Blood has 4 main components:
1) PlASMA - liquid part of the blood (pale yellow colour), mainly consisting of water. It is essentially the blood without the blood cells. It carries:
- red and white blood cells and platelets
- digested food molecules from the gut to the body cells
- CO2 from the body cells to the lungs
- Urea from the liver to the kidneys
- Hormones which act as chemical messengers
- Heat energy
2) PLATELETS - help clot the blood by "clumping" together.
- stops blood loss and also prevents microorganisms entering the wound (infection)
- in a clot, platelets are held together by a mesh of a protein called "fibrin".
3) RED BLOOD CELLS - adapted to carry O2 around the body. The O2 molecule attaches to the haemoglobin protein which the red blood cells are filled with. This is how they're adapted:
- small and have a biconcave shape to give a large surface area for absorbing and releasing oxygen
- contain haemoglobin (gives blood its colour) - it contains a lot of iron. In the lungs, the oxygen reacts with the haemoglobin to form oxyhaemoglobin. In body cells, the reverse reaction happens to release oxygen into the…