Arteries & Veins
Arteries carry blood FROM the heart at a HIGH PRESSURE...
- Narrow lumen (generates high pressure, ensures rapid delivery of the blood)
- Lots of smooth muscle (alters diameter of lumen to vary blood flow) and elastic fibres (allows artery to constrict and recoil to alter blood flow)
- Endothelim (protect inner wall of the artery - susceptible to atherosclerosis and blood clotting because of damage due to high pressure blood delivered)
- Outer coat - connective tissue with more collagen fibres
Veins carry blood TO the heart at a LOWER PRESSURE...
- Wide lumen (lower pressure - blood does not need to be generated at a high pressure unlike and artery does)
- Little smooth muscle and elastic fibres (less need for blood flow to be varied due to lower pressure)
- Endothelium (protect the inner wall of the vein)
- Outer coat - connective tissue with less collagen fibres
- Valves - Prevent backflow of blood and push blood foward towards the heart
Heart - Arteries - Arterioles - Capillaries - Venules - Vein - Heart
(Oxygenated blood from the arteries that branch off the aorta lose oxygen and gain carbon dioxide as they join with capillaries and turn into veins where the blood is deoxygenated and the blood returns to the right atrium of the heart via the inferior or superior vena cava as deoxygenated blood)
Capillaries - squamous epithelium (single layer of cells - ensures rapid diffusion and gas exchange of carbon dioxide and oxgen - exchange with cells - oxygen into cells)
How does blood move through the vessels?
Heart contracts (systole) - blood forced into arteries and elastic fibres allow them to stretch to accommodate the blood
Heart relaxes (diastole) - elastic fibres allow arteries to recoil, behind the blood, helping the push the blood foward towards the heart