- Paneth cells: found deep in crypts that release antimicrobial agents
- villus epithelium replaced every 2-4 days
what are the modifcations in the diff regions of the SI
- Duodenum: in submucosa -> secretes bicar
- Duodenal glands
- Serosa
- muscularis externa
- Ileum
- aggregated lymphoid modules (big colelction of lymphocytes
- Jejunum
* call have plicucircularis
describe the secretions of your SI
- secreted in response to distension or iritation of mucosa by hypertonic or acidic chyme
- slightly alkaline pH (7.4-7.8) & isotonic with blood plasma
- largely water, enzyme-poor, but contains mucus
- facilitates transport and absorption of nutrients
describe the process of digestion in the small intestine
- Chyme from stomach contains
- > patially digested carbohydrates & proteins
- > undigested fats (lipase so far has been minmal
- spends 3-6 h in SI: most water is absorbed, all nutriends are absorbed
describe the liver
- largest gland in body (3 lbs)
- 4 lobes based on surface features (8 based on vascular & biliary suply)
- right, left, caudate and quadrate lobe
- has a falciform ligament (actually a mesentary)
How does blood get to the liver
blood enters liver at Porta hepatis via
- Hepatic arteries
- Hepatic portal veins
- blood exits liver through hepatic veins (into IVC)
*have two capillary networks in row: artery -> cap -> vein -> vap
locations of hepatic veins and arteries
Describe the microscopic anatomy of Liver
shape of lovules
- liver lobules: hexagonal structure
- filter & process nutrient rich blood
- copmosed of plates of hepatocytes radiating from longitudinal central vein
liver microscopic anatomy
describe the innervation
- middle central vein
- Portal triad: at each corner of lobule (bile duct, branch of hepatic portal bein and branch of hepatic artery)
- liver sinusoids (leaky capillaries between hepatic plates)
- kupffer cells (stellate macrophages)
describe Kupffer cells
aka stellate macrophages
- in liver sinusoids
- self-sustaining population of macrophages within liver
- remove debris (bacteria, worn out blood cells)
- act as gate keeper for mmune response (in addition to lymphoid tissues)
describe the biliary tree
- right and left hepatic druct feed into the common hepatic duct
- the common hepatic duct and cystic duct from the gall bladder feed into bile duct -> pacreas
describe hte functional relationship involved in the storage and ejection of bile
- Liver continuously secretes bile
- Bile is stores & concentrated in the gallbladder
- Duodenum releases CCK whcih triggers dilation of hepatopancreatic sphincter & contraction of gall bladder
*ejects bile into duodenum thru duodenal ampulla
- Bile salt emulsificating lipid droplet in digestive tract lumen
describe enterohepatic circulation
- Bile salts (cholic & chenodeoxycholic acids) are secreted into duodenum
- As bile salts travel through small intestine they allow lipid digestion & absorption to occur (bc of emulsification)
- 95% of bile salts are reabsorbed by ileum
- Reabsorbed bile salts travel via hepatic portal bein back to liver *only 5% of bile salts are newly synthesized each time
*blood goes to liver so bile salts recycled
