Physiology

1. Physiology Cardiovascular System

2. Physiology Circulatory System • Heart • Pump • Separates the two circulations • Systemic Circulation • Pulmonic Circulation

3. Vessels Each Circulatory System Consist of 3 types of vessels: • Arteries • Veins • Capillaries

4. Vessel Wall Structure of vessel walls The walls of arteries and veins contain three distinct layers: • Tunica interna • Tunica media • Tunica externa

5. Tunica Interna Tunica Interna • Innermost layer of a blood vessel • Includes the endothelial lining and an underlying layer of connective tissue with a variable amount of elastic fibers. • In arteries the outer margin of the Tunica Interna contains a thick layer of elastic fibers called the Internal Elastic Membrane.

6. Tunica Media Tunica Media • Middle layer • Contains concentric sheets of smooth muscle in a framework of loose connective tissue.

7. Tunica Media • Collagen fibers bind the tunica media to the tunica interna and tunica externa. • The thickest layer in the wall of a small artery is the tunica media • The tunica media is separated from the tunica externa by the External Elastic Membrane.

8. Tunica Externa Tunica Externa (tunica adventitia) • Outermost layer • Contains collagen fibers with scattered bands of elastic fibers. • Blends into the connective tissue of adjacent tissue. • In the veins it is thicker than the tunica media and contains networks of elastic fibers and bundles of smooth muscle cell.

9. Artery versus Vein

10. Artery Properties of Arteries: • Elasticity – allows passive changes in vessel diameter in response to changes in blood pressure. • Contractility – gives them the ability to change diameter actively primarily under the control of the sympathetic division of the autonomic nervous system.

11. Contractility SNS Vasoconstriction Vasodilation = =

12. Contractility Vasoconstriction • Afterload • Blood Pressure • Capillary blood flow

13. Contractility Vasodilation • Afterload • Blood Pressure • Capillary blood flow

14. Artery Type of Arteries: • Elastic (conducting) arteries • Muscular (distribution) arteries • Arterioles (resistant vessels)

15. Elastic Arteries Elastic (conducting) arteries • Diameter up to 2.5 cm • Transport large volume of artery from the heart.

16. Elastic Arteries • Walls have high density of elastic fibers and few muscle fibers. • Resilient wall.

17. Elastic Arteries • Tolerate pressure changes that occur during the cardiac cycle. • Examples are the Pulmonary and aortic trunks and their branches.

18. Elastic Arteries Ventricular systole BP rises Cushions the Sudden rise in pressure Expansion

19. Elastic Arteries Ventricular diastole BP falls Slows the drop in pressure Recoil

20. Muscular Artery Muscular (distribution) arteries • Distribute blood to the skeletal muscle and internal organs • Lumen diameter approximately 0.4 cm.

21. Muscular Artery • Thick tunica media containing more smooth muscle cell than that of Elastic artery. • Examples are External Carotid arteries, Brachial arteries and Femoral arteries.

22. Arterioles Arterioles (resistant vessels) • Internal diameter < 30 micrometer • Poorly defined tunica externa • Tunica media in the larger arterioles consist of one or two layers of smooth muscle. • The tunica media of the smallest arterioles contains scattered smooth muscle that do not form complete layers.

23. Resistance • The force opposing blood flow is called resistance (R). • Arterioles are called resistance vessel.

24. Resistance Vessels Smaller Muscular Arteries&Arterioles Resistance Increase SNS

25. Resistant Vessels Smaller Muscular Arteries&Arterioles Resistance Decrease O2

26. Capillaries • Thin walled • Permits exchange between blood and interstitial fluid. • Slow blood flow allowing sufficient time for diffusion and active transport.

27. Capillaries • Consist of an endothelial tube inside a delicate basement membrane. • There is no tunica media or externa • Measures 8 micrometer in diameter.

28. Capillaries There are two types of capillaries • Continuous capillaries • Fenestrated capillaries.

29. Continuous Capillaries • Found in all tissues except epithelia and cartilage. • Permits diffusion of water, small solutes and lipid soluble materials into the surrounding interstitial fluid.

30. Continuous Capillaries • Allow vesicular transport of substance. • Prevents the loss of blood cells and plasma proteins.

31. Fenestrated Capillaries Fenestrated capillaries. • Contains pores that span the endothelial lining. • Permit rapid exchange of water and solutes as large as small peptides, between plasma and the interstitial tissue.

32. Fenestrated Capillaries • Found in choroid plexus of the brain and in endocrine organs (hypothalamus, pituitary, pineal and thyroid glands • Located along absorptive areas of the intestinal tract and at filtration sites in the kidneys.

33. Sinusoids • Resembles fenestrated capillaries • Have gaps between adjacent endothelial cells. • Thin or absent basement membrane. • Blood moves through them very slowly maximizing the time available for exchange across the sinusoidal walls.

34. Capillary Bed • Capillaries do not function as individual units. • Function as part of an interconnected network called a capillary bed or capillary plexus. • A single artery give rise to dozens of capillaries that empty into several venules. • The entrance to each capillary is guarded by a band of smooth muscle called a pre-capillary sphincter.

35. Capillary Bed Contraction of Pre-capillary Sphincter Relaxation of Pre-capillary Sphincter Reduced Flow Increased flow

36. Capillary Bed Capillary bed contains • Metarteriole – initial segment of passage way containing smooth muscles capable of changing diameter • Thoroughfare channel – distal part of the passage way. • Arteriovenousanastomosis – direct connections between arterioles and venules.

37. Vasomotion Cycling of contraction and relaxation of smooth muscles that changes blood flow through capillary bed.

38. Vasomotion Controlled by • concentration of chemicals • concentration of dissolved gasses in the interstitial fluid.

39. Veins • Veins collect blood from all tissues. • Walls thinner than corresponding arteries. • Larger in diameter than corresponding arteries.

40. Veins • Pressure in veins are lower. • Thinner wall and lower portion of smooth muscle – more distensible. • Expand easy – Capacitance vessels.

41. Types of Veins • Venules • Medium-Sized Veins • Large Veins

42. Types of Veins Venules • Collect blood from the capillaries • Varying widely in size and character • Average internal diameter is 20 µm • Venules < 50 µm lacks a tunica media

43. Types of Veins Medium-Sized Veins • Range from 2 to 9 mm • Comparable in size to muscular arteries. • Thin tunica media with few smooth muscle cells. • Thickest layer is the tunica externa – contains longitudinal strands of elastic and collagen fibers.

44. Types of Veins Large Veins • Includes SVC, IVC and their tributaries. • All tunica layers are present. • Slender tunica media is surrounded by a thick tunica externa.

45. Valves • Folds of the tunica interna • Projects from the vessel wall • Points in the direction of blood flow

46. Valves • Permits blood flow in one direction. • Prevents backflow of blood towards the capillary. • Compartmentalize the blood – dividing the weight of the blood between the compartments.

48. Physiology Lungs Capillaries Pulmonic Circulation Arterial Pulmonic Circulation Venous Heart Right side Heart Left Side Systemic Circulation Venous Body Tissue Capillaries Systemic Circulation Arterial

49. Pulmonic Circulation RT Lung Pulmonic Circulation LT Lung Systemic Circulation Right Side Head, Neck Upper Limb Thorax Systemic Circulation Left Side Head, Neck Upper Limb Thorax Systemic Circulation Abdomen Lower Limbs

50. Pulmonic Circulation RT Lung Pulmonic Circulation LT Lung Systemic Circulation Right Side Head, Neck Upper Limb Systemic Circulation Left Side Head, Neck Upper Limb Systemic Circulation Thorax, Body Lower Limbs