Moving on with bones

Have you ever thought what would happen if we didn't have bones? Well, we will be floppy like a beanbag, won't we? Could you walk? Forget it. Could you stand up? No way. Without bones, you'd be just a puddle of skin and guts on the floor.

Remember, last week we discussed that bones have two purposes. Some, like your backbone, provide the structure which enables you to stand erect, instead of lying like a puddle on the floor.

Other bones protect the delicate, and sometimes soft, insides of your body. Your skull, a series of fused bones, acts like a hard protective helmet for your brain. The bones, or vertebrae, of your spinal column surround your spinal cord, a complex bundle of nerves. Imagine what could happen to your heart and lungs without the protective armour of your rib cage!

How many bones do humans have?

When you were born, you had over 300 bones. As you grew, some of these bones began to fuse together. The result? An adult has only 206 bones!

How do bones move?

With a lot of help. You need muscles to pull on bones so that you can move. Along with muscles and joints, bones are responsible for you being able to move. Your muscles are attached to bones. When muscles contract (become smaller or shorter), the bones to which they are attached act as levers and cause various body parts to move.

You also need joints which provide flexible connections between these bones. Your body has different kinds of joints. Some, such as those in your knees, work like door hinges, enabling you to move back and forth.

Those in your neck enable bones to pivot so you can turn your head. Still other joints like the shoulder enable you to move your arms 360 degrees like a shower head.

Are bones alive?

Absolutely. Bones are made of a mix of hard stuff that gives them strength and tons of living cells which help them grow and repair themselves. Like other cells in your body, the bone cells rely on blood to keep them alive. Blood brings them food and oxygen and takes away waste.

If bones weren't made of living cells, things like broken toes or arms would never mend. But don't worry, they do.

That's because your bone cells are busy growing and multiplying to repair the break! How? When you break your toe, blood clots form to close up the space between the broken segments. Then your body mobilises bone cells to deposit more of the hard stuff to bridge the break.

Where is the largest joint in the body?

The knee joint is the largest and most complex joint in the body. The knee is the joint where the thighbone meets the large bone of the lower leg. The knee ligaments are the strongest connections between the femur and the tibia. Ligaments keep the bones from moving out of position.

What's bone marrow?

Many bones are hollow. Their hollowness makes bones strong and light. It's in the centre of many bones that bone marrow makes new red and white blood cells.

Red blood cells ensure that oxygen is distributed to all parts of your body and white blood cells ensure you are able to fight germs and disease. Who would have thought that bones make blood!

Where are the vertebrae?

The vertebrae form a column of bones in the spine. The spine is the part of the skeleton that extends down the middle of the back. The spine plays an important role in posture and movement, and it also protects the spinal cord.

Did you know that the human spine consists of 33 vertebrae? But some of them grow together in adults. There are seven cervical (neck), 12 thoracic (chest region), five lumbar (lower back), five sacral (hip region) and four coccygeal (tailbone region) vertebrae.

Most vertebrae have fibrous intervertebral discs between them to absorb shock and enable the spine to bend.

Where is the humerus bone?

The humerus bone is in the arm. The elbow is the joint that connects a person's upper arm with the forearm. The humerus or the bone of the upper arm and the radius and ulna (the bone of the forearm) meet at the elbow. The three bone connections form three smaller joints within the elbow.

These smaller joints permit certain movements. The humerus-ulna joint and the humerus-radius joint allow a person to bend the forearm up and down. The radius-ulna joint and the humerus-radius joint permit a person to rotate the forearm and to turn the palm of the hand up and down.

A capsule (pouch) of tough connective tissue surrounds the elbow joint. This capsule and several ligaments hold the bones in place.

Bone facts

* The human hand has 27 bones; your face has 14!

* The longest bone in your body is your thigh bone, the femur - it's about 1/4 of your height. The smallest is the stirrup bone in the ear, which can measure 1/10 of an inch.

* Did you know that humans and giraffes have the same number of bones in their necks? Giraffe neck vertebrae are just much, much longer!

* You have over 230 moveable and semi-moveable joints in your body.

* The patella (or knee cap) is a small, flat, triangular bone in front of the joint. It is not directly connected with any other bone. Muscle attachments hold it in place.