1. Anatomy and Physiology, Sixth Edition
Rod R. Seeley Idaho State University
Trent D. Stephens Idaho State University
Philip Tate Phoenix College
Chapter 21
Lecture Outline*
*See PowerPoint Image Slides for all figures and tables pre-inserted into PowerPoint without notes.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. Peripheral Circulation and Regulation
Chapter 21
Peripheral Circulation and Regulation

3. Peripheral Circulatory System
Systemic vessels
Transport blood through most all body parts from left ventricle and back to right atrium
Pulmonary vessels
Transport blood from right ventricle through lungs and back to left atrium
Blood vessels and heart regulated to ensure blood pressure is high enough for blood flow to meet metabolic needs of tissues

4. Blood Vessel Structure
Arteries
Elastic, muscular, arterioles
Capillaries
Blood flows from arterioles to capillaries
Most of exchange between blood and interstitial spaces occurs across the walls
Blood flows from capillaries to venous system
Veins
Venules, small veins, medium or large veins

5. Capillaries Capillary wall consists mostly of endothelial cells
Types classified by diameter/permeability
Continuous
Do not have fenestrae
Fenestrated
Have pores
Sinusoidal
Large diameter with large fenestrae

6. Capillary Network
Blood flows from arterioles through metarterioles, then through capillary network
Venules drain network
Smooth muscle in arterioles, metarterioles, precapillary sphincters regulates blood flow

7. Structure of Arteries and Veins
Three layers except for capillaries and venules
Tunica intima
Endothelium
Tunica media
Vasoconstriction
Vasodilation
Tunica adventitia
Merges with connective tissue surrounding blood vessels

8. Structure of Arteries Elastic or conducting arteries
Largest diameters, pressure high and fluctuates
Muscular or medium arteries
Smooth muscle allows vessels to regulate blood supply by constricting or dilating
Arterioles
Transport blood from small arteries to capillaries

9. Structure of Veins Venules and small veins Medium and large veins
Tubes of endothelium on delicate basement membrane
Medium and large veins
Valves
Allow blood to flow toward heart but not in opposite direction
Atriovenous anastomoses
Allow blood to flow from arterioles to small veins without passing through capillaries

10. Blood Vessel Comparison

11. Aging of the Arteries Arteriosclerosis Atherosclerosis
General term for degeneration changes in arteries making them less elastic
Atherosclerosis
Deposition of plaque on walls

12. Pulmonary Circulation
Moves blood to and from the lungs
Pulmonary trunk
Arises from right ventricle
Pulmonary arteries
Branches of pulmonary trunk which project to lungs
Pulmonary veins
Exit each lung and enter left atrium

13. Systemic Circulation: Arteries
Aorta
From which all arteries are derived either directly or indirectly
Parts
Ascending, descending, thoracic, abdominal
Coronary arteries
Supply the heart

14. Branches of the Aorta

15. Major Arteries

16. Head and Neck Arteries

17. Arteries of the Brain

18. Head and Thorax Major Arteries

19. Arteries of Upper Limb and Shoulder

20. Arteries of Abdomen and Pelvis

21. Arteries of Pelvis and Lower Limb

22. Arteries of Lower Limb

23. Systemic Circulation: Veins
Return blood from body to right atrium
Major veins
Coronary sinus (heart)
Superior vena cava (head, neck, thorax, upper limbs)
Inferior vena cava (abdomen, pelvis, lower limbs)
Types of veins
Superficial, deep, sinuses

24. Major Veins

25. Veins of Head and Neck

26. Head and Thorax Veins

27. Veins of Shoulder and Upper Limb

28. Veins of Thorax

29. Hepatic Portal System

30. Veins of Abdomen and Pelvis

31. Veins of Pelvis and Lower Limb

32. Veins of Lower Limb

33. Dynamics of Blood Circulation
Interrelationships between
Pressure
Flow
Resistance
Control mechanisms that regulate blood pressure
Blood flow through vessels

34. Laminar and Turbulent Flow
Laminar flow
Streamlined
Outermost layer moving slowest and center moving fastest
Turbulent flow
Interrupted
Rate of flow exceeds critical velocity
Fluid passes a constriction, sharp turn, rough surface

35. Blood Pressure Measure of force exerted by blood against the wall
Blood moves through vessels because of blood pressure
Measured by listening for Korotkoff sounds produced by turbulent flow in arteries as pressure released from blood pressure cuff

36. Blood Pressure Measurement

37. Blood Flow, Poiseuille’s Law and Viscosity
Flow decreases when resistance increases
Flow resistance decreases when vessel diameter increases
Viscosity
Measure of resistance of liquid to flow
As viscosity increases, pressure required to flow increases
Blood flow
Amount of blood moving through a vessel in a given time period
Directly proportional to pressure differences, inversely proportional to resistance

38. Critical Closing Pressure, Laplace’s Law and Compliance
Vascular compliance
Tendency for blood vessel volume to increase as blood pressure increases
More easily the vessel wall stretches, the greater its compliance
Venous system has a large compliance and acts as a blood reservoir
Critical closing pressure
Pressure at which a blood vessel collapses and blood flow stops
Laplace’s Law
Force acting on blood vessel wall is proportional to diameter of the vessel times blood pressure

39. Physiology of Systemic Circulation
Determined by
Anatomy of circulatory system
Dynamics of blood flow
Regulatory mechanisms that control heart and blood vessels
Blood volume
Most in the veins
Smaller volumes in arteries and capillaries

40. Cross-Sectional Area
As diameter of vessels decreases, the total cross-sectional area increases and velocity of blood flow decreases
Much like a stream that flows rapidly through a narrow gorge but flows slowly through a broad plane

41. Pressure and Resistance
Blood pressure averages 100 mm Hg in aorta and drops to 0 mm Hg in the right atrium
Greatest drop in pressure occurs in arterioles which regulate blood flow through tissues
No large fluctuations in capillaries and veins

42. Pulse Pressure Difference between systolic and diastolic pressures
Increases when stroke volume increases or vascular compliance decreases
Pulse pressure can be used to take a pulse to determine heart rate and rhythmicity

43. Capillary Exchange and Interstitial Fluid Volume Regulation
Blood pressure, capillary permeability, and osmosis affect movement of fluid from capillaries
A net movement of fluid occurs from blood into tissues. Fluid gained by tissues is removed by lymphatic system.

44. Fluid Exchange Across Capillary Walls

45. Vein Characteristics and Effect of Gravity on Blood Pressure
Venous return to heart increases due to increase in blood volume, venous tone, and arteriole dilation
Effect of Gravity
In a standing position, hydrostatic pressure caused by gravity increases blood pressure below the heart and decreases pressure above the heart

46. Control of Blood Flow by Tissues
Local control
In most tissues, blood flow is proportional to metabolic needs of tissues
Nervous System
Responsible for routing blood flow and maintaining blood pressure
Hormonal Control
Sympathetic action potentials stimulate epinephrine and norepinephrine

47. Local Control of Blood Flow by Tissues
Blood flow can increase 7-8 times as a result of vasodilation of metarterioles and precapillary sphincters in response to increased rate of metabolism
Vasodilator substances produced as metabolism increases
Vasomotion is periodic contraction and relaxation of precapillary sphincters

48. Nervous Regulation of Blood Vessels

49. Short-Term Regulation of Blood Pressure
Baroreceptor reflexes
Change peripheral resistance, heart rate, and stroke volume in response to changes in blood pressure
Chemoreceptor reflexes
Sensory receptors sensitive to oxygen, carbon dioxide, and pH levels of blood
Central nervous system ischemic response
Results from high carbon dioxide or low pH levels in medulla and increases peripheral resistance

50. Baroreceptor Reflex Control

51. Baroreceptor Effects

52. Chemoreceptor Reflex Control

53. Effects of pH and Gases

54. Long-Term Regulation of Blood Pressure
Renin-angiotensin-aldosterone mechanism
Vasopressin (ADH) mechanism
Atrial natriuretic mechanism
Fluid shift mechanism
Stress-relaxation response

55. Renin-Angiotensin-Aldosterone Mechanism

56. Vasopressin (ADH) Mechanism

57. Long Term Mechanisms Fluid shift Atrial natriuretic Stress-relaxation
Movement of fluid from interstitial spaces into capillaries in response to decrease in blood pressure to maintain blood volume
Stress-relaxation
Adjustment of blood vessel smooth muscle to respond to change in blood volume
Atrial natriuretic
Hormone released from cardiac muscle cells when atrial blood pressure increases, simulating an increase in urinary production, causing a decrease in blood volume and blood pressure

58. Shock Inadequate blood flow throughout body Three stages
Compensated: Blood pressure decreases only a moderate amount and mechanisms able to reestablish normal blood pressure and flow
Progressive: Compensatory mechanisms inadequate and positive feedback cycle develops; cycle proceeds to next stage or medical treatment reestablishes adequate blood flow to tissues
Irreversible: Leads to death, regardless of medical treatment