Digestion

Salivary glands secrete saliva, which contains an enzyme that breaks down starch Food is moistened to help chewing Mastication (chewing) – increases the surface area and mixes saliva enzymes and water with the food Esophagus – long tube that’s the food delivery system to the stomach

Stomach - contains strong acids, enzymes and fluids that mix, toss and grind foods The pepsin enzyme breaks down bonds found in proteins Small Intestine – the site where actual digestion takes place Approximately 20 feet in length Carbohydrates, lipids, and proteins are broken into smaller units and absorbed into the blood stream

Pancreas – secretes pancreatic juice and a bicarbonate that neutralizes stomach acid that makes its way into the small intestine Gallbladder – stores bile Liver - makes bile and digests lipids Large intestine – absorbs water and some minerals into the blood

Liver Liver processes nutrients to send to other parts of body Detoxifies harmful substances ingested Too many harmful substances ingested causes hardening of liver – cirrhoses

Rectum – undigested waste is passed for excretion The brain is the control center for this whole process Hypothalamus regulates appetite and hunger

Other Terms Ingestion – eating and swallowing food and liquids Digestion – the breakdown of food into its individual nutrients Absorption – nutrients in touching the wall of the GI tract for an extended period of time

Transportation – nutrients are transported in the blood to the liver where they’re processed and sent to parts of the body to use Peristalsis – layers of muscles squeeze and push food along the GI tract Slows down as HUMANS age increasing the risk for constipation

When food goes from ingestion to excretion is takes hrs High in fiber diet shortens time Gastric mucus lines stomach to inhibit the acids from eating the stomach lining

Ruminant Digestion 3 preliminary compartments and a “true stomach” It moves food into the rumen and the omasum The reticulum also causes the regurgitation of food and acts as a collection compartment for foreign objects

Rumen The rumen is a large fermentation chamber (adult cattle about 125 L) which has a very high population of micro-organisms, mainly bacteria Bacteria secrete the enzymes necessary for cellulose breakdown to utilize roughage Has textured surface, lined with projections (rumen papillae) The rumen, along with the omasum, absorb the by-products of bacterial fermentation(fatty acids)

Omasum The omasum "manyplies" contains many flat tissue folds that help grind food Folds also help remove water from the food on the way to the abomasum

Abomasum Secretes gastric “juices” Kills bacteria that came from rumen “True Stomach”

Ruminants They have no upper canine teeth, or incisors, and have long, thick and rough tongues Chewing the cud helps reduce feed particle size, and mixes saliva into the feed Classic example of symbiotic association between mammal and micro-organism