The Circulatory System (Cardiovascular)


The Cardiovascular system consists of the Heart and Lungs and blood – they are interdependent and are all connected.

What are the functions of the blood?

  • Oxygen is conveyed from the lungs to the cells and carbon dioxide is conveyed away from the cells to the lungs. Heat and waste products conveyed away from the cells & hormones from glands to the cells.
  • The blood is responsible for the regulation of the pH of the body and temperature and water content of the cells.
  • Protection: the blood protects the cells against foreign microbes and toxins and has the ability to clot and so protect the body against excessive blood loss.

Components of blood:

  • Red blood cells: Erythrocytes take up oxygen from the lungs and circulate it around the body.
  • White blood cells: Leucocytes are the cells of the immune system that are involved in protecting the body against both infectious diseases and foreign invaders.
  • Platelets: Thrombocytes are a component of blood whose function (along with the coagulation factors) is to stop bleeding by clumping and clotting blood vessel injuries.
  • Blood plasma: fifty-five percent of blood is composed blood plasma, a watery, straw-coloured liquid that contains dissolved substances. 91.5% of it is water while the other 8.5% is dissolved substances (solutes – proteins, electrolytes, nutrients, gasses, and waste)

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