Human Digestive System - JFK Pg 64-70 Biology

- one way passage (gastrointestinal tract)/GI Tract for ingested food together with certain accessory organs that assist the digestive functions of the system.

- hollow tube with an opening at each end.

- food materials in GI tract are actually outside the body tissues

- food is moved through tract by slow, rhythmic muscular contractions called peristalsis

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Structures - include teeth, tongue and openings of salivary glands

- teeth - break down pieces of food mechanically into smaller pieces to expose a larger surface for enzyme action

- salivary glands - secrete saliva, which flows through ducts into the mouth.
-- Saliva contains the enzyme salivary amylase, which begins the digestion of starch, a carbohydrate.
- (Amyl-comes from Greek word meaning starch).

- tongue - acts to help mix the chewed food with saliva and to move it to the back of the mouth for swallowing

Structure - The esophagus is a muscular tube that connects the mouth to the stomach

- The act of swallowing moves food into the esophagus.

- Peristalsis of the muscular walls of the esophagus moves food to the stomach

Structure

- The stomach is a muscular sac
- Its lining contains gastric glands that secrete enzymes and hydrochloric acid
- (Gastr - comes from a Greek word meaning belly and refers to the stomach.)

- Muscular contractions of the stomach wall mix the food with digestive juices
- The enzyme gastric protease begins the digestion of proteins
- The hydrochloric acid provides the proper pH for maximum effectiveness of the gastric protease

Structure

- The small intestine is a long, coiled tube of small diameter.
- Its lining contains intestinal glands that secrete digestive enzymes into the intestine.
- Partially digested food enters the small intestine from the stomach

Liver & Pancreas

- secretes bile, which is stored in the gall bladder and passes through a duct into the intestine

- secretes pancreatic juice through a duct into the intestine

Bile
Pancreatic Juice
Intestinal Juice

Bile
- does not contain enzymes.
- Its function is to mechanically break down (emulsify) fats into very small droplets, thus increasing the surface area of the fats for more rapid digestion by lipases