Digestive SystemMs. Bowman

Digestive System• Functions• Takes food in• Breaks food down into nutrient molecules• Absorbs nutrients into the bloodstream• Rids the body of indigestible remains

• Organs of digestive system fall into 2 categories• Those of alimentary canal• Accessory organs

Alimentary Canal• Also called gastrointestinal (GI) tract• Continuous muscular digestive tube that winds through

the body• Functions

• Digests food• Absorbs nutrients through lining into the blood

• Organs• Mouth• Pharynx• Esophagus• Stomach• Small intestine• Large intestine• Anus

Alimentary Canal• Over 30 ft in length• The food material in this canal is technically

outside the body because the canal is open to the external environment at both ends

Accessory Organs• Teeth• Tongue• Gallbladder• Salivary glands• Liver• pancreas

Digestive Process1. Ingestion-taking food into the mouth2. Propulsion-moves food through the alimentary canalo Includes swallowing and peristalsis (major means of propulsion;

involves alternating waves of contraction and relaxation of muscles in the organ walls

3. Mechanical Digestion-physically prepares food for chemical digestion by enzymes

o Includes chewing, mixing of food with saliva by tongue, churning food in the stomach, and segmentation (mixes food with digestive juices and increases efficiency of absorption)

4. Chemical Digestion-series of catabolic steps in which food molecules are broken down into their chemical building blocks

o Food broken down by enzymeso Starts in the mouth and is complete in the small intestine

Digestive Process

5. Absorption-passage of digested end products from the GI tract through the mucosal cells into the blood or lymph

o Small intestine is the major absorptive site

6. Defecation-eliminates indigestible substances from the body via the anus in the form of feces