(1) Bones and the human skeleton

In the diagram details of the bones of the hands and the feet are not shown.

 

Bones are made of tough calcium based materials and softer tissue.

 

The out layers of bone is made from strong and had tissues based on calcium compound molecules.

 

This makes bones strong and rigid - they don't bend easily.

 

The inner layers of bone are made from more softer spongy tissue, but still a fairly strong material.

 

The skeletal system as a whole has four main functions.

1. Protection

The bones are hard and protect the soft tissue of the organs of the body. e.g. the skull protects the brain, the ribs protect the lungs and heart, the backbone spinal cord that protects the nerve cells of the central nervous system that connects with the brain - this is why spine injuries are potentially very serious and harmful.

2. Support

The skeleton provides a strong framework on which the rest of the body 'hangs'. All the soft tissues of the organs are supported by the skeleton allowing us to stand up without the organs falling down!.

3. Movement

Muscles are attached to bones (details in the next section).

The action of muscles allows the skeleton to move when joints allow movement of two or more bones in a bending actions.

We could not move unless e.g. elbow or knee joints can bend in two directions raising or lowering actions.

4. Production of blood cells

Certain of the long bones e.g. the humerus and femur, contain a soft tissue called bone marrow in the middle of them.

Bone marrow produces red blood cells, essential for transporting oxygen to cells using the haemoglobin molecule.

See Respiration - aerobic and anaerobic in plants and animals, investigations

Bone marrow also produces white blood cells that help fight harmful infections that enter your body.

See Keeping healthy - communicable diseases

and Keeping healthy - non-communicable diseases

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