chapter 34- animal nutrition and the digestive system

simple animals have a

gastrovascular cavity

more complex animals (vertebrates) have a

alimentary canal

gastrovascular cavity

digestive system consisting of a single opening

alimentary canal

digestive system with a mouth and anus

human digestion

mastication, swallowing, stomach, small intestine, large intestine

mastication (chewing)

mechanical breakdown of food, mixes food with saliva (now called a bolus)

bolus + food

moistens, some enzymatic digestive

swallowing

begins peristalsis (involuntary), epiglottis works to send bolus to esophagus, not trachea

peristalsis

wave-like movements of muscle tissue

stomach

very low pH, cells lined with mucus to prevent self-digestion, acid-resistant enzymes used to break apart proteins, creates chyme

stomach pH

denatures (unfolds) proteins, kills/inactivates many pathogens

chyme

mixture of partially digested food and stomach juices

gastro-esophageal sphincter prevents

chyme from entering esophagus

pyloric sphincter ensures

chyme exits stomach gradually

small intestine

walls liked with villi, cells with microvilli (increase surface area to absorb)

3 parts of small intestine

duodenum, jejunum, ilium

duodenum

chyme mixed with pancreatic juices (from pancreas)

duodenum juices

neutralize acidity of chyme, contain digestive enzymes, bile mixed with chyme to emulsify fats

bile

made by liver and stored in gall bladder

jejunum

majority of breakdown and absorption occurs

ilium

bile salts and vitamins absorbed

nutrients are absorbed into bloodstream

sent to liver for processing and distribution

large intestine length

shorter than small i, larger in diameter

large intestine

bacteria breakdown fiber and release some vitamins, absorbs water and bacterial products, compacts waste

anal sphincter

controls elimination of feces

herbivore

have evolved digestive system that enable cellulose digestion

ruminants (cows/goats)

have 4 chambered stomach, regurgitates contents of 1st chamber to chew again

4 chambered stomach

rumen, etc

rumen

large chamber where bacteria breakdown cellulose

nonruminant (rabbits/rodents)

have large cecum of large intestine

nonruminant cecum

houses bacteria that breakdown cellulose

nonruminant problem/solution

best absorption of nutrients in small intestine and cecum, is after small intestine/coprphagy

coprophagy

eat own feces (produce 2 droppings)

vitamins, certain minerals and essential amino acids

must be acquired from food, not made by human body