The Digestive System

Chapter 22-3

Science Words/Objectives

• Digestion

• Mechanical digestion

• Chemical digestion

• Saliva

• Peristalsis

• Chyme

• Villi

Objectives

• Distinguish between mechanical and chemical digestion

• Mane the organs of the digestive system and describe what takes place in each

• Explain how homeostasis is maintained in digestion

Processing food

• Digestion- the process that breaks down food into small molecules so they can move into the blood.

Introduction to Digestion

Digestive system

• Mouth

• Esophagus

• Stomach

• Small intestine

• Large intestine

• Rectum

• anus

• Does not pass thru the liver, pancreas, gallbladder- they produce or store enzymes and chemicals that help break down food as it passes through the digestive tract

Parts of digestive system,

Enzymes

• Are molecules that speed up the rate of chemical reactions in your body.

• Enzymes in the mouth, stomach, small intestine,.

• Breaks down proteins and fats

Where and How digestion occurs

• Mechanical digestion-takes place when food is chewed and mixed in the mouth and churned in the stomach.

• Chemical digestion-breaks down large molecules to small molecules. Mouth, stomach and small intestine

Forms of Digestion

Mouth

• Mechanical digestion starts with your teeth.

• Chemical digestion starts with your saliva.

• Saliva-produced by 3 glands, is water, mucus, and salivary amylase(enzyme)

• Moved by tongue- swallowed into esophagus.

The Mouth

Esophagus

• Muscular tube 25 cm long, 4-10 seconds to go through it

• No digestion takes place

• Smooth muscles move food by squeezing.

• Peristalsis- waves or contractions

The Esophagus

Stomach

• Is a muscular Bag.

• As food enters it expands and the folds smooth out

• Mechanical and chemical digestion

• Changes into a thin watery liquid called chyme, which goes into the small intestine

The Stomach

Small Intestine

• 4-7 meters in length• Enters the duodenum

where most of all digestion takes place.

• Liver produces bile to help break down food

• Pancreas produces enzymes to break down fats and proteins

Small IntestineGall Bladder and

Pancreas

Small intestine

• The small intestine has ridges and folds, the folds are covered with tiny fingerlike projections called villi.

• Villi make the surface of the intestine greater so that there are more places for food to be absorbed.

Large Intestine

• Main job is to absorb liquid from chyme- undigested materials become more solid.

Large intestine

The Role of Bacteria

• Bacteria feed on cellulose and produce several vitamins that you need

Digestion and Nutrients

Digestion and Nutrients

Homeostasis

• The regulation of steady, life maintaining conditions inside an organism or cell, despite changes in its environment.

• Water is removed and returned to the body

References

• Glencoe Life Science

• UnitedStreaming.com

• Adam.com