Blood Vessels

Functions

Veins and Venules: Carry blood from tissues TO heart (towards)

Capillaries: Allow exchange of materials between the blood and tissues

Arteries and Arterioles: Carry blood to tissues FROM heart (away)

Walls

Veins and Venules: Thin and mainly collagen

Capillaries: Very thin permeable walls, only one cell thick to allow exchange of materials

Arteries and Arterioles: Thick walls with smooth elastic layers to resist high blood pressure and muscle layer to aid pumping

Lumen (cavity of tube of an organ)

Veins and Venules: Large to prevent back flow

Capillaries: Very small

Arteries and Arterioles: Small

Valves

Veins and Venules: Many; prevent back flow

Capillaries: No valves

Arteries and Arterioles: No valves (except heart)

Blood Pressure

Veins and Venules: Low

Capillaries: Falls in capillaries

Arteries and Arterioles: High

Oxygen Levels of Blood

Veins and Venules: Deoxygenated (except in pulmonary vein)

Capillaries: Changes from oxygenated to deoxygenated (except in lungs)

Arteries and Arterioles: Oxygenated (except in pulmonary artery)

Arterioles

Small arteries

Aneurysm

Weakened artery

Less oxygen and nutrients delivered to tissues aka cell death

Vasoconstriction

Narrowing of blood vessels (happens when arterioles constrict)

Vasodilation

Widening of blood vessels (happens when arterioles dilate)

Atherosclerosis

Degeneration of the blood vessels caused by the accumulation of fat deposits along the inner wall

Prevent? Low fat diets, regular + controlled exercise

When does bruising occur?

When the blood rushes into the spaces between tissues

Why are capillaries leaky? Why can’t the veins and arteries be leaky?

Need to be leaky for oxygen to diffuse through it (exchange gas and nutrients)

Veins and arteries can’t be leaky because blood pressure would decrease and internal bleeding will happen

Difference between veins and venules

Veins have a greater diameter

How do veins deliver blood to the heart?

Valves that steer blood towards the heart. They open up one way through skeletal muscles contracting.