Physiology Flashcards
(7 cards)
name 3 anatomic and histologic features of the intestinal wall that facilitates absorption
- mucosal surface has many folds which increases SA
- villi
- microvilli
what are the 4 goals of ion and water transport in the intestinal tract?
- provide appropriate substrates for various processes (gastric acid, stomach mucosal protection, neutralization of HCl, Na/K secondary active transport of solutes)
- maintain correct pH of GI lumen
- maintain correct osmolarity of GI lumen
- contribute to plasma osmolarity maintenance
describe 7 features that allow ions and wateer to be absorbed from the intestinal tract
- leaky tight junctions (allow passive transport)
- wide intercellular spaces (allow for passive transport)
- polarized cells (allow for directional movement)
- microvilli (increase SA for absorption and secretion)
- abundant basolateral membrane (increased SA)
- 2 outsides (GI lumen + basolateral interstitium) allows transport into 2 diff areas and maintenance of 2 gradients
- proximity to vascular channels (allows removal of ions)
describe thee absorption of water
water is transported through the GI systeem by passive diffusion
it always follows something (Na, Cl, AAs, glucose)
when digesta is dilute, water is absorbed through mucosa into blood by osmosis
when digesta is hyperosmotic, water travels from plasma into digesta
how is chloride absorbed?
diffusion (follows Na)
Na is absorbed through epithelium and creates electronegativity in chyme
Paracellular space is electropositive
Cl moves along gradient to follow Na
how is bicarbonate absorbed?
When Na is absorbed, H ions are secreted into the GI lumen. H combines with bicarb to form carbonic acid
Carbonic acid dissociates to form water and CO2
CO2 is absorbed in the blood, water remains in chyme within intestines
how is calcium absorbed?
actively absorbed from duodenum
controlled by body’s daily need for calcium
PT hormone activates vitamin D
vitamin D enhances Ca absorption
