Cardiovascular System

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

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

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

13. Tunica Media • Maintains elasticity and contractility

14. Tunica Externa • Rich in elastic and collagen fibers

16. Functional Properties of Arteries • Elasticity • Contractility

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

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

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

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

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

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

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

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

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

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

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

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

29. Capillaries • Connect arterioles and venules

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

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

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

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

34. Capillaries • Two types; • Continuous • Fenestrated

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

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

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

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

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

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

41. Pinocytosis • Large fats cross via pinocytosis

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

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

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

45. Sinusoids • Discontinuous capillaries

46. Sinusoids • Present in the liver

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

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

49. Venules • Merges to form veins

50. Venules • Drain blood from capillaries into veins