Childrens Illustrated Encyclopedia

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466

skeletons

The many girders that make

up the Eiffel Tower act in the

same way as the bones of

a skeleton, keeping the

structure upright.

Chitin

insects, spiders, and scorpions have skeletons

on the outside rather than the inside of their

bodies. they are made of a tough plasticlike

substance called chitin. this is built up from

layers of fiber arranged in different directions,

similar to plywood.

Nicknamed “Beetle”

because of its

shape, this car’s

bodywork is an

exoskeleton

The circular

wall of a

wading pool

is held up by

the water

contained

within it.

Spine

the spine, or backbone, runs

down the back of the body. it

supports the skull and upper

body and allows them to twist

and bend. Animals, known as

vertebrates, which include

humans, get their name from

the flexible row of spine

bones, called vertebrae that

protect the spinal cord. the

spine can flex and bend

because each vertebra can

move slightly against the

next one.

hydroStAtiC Skeleton

Some skeletons are made from materials that are

not rigid at all. instead, they are divided into

compartments that can be filled with fluid, and

this hydrostatic pressure makes them rigid.

Many of the microscopic cells that form

plants and animals keep their shape in this

way, and so do some artificial objects.

pneuMoStAtiC Skeleton

Just as hydrostatic skeletons are inflated

with liquid to make them more rigid and

provide support, some animals are

supported by structures filled with gas.

Gases are much lighter than liquids

so they enable animals, such as

the portuguese man-of-war, to

float on and be blown across

the surface of the water.

externAl Skeleton

Skeletons that cover the outside

of the body of animals, such as insects,

are called exoskeletons. Many

objects made by people also have

exoskeletons, rather than internal

ones. Modern cars, for instance, are

made like this. Flat sheet metal is

molded into curved shapes to make a

strong outer shell to protect the inside.

Chitin

The Portuguese man-of-war

floats on the surface of

the ocean supported

by a gas-filled

bladder.

The body of an earthworm is

filled with pressurized fluid.

Animals

human body

Muscles and movement

Find out more

Compressed air pushes

the structure of this

inflatable life raft

into shape

and holds

it rigid.

Tentacles hang

from the gas-

filled bladder.

The

coccyx,

or “tail”.

Volkswagen “Beetle”

Beetle

Earthworm

Human spine

The spine is

made up of

26 linked

vertebrae.

Fibrous disks

between

vertebrae act

as shock

absorbers

during walking

and allow the

spine to bend.

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