Answer the following questions in your own words.

Explain the structure and function of human blood.

Blood consists of many component parts (constituents).

These include:

● 55% Plasma

● 45% Components (sometimes called 'formed elements'), i.e. blood cells.
Of these,

o 99% are red blood cells, and

o 1% are white blood cells and blood platelets

Plasma is a yellowish color fluid, made up of water (~90%) and some dissolved nutrients, proteins, hormones and waste products.

Blood consists of three types of blood cells. These are:

i. Red Blood Cells: They contain a red pigment called hemoglobin, which transports oxygen to all body cells.

ii. White Blood Cells: They fight against germs that enter the body. Thus, they protect the body from diseases.

iii. Platelets: When we get injured, bleeding stops after some time. This happens because of the activity of platelets, which help in the clotting of blood.

Functions of blood:

1. Transports

o Dissolved gases (e.g. oxygen, carbon dioxide)

o Waste products of metabolism (e.g. water, urea)

o Hormones

o Enzymes

o Nutrients (such as glucose, amino acids, micro-nutrients (vitamins & minerals), fatty acids, glycerol)

o Plasma proteins (associated with defence, such as blood-clotting and anti-bodies)

o Blood cells (incl. white blood cells 'leucocytes', and red blood cells 'erythrocytes').

2. Maintains Body Temperature

3. Controls pH

The pH of blood must remain in the range 7.32 to 7.45; otherwise it will begin to damage cells.

4. Removes toxins from the body

The kidneys filter all of the blood in the body (approx. 8 pints), 36 times every 24 hours. Toxins removed from the blood by the kidneys leave the body in the urine. (Toxins also leave the body in the form of sweat.)

5. Regulation of Body Fluid Electrolytes

Excess salt is removed from the body in urine, which can contain around 10 g salts per day in the cases of people eating 'western' diets that contain more salt than the body requires.