digestion - exam 2 Flashcards
how can simple animals have direct exchange w/ the environment
thin, flat shape
very few cell layers
live in moist environments
specialized exchange surfaces for complex animals
composed of living cells
thin
large surface area – folds & branches
moist – intersitital fluid
external or internal
connected to circulatory system
herbivore teeth
ridges & grooves good for grinding up the cellulose in plants
carnivore teeth
sharp to rip flesh
digestive tract
mouth –> esophagus –> stomach –> small intestine –> large intestine –> rectum –> anus
mechanical digestion in mouth
physical breaking down of food
use teeth to chew – bolus
chemical digestion in mouth
using enzymes to break down food
salivary amylase
breaks down starch
mucus
coats bolus & helps it slip down the esophagus
antibacterial agents
makes sure we don’t get sick from bacteria on food
mechanical digestion in stomach
peristalsis / churning
chemical digestion in stomach
gastric juice digests proteins
Hydrochloride acid
pH 2
kills bacteria
denatures proteins
activates protease
pepsin
protease
enzyme that breaks down proteins
can activate pepsinogen
why don’t pepsin & HCl damage cells that make them
they make inactive forms & release them into the lumen - where they are activated
chief cell
makes pepsinogen
pepsinogen
inactive form of pepsin
parietal cell
HCl
activates pepsinogen
why aren’t cells lining stomach damaged by pepsin & HCl
gastric juices not released until food arrives in stomach
mucus cells secrete protective mucus
rapid mitosis – the cells do get destroyed by HCl but they are replaced very quickly