The composition of blood.

The composition of blood. 

ZIMSEC O Level Combined Science Notes: Blood and its properties

  • Blood circulating in a mammal constitutes about 7.5% of its body mass.
  • An average human weighing between 68-80 kgs has about 4.7 to 5 litres of blood in their body
  • Blood can be considered as tissue because it contains millions of cells.
  • These cells tend to be similar and they also perform similar functions:
  • They carry out transport functions and protect the mammal disease
  • Blood tissue is made up of a fluid called plasma
  • Red and white blood cells float within this plasma
  • Glucose and amino acid molecules are also found in the plasma in dissolved form

Functions of Blood

  • Blood has several major functions.
  • First it acts as a transport medium
  • It carries substances around the body
  • These substances include dissolved food, oxygen and plasma proteins which are all carried to where they are needed
  • Blood also carries waste substances produced by the body cells to excretion organs such as lungs and kidneys
  • Blood also helps with heat distribution from the internal organs to the fingers and toes
  • Homeostasis-is the maintenance of temperature, water, salt and glucose levels at a constant optimum levels
  • Blood plays a critical role in the homeostasis process
  • The white blood cells attack foreign particles and germs( viruses and bacteria) which invade the mammal’s body
  • The blood’s platelets are responsible for clotting of the blood where there is a wound or injury.
  • They release enzymes which convert special plasma proteins into  a blood clot to stop the flow of blood.
  • This prevents the mammal from dying as a result of excessive blood loss
  • The clot also prevents the further entry of germs into the mammal’s body

To access more topics go to the Combined Science Notes page.

Quick NetOne, Econet, And Telecel Airtime Recharge