Lecture 33 Flashcards
GI tract
function of oral phase
lubricate and moisten food
solubilization of material for taste
How does oral cavity break down food
everything mechanically broken down
chemically
carbs- salivary amylase
fats- lingual lipase
neutralizing germs by enzymes
How does swallowing occur?
tongue pushes down bolus which lead the epiglottis to cover the trachea and the stretch receptors allow the upper esophageal sprinter to open. the esophagus uses peristalsis to push down the food
functions of the stomach (gastric phase)
chemically and mechanically digest, protect and store food
Why does the stomach have an mucus bicarbonate layer
the layer is to protect the stomach lining from the acidity of the HCl. if it is breached one could get an stomach ulcer
What gets digested in the stomach?
fats and proteins
How does gastric phase break down proteins?
1) the HCl denatures the proteins so they unfold
2) Pepsinogen is turned into pepsin by the HCl to cleave the bonds into amnio acids
where does HCl come from?
the parietal cells in gatric pit
where does the mucus and bicarbonate come from
mucus(globlet) and neck cells
How does gastric phase break down fats?
1) Course emulsification of fats by the motility
2) gastric lipase to break down into free fatty acids and monoglycerides
what are the enzymes used in the stomach and where do they come from?
pepsin and gastric lipase comes form the chief cells
function of the small intestine
digestion, absorption, and secretion.
regulation of gastric emptying
What is in the walls of the small intestines?
-enterocyctes: has microvilli to create a brush border where digestive enzymes can break down the nutrients and absorptions
- globet cells: mucus for lubrications
- lacteals: absorb into fats lympathtic
- capillaries: absorb nutrients
what is the exocrine pancreas
- acinar cells to secrete the digestive enzymes like proteases, amylases and lipases
- duct cells to transport bicarbonate to neutralize the acids chyme from stomach not the intestine.
how do the pancreas secretions get into the small intestine?
it gets in by the pancreas duct that does through the splinter of oddi to the duodenum
what is bile and where is it from
bile is NOT an enzyme
it is a solution of bile salts and cholesterol to to help emulsify and absorb fats
it is made in the liver but concerted in the gallbladder
how does the small intestine digest carbs?
pancreatic amylase and the brush border enzymes in the duodenum and jejumn
what is the 3 types of monosaccharides?
glucose, fructose and galactose
where are the disaccharides converted into monosaccharides and what brush border enzymes break them down?
the small intestine
maltose - maltose (2 glucoses)
sucrase- sucrose (1 fructose, 1 glucose)
lactase - lactose (1 glucose, 1 galactose)
How does the small intestine digest proteins
mechanically by segmental contractions
chemically by peptidases
example of peptidases
pancreatic enzymes like chymotrypsin
endopeptidases - cut in middle
exopepetidases- cut at the ends
how does the small intestines digest fat
fine emulsification by bile salts and pancreatic lipase
how does bile help digest fat
they are amprotic so the hydrophobic side sticks to the fat and the hydrophilic side goes to the water
it creates smaller pieces called micelles and are brought towards the enterocytes
how is fat absorbed (details)
1) bile salts surround the large fat droplets
2) pancreas lipase and colipase breaks them down into monoglycerides and free fatty acids turning them into micelles
3) the micelles go to the cells
- cholesterol transports through cells
- fatty acids and monoglycerides diffuse in
4) the cholesterol combines with protein and the fatty acids to turn chylomicrons in the smooth ER & Golgi apparatus
5) they are removed by the lacteals
