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THE DIGESTIVE SYSTEM

7-3.3 Recall the major organs of the human body and their functions within their particular body system.

Functions of the Digestive System:

Breakdown food into nutrients that the body can use

Absorb nutrients necessary for energy, growth and

maintenance

Rid the body of solid wastes

Why am I Hungry?

You need food to provide energy for your body.

Food contains Nutrients that are important

substances that enable you to move, grow, and

maintain homeostasis.

Examples of Nutrients: Proteins, Carbohydrates, fats,

and water.

What Jobs do Nutrients Have in My

Body?

Proteins: Growth & Repair

Makes your muscles, bones, and skin

Carbohydrates: Energy for Cells

and contain cellulose which helps in

digestion.

Fat: Energy Storage

Water: Necessary for all living

things. More than ½ your body is

made up of water.

Digestion: What happens to My Lunch?

Before you can use nutrients, food most be broken

down into smaller substances.

Digestion is the process of breaking down food into

usable materials.

Types of Digestion:

Mechanical:

Physical changes

Break food into smaller pieces

Occurs in Mouth when Chewing

Chemical:

Actually change food into different substances

Ex. Saliva in mouth changes starch to sugars

The change in taste is a chemical reaction

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The Digestive System:

Performs the complex jobs of moving and breaking down food.

Includes:

Mouth- Mechanical Digestion

Salivary Glands

Stomach

Small Intestine

Large Intestine

Liver

Gallbladder

Pancreas

Movement of Food Through Digestive

System

Food is moved in wavelike contractions called Peristalsis

Mucous Glands can be found throughout the entire system

to keep food moist.

Mouth and Esophagus

Mouth

Teeth break food down via mechanical digestion

Saliva softens food and begins chemical digestion

Esophagus

Muscle contractions of peristalsis move solid food from

the throat to the stomach in about eight seconds. Liquids

take about two seconds!

Digestive System

Liver

Largest Internal Organ

Filters blood

Produces Bile which breaks down fat

Gallbladder

Stores bile to be sent to the small intestine.

Pancreas

Produces digestive juices that help break down food in

small intestine.

Digestive System Continued

Strong muscles in the stomach mix and mash food.

Stomach acid breaks down food.

Small Intestine

Partially digested food moves from stomach

Uses digestive juices from pancreas, liver, and gallbladder to breakdown nutrients.

Tiny folds called villi that absorb nutrients.

Large Intestine

Water and other nutrients are absorbed.

Tightly packs waste and sends it to the rectum for disposal.

Digestion Guided NotesDigestion: process of breaking down food into

smaller, usable materials

1. The body needs energy and materials

a. Need food for energy

b. Need materials from food

• Those materials are called nutrients

2. Nutrients include:

a. Water- no nutritional value but needed for

bodily functions

b. Proteins: building blocks, used for cell growth

and repair (muscles, bones, skins)

c. Carbohydrates: provide cells with energy (this

is the glucose we use in respiration)

d. Fat: stores energy

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Digestion3. The digestive system moves and breaks

down food

a. Peristalsis: moves food through the digestive

system (contractions to push through)

• Why we can swallow while on our heads

Mechanical digestion

a. teeth breaking food into smaller pieces

b. stomach breaks food by mashing and pounding

Chemical digestion

c. changes the chemical composition of food

DigestionMaterials are broken down as they move

through the digestive tract

a. Mouth: both chemical and mechanical

digestion (teeth, saliva)

b. Esophagus: muscle contractions of peristalsis

move food from throat to stomach

c. Stomach: both mechanical and chemical

• strong muscles here mix and mash food into

smaller parts

• hydrochloric acid (HCL) breaks down food

chemically

– acid could eat through stomach but we

have a lining that is replaced every 3 days

• also have some absorption of nutrients here

Digestiond. Small intestine: partially digested food moves

from stomach to SI

• most of the nutrients made available during

digestion are absorbed in the small intestine

• structures called villi found here, they contain

folds that absorb the nutrients.

– Once absorbed by the villi, nutrients are absorbed

by the circulatory system (talk about that later in

year)

d. Large Intestine: water and some other nutrients

are absorbed here

• Most of the materiel left after water removed is

waste and moves to the rectum

The digestive system breaks down food.2.2

SECTION

OUTLINE

FunctionStructure

Mouth

Esophagus

Stomach

Small

intestine

Large

intestine

chemical and mechanical

digestion

movement of food by

peristalsis from mouth to

stomach

chemical and mechanical

digestion; absorption of

broken-down nutrients

chemical digestion;

absorption of broken-down

nutrients

absorption of water and

broken-down nutrients,

elimination of wastes

mouth

esophagus

stomach

small

intestine large

intestine

Introduction to the Human Body:

How are our bodies organized?

? ?

Review

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All living things are made of CELLS! Cells

have specialized jobs, and are organized in

your body. For example, blood cells.

CELLS

TISSUES

ORGANS

ORGAN SYSTEM

ORGANISM (BODY)

A TISSUE is a group of similar cells that all

do the same thing (they have the same

function). For example, Muscle Tissue

An ORGAN is a structure made of different

tissues. The organ does a specific, complex

job. For example, Heart

An ORGAN SYSTEM is a group of organs

that work together to perform a major job.

For example, Digestive System

An ORGANISM is a living thing, with organ

systems that work together to keep a body

alive. For example, Human Beings

The Digestive System

The Digestive System

The digestive system has 3 main functions:

1. It breaks down foodinto particles that the body can use.

2. It absorbs nutrientsinto the blood.

3. It eliminates wastefrom the body.

Mouth

Esophagus

The Digestive System

Digestion can happen in two ways:

1. Mechanical digestion: foods are physically broken down into smaller parts (like by teeth).

2. Chemical digestion: Chemicals called ENZYMES break foods into their smaller “building blocks” (for example, starch gets broken down into sugar).

Mouth

Esophagus

Fill this chart The Digestive System

• MOUTH: your teeth break down food into smaller pieces (mechanical digestion). Saliva has enzymes that start chemical digestion.

• ESOPHAGUS: smooth muscles push food down to the stomach(peristalsis).

Mouth

Esophagus

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The Digestive System

• Most digestion happens in the Stomach:

• Mechanical digestionoccurs when the stomach muscles churnthe food.

• Chemical digestionhappens when stomach acid breaks down food.

Stomach

Esophagus

Mouth

The Digestive System

• Liver, gallbladder and pancreas: produces & stores chemicals (enzymes) that help digest food in the small intestine.

Stomach

Esophagus

Mouth

Liver

Gallbladder Pancreas

The Digestive System

• Small intestine:completes chemical digestion and absorbs nutrients for the body. The nutrients pass through the villi into blood vessels.

• Large intestine: water is reabsorbed by the body.

• Rectum: compresses waste into a solid form.

Stomach

Esophagus

Mouth

Liver

Gallbladder Pancreas

Small

intestine

Large

intestine Rectum

Acting Out the Digestive System

Teeth

Saliv

a

Esop

hag

us

Sto

mach

Pancre

as

Sm

all

Inte

stine

Larg

e

Inte

stine

Blo

od

Rectu

m

The teeth grind

the food

(mechanical

digestion).

The esophagus

uses muscles to

push food down

to the stomach.

The stomach

churns food and

uses stomach

acid to dissolve

it.

The pancreas

excretes

chemicals to

help dissolve

food.

The small

intestines

absorb

nutrients and

send them to

the blood.

The blood

delivers the

nutrients to the

body.

The large

intestines

reabsorb water

for the body.

The rectum

compresses

and removes

waste from the

body.

The saliva uses

chemicals to

break down the

food.

GRAPHIC ORGANIZER

Esophagus pushes food from mouth to stomach.

In the mouth, the teeth break food into smaller pieces and saliva begins to break down starches.

Large intestine absorbs water and eliminates waste.

In the stomach, food is churned and mixed with digestive juices that break down protein.

In the small intestine, almost all chemical digestion and absorption occurs.

Eating Healthy

Reading Food Labels & Using the Food Pyramid

Eat Sparingly

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Humans need to get a combination

of SIX NUTRIENTS to keep their

bodies healthy:

• FATS

• CARBOHYDRATES

• PROTEINS

• VITAMINS

• MINERALS

• WATER

Why are these nutrients important?

• FATS – provide energy, part of cell membrane, acts as insulation & protection for internal organs.

• CARBOHYDRATES – provide energy and raw materials for body.

• PROTEINS – important raw material for body parts (muscles, etc).

• VITAMINS & MINERALS – used in a variety of chemical reactions in the body.

• WATER – body’s vital processes take place in water.

Few foods have all of the nutrients

you need, so you need to eat a

BALANCED, HEALTHY DIET that

has a VARIETY of foods to provide

the proper amount of nutrients to

keep your body healthy.

There are 2 things that can help

you plan a healthy diet:

1) FOOD GUIDE PYRAMID

2) FOOD LABELS

FOOD GUIDE PYRAMID

This pyramid classifies

foods into SIX groups

and indicates how

many SERVINGS of

each group should be

eaten to maintain a

HEALTHY diet.

Eat Sparingly

FOOD LABELS

These labels allow you

to EVALUATE the

NUTRITIONAL VALUE

of a food.

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When reading a food

label, be sure to:

a) Check the MAIN INGREDIENTS. What’s listed first & second?

b) Identify SUGARS and FATS. Look for words that end in –ose (glucose, fructose, sucrose). These are sugars. Oil, butter, and lard are fats.

When reading a food

label, be sure to:

c) Check the SERVING SIZE.

Is there more than 1 serving

in a package?

d) Count the CALORIES. Most

teens should eat about 2,000

– 3,000 calories a day. What

portion of the calories come

from fat? Watch out if more

than ½ the calories come from

fat.

When reading a food

label, be sure to:

e) Look for the 6

ESSENTIAL NUTRIENTS.

f) Watch for SODIUM &

CHOLESTEROL. It’s best

to avoid foods that are

high in these substances.

When reading a food

label, be sure to:

g) Figure out the FAT CONTENT. What kinds of fats are included? Saturated & Trans-fats are “bad” fats, but avoid eating foods that are too high in any fat.

h) Note the VITAMINS & MINERALS. Look for important vitamins (A, C, D, etc) and minerals (calcium, iron).