Blood Vessels Flashcards
What are the three main kinds of blood vessels?
Arteries, veins and capillaries.
Describe Arteries.
They have thick elastic walls to withstand the high pressure of the blood being pumped through them and they also have small lumens to help maintain high blood pressure. They carry blood away from the heart and the blood pressure within them is high. They carry oxygenated blood except for the pulmonary artery. The arteries divide into arterioles and then capillaries. They also lie deep within the body.
Describe Capillaries.
They have one cell thick, cell walls to enable quick and easy diffusion of substances. They carry blood from the arteries and arterioles to the body cells and tissues. Blood pressure decreases in the capillaries. Blood flow is smooth and slow. The blood loses oxygen to cells and gains carbon dioxide from them. The capillaries also join up to form venules and then veins.
Describe Veins.
Veins have thin elastic walls and large lumens to reduce resistance and enable blood to flow freely. They carry deoxygenated blood to the heart be re oxygenated in the lungs except the pulmonary vein. The blood pressure is low. They also have valves to prevent the back flow of blood and keep it flowing in one direction as there is low pressure on the veins. They are close to the surface of the body.
