1. The Blood Vessels and Blood Pressure
Chapter 10
The Blood Vessels and Blood Pressure
Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

2. Blood Flow
Blood is constantly reconditioned so composition remains relatively constant
Reconditioning organs receive more blood than needed for metabolic needs
Digestive organs, kidneys, skin
Adjust extra blood to achieve homeostasis
Blood flow to other organs can be adjusted according to metabolic needs
Brain can least tolerate disrupted supply
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

3. Distribution of Cardiac Output at Rest
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

4. Blood Flow
Flow rate through a vessel (volume of blood passing through per unit of time):
Directly proportional to the pressure gradient
Inversely proportional to vascular resistance
F = ΔP R
F = flow rate of blood through a vessel
ΔP = pressure gradient
R = resistance of blood vessels
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

5. Blood Flow
Pressure gradient is pressure difference between beginning and end of a vessel
Blood flows from area of higher pressure to area of lower pressure
Resistance is measure of opposition of blood flow through a vessel
Depends on 3 things:
Blood viscosity
Vessel length
Vessel radium
Major determinant of resistance to flow is vessel’s radius
Slight change in radius produces significant change in blood flow
R is proportional to 1 r4
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

6. Relationship of Resistance and Flow to Vessel Radius
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

7. Animation: Measuring blood pressure

8. Animation: Arteries as pressure reservoir

9. Vascular Tree Closed system of vessels Consists of Arteries Arterioles
Carry blood away from heart to tissues
Arterioles
Smaller branches of arteries
Capillaries
Smaller branches of arterioles
Smallest of vessels across which all exchanges are made with surrounding cells
Venules
Formed when capillaries rejoin
Return blood to heart
Veins
Formed when venules merge
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

10. Basic Organization of the Cardiovascular System
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

11. Animation: Flow velocity

12. Animation: Vein function

13. Arteries Specialized to
Serve as rapid-transit passageways for blood from heart to organs
Due to large radius, arteries offer little resistance to blood flow
Act as pressure reservoir to provide driving force for blood when heart is relaxing
Arterial connective tissue contains
Collagen fibers
Provide tensile strength
Elastin fibers
Provide elasticity to arterial walls
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

14. Arteries as a Pressure Reservoir
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

15. Blood Pressure Force exerted by blood against a vessel wall Depends on
Volume of blood contained within vessel
Compliance of vessel walls
Systolic pressure
Peak pressure exerted by ejected blood against vessel walls during cardiac systole
Averages 120 mm Hg
Diastolic pressure
Minimum pressure in arteries when blood is draining off into vessels downstream
Averages 80 mm Hg
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

16. Blood Pressure Can be measured indirectly using sphygmomanometer
Korotkoff sounds
Sounds heard when determining blood pressure
Sounds are distinct from heart sounds associated with valve closure
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

17. Blood
Pressure
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

18. Pulse Pressure
Pressure difference between systolic and diastolic pressure
Example
If blood pressure is 120/80, pulse pressure is 40 mm Hg (120mm Hg – 80mm Hg)
Pulse that can be felt in artery lying close to surface of skin is due to pulse pressure
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

19. Mean Arterial Pressure
Average pressure driving blood forward into tissues throughout cardiac cycle
Formula for approximating mean arterial pressure
Mean arterial pressure = diastolic pressure +
⅓ pulse pressure
At 120/80, mean arterial pressure = 80 mm Hg +
⅓ (40 mm Hg) = 93 mm Hg
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

20. Arterioles Major resistance vessels
Radius supplying individual organs can be adjusted independently to
Distribute cardiac output among systemic organs, depending on body’s momentary needs
Help regulate arterial blood pressure
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

21. Arterioles Mechanisms involved in adjusting arteriolar resistance
Vasoconstriction
Refers to narrowing of a vessel
Vasodilation
Refers to enlargement in circumference and radius of vessel
Results from relaxation of smooth muscle layer
Leads to decreased resistance and increased flow through that vessel
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

22. Arteriolar Vasoconstriction and Vasodilation
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

23. Arterioles Only blood supply to brain remains constant
Changes within other organs alter radius of vessels and adjust blood flow to organ
Local chemical influences on arteriolar radius
Local metabolic changes
Histamine release
Local physical influences on arteriolar radius
Local application of heat or cold
Chemical response to shear stress
Myogenic response to stretch
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

24. Magnitude and Distribution Of the Cardiac Output at Rest
and During Moderate Exercise
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

25. Arterioles
Specific local chemical factors that produce relaxation of arteriolar smooth muscle
Decreased O2
Increased CO2
Increased acid
Increased K+
Increased osmolarity
Adenosine release
Prostaglandin release
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

26. Arterioles Local vasoactive mediators Endothelial cells
Release chemical mediators that play key role in locally regulating arteriolar caliber
Release locally acting chemical messengers in response to chemical changes in their environment
Among best studied local vasoactive mediators is nitric oxide (NO)
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

27. Functions of Endothelial Cells
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

28. Functions of Nitric Oxide (NO)
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

29. Arterioles Extrinsic control
Accomplished primarily by sympathetic nerve influence
Accomplished to lesser extent by hormonal influence over arteriolar smooth muscle
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

30. Arterioles Cardiovascular control center In medulla of brain stem
Integrating center for blood pressure regulation
Other brain regions also influence blood distribution
Hypothalamus
Controls blood flow to skin to adjust heat loss to environment
Hormones that influence arteriolar radius
Adrenal medullary hormones
Epinephrine and norepinephrine
Generally reinforce sympathetic nervous system in most organs
Vasopressin and angiotensin II
Important in controlling fluid balance
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

31. Capillaries Thin-walled, small-radius, extensively branched
Sites of exchange between blood and surrounding tissue cells
Maximized surface area and minimized diffusion distance
Velocity of blood flow through capillaries is relatively slow
Provides adequate exchange time
2 types of passive exchanges
Diffusion
Bulk flow
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

32. Capillaries
Narrow, water-filled gaps (pores) lie at junctions between cells
Permit passage of water-soluble substances
Lipid soluble substances readily pass through endothelial cells by dissolving in lipid bilayer barrier
Size of pores varies from organ to organ
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

33. Capillaries Under resting conditions many capillaries are not open
Capillaries surrounded by precapillary sphincters
Contraction of sphincters reduces blood flowing into capillaries in an organ
Relaxation of sphincters increases blood flow
Metarteriole
Runs between an arteriole and a venule
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

34. Lymphatic System Extensive network of one-way vessels
Provides accessory route by which fluid can be returned from interstitial to the blood
Initial lymphatics
Small, blind-ended terminal lymph vessels
Permeate almost every tissue of the body
Lymph
Interstitial fluid that enters a lymphatic vessel
Lymph vessels
Formed from convergence of initial lymphatics
Eventually empty into venous system near where blood enters right atrium
One way valves spaced at intervals direct flow of lymph toward venous outlet in chest
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

35. Lymphatic System Functions Return of excess filtered fluid
Defense against disease
Lymph nodes have phagocytes which destroy bacteria filtered from interstitial fluid
Transport of absorbed fat
Return of filtered protein
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

36. Lymphatic
System
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

37. Edema Swelling of tissues
Occurs when too much interstitial fluid accumulates
Causes of edema
Reduced concentration of plasma proteins
Increased permeability of capillary wall
Increased venous pressure
Blockage of lymph vessels
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

38. Veins Venous system transports blood back to heart
Capillaries drain into venules
Venules converge to form small veins that exit organs
Smaller veins merge to form larger vessels
Veins
Large radius offers little resistance to blood flow
Also serve as blood reservoir
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

39. Veins Factors which enhance venous return
Driving pressure from cardiac contraction
Sympathetically induced venous vasoconstriction
Skeletal muscle activity
Effect of venous valves
Respiratory activity
Effect of cardiac suction
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

40. Factors that Influence Venous Return
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

41. Mean Arterial Pressure
Blood pressure that is monitored and regulated in the body
Primary determinants
Cardiac output
Total peripheral resistance
Mean arterial pressure = cardiac output x total peripheral resistance
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

42. Determinants of Mean Arterial Pressure
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

43. Mean Arterial Pressure
Constantly monitored by baroreceptors (pressure sensors) within circulatory system
Short-term control adjustments
Occur within seconds
Adjustments made by alterations in cardiac output and total peripheral resistance
Mediated by means of autonomic nervous system influences on heart, veins, and arterioles
Long-term control adjustments
Require minutes to days
Involve adjusting total blood volume by restoring normal salt and water balance through mechanisms that regulate urine output and thirst
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

44. Baroreceptor Reflexes to Restore Blood Pressure to Normal
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

45. Blood Pressure
Additional reflexes and responses that influence blood pressure
Left atrial receptors and hypothalamic osmoreceptors affect long-term regulation of blood pressure by controlling plasma volume
Chemoreceptors in carotid and aortic arteries are sensitive to low O2 or high acid levels in blood
reflexly increase respiratory activity
Associated with certain behaviors and emotions mediated through cerebral-hypothalamic pathway
Exercise modifies cardiac responses
Hypothalamus controls skin arterioles for temperature regulation
Vasoactive substances released from endothelial cells play role
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

46. Blood Pressure Abnormalities
Hypertension
Blood pressure above 140/90 mm Hg
2 broad classes
Primary hypertension
Secondary hypertension
Hypotension
Blood pressure below 100/60 mm Hg
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

47. Hypertension Most common of blood pressure abnormalities
Primary hypertension
Catchall category for blood pressure elevated by variety of unknown causes rather than by a single disease entity
Potential causes being investigated
Defects in salt management by the kidneys
Excessive salt intake
Diets low in K+ and Ca2+
Plasma membrane abnormalities such as defective Na+-K+ pumps
Variation in gene that encodes for angiotensinogen
Endogenous digitalis-like substances
Abnormalities in NO, endothelin, or other locally acting vasoactive chemicals
Excess vasopressin
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

48. Hypertension Secondary hypertension
Accounts for about 10% of hypertension cases
Occurs secondary to another known primary problem
Examples of secondary hypertension
Renal hypertension
Endocrine hypertension
Neurogenic hypertension
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

49. Hypertension Complication of hypertension Congestive heart failure
Stroke
Heart attack
Spontaneous hemorrhage
Renal failure
Retinal damage
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

50. Hypotension Low blood pressure Occurs when
There is too little blood to fill the vessels
Heart is too weak to drive the blood
Orthostatic (postural) hypotension
Transient hypotensive condition resulting from insufficient compensatory responses to gravitational shifts in blood when person moves from horizontal to vertical position
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

51. Hypotension Circulatory shock
Occurs when blood pressure falls so low that adequate blood flow to the tissues can no longer be maintained
4 main types
Hypovolemic (“low volume”) shock
Cardiogenic (“heart produced”) shock
Vasogenic (“vessel produced”) shock
Neurogenic (“nerve produced”) shock
Chapter 10 The Blood Vessels and Blood Pressure Human Physiology by Lauralee Sherwood ©2010 Brooks/Cole, Cengage Learning

52. Animation: Pattern of blood circulation

53. Animation: Lymph vessels and lymph nodes

54. Animation: Blood vessel anatomy