THE DIGESTIVE SYSTEM

N: 80 - 82

Function

The main function of the digestive system is to break down macromolecules into substances the body can use

Digestion

Food provides (most of) the nutrients we need to survive

Food is processed in 4 stages:1. Ingestion2. Digestion3. Absorption4. Elimination

Differences in other animals...

Differences in other animals...

Differences in other animals...

Can you think of any others?

The digestive tract is a tube that runs from the mouth to the anus. Food passes through the tract and its related organs.

The accessory organs are ones that assist in the process of digestion, food does not travel through them.

The digestive tract

In the mouth...

Digestion begins in the mouth

1.Mechanical destruction of food specialized, omnivorous teeth why do we chew food?

2.Enzymatic breakdown of food saliva enzymes break chemical

bonds (remember the soda cracker?)

What does it eat?

What does it eat?

What does it eat?

What does it eat?

Through the pharynx and esophagus...

Peristalsis occurs in the esophagus and small and large intestines to move food

Peristalsis – involuntary smooth musclecontractions that force contents onward

To the stomach...

The human stomach contains complex gastric juices that continue the breakdown of food

These juices contain... mucus

hydrochloric acid

enzymes

*Just beyond the stomach...

The “chyme” is treated by accessory organs

Into the small intestine...

In the small intestine (~6m long), macromolecules are digested into monomers and absorbed into the blood stream

Villi & microvillimaximize the absorptivesurface area

Absorption into blood

The large intestine home-stretch...

Unabsorbed materials enter the large intestine (~1.5m long)

Primary roles: House helpful bacteria Absorb water

10 trillion bacterial cells convert undigestible nutrients into things we can use

Finally, the rectum & anus!

Rectum holding area for feces absorbs a little water

Anus sphincter that releases feces

Homeostasis

Define the following:1. Ulcer2. Colon cancer3. Gall stones4. Cirrhosis

What is a stomach ache? What causes them?

What causes diarrhoea and constipation?