Blood Vessels Flashcards
What is the role of a blood vessel?
To transport nutrients, gases and wastes to where they are required around the body.
Describe the structure and function of arteries.
Arteries carry blood away from the heart. Arteries have thick, elastic walls to withstand the pressure of the blood being pumped away from the heart. The elasticity of the smooth muscle layer allows the artery to expand when a pulse of blood moves through, and contract back to original diameter, aiding the push of blood.
Describe the structure and function of the veins.
Veins return blood to the heart. They have thinner walls than arteries because blood is travelling at a lower pressure. The muscle layer does not contain many elastic fibres as they do not have to stretch and recoil. The internal diameter of the lumen (cavity) is larger than that of an artery to allow for easy blood flow.
What features of veins ensure blood only flows towards the heart and not backwards?
To aid one-directional flow, muscles surrounding veins contract and relax to move the walls of the vein to push the blood. Additionally, veins have internal valves at regular intervals that are closed by backward moving blood, and forced open by forward moving blood.
Describe the structure and function of capillaries.
Capillaries are tiny vessels that bring blood in close contact with tissues, enabling the exchange of substances. They are one cell thick, allowing for easy diffusion of substances. This thinness also forces blood cells to flow in single-file, allowing for the slow process of diffusion to take place. Capillaries form an expansive network to ensure no cells are far away from blood supply.
