Skeleton

 

Skeleton

Why do we have bones in our body?

THE BONES FORMTHE STRONG, rigid framework called the skeleton. It supports the body. Not only is it an anchor for your muscles, but it supports your skin and other tissues also. It also provides protection to your heart, brain and other organs. Without the bones, you would flop on the foor like a jelly.

How many bones do you have?

A baby's skeleton has oveer 300 bones, but some fuse fogether as it grows. An adult has 206 bonesthough some people have extra bones in their back.

What is inside a bone?

In the centre of bones isa thick Soft, jelly-like material called the bone marrow. This makes blood cells like red blood cells and white blood cells.

Why are bones strong?

The fough outer casing of the bones is a combination of two things one that makes them flexible and the ofher which makes them stiff. The flexible material is collagen in the form of strong, stretchy strands. The stiff material is made of hard deposifs of calcium and phosphate minerals.

Why don't bones weigh you down?

Though there are So many bones, they are incredibly light because they are full of holes. Inside the bone casing is a crisscross honeycomb structure of struts called trabeculae.                                 

  What are joints?

Places where two bones meet is called a joint. The joints of the skull are completely rigid. But most Joints allOw the bones fo move. The end of each bon is shaped to allow it fo move in a paticular way. The knee is a hinge joint that lets the ower leg swing back and k forward. The hip is a ball and Socket joint that lets you rofate your leg all round.

 

What do muscles do?

Muscles make our body move. Muscles Work by making themselves shorter or by contracfing. As the muscle contracts, if pulls. When the muscle on the front of your upper arm gefs shorfer, if pulls up your forearm.

Are there different kinds of muscles?

Yes. The skeletal muscles Cover the skeleton. They make your body move Muscles inside your body called the involunfary muscles move foOod fhrough your gut and control your blood flow without you being aware of it. The cardiac muscle is found in the heart. muscle is found in the heart.

Inside a muscle

A muscle is made of bundles of fibres which in turn are made of strands called fibrils, which are further made up of myofibrils.

Why do muscles work in pairs?

Muscles can only pull themselves shorter. They need a partner working the opposite way fo pull them out again. The upperarm has biceps muscles at the front, which shorten to lift your forearms. The Triceps muscles are at the back to pull it down again.

How do muscles work?

The muscles are composed of bundies of tiny fibres that get thicker and shorter when the muacle is working. the fibre s made of inferiocking strands of fwo matenals, actin and myosin. The myosin has ittie Chemical looks which twist ond tug on the actn to make the muscle shorter.

How are bones and muscles attached?

Tough cords coled tendons attach the muscles to the bones lough cords caled ligaments bind the bones together.

Different kinds of Joints

Ø Ball and socket joints like the shoulder and hip allow free movement in many directions.

Ø The swivel joint between your skull and spine lets you turn your head to the left and right.

Ø In your thumbs, two saddle-shaped bone ends fit snugly to combine strength and free movement.

Ø Hinge join like those in the knee and elbow swing only two ways like door, but are strong.

 

 

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