The Digestion and Absorption of Food
531
Organ
Exocrine
secretions
Functions
Mouth and
pharynx
Esophagus
Stomach
Pancreas
Liver
Gallbladder
Small intestine
Large intestine
Salt and water
Mucus
Amylase
Chewing begins; initiation of swallowing reflex
Moisten food
Lubrication
Polysaccharide-digesting enzyme
Move food to stomach by peristaltic waves
Lubrication
Mucus
Store, mix, dissolve, and continue digestion
of food; regulate emptying of dissolved
food into small intestine
Solubilization of food particles; kill microbes;
activation of pepsinogens to pepsins
Protein-digesting enzymes
Lubricate and protect epithelial surface
HCl
Pepsins
Mucus
Secretion of enzymes and bicarbonate;
also has nondigestive endocrine functions
Digest carbohydrates, fats, proteins, and
nucleic acids
Neutralize HCl entering small intestine
from stomach
Enzymes
Bicarbonate
Secretion of bile; many other nondigestive
functions
Solubilize water-insoluble fats
Neutralize HCl entering small intestine
from stomach
Elimination in feces
Bile salts
Bicarbonate
Organic waste
products and
trace metals
Store and concentrate bile between meals
Digestion and absorption of most substances;
mixing and propulsion of contents
Food digestion
Maintain fluidity of luminal contents
Lubrication
Enzymes
Salt and water
Mucus
Storage and concentration of undigested
matter; absorption of salt and water; mixing
and propulsion of contents; defecation
Lubrication
Mucus
Salivary glands
Figure 15–3
Functions of the gastrointestinal organs.
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