Midterm 2 part 1: small intestine digestion

omasum

causes some delay or retention of digestion

are AA, glucose, or LCFA absorbed in the omasum?

no

what is absorbed in the omasum?

• mainly water

• some VFA absorption

abomasum

• true stomach

• low pH due to secretion of HCl

• start of protein digestion

what is absorbed in the abomasum?

nothing

does anything happen to carbs and lipids in the abomasum?

no

small intestine

only place where absorption of glucose , AAs, and LCFAs occurs 

what facilitates absorption in the small intestine?

massive surface area

what initiates digestion in the small intestine?

pancreatic enzymes

what pH is optimal for function of enzymes in small intestine?

pH~6

where do AA and glucose go that are absorbed in the small intestine?

into the bloodstream and then to the liver

do LCFA go to the liver?

no, they bypass the liver

enterocyte

absorptive cell in small intestine

what are microvilli?

the brush border of the small intestine

where does absorption happen in the small intestine?

at the microvilli, end products of digestion are absorbed

accessory organs

• pancreas

• liver

• gallbladder

accessory organ function

important for digestion

are the accessory organs part of the GIT?

no, but they are important for GIT function

pancreas

• bicarbonate (NAHCO3) secretion

• secretion of protease, amylase, and lipase

liver

synthesis of bile

gallbladder

storage and secretion of bile

what happens to starch in the lumen of the small intestine?

broken down by amylase into maltose

what happens to maltose in the mucosa?

broken down by maltase into glucose

what happens to glucose in the small intestine?

glucose is absorbed into the enterocyte by a transporter and then enters the blood stream

what happens to polypeptides in the small intestine?

broken down by protease into smaller peptides in the lumen

what happens to the smaller peptides in the lumen?

broken down by peptidase into amino acids in the mucosa

what happens to the amino acids in the small intestine?

they are absorbed into an enterocyte by transporters and then go into the bloodstream

where do amino acids go once absorbed in the enterocytes?

into the blood

what happens to triglycerides in the small intestine?

emulsified by bile breaking them into tiny micelles

what happens to emulsified fats in the small intestine?

broken down by lipase into 1 monoglyceride + 2 free fatty acids

what happens to monoglyceride + fatty acids in small intestine?

they are absorbed into the enterocyte by transporters

what happens to monoglyceride + fatty acids in the enterocyte?

re-esterification occurs reforming a triglyceride

what happens to newly formed triglycerides in the enterocyte?

they are packaged into chylomicrons for transport

what happens to the triglycerides after they are packaged into chylomicrons?

they go into the lymph

large intestine

• absorption of water and minerals

• microbial fermentation

• storage of waste

is microbial fermentation aerobic or anaerobic in the large intestine?

anaerobic to generate more VFAs

large intestine structure

few villi because nutrient absorption is mostly complete by end of small intestine

is there mucosal phase digestion for triglycerides?

no, everything happens in the lumen