The Circulatory System
- Function : supply the needs of your body cells and remove waste material.
- 3 elements : pipes (blood vessels) , the pump (heart) , medium (blood).
- Humans have double circulation :
- 1) Carries blood from your heart to your lungs and back again to exchange oxygen and carbon dioxide with the air.
- 2) Carries blood all around the rest of the body and back again.
- It makes the circulatory system very efficient. Fully oxygenated blood returns to the blood from the heart from the lungs and then sent off to other parts.
- 3 main types of blood vessel :
- 1) Artery = thick walls, small lumen, thick layer of muscle and elastic fibres.
- They carry blood away from the heart to the organs of the body. This is usually oxygenated blood so it is bright red. They stretch as blood goes through them and return to shape after. This is felt as a pulse when the arterie are close to the surface.
- 2) Veins = relatively thin walls, large lumen, valves.
- They carry blood towards the heart, low in oxygen so deep purply red colour. Do not have a pulse, have valves to prevent back flow of blood.
- 3) Capillary = very thin walls, small vessel with narrow lumen.
- Capillaries have thin walls so substances needed by the body like oxygen can pass out of cells by diffusion and vice versa.
- The heart is made up of 2 pumps, beats together 70/min. The walls are almost all muscle, supplied with oxygen through the blood vessels.
Transport in the Blood
- The liquid part of blood is called plasma. It carries red blood cells, white blood cells and platelets.
- White blood cells = part of immune system/ defence against disease.
- Platelets = clotting of the blood
- Red blood cells and blood plasma = transporting materials.
- Blood plasma is a yellow liquid - red colour comes from red blood cells. The plasma transports all of the blood cells and others around the body.
- Carbon dioxide made in the organs is carried in plasma to the lungs.
- Urea, a waste product formed in your own liver from proteins is carried in plasma to the kidneys.
- All small, soluble products pass into the blood from the gut.
- More red blood cells than any other type of cell in the body. 5 million in 1mm squared of blood. They pick up oxygen from your lungs and carry it to the tissues and cells where needed.
- Adaptations :
- 1) biconcave discs = pushed in on both sides, increase S.A. : volume ratio which diffusion can take place over.
- 2) Haemoglobin = special red pigment which can carry oxygen.
- 3) No nucleus so more room for haemoglobin.
Formation and breakdown of Oxyhaemoglobin
- Large protein molecule folded around 4 iron atoms in a high concentration of oxygen, like in the lungs, haemoglobin reacts with the oxygen to make Oxyhaemoglobin.
- It is bright red colour which is why most arteries are bright red.
- In areas of low…