BiologyExchange.co.uk Shared Resource

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BiologyExchange.co.uk Shared Resource

  1. 1. Blood Vessels
  2. 2. Blood Vessels
  3. 3. Blood Vessels
  4. 4. Human arteries and veins
  5. 5. Human arteries and veins
  6. 8. Arteries
  7. 9. <ul><li>The wall of an artery consists of three layers. </li></ul><ul><li>The innermost layer (tunica intima) is endothelium with a connective tissue membrane. </li></ul><ul><li>The middle layer (tunica media) is smooth muscle & elastic fibres. It’s usually the thickest layer. It changes the vessels diameter to regulate blood flow & pressure. </li></ul><ul><li>The outermost layer (tunica adventitia) is connective tissue with elastic & collagen fibres. </li></ul>Arteries
  8. 10. <ul><li>Arteries carry blood away from the heart. </li></ul><ul><li>Pulmonary arteries transport blood that has a low oxygen content from the right ventricle to the lungs. </li></ul><ul><li>Systemic arteries transport oxygenated blood from the left ventricle to the body tissues. </li></ul><ul><li>Blood is pumped from the ventricles into large elastic arteries that branch repeatedly into smaller and smaller arteries until the branching results in microscopic arteries called arterioles. </li></ul><ul><li>The arterioles play a key role in regulating blood flow into the tissue capillaries. </li></ul><ul><li>About 10 percent of the total blood volume is in the systemic arterial system at any given time. </li></ul>Arteries
  9. 11. Arteries
  10. 12. Capillaries
  11. 13. <ul><li>Transported substances (like CO 2 and O 2 ) enter & leave the blood here. </li></ul><ul><li>No exchange of materials takes place in the arteries and veins because their walls are too thick and impermeable. </li></ul><ul><li>Capillaries are very narrow and their wall is one cell thick. </li></ul><ul><li>They have a huge surface area : volume ratio, helping rapid diffusion of substances between blood and cells. </li></ul><ul><li>Capillaries are arranged in networks called capillary beds feeding a group of cells, and no cell in the body is more than 5 cells away from a capillary. </li></ul>Capillaries
  12. 14. Capillary
  13. 16. Capillary
  14. 17. <ul><li>Veins are the blood vessels that carry deoxygenated blood back to the heart. </li></ul><ul><li>The walls of the veins are thinner than the arteries, they have the same three layers in them. There is less muscle and elastic tissue in the middle layer. </li></ul><ul><li>Some veins have valves in them to ensure the flow of blood travels to the heart, and not backwards. </li></ul><ul><li>The smallest of the veins (furthest away from the heart) are known as venules. </li></ul><ul><li>Veins contain about 75% of blood at any time. </li></ul>Veins
  15. 18. Veins
  16. 19. <ul><li>The elastic recoil of arteries </li></ul><ul><li>Gravity (head and shoulders) </li></ul><ul><li>Negative pressure in the thorax having a suction effect on blood in the inferior vena cava </li></ul><ul><li>The contraction of skeletal muscles helping to force blood through veins by squashing them (most important in the legs) </li></ul>Other factors aiding the circulation of blood
  17. 22. Flow dynamics

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