Blood Vessels - Biology

• elastic fibres are made of elastin, they stretch and recoil providing vessel with flexibility
• arterioles have more muscle and less elastic fibres, they have little pulse surge and they construct and dilate to move blood flow.
• smooth muscle contracts and relaxes changing the size of the lumen
• collagen provides structural support to maintain the shape and volume of the vessel
• both arteries and arterioles carry blood under high pressure, the narrow lumer helps to maintain this. thick elastic and muscle layers allow the vessel to expand with heart beats and then recoils (gives pulse)
• arterioles carry blood from the arteries to the capillaries.
• arterioles are smaller in diameter
• The muscle layer is thicker than in arteries and elastic layer is thinner than in arteries.
• • There are no valves in arteries. This is because the blood is always under high pressure, so it doesn’t flow backwards. Except in the case of the arteries leaving the heart, which have valves.
• • Arteries carry oxygenated blood away from the heart. This filters into arterioles, which lead to the rest of the body.
• • Smooth muscle helps blood flow. Smooth muscle lined with smooth endothelium reduces friction and creates less restriction for the blood to move through.
• (arterioles) The muscle layer is thicker so that the movement of blood into the capillaries can be controlled, and the elastic layer is thinner because blood pressure is lower in the arterioles.
• • Veins transport deoxygenated blood from the body back to the heart.
• • The muscle and elastic layers are relatively thin. The muscle layer is thin because constriction isn’t needed to control the flow of blood to the tissues as veins take blood back to the heart. The elastic layer is thinner because the blood is transported slowly and under low pressure, so the veins won’t burst.
• • Veins have valves. As blood pressure in the veins is so low, the valves ensure that blood doesn’t flow backwards.
• Veins have a wide lumen. This maximises the volume of blood that is carried to the heart.
• Veins has a weak pulse of blood. This indicates that there is very little elastic tissue or smooth muscle as the veins don’t need to stretch or recoil.