Blood consists of a liquid (55% by volume) and other solid particles (45%), including several types of cells. The liquid is called plasma. The plasma is mainly water, but it has many things dissolved in it. These substances are either needed by cells of the body, but tissue fluid derived from blood either brings or takes them away, in solution. It also protects all the body’s cells from damage due to osmosis.
Types of substances that may be in solution in it.
- digested food
- waste substances
Specific substance :
Food: Glucose-> amino acids etc.
Testosterone, insulin, ADH etc
CO2 and urea
Red Blood Cells
There are about 5 million red cells in 1 mm3 of blood – which about 50 times bigger than a single drop! 1000 mm3 make 1 cm3 (1ml), & 1000 cm3 make 1 dm3 (1L).
There are, on average, 5.5 litres of blood in the human body.
There are about 2.5 x10^13 red blood cells in your body.
Compared with ordinary cells, red cells have something missing, and something that no other cells of the body possess. Red blood cells have no nucleus. But they have haemoglobins. The main function of a red blood cell is to transport oxygen. The red blood cells appear bright red when it is oxygenated or it can appear dull red when it is deoxygenated. Because it consists of many similar cells, blood can also be called a tissue.
White Blood Cells
White blood cells or called white cells because they often leave the blood. The amount of white cells is in fact about 600 times fewer than red blood cells. However they can leave the blood system and move towards micro-organisms (mostly bacteria and viruses) which are causing infections in any part of the body. White cells share the function of fighting diseases, and we make use of them in vaccination to give us immunity against diseases.
Types of White Cells
- Phagocyte = engulf and destroy invading microorganisms.
o Lobed nucleus
o Cytoplasm with granules