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Cardiovascular System

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  1. Cardiovascular System Blood Vessels

  2. Anatomy of Blood Vessels • Arteries carry blood from the heart to the tissues

  3. Anatomy of Blood Vessels • Arterioles are small arteries that connect to capillaries

  4. Anatomy of Blood Vessels • Capillaries are the site of substance exchange between the blood and body tissues

  5. Anatomy of Blood Vessels • Venules connect capillaries to larger veins

  6. Anatomy of Blood Vessels • Veins convey blood from the tissues back to the heart.

  7. Arteries • Tunica interna (intima) – innermost • Tunica media – middle layer • Tunica externa – outer layer

  8. Tunica Intima • Composed of; • simple squamous epithelium (endothelium) • Internal elastic membrane

  9. Tunica Media • Rich in smooth muscle and elastic fibers

  10. Tunica Media • Maintains elasticity and contractility

  11. Tunica Externa • Rich in elastic and collagen fibers

  12. Functional Properties of Arteries • Elasticity • Contractility

  13. Elasticity • Due to the elastic tissue in the tunica intima and media

  14. Elasticity • Allows arteries to accept blood under great pressure from the contraction of the ventricles

  15. Contractility • Due to the smooth muscle in the tunica media

  16. Contractility • Allows arteries to increase or decrease lumen size

  17. Contractility • Sympathetic stimulation of alpha 1 receptors on cutaneous arteries causes vasoconstriction

  18. Contractility • Sympathetic stimulation of beta 2 receptors on arteries supplying skeletal muscle causes vasodilation

  19. Elastic Arteries • Elastic Arteries – Large arteries with more elastic fibers and less smooth muscle

  20. Elastic Arteries • Example: aorta, sublcavian, and pulmonary arteries

  21. Elastic Arteries • Also called conducting arteries because they conduct blood from the heart to medium sized arteries

  22. Muscular or distributing arteries • Medium sized and have a large amount of smooth muscle and distribute blood to various parts of the body

  23. Muscular or distributing arteries • Examples: brachial, femoral, and popliteal arteries

  24. Arterioles • Very small arteries that deliver blood to capillaries

  25. Capillaries • Connect arterioles and venules

  26. Capillaries • Microcirculation – flow of blood through the capillaries

  27. Capillaries • Capillaries are found near almost every cell in the body

  28. Capillaries • Function – Permit the exchange of nutrients and wastes between the blood and tissue cells

  29. Capillaries • Composed of a single layer of cells (endothelium) and a basement membrane

  30. Capillaries • Two types; • Continuous • Fenestrated

  31. Capillaries • Continuous – composed of endothelial cells that form a continuous tube that contains gaps between cells called intercellular clefts

  32. Capillaries • Fenestrated capillaries – plasma membrane contains small pores

  33. Capillaries • Materials can cross the blood capillary walls in four ways

  34. Capillaries Four Ways; • Intercellular clefts • Trancytosis using pinocytic vesicles • Diffusion • Fenestrations

  35. Intercellular clefts • Open in response to histamine (released during inflamation) making capillaries more leaky

  36. Intercellular clefts • This allows fluid and wbc, and antibodies to go from the bloodstream to the site of infection

  37. Pinocytosis • Large fats cross via pinocytosis

  38. Diffusion • Water, CO2, and O2 cross capillaries by diffusion

  39. Fenestrations • Allow small molecules such as water and electrolytes to get into the urine

  40. Fenestrations • Prevent large proteins and red cells from getting into the urine

  41. Sinusoids • Discontinuous capillaries

  42. Sinusoids • Present in the liver

  43. Sinusoids • Allow large molecules such as protein and bilirubin to get from the bloodstream into hepatocytes

  44. Venules • They are small vessels that are formed from the union of several capillaries

  45. Venules • Merges to form veins

  46. Venules • Drain blood from capillaries into veins

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