the human body.pdf

The Human Body

Teacher Information

Skeleton

The adult body contains about 206 bones. The smallest bones are in the middle ear. The

largest bone is the thighbone. Bones contain living tissue, blood vessels, and nerves. They

are covered by a tough membrane that contains bone-forming cells and blood vessels.

Calcium, phosphorous, and other minerals are stored in bones and are sent to other tissues

when they are needed.

Muscles

The human body has three types of muscles used for movement of the skeleton, movements

of internal systems, and movement of the heart. The cardiac muscles are the strongest in the

body. They work day and night pumping blood through the body.

Five Senses—Receptor Cells

Sense organs collect information with cells called receptor cells. These cells collect information

from light waves, sound waves, pressure, or even tiny molecules floating in the air. This

information is converted into electrical signals and carried to the brain.

Five Senses—Sight

When we look at something, light rays reflected from the object pass through the transparent

cornea. The lens then focuses the light rays on the retina, forming an image in reverse and

upside down. Electrical signals are transmitted from the retina to the brain, which “sees” the

image right side up.

Rods and cones are specialized receptor cells in the retina that contain light-sensitive

chemicals. Rods see black and white. Cones see color.

Five Senses—Hearing

Ears are organs of hearing and balance. They receive sound waves and change them into

electrical signals that are “heard” by the brain. Receptor cells in the three semicircular canals

help you to stay upright.

Hairs and wax in the outer ear trap dust and other particles, keeping them away from the

eardrum. The middle ear carries sound vibrations from the eardrum to another thin sheet of

skin, the oval window, that concentrates the sound. In the inner ear, receptor cells in the

cochlea, a fluid-filled, snail-shaped tube, convert sound waves to electrical signals that are

carried to the brain by the acoustic nerve.

A narrow tube (eustachian tube) connects the ears and the throat. It is normally closed, but it

opens automatically when you swallow or yawn. This helps to equalize the pressure inside and

outside your eardrum.

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Printed in U.S.A.

EMC 863

Author: Jo Ellen Moore

Editor: Marilyn Evans

Illustrator: Jo Larsen

Designer: Jo Larsen

Desktop: Jo Larsen

My External Parts

head

hand

neck

shoulder

wrist

chest

arm

elbow

abdomen

waist

hip

thigh

knee

leg

foot

ankle

My External Parts

Each outside (external) part of your body has a job.

These parts help you move, work, and play.

My Skeleton

skull

wrist

bones

collarbone

shoulder blade

arm

bones

rib cage

backbones

hipbone

tailbone

fingers

thighbone

kneecap

shinbone

anklebone

toes

My Skeleton

The bones in your body are your skeleton . These bones

give your body its shape. They hold you up and help you

move. Your bones can heal if they are broken. Your bones

grow longer as long as you are growing.

Some bones in your skeleton have special jobs. These

bones protect the soft parts of your body. The bones of

your skull protect your brain. The bones in your rib cage

protect your heart and lungs. The bones in your backbone

protect the nerves inside.

Many of your bones have red marrow inside. The red

marrow makes new blood for your body.

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