Module 8: The structure and function of the cardiovascular system

Table of Contents

1. Introduction to the cardiovascular system
2. The heart
3. Labelling the heart activity
4. The valves in the heart
5. Circulation
6. Blood Vessels
7. Characteristics of blood vessels activity

Blood Vessels

The circulatory system sometimes referred to as the vascular system consists of the arteries, veins and capillaries through which the heart pumps blood around the body. It ensures that every cell in the body receives an adequate supply of oxygen and nutrients and removes any waste products such as carbon dioxide and water.

Arteries

• The arteries always carry blood away from the heart.
• They have thick muscular walls which enables them to cope with the high pressure of blood within them.
• The blood within arteries is generally bright red as it is oxygenated. The one exception to this is the pulmonary artery as this is carrying de-oxygenated blood from the heart to the lungs.
• Most arteries lie deep in the body, however, some such as the carotid artery are nearer the surface and it is in these places that a pulse can be felt.
• By branching and re-branching the arteries progressively become smaller and are known as arterioles. These arterioles then join the smallest blood vessels known as capillaries and it is here that tissue diffusion occurs.

Capillaries

• Capillaries are the essential link between arterioles and venules.
• Capillaries are tiny vessels with semi permeable membranes.
• It is in the capillaries that the exchange of material between the blood and tissues take place, this process is known as tissue diffusion.

Veins

• Veins always carry blood back towards the heart.
• 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.
• They have thin walls 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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Click here for more information on blood vessels

The above link is an NLN resource - (c) LSC