mouth/teeth - for chewing (mastication)
- sharp teeth in carnivores for cutting
- flat teeth in herbivores for grinding
- both types in omnivore
- saliva - mucous solution
- makes food easier to swallow
- contains amylase >> breaks down starch into disaccharide
- epiglottis prevents food from entering respiratory tract
esophagus - 1/3 skeletal muscle, 2/3 smooth muscle
- peristalsis - rhythmic waves of muscle contraction
- cardiac sphincter - ring of smooth muscle preventing food in stomach from coming back into esophagus
stomach - sac part of digestive tract
- can expand due to folds on interior
- extra layer of smooth muscle for churning food, mixing w/ gastric juice
- parietal cells - secrete hydrochloric acid, intrinsic factor (for red blood cells)
- chief cells - secrete pepsinogen (weak protease)
- only proteins digested in stomach
- kills most of bacteria w/ acid, survivors go on to live in large intestine
- ulcer - acid eating hole through stomach wall
- pyloric sphincter - leads to small intestine
small intestine - limited capacity >> digestion takes time
- duodenum - 1st 25 cm of small intestine
- receives chyme from stomach, digestive enzymes from pancreas, bile from liver
- digests larger food molecules
- villi - fingerlike projections w/ microvilli on plasma membrane
- greatly increases surface area >> better absorption
- brush border enzymes in epithelial membrane
- nutrients go into capillaries, to hepatic portal vein
pancreas - secretes fluid to duodenum through pancreatic duct
- exocrine gland
- sends enzymes that are activated by brush border enzymes in intestine
- islets of Langerhans - produces insulin, glucagon for glucose level in blood
liver/gallbladder - largest internal organ
- bile - contains bile pigments, bile salts
- bile pigments from destruction of red blood cells
- jaundice - when bile pigments can’t leave liver
- bile salts - break down fat droplets in duodenum
- gallstone - formed by hardened cholesterol, blocks bile duct
- 1st organ to receive digestion products
large intestine (colon) - connects to small intestine at cecum, appendix
- no digestion, only limited absorption
- no villi in inner surface
- purpose = concentrate waste material
- waste gets compacted/stored
- feces - waste material, exit through rectum to anus
- undigested fiber >> bacterial fermentation produces more gas
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