Lesson 6Digestive System

AIM: How does the digestive system work to maintain a stable and healthy body?

Do Now: What are you doing?

What is the Digestive System?

Digestion – the process that breaks down food into forms that the body can use.

Digestive system- organs that break down food into molecules.

Food provides proteins and nutrients the body needs.

3 Functions of the Digestive System

1. It breaks down food into molecules the body uses.

2. The molecules are absorbed into the blood stream and carried through to the body.

3. Wastes are eliminated from the body.

Parts of the Digestive system

Esophagus

Stomach

Small Intestine

Large Intestine

Liver

Gall Bladder

Pancreas

2 types of Digestion

There are two ways that digestion takes place.

1. Mechanical Digestion

2. Chemical Digestion

Together these two processes change food to atoms and molecules.

Mechanical DigestionIs a physical change that results in breaking up food into smaller pieces.

Done by the mouth and teeth.

Chewing

Mixing

Biting

Tearing

Chemical DigestionChemicals break

down large molecules into smaller parts.

Is a chemical change that breaks down your food.

Ex: saliva, acid in the stomach and small intestine.

Video: 5:35-8

Enzyme- a protein that produces chemical reactions

Check For UnderstandingWhich statement about digestion is true?

A.Saliva digests food mechanically; teeth digest it chemically.

B.Mechanical digestion and chemical digestion occur in the large intestine.

C.Enzymes digest food chemically; teeth digest food mechanically.

D.Chemical digestion mashes up food; mechanical digestion breaks it up with enzymes.

Do NowAIM: What is the difference

between mechanical and chemical digestion?

Write heading and AIM in notebook.

As soon as you are completely quiet, I will distribute something….

Digestion in the mouth1. Put half the cracker in your

mouth and chew. In your notebooks, record what it tastes like. Sweet? Plain? Hard? Soft? Salty? (bullets are fine.)

2. When I say to begin, you will put the second half of the cracker in your mouth, but you WILL NOT chew it.

You will keep it in your mouth for 1.5 minutes. When I give you the signal, think about the following questions:

A. What does it feel like at first?

B: after 1 minute?

C. After 1.5 minutes?

D. When you chew it?

Human Digestionhttp://www.discovery.com/tv-shows/other-shows/

videos/assignment-discovery-shorts-06-07-07-08-human-digestion.htm

The Steps of Digestion1.Mouth

Where food enters the digestive system.

In the mouth food is chewed up

Teeth bite the food and chew it before it moves on to the tongue

The tongue moves the food around mixing it with saliva.

Saliva

Is a secretion that contains an enzyme important for breaking down food.

Within the mouth both mechanical and chemical digestion occur.

2. EsophagusA muscular tube that

connects the throat to the stomach

Is about 10 inches long

It takes about 4-10 seconds for food to move down your esophagus.

No digestion takes place here.

Esophagus continuedThe walls of the

esophagus are layered with muscles that squeeze and push food along in process called “Peristalsis”

Food travels through the esophagus towards the stomach.

3. Stomach the stomach is a

muscular bag like organ that can shrink and stretch.

Food is temporarily stored here

Stomach continuedBoth chemical

and mechanical digestion

Mechanical: The muscles of the stomach contract mixing all of the food inside it together

Chemical: food is mixed with enzymes and strong digestive juices like hydrochloric acid to break it down

Stomach continuedStomach also produces

mucus which protects the wall from the strong digestive juices .

Food moves through your stomach in 2-4 hours.

Turns partially digested food into a watery substance- Chyme

AIM: How does the digestive system get nutrients to our cells? (How does a turkey sandwich give us energy?)

Do Now: Write heading and AIM. In notebooks, write down some possible answers to the AIM question.

4. Small IntestineAbout 22 feet long!!!

Finishes chemical digestion of food.

Absorbs nutrients and sends them to the bloodstream

Villi – finger-like structures covering inner wall, allow for absorption of nutrients

Small Intestine: Part 1: Duodenum

First part of the small intestine which is connected to the stomach.

Most digestion takes place here

Bile from the liver is added to help break down particles.

5. Large Intestine

About 5 Feet long

• Absorbs what the small intestine does not absorb

• Takes undigested food and turns it into waste.

• LI keeps water in your body to maintain homeostasis.

• Video 8:50-11

You can lose a large part of your large intestine and still survive

Check For UnderstandingWhich is a function of the large intestine?

A.It absorbs nutrients from food and puts them into the bloodstream

B.It takes nutrients to all the cells of your body

C.It breaks down food chemically

D.It absorbs extra liquid from food your body could not digest

Liver

• Affects digestion by producing bile• Bile- Helps digest fat

Processes nutrients in the blood, filters out toxins and waste.

Is often called the body’s energy factory.

You cannot live without a liver, although you can live with a part of one.

Drinking alcohol damages the liver.

Gall BladderStores bile from

the liver.

Delivers bile when food is digested.

Fatty diets can cause gallstones.

You can live without a gallbladder.

PancreasProduces

digestive juices for further break down food.

Regulates blood sugar by producing insulin. (homeostasis)**

If it does not work you get diabetes.

BacteriaMany types of bacteria

live in your body and organs

Some are good for you

Bacteria in the digestive system make vitamins you need.-Vitamin K and two B vitamins.

Vitamin K- blood clotting

Vitamin B-helps nervous system.