Module 8: The structure and function of the cardiovascular system

The Body in Action

1. Introduction to the cardiovascular system
2. The heart
   1. Structure of the heart
   2. The heart valves
3. Labelling the heart activity
4. Circulatory system
   1. Animation of the circulation systems
5. Blood vessels
   1. Arteries
   2. Capillaries
   3. Veins
6. Characteristics of blood vessels activity
7. Function of the cardiovascular system
8. Function of the blood

Veins

After diffusion the blood moves from the capillaries into the tiniest of veins know as venules which then join to form larger and larger veins. The veins always carry blood back towards the heart. They have thin walls that are less muscular than the arteries as they do not have to withstand the same pressure as arteries. The blood within the veins is of a bluish colour as the majority of it is de-oxygenated. The one exception to this is the pulmonary vein as this is carrying oxygenated blood from the lungs back to the heart.

Since the blood is at low pressure in the veins they are supplied with valves at regular intervals to prevent back flow and to keep the blood flowing in one direction.

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