Cells

Cells

Apart from water the rest of the body is built from a huge number of complicated chemicals. These chemicals, together with water, are assembled into tiny building blocks called cells. Each cell is self-contained and has a particular function of the body. There are more than 50,000 billion cells in our body. The shape and appearance of a cell depends on what type of job it has to do. Nerve cells are long and thread – like and can carry messages around the body along the nervous system. Red blood cells are so tiny that they can only be seen under a microscope and are like flattened discs.

The sole function of the blood cell is to combine with oxygen in the lungs and to exchange the oxygen for carbon dioxide in the tissues. White blood cells are shapeless so they can squeeze between other cells and attack invaders such as bacteria. Other cells control the production of essential substances called proteins.

BLOOD

BLOOD

Our blood is red because of the substance, haemoglobin, which is contained in our red blood cells (red corpuscles).The function of these specialised cells is to carry oxygen from our lungs to wherever it is needed in the body. They are formed in our bone marrow and the haemoglobin in them

, which is made of iron and protein, becomes redder as it picks up oxygen. It loses this colour as it deposits oxygen in other cells and picks up carbon dioxide to carry back to the lungs, which is why some of the blood vessels in our hands and arms appear blue through our skin.

As well as carrying oxygen and carbon dioxide, the blood carries nutrients to the cells, so that they can perform their functions, and for cell repair and growth. Waste products are carried back to the liver for removal. As well as the red cells, our blood also carries white blood cells, which help to fight off disease. All of the heart cells and nutrients are carried in a pale yellow, thick liquid which is called plasma. The other materials carried in the plasma include a substance called fibrinogen, which helps the blood to clot when we cut ourselves.