3.2 THE DIGESTIVE SYSTEM

DIGESTIVE SYSTEMThe digestive system has 4 primary functions:IngestionDigestionAbsorptionEgestion

INGESTION & EGESTION

Ingestion refers to the consumption of a substance (1st step).

Egestion refers to the removal of unwanted materials from the body. (Last step)

DIGESTIONDigestion is the mechanical and

chemical breakdown of food into smaller components. (2nd step) It is the breakdown of large food molecules into

smaller ones.

FatProteinsCarbohydrates

Waste

ABSORPTION (FIG. 3.16, PG. 98) Absorption is the process by which digested

food nutrients and water are taken from the intestine and moved throughout the body. (3rd step)

Body (Through Blood Vessels)

Body (Through Blood Vessels)

DIGESTIVE SYSTEM LABELLED

Gallbladder Pancreas

SCENARIO: EATING A BURGER

The burger enters the oral cavity (i.e. the mouth)

A bite is taken out of the burger and chewing proceeds (mechanical digestion)

The salivary glands secrete amylase to breakdown the carbohydrates. (chemical digestion)

Once the food has been broken down into small enough pieces, the food is swallowed.

DOWN THE ESOPHAGUS TO THE STOMACH

The partly digested food travels through the pharynx (throat) down the esophagus through peristaltic contractions.

DIGESTION IN THE STOMACH The food passes through a sphincter into

the stomach where gastric juices surround the food.Hydrochloric acid and the enzyme pepsin

break down most of the protein. (chemical digestion)

The stomach then covers the food in mucus and sends the food down to the small intestine (duodenum)

THE SMALL INTESTINE The pancreas, liver, and gall

bladder release chemicals to help break down the food further.

The small intestine contains millions of tiny folds called villi and microvilli Provides increased area for

absorption Nutrients and water can be

reabsorbed into the bloodstream

THE LARGE INTESTINE Includes the colon, rectum, and anus Mainly absorbs water

Also absorbs vitamins and various saltsUndigested food leaves as feces (E.g. Corn)

Read pg. 93 - 99Complete “Digestive System”

WorksheetDo # 1 – 4 on pg. 99

IT TAKES GUTS