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.