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Blood Vessels

ACCESS HEHuman Biology.

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Introduction

Blood vessels are tubular in shape and their function is to form a network to transport the blood around the body,

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Circulatory System (General).

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Blood Vessels (Three Types).

Arteries.

Veins.

Capillaries.

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Structural differences between Arteries and Veins.

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Arteries:

Carry blood away from the heart to the rest of the body.

Carry oxygenated blood except the pulmonary artery. Blood travels at a higher pressure. Arteries have a small lumen. Arteries eventually form into smaller vessels called

arterioles. Contain no valves. Tend to lie deeper in the body. Have thicker muscular walls.

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Veins:

Carry blood to the heart from the body Carry deoxygenated blood except the pulmonary vein Blood travels at a lower pressure Veins have a large floppy lumen. The veins eventually form into smaller vessels called

venules Veins are situated in between muscles & contain valves

to prevent the blood flowing backwards Lie more superficially in the body Have thinner muscular walls

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Capillaries:

Narrow blood vessels which have very thin walls, just one cell thick

Substances can pass through its walls Exchange oxygen and nutrients for carbon

dioxide and wastes within all cells and tissues

Forms the link between arterioles and venules

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Arteries, Veins and Capillaries.

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Journey of the blood

1. When ventricles of the heart contract, oxygenated blood is forced out of the heart from the left side, and on its journey around the body in vessels called arteries.

2. The oxygenated blood travels at a faster pace and under higher pressure due to the force of the heart pumping it around the body.

3. Eventually the blood will pass into smaller vessels called arterioles.

4. The arterioles eventually form into even smaller vessels called capillaries.

5. Because capillaries are so small, they form an intricate network around all of the tissues and cells within the body.

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Journey of the Blood (Cont).

6. The capillary walls are only one cell thick and allow certain substances to pass out through the capillary walls to bathe the cells with vital oxygen and nutrients.

7. Waste products and carbon dioxide are produced by the cells and these pass back into the capillaries via a similar process.

8. The capillaries take away the waste products and carbon dioxide and eventually form into larger vessels called venules.

9. The venules eventually form into larger vessels called veins.

10. Veins carry the deoxygenated blood back to the heart under lower pressure, as the blood starts to slow down after its long journey around the body.

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Journey of the Blood (Cont).

11. To assist the return of the deoxygenated blood the veins are located in-between muscles. When the muscles contract they squeeze the veins forcing the blood upwards and onwards.

12. Valves are also located within the veins to prevent the blood from flowing backwards.

13. On its journey, any waste products are filtered from the blood and removed from the body via the urinary and excretory systems.

14. Eventually the blood returns back to the heart15. The blood is then pumped into the lungs to be

replenished with oxygen and have the carbon dioxide removed.

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Arteries of the head

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Arteries of the body

Oxygenated blood is transported to all cells and tissues of the body via the arteries.

The aorta is the main artery that leaves the heart.

This then branches off to form further arteries.

Arteries become smaller to supply all areas of the body.

Small arteries are called arterioles.

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Veins of the head

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Veins of the body

Deoxygenated blood is transported from all cells and tissues in the body back to the heart.

Small veins are called venules.

Venules become veins. The largest veins are

the superior and inferior vena cava.

The superior and inferior vena cava returns the deoxygenated blood back to the heart.