The Digestive System Function: To breakdown food into molecules that can be used by the body for growth, repair, and energy. Form: Many organs, and digestive enzymes.

The mouth Teeth: Mechanical Digestion Coated in enamal Different teeth = different function Incisors & Canines = bite, tear, rip Molars & Premolars = chew Tongue: Swallowing Amylase: Digestive Enzyme (chemical digestion) Food is formed into a bolus (ball of chewed food mixed with enzymes)

The Esophagus Connects the mouth to the stomach Food moves by peristalsis Rhythmic contractions of the smooth muscle of the esophagus

The Stomach Food enters through the cardiac sphincter, a circular muscle at the top of the stomach. Mechanical digestion: Churning and mixing Chemical digestion: enzymes Pepsin: Breaks down protein HCl Hydrochloric-Acid: provides the acidic environment that pepsin works best in Mucous membrane: protects stomach from acid Many folds of the stomach allow for increased surface area and the ability to stretch Partially digested food leaves the stomach through the pyloric sphincter as chyme.

Small Intestine Longest organ of digestion Starts with the duodenum Where digestion is completed Nutrients are absorbed by Villi: Digestive enzymes from the pancreas, gall bladder, and liver are added to the small intestine Food moves by peristalsis

Villi Coat the small intestine Increase surface area Increase absorption

Liver, Gallbladder & Pancreas Liver makes bile Gallbladder store bile Bile Combination of salts that emulsifies or breaks down fat into smaller droplets Pancreas adds enzymes and a neutralizing solution Produces hormones that regulate blood sugar levels (insulin)

The Large Intestine Absorption of water Bacteria produce important vitamins (K) Ends with the rectum and anus Mass peristalsis pushes undigested remains out of the body.

How Do Bacteria Obtain Energy Photosynthesis: Energy obtained from the sun Chemosynthesis: Energy obtained by digesting non living substances (rock, metals, sulfurs) Heterotrophic: Energy obtained by digesting biotic substances by creating secreting powerful enzymes and absorbing the nutrients directly into the bacteria cell.

Protozoan Filter feed Photosynthesis Surrounding and absorbing. Many protozoan have bacteria that aid in digestion

Plants Plants obtain their food by photosynthesis Energy from the sun converts carbon dioxide and water in to sugar and oxygen Water is drawn up by roots and carbon dioxide is absorbed by the leaves. Chloroplast are the organelles that photosynthesize.

Fungus Secrete a digestive enzyme and then absorb the digested food into body Digestion is external Feed on dead, dying or living organisms Do not use photosynthesis

Arthropods Very simple plan But similar to that of mammals Termites have protozoan in there gut to help digest wood.

Birds, Crocodiles, and Earthworms All have a gizzard like organ to help grind food. Gizzards are filled with stones Dinosaurs also had gizzards

Cows Stomach Contains different chambers to increase effectiveness of digestion Bacteria very important in digestion of plant material.