23 14-18 Flashcards
Small intestine adaptations
- Circular folds/plicae circulares
- Villi
- Microvilli
- Blood capillaries (pick up H2O based nutrients)
- Lacteals (absorb lipids)
- Length of intestine
- GALT (immunity)
Gross anatomy of small intestine
Pyloric sphincter - Duodenum 10” - Jejunum 8’ - Ileum 12’ - Ileocecal valve Has accesory organs: Liver, gallbladder, pancreas
Micro anatomy of small intestine
Highly adapted for absorption: Plicae circulare/villi/microvilli.
Simple columnar absorptive cells with tight junctions and goblet cells.
Intestinal crypts/crypts of lieberkuhn intestinal crypt cells (secrete intestinal juice that serves as a carrier fluid for absorbing nutrients from chyme.)
Enteroendocrine cells/enterogastrones secretin-CCK.
Intraepithelial lymphocytes,
Paneth cells (defensins/lysozyme),
Peyer’s patches/GALT - these three are immune cells.
Duodenal glands in submucosa - secrete alkaline mucus
Small intestine function
complete digestion, most of absorption, protection/immunity
What type of cells are in the intestinal crypts?
Crypt epithelial - secrete intestinal juice, a watery mixture that contains mucus and is a carrier fluid.
Enteroendocrine cells - secretin, cholecystokinin.
IELs - intraepithelial cells that are T cells.
Paneth cells are deep in the crypt – defensins/lysozyme
How much saliva per day? Stomach juice? Intestinal juice?
1.5, 2L, 1-2L slightly alkaline
Function of liver
Protein synthesis (albumin/fibrinogen/alpha-beta globulins/hepcidin) Urea synthesis Storage (2 hrs glycogen) Hormones (EPO/TPO/angiotensinogen/IGF) Detox (#1 goal) Ooooox Glucose and fat metabolism
Bile formation
Liver role in digestion
Synthesis and secretion of bile - bile acts like a detergent, breaks fat into smaller pieces
What is bile?
Mostly water with some ions, bilirubin, cholesterol and lipids know as bile salts.
Special cells in the liver?
Kupffer - phagocytes and APCs
Embedded in sinusoid walls
Liver anatomy
3.5 lbs, hepatocytes, sinusoids, L/R lobes, falciform ligament (attaches ventrally).
Blood supply is hepatic artery, hepatic portal vein
Enzymes?
Mouth: salivary amylase, lingual lipase
Stomach: pepsin, gastric lipase
Small intestine: pancreatic amylase, trypsin, chymotrypsin, pancreatic lipase
Brush border: dexrinase, glucoamylase, amylase, lactase, maltase, sucrase, aminopesidase, carboxype
gallbladder anatomy and function
4” long, thin walled muscular sac.
Inferior surface of R lobe of liver
Concentrates bile by absorbing water and ions.
Honeycomb folds that allow it to expand.
Expels bile out of cystic duct –> bile duct.
Regulation of bile and pancreatic secretion and entry into small intestine. 6 steps
- Entrance of chyme into duodenum causes the release of CCK and secretin from duodenal enteroendicrine cells.
- CCK/secretin enter bloodstream.
- CCK induces secretion of enzyme rich pancreatic juice. Secretin causes secretion of HCO3- rich pancreatic juice.
- Bile salts (major stimulus) and some secretin stimulate liver to produce bile more rapidly.
- CCK (via bloodstream) causes gallbladder to contract and hepatopancreatic sphincter to relax; bile enters duodenum.
- During cephalic and gatric phases, vagal nerve stimulation causes weak contraction of gallbladder.
Secretin
Causes HCO3- secretion from pancreas.
Targets liver to ↑ bile production.
CCK
Causes enzyme secretion from pancreas.
Causes gallbladder to release bile.
Pancreas/pancreatic juice contribution to digestion?
Alkalinity (neutralizes low pH of chyme), enzymes.
Migrating motor complex
Intestinal housekeeper, happens between meals/fasting.
Stimulated by hormone motilin (released by duodenal mucosa).
Successive waves of peristalsis, each occurring further down the line than the last.
Prevents bacteria from lg int from entering sm int.
Motility of small intestine
Most common - segmentation
Migrating motor complex
