functions of digestive system

8. Elimination

* waste products of digestion are removed from the body * primarily in the large intestine, *water and salts are absorbed, changing the material in the digestive tract from liquefied to semi-solid.

Mucus,

*entire digestive tract, lubricates the food and the lining of the tract. * coats and protects the epithelial cells of the digestive tract from mechanical abrasion,stomach acid, and digestive enzymes. * contain large amounts of water,

3. propulsion

24-36 hours Each segment of the digestive tract is specialized to assist in moving its contents from the oral end to the anal end: deglutition, peristalsis, Mass movements

5. Secretion

As food moves through the digestive tract, secretions are added to lubricate, liquefy, buffer, and digest the food. *mucus , water

2. mastication

Chewing mechanical digestion that leads to chemical digestion increase the total surface area of food for digestion.

1. ingestion

Intake of food into stomach

peristalsis

Involuntary waves of muscle contraction that keep food slowly moving along in one direction through the digestive system.

4. Mixing.

Some contractions do not propel food from one end of the digestive tract to the other but, rather, move it back and forth within the digestive tract to mix it with digestive secretions and help break it into smaller pieces.

6. Digestion

breakdown of large organic molecules into their component parts * carbohydrates into monosaccharides, * proteins into amino acids, * triglycerides into fatty acids and glycerol.

Mass movements

contractions that move material in some parts of the large intestine. extend over much larger parts of the digestive tract than peristaltic movements

chemical digestion

digestive enzymes secreted along the digestive tract. * Large organic molecules must be digested into their component parts before they can be absorbed by the digestive tract. *Minerals and water are not broken down before being absorbed. *Vitamins are also absorbed without digestion (they lose their function if their structure is altered by digestion).

defecation.

feces eliminated from the digestive tract

feces,

liquefied semi-solid waste products,

water

liquefies the food, making it easier to digest and absorb.

mechanical digestion

mastication and mixing of food

Segmental contractions

mixing contractions that occur in the small intestine

7. Absorption

movement of molecules out of the digestive tract and into the circulation or into the lymphatic system. The mechanism by which absorption occurs depends on the type of molecule involved * Molecules pass out of the digestive tract by diffusion, facilitated diffusion, active transport, symport,or endocytosis

Peristaltic waves

muscular contractions consisting of a wave of relaxation of the circular muscles in front of the bolus, followed by a wave of strong contraction of the circular muscles behind the bolus, which force the bolus along the digestive tube *travels the length of the esophagus in about 10 seconds. *in the small intestine usually travel only short distances.

Enzymes

secreted by the oral cavity, stomach,small intestine, and pancreas break down large food molecules into smaller molecules that can be absorbed by the intestinal wall.

deglutition

swallowing