Arteries, Arterioles, Veins, Venules, & Capillaries

Arteries Large hose-like vessels Carry blood away from the heart. Have thick, multi- layered muscular walls. Walls are capable of stretching to accommodate the “pulse” of blood when the heart beats.

Arteries Capable of expanding and contracting to change and maintain the blood pressure. NO valves Blood spurts Blood inside them is high in oxygen & low in carbon dioxide except in pulmonary artery.

Arteries Blood inside is bright red Blood inside is under High pressure Examples: Coronary (heart), Brachial (arms), Carotid (head), Femoral (legs), Renal (kidney).

Arterioles Tiny branches off of the arteries. Cannot be seen with unaided eye - microscopic Thinner, less muscular walls (compared to arteries) Feed blood into the capillaries. Narrower than arteries, but wider than capillaries.

Capillaries Flow and pressure of blood is controlled by sphincters that are outside of the capillaries. Microscopic vessels ~ 8 µm in diameter. Erythrocytes (rbc’s) pass through in single file. Walls are only one cell thick (to facilitate diffusion of materials/exchange).

Capillaries Thinness allows for easy diffusion outward or inward through the single cell layer. Form capillary beds - networks of vessels linking arterial and venous blood.

Capillaries Oxygen, nutrients and other materials move out of the capillaries and into the extra- cellular fluid and then into cells. Carbon dioxide, wastes and other materials are picked up and move into the capillaries: (both involve diffusion for the movement).

Venules Vessels larger than capillaries but smaller (i.e. narrower and thinner walls) than veins.

Veins Larger inside diameter compared to arteries Take blood towards the heart Thinner, less muscular walls than arteries, but still 3 layers No stretching or contracting of walls except by external muscles. Contain valves to help return the blood to the heart (compensate for lower venous pressure, less muscle in walls, and large diameter).

Veins - Valves

Veins Blood: Moves smoothly. Low in oxygen except pulmonary circulation. Dull red. Low pressure. Examples: cardiac (heart), brachial (arms), jugular (head), femoral (legs), renal (kidney).

Varicose Veins (copy this) When the valves don’t function properly, blood leaks backwards and pools in veins Veins sag, stretch and swell, creating bulging knarled vessels

The END!!