1. The Cardiovascular System: Blood Vessels and Hemodynamics
A. Anatomy of blood vessels
1. Arteries
a. Elastic (conducting) arteries
b. Muscular (distributing) arteries
c. Anastomoses
2. Arterioles
3. Capillaries
4. Venules
5. Veins
6. Blood distribution
B. Capillary exchange
a. Diffusion
b. Vesicular transport
c. Bulk flow (filtration and reabsorption)
C. Hemodynamics: physiology of circulation
1. Velocity of blood flow
2. Volume of blood flow
a. Blood pressure
b. Peripheral resistance
3. Venous return
D. Control of blood pressure and blood flow
1. Cardiovascular center
a. Input to cardiovascular center
b. Output from cardiovascular center
2. Neural regulation
a. Baroreceptors
b. Chemoreceptors
3. Hormonal regulation
4. Autoregulation (local control)
E. Blood vessel routes

2. Arteries 1. lumen 2. tunica intima a. endothelium
b. internal elastic lamina
3. tunica media
4. tunica adventitia

3. Arterial Properties 1. elasticity 2. contractility a. vasoconstriction
b. vasodilation

4. Arterial Types 1. elastic (conducting) a. elastin
b. pressure reservoirs
2. muscular (distributing)
a. great contractility
b. blood shunting
c. anastomoses
d. collateral circulation
Muscular Arteries
Elastic
arteries
Muscular Arteries

5. Arterioles
1. highest contractility
2. blood shunting

6. Routing of Blood Flow

7. Capillaries 1. microscopic 2. distribution 3. exchange
4. simple squamous
5. precapillary sphincters
6. vasomotion
Endothelium basement membrane

8. Capillary Types
1. continuous
2. fenestrated
3. sinusoids

9. Venules and Veins 1. same basic tunics 2. larger lumen
3. thinner tunica media
4. very distensible
5. valves
Valve

10. Blood Reservoirs
Skin, liver, and
spleen

11. Capillary Exchange 1. diffusion 2. vesicular transport 3. bulk flow
a. filtration
b. reabsorption
c. Starling's law of the capillaries
What is vasomotion?

12. Bulk Flow is Dependent On Four Pressures
1. blood hydrostatic pressure (BHP = 30 mm Hg-arterial)
(outward force) = 10 mm Hg-venous
2. interstitial fluid hydrostatic pressure
(IFHP = 0 to -3(suction) mm Hg) (inward force)
3. blood colloid osmotic pressure
(BCOP = 28 mm Hg) (inward force)
4. interstitital fluid osmotic pressure
(IFOP = 8 mm Hg) (outward force)

13. Net Filtration Pressure (Arterial End)
NFP = outward forces - inward forces
= (BHP + IFOP) - (BCOP + IFHP)
= (30 + 8) - (28 + 0)
= (38) - (28)
= +10 mm Hg
If IFHP was (-3) then NFP = 13 mm Hg
net flow of fluid is? out of the capillary
(filtration)

14. Net Filtration Pressure- Venous End
NFP = outward forces - inward forces
= (BHP + IFOP) - (BCOP + IFHP)
= (10 + 8) - (28 + 0)
= (18) - (28)
= -10 mm Hg
If IFHP was (-3) then NFP = -7 mm Hg
net flow of fluid is? into of the capillary
(reabsorption)

15. The Forces of Capillary Filtration and Absorption

16. Capillary Exchange

17. total cross sectional area
Hemodynamics
Blood flow (ml/min)
Perfusion (ml/min/g)
Blood flow velocity (mm/sec)
Cross-sectional area (cm2)
capillaries (2500 cm2)
venules (250 cm2)
1200 mm/sec
total cross sectional area
15 mm/sec
Flow α ∆Pressure
Resistance
(80 cm2)
veins
aorta (2.5 cm2)
If total cross-sectional area
then velocity
(aorta to capillaries)
velocity
arteries (20 cm2)
arterioles (40 cm2)
5 mm/sec
0.4 mm/sec
80 mm/sec (IVC)
venae cavae (8 cm2)
If total cross-sectional area
then velocity
(capillaries to venae cavae)
Relationship between blood flow velocity and total cross-sectional area of the vascular tree

18. Blood Pressure 1. What is blood pressure? 2. direct determinants of BP
a. cardiac output
b. blood volume
c. peripheral resistance

19. Volume of Blood Flow CO = SV x HR
= 5.25 L/min (the volume of blood circulating
through systemic or pulmonary
vessels each minute)
Two other factors influence cardiac output:
1) blood pressure
2) resistance (opposition)
CO = mean arterial blood pressure (MABP)
resistance (R)

20. Resistance (Opposition to Flow)
1. blood viscosity
2. total blood vessel length
3. blood vessel radius

21. Systemic vascular resistance (SVR) (total peripheral resistance (TPR)
1. major function of arterioles
2. vasodilation vs vasocontriction
a. Blood flow is proportional to the fourth power of vessel radius.
r = 1 mm r4 = 14 = flow = 1 mm/sec
r = 2 mm r4 = 24 = flow = 16 mm/sec
r = 3 mm r4 = 34 = flow = 81 mm/sec
b. Therefore, a 3-fold change in resistance exerts an 81-fold change in velocity.

22. Mechanisms of Venous Return
1. decreasing x-sec area
2. venous valves
3. muscle pumps
4. respiratory pump

23. Control of Blood Pressure and Blood Flow
The cardiovascular center (CVC) consists of three groups of neurons:
1. cardioacceleratory neurons
2. cardioinhibitory neurons
3. vasomotor neurons

24. Nervous Input to Medullary Cardiovascular Center
CVC Input
1. input
a. higher brain centers
b. baroreceptors
c. chemoreceptors
Nervous Input to Medullary Cardiovascular Center
higher brain
cerebral cortex
limbic system
hypothalamus
baroreceptors
(blood pressure)
chemoreceptors
(O2, H+, CO2)
medulla
oblongata

25. CVC Output 2. output a. vagus (X) nerve b. sympathetic neurons
(1) heart
(2) arterioles
Nervous Output From Medullary Cardiovascular Center
Medulla oblongata
vagus nerve (X)
heart
(decrease rate)
cardiac accelerator nerves (sympathetic)
heart (increase rate
and contractility)
vasomotor nerves (sympathetic)
blood vessels
(vasoconstriction and vasodilation)

26. Neural Control of the Heart Reflexes
Reflexes activate the Vasomotor center – results in vasoconstriction/vasodilation of arterioles
Baroreflexes and chemoreflexes
carotid sinus and aortic sinus reflexes
right atrial (Bainbridge) reflex
Medullary ischemic reflex
carotid sinus baroreceptors
sensory fibers in c.n. IX
aortic sinus baroreceptors
SA node
AV node
parasympathetic fibers in c.n. X
sympathetic fibers in spinal nerves
cerebrum
hypothalamus
cardiovascular center in medulla
spinal cord

27. Baroreceptor Reflex

28. Chemoreceptor Reflex

29. Negative Feedback of Neural Control
CONTROLLED CONDITION
a stimulus or stress disrupts homeostasis by causing a decrease in blood pressure
RETURN TO HOMEOSTASIS
increased blood pressure
RECEPTOR
baroreceptors in carotid and aortic sinuses are stretched less, resulting in decreased rate of nerve impulses to the cardiovascular center
EFFECTORS
contractility = stroke volume
heart rate
therefore cardiac output
3. vasoconstriction = resistance
CONTROL CENTER
1. increased sympathetic output via
cardioacceleratory center
2. decreased parasympathetic output
from cardioinhibitory center

30. Hormonal Regulation 1. epinephrine and norepinephrine
potent vasoconstrictor  increased resistance  increased BP
increased HR + increased SV = increased CO  increased BP
2. antidiuretic hormone
increases water retention by kidneys  increased blood volume  increased BP
3. angiotensin II
4. aldosterone
promotes sodium retention by kidneys
increased water retention  increased blood volume  increased BP
5. atrial natriuretic peptide
decreases sodium retention by kidneys
decreased water retention  decreased blood volume  decreased BP

31. Autoregulation Ability of tissues to regulate their own blood supply
Metabolic theory of autoregulation
Inadequate perfusion =
A. Decreased O2  vasodilation
B. Increased wastes (CO2, H+, K+, adenosine)  vasodilation
Adequate perfusion again = vasoconstriction
Vasoactive Chemicals
- secreted by platelets, endothelial cells, perivascular tissues with trauma
- Examples include Histamine, prostaglandins, bradykinin stimulate vasodilation
Reactive hyperemia

32. Summary of Blood Pressure Control
decreased blood pressure
leads to
decreased activity of baroreceptors in carotid and aortic sinuses
leads to
negative feedback
increased activity
decreased activity
decreased nervous input to cardioinhibitory center
leads to
increased activity of the:
cardioacceleratory center
vasomotor center
leads to
increased sympathetic output from spinal cord
norepinephrine secretion causes
increased stroke volume
increased heart rate
leads to
increased vasoconstriction
leads to
increased cardiac output
leads to
increased resistance
leads to
increased blood pressure

33. Blood Vessel Routes (see Handout)

34. Beginning of the Aorta

35. Arterial Supply Head and Neck

36. Arterial Circle of the Brain- Circle of Willis

37. Arterial Supply to the Upper Arm

38. Arterial Supply to the Thorax

39. Arterial Supply to the Abdomen

40. Arterial Supply to the Pelvic Region and Lower Limb