Skeletal SystemVocabulary

Imagine a giant skyscraper reaching up into the sky. Up at the very top there are hundreds of workers busy doing their jobs. No matter what the weather is like outside, these workers feel safe, because they know that the building was built very strong. Even on windy days, the building will not fall over.

What gives buildings their super strength? The secret is in their bones. Well, sort of. Buildings are built around a steel framework. This framework holds the weight and allows the builders to go as high as they want.Your body is similar to a skyscraper. A small ant might look up at you and think “wow, what keeps that large animal from falling over?” The secret to your strength lies in your bones.

Just like a skyscraper, your body is built around a hard and strong framework. Instead of steel and concrete, your bones are made out of very hard materials

In a building, workers use nails, bolts, glue and concrete to hold the building to the framework. Your body has similar materials, such as ligaments and muscles, which hold everything together.

Your body is made up of four main types of bones. Long bones such as the bones in your arms and legs, short bones such as the bones in your hands, feet and spine, flat bones which protect your organs and provide a place for muscles to attach, and irregular bones, which are simply all the bones that are not long, short or flat.

Functions of the Skeletal System

In order to provide your body with the strength you need to keep your shape, to move, to hold your weight, and to protect your organs, your bones need to be very strong.

• Provides Support• Provides Shape• Provides Protection• Allows movement• Holds you up

Bones Make Blood?

• Your bones have one more very important function. In addition to providing strength and protecting your body, your bones also are where blood is created. Your blood is alive. It is made up of millions and millions of tiny blood cells. These cells only live for a few months. This means that your blood supply must constantly be regenerated.

…Bone Marrow…

• If you could see into the very center of your bones you would find a soft spongy material called bone marrow. This marrow is where new baby blood cells are being created. Whenever you bleed or your blood cells die of old age, they are replaced by new blood cells that come from inside your bones.

Parts of the Bone

Bone Marrow

PeriosteumCompact Bone

Spongy Bone

Periosteu

m

•The outer surface of bone is called the periosteum (say: pare-ee-os-tee-um). It's a thin, dense membrane that contains nerves and blood vessels that nourish the bone.

Compa

ct Bon

e

•The next layer is made up of compact bone. This part is smooth and very hard. It's the part you see when you look at a skeleton.

Spongy Bon

e

•Within the compact bone are many layers of Spongy bone or Cancellous bone. It is not quite as hard as compact bone, but it is still very strong In many bones, the cancellous bone protects the innermost part of the bone

Bone

Marrow

•Bone marrow is sort of like a thick jelly, and its job is to make blood cells.

SKELETAL SYSTEM

Ball and Socket Joint

a ball moves within a socket so as to allow rotary motion in every direction within certain limits.

Gliding Joint

a freely moving joint in which allowsonly gliding motions.

Hinge Joint as found in the

elbows and the joints of the fingers and toes. Hinge joints allow movement in only one direction.

Pivot Joint

• allows rotation around an axis. The neck and forearms have pivot joints