GI Tract Flashcards
What are the sections of the GI tract?
-headgut
-foregut
-midgut
-hindgut
What section of the GI tract differs the most between species?
foregut
Digestive system
the digestive tract and liver, pancreas, and gallbladder
Digestive tract
the path/organs involved in digestion from mouth to anus
Function of the GI tract
-protection from microbial infections
-transport ingested food
-solubilize nutrients
-absorb nutrients
-excrete undigested residue and metabolic waste
Mechanical digestion
-chewing
-GI tract contractions
-gizzard in birds
Chemical digestion
-in the stomach/proventriculus/abomasum
-HCl and bile salts (small intestine)
Enzymatic hydrolsis
macromolecules are broken down into constituent parts
Two basic types of digestion
-simple hydrolytic
-fermentative
Microbial activity of rumen contents
-make the energy in cellulose available
-synthesize B vitamins
-utilize nonprotein nitrogen or poor-quality dietary protein
Gas production by ruminal ingesta
-CO2
-methane
Properties of saliva
-lubricant (contains mucin)
-pig and humans have amylase
-ruminants have buffering acids
What are the major buffers in ruminant saliva?
-bicarbonate
-phosphate
Secretions that aid in digestion
-enzymes
-saliva
-acids/bases (HCl and HC3)
-biliary secretions (bile salts and buffers)
-hormones (gastrin, secretin, CCK, somatestatin)
What is saliva stimulated by?
-psychic reflex
-food in mouth
-in ruminants: stimulation of cardiac region of the stomach by tactile stimuli
Gastrin function
stimulation of acid secretion by gastric glands
Secretin function
stimulation of volume and bicarbonate outputs of pancreatic secretion and in some species bile
CCK
contraction of gallbladder and pancreas; stimulates synthesis of pancreatic enzymes; enhances insulin release; inhibits gastric acid secretions
Somatostatin
inhibits release of gastrin, secretin, and CCK and inhibits ion transport to intestines
Enzyme secretions in the mouth
salivary amylase in pigs and humans
Enzyme secretions in the stomach
-pepsinogen
-HCl
Enzyme secretions in the pancreas
-pancreatic amylase
-trypsinogen
-chymotrypsinogen
-lipase
Enzyme secretions in the liver
bile
Enzyme secretions in the small intestine
lactase
Primary enzyme of starch digestion
amylase
Products of starch digestion
maltose and glucose
Primary enzyme of maltose digestion
maltase
Products of maltose digestion
glucose
Primary enzymes of lactose digestion
lactase
Products of lactase digestion
glucose and galactose
Primary enzymes of sucrose digestion
sucrase
Products of sucrose digestion
glucose and fructose
Primary enzyme of lipid digestion
lipase
Products of lipid digestion
-monoglycerides
-glycerol
-fatty acids
Primary enzymes of protein digestion
-pepsin
-trypsin
-chymotrypsin
-carboxypeptidase
-aminopeptidase
-dipeptidase
Products of protein digestion
peptides and amino acids
