Gut Digestion and Absorption

digestion

the process of breaking down food by mechanical and enzymatic action in the alimentary canal into substances that can be used by the body

absorption

the process by which products of digestion are absorbed by the blood to be supplied to the rest of the body

where does most of the absorbtion in the body take place

small intestine

what are the digestive cells in the stomach

parietal cells

cheif cells

enteroendocrine cells

villi

small, finger like projections that protrude from the mucosal lining to increase nutrient absorption surface area

microvilli

hair-like projection that aid in absorption of nutrients

the mucosal epithelial cell layer of small intestien houses what

enterocytes

brush border

goblet cells

crypt cells

enterocytes

absorptive cells

brush border

microvilli-covered cells expressing digestive enzymes

goblet cells

secrete mucus

crypt cells

epithelial stem cell which replenish dead/sloughed off cells

what are the wasy nutrients are absorbed

• co-transport

• facilitated diffusion

• osmosis

• simple diffusion

most carbs in diets are ____

polysaccharides

dissacharides

sucrose

lactose

monosaccharides

glucose

fructose

where is polysacchairdes digested

it is digested by salivary and pancreatic amylase

salivary amylase is inactivated by ____

acids in the stomach

pancreatic amylase continures polysacchairde digestion in the ___

small intestine

amylases reduce starch and glycogen to either or _

• maltose

• limit dextrins

digestion of carbs to monosaccharides is completed by ___

brush border enzymes bound to the apical membranes of absorptive cells lining the small intestine

dextrin and glycoamylase

break down limit dextrins and straight chain glucose polymers into glucose monomers

sucrase

hydrolyzes sucrose into glucose and fructose

lactase

hydrolyze lactose to glucose and galactose

maltase

hydrlyze maltose to two glucose molecules

fructose is absorbed by ___

facilitated diffusion

glucose and galactose enter epithelial cells by ___

active cotransport

monosaccharides enter blood stream through ___

facilitated diffusion across basolateral membrane

zymogens

to protect the secretory cells from digestion enzymes are stored in cells in an inactive form

secreyed zymogens are converted into active enzymes by ___

proteolytic activation

pepsinogen is secreted by ____ of ___

chief cells of the stomach

pepsinogen is partially activated by hydorgen ions secreted by the ___ of the stomach

parietal cells

what brush border enzyme converts trypsinogen to trypsin

enterokinase

carboxypeptidases and aminopepdidase

finish protein digestion by cleaning amino acids from the carboxyl and amino ends of a polypeptide chain, respectively

small peptides and amino acids are ___ into intestinal epithelial cells

actively transported

amino acids are transported across basolateral membrane by ___ and diffuse into the blood

facilitated diffusion

bile salts

facilitate the action of digestive enzymes by emulsifying fat globules down into smaller droplets

bile salts are synthesized by ___ and secreted in the _

hepatocytes

bile

lipid containing chylomicrons are transported into the ___ underlying the epithelial cell layer

lympatic vessel

vitamins

consumed in absorptive state and do not undergo digestion

hydrphobic/fat soluble vitamined ADEK

absorbed with lipids

water soluble vitamines

absorbed by active transport or facilitated diffusion

minerals

absorption occurs by acitve transport

• 80% enters the GI tract through secretions

• 20% ingested

calcium absoprtion

regulated based on bodies needs

• enhanced but 1,25 OH vitamin D3 increasing the amount of calcium binding protein

iron absorption

can be absorbed in reduced inorganic form and when bound to heme

water absorption

driven by osmotic gradient across mucosal epithelium created by the transport of solutes from lumen to interstitial fluid

what are the sources of water

• drinking water

• secretions from stomach, intestine, accessory glands