July 18, 2021
Blood Vessels are Designed for Their Function
There are three different types of blood vessel
You will have to know about all of them in I/GCSE Biology
- Arteries- take blood away from the heart
- Capillaries- these are involved in the exchange of materials at the tissues
- Veins- take blood to the heart
Arteries Carry Blood Under Pressure
- The heart pumps the blood out at high pressure so the artery walls are strong and elastic
- The walls are thick compared to the size of the hole down the middle (the lumen) They contain think layers of muscle to make them strong
- The largest artery in the body is the Aorta
Capillaries are really small
- Arteries branch into capillaries
- Capillaries are really tiny- too small to see
- They carry the blood really close to every cell in the body to exchange substances with the,
- They have permeable walls, so substances can diffuse in and out
- They supply food and oxygen, and take away wastes like CO2
- Their walls are usually only one cell think. This increases the rate of diffusion by decreasing the distance over which it happens
Veins Take Blood Back to the Heart
- Capillaries eventually join up to form veins
- The blood is at lower pressure in the veins so the walls don't need to be as thick as artery walls
- They have a bigger lumen than arteries to help the blood flow despite the lower pressure
- They also have valves to help keep the blood flowing in the right direction
- The largest vein in the body is the vena cava
Reference: https://i.ytimg.com/vi/Oq3SbxO8RB0/maxresdefault.jpg
Drafted by Catrina (Biology)