Topic 2a - Tissues, organs and organ systems ( 4. circulatory system - the blood vessels )

Question 1

what are arteries

Answer 1

blood vessels that carry blood away from the heart and toward the organs. the blood is pumped out of the heart at high pressure so the artery walls are strong and elastic. they contain thick layers of muscle to make them strong. and they have elastic fibres to allow them to stretch and spring back.

Question 2

what are capillaries

Answer 2

arteries branch into capillaries. they carry blood really close to every cell in the body to exchange substances with them. supply food and oxygen to cells and take away waste products like co2.
really small, permeable walls, so substances being exchanged with cells can be diffused in and out. Walls are usually only one cell thick. this increases the rate of diffusion by decreasing the distance over which it occurs. also narrow, gives large surface area which also increase the rate of diffusion

Question 3

what are veins

Answer 3

capillaries eventually joins up to to form veins. veins carry blood to the heart. the blood is at a lower pressure so the walls do not have to be as thick. veins have a bigger lumen to help blood flow. also have valves to keep blood flowing in the right direction.