27: Small Intestine Flashcards
length of Small intestine
10 ft in live people
19.7 in cadavers due to muscle tone loss
length of the 3 sections
duodenum: 10 inches
jejunum: 8..2 feet
ileum: 11.5 feet
ends at ileocecal valve
absorptive cells
microvilli
most absorption happens at surface of microvilli
goblet cells
has signficant area where secretion can hapen
eteroendcorine cell
secretes secritin, cholecystokin, GIP (hormones)
cell type (epithelium)
simple columnar epi
4 cell types of SI
absorptive cell
goblet cell
enteroendocrine cell
paneth cell
paneth cell
secretes lysosome and capable of phagocytosis
Villi/Microvilli functions
inc SA for abs
brush border enzymes on surface–> chem breakdown (carbs and proteins_
cell division at base: new cells that move up
Carb digestion enzymes
mouth: salivary amylase
stomach: mechanical
duodenum: pancreatic amylase
brush border enzymes: maltase, sucrase, lactase
brush border enzymes:
maltase, sucrase, lactase
produce monosaccharides from disaccarides
lactose intolerance: no lactase: bacteria ferment the sugar
Glucose and galactose absorption into epicells:
glucose and galactose: sodium symporter (2ndary active transport)
movement of monosacchs out of epis into bloodstream
facilitated diffusion
Protein digestion locations
stomach
SI
brush border enzymes
Protein digestion in stomach
HCl denatures proteins
pepsin turns into peptides (AA chains)
Protein digestion in SI
pancreatic enzymes: split peptide bonds between different AAs
Protein digestion in brush border enzyme
aminopeptidase: split AAs at amino end
dipeptidase: split dipeptides
absorption of amino acids and dipeps into epicells of duodenum and jejjunm
active transport (2ndary) with Na+ or H+ ions (symporters)
movement into blood stream of amino acids
diffusion
Lipid digestion locations
mouth
stomach
SI
Lipid digestion in mouth
lingual lipase
Lipid digestion in stomach
gastirc lipase
infants
Lipid digestion in SI
emulsification by bile from liver–> miscells
pancreatic lipase: split triglyccerides into FAs and monoglycerides
no lipase in brush border!
Water absorption
9 L enter GI tract daiily
SI absorbs 8 L
LI absorbs 90% of last liter
abs by osmosis through cell walls into vascular capps in villi
Absorption of vitamins
fat soluble
water soluble
B12: problem causer
abso of fat soluble vitamins
travel in micelles and absorbed by simple diffusion with lipids
abso of water soluble vitamins
diffusion
B12 abs
has to combine with intrinsic factor from stomach p-cells b4 transport to ileum. abs by receptor mediated endocytosis
electrolyte sources
GI exocrine secretions foods and liqueds diffusion by diffusion and 2ndary AT NA and K Cl-, iodine, nitrate iron, magnesium, phosphate CA++
sodium and potassium abso
active transport
chloride, iodide, nitrate abso
passive
iron, magnesium, phospate
active transport
intestinal Ca++
requires vit. D and PTH
abso of small/short chain fatty acids
simple diffusion into abso cells and bloodstream
b/c easy to get through lipid bilayer
abso of larger lipids/long chain FAs/ monoglycerides
seqestered w/in micelles after emulsification (bile)
enter cells by simple diffusion, leave bile salts in gut
fat soluble vitamins
ADEK
enter cell with the lipid
lipids inside epi cells
fats rebuilt into triglycerides, coated with proteins to make chylomicrons
chylomicrons leave…
by exocytosis into a lacteal
travel in lymph system to reach subclavian veins
removed from blood by liver and fat tissue
fructose absorption into epicells:
facillitated diffusion
