BLOOD VESSELS By: Ms. Reis

Blood Vessels 3 types of blood vessels form a network of tubes throughout the body to transport the blood. 1. Arteries 2. Capillaries 3. Veins

Arteries Arteries – blood vessels that carry oxygenated blood away from the heart to tissues where it is needed. The aorta is the largest artery in the body carrying blood from the heart to the tissues.

Arteries Arteries have elastic walls that allow it to first expand as blood passes through then snap back again. This movement keeps blood flowing in the right direction, and provides an additional pumping motion to help force the blood through the blood vessels. Arteries branch at their ends into smaller arteries that then join capillaries.

Capillaries Arteries and veins are linked together by capillaries Nearly every tissue within the body is within 0.1 mm of a capillary.

Capillaries: the Site of Gas and Fluid Exchange Capillaries are the site of fluid and gas exchange between the blood and cells. Oxygen and nutrients diffuse from the blood into the surrounding tissue. Carbon dioxide and other wastes pass from the body tissues into the blood.

Capillaries Capillaries are tiny: Because of their small diameter red blood cells must travel through capillaries in single file. Capillaries have thin walls: The thin capillary wall allows substances to diffuse between the blood and tissues

Capillary

Capillaries Oxygenated blood, which appears red in colour, takes on a purple-blue colour as it leaves the capillary. The deoxygenated blood collects in small veins called venules.

Veins Veins – blood vessels that return deoxygenated blood back to the heart where it can become oxygenated. Once blood reaches the veins after passing the fine network of capillaries it is travelling very slowly.

Blood Vessels: A Comparison Arteries have thicker walls than veins to withstand the greater pressure that the blood exerts on the wall of the artery.

Blood Vessels: A Comparison Veins have thinner walls but a larger inner circumference. As a result veins lack the elasticity of the artery, but have a greater capacity to carry blood. The venous system contains twice as much blood as the arterial system.

ARTERY CAPILLARY VEIN Wall is composed of 3 layers of cells Wall is one cell thick Thinner wall than artery High elasticity No elasticity Little elasticity but has valves Smaller diameter than veins very narrow diameter Larger diameter than arteries Carries blood away from the heart Site of gas exchange with tissue cells Carries blood toward the heart

Varicose Veins If valves do not function properly gravity carries blood to the feet and blood pooling occurs. This results in veins distending/expanding. Both genetics and lifestyle are factors.