Transcript Powerpoint 20 Vessels - People Server at UNCW

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
Arteries
1. lumen
2. tunica intima
a. endothelium
b. internal elastic lamina
3. tunica media
4. tunica adventitia
Arterial Properties
1. elasticity
2. contractility
a. vasoconstriction
b. vasodilation
Arterial Types
1. elastic (conducting)
a. elastin
b. pressure reservoirs
2. muscular (distributing)
a. great contractility
b. blood shunting
c. anastomoses
d. collateral circulation
Elastic
arteries
Muscular
Arteries
Muscular Arteries
Arterioles
1. highest contractility
2. blood shunting
Routing of Blood Flow
Capillaries
1.
2.
3.
4.
5.
6.
microscopic
distribution
exchange
simple squamous
precapillary sphincters
vasomotion
Endothelium
basement membrane
Capillary Types
1. continuous
2. fenestrated
3. sinusoids
Venules and Veins
1.
2.
3.
4.
5.
same basic tunics
larger lumen
thinner tunica media
very distensible
valves
Valve
Blood Reservoirs
Skin, liver, and
spleen
Capillary Exchange
1. diffusion
2. vesicular transport
3. bulk flow
a. filtration
b. reabsorption
c. Starling's law of the capillaries
What is vasomotion?
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)
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)
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)
The Forces of Capillary Filtration
and Absorption
Capillary Exchange
Hemodynamics
veins
(80 cm2)
velocity
Relationship between blood flow velocity and total
cross-sectional area of the vascular tree
80 mm/sec (IVC)
5 mm/sec
0.4 mm/sec
arterioles
(40 cm2)
15 mm/sec
1200 mm/sec
total cross
sectional area
venae cavae
(8 cm2)
If total cross-sectional area
then velocity
(capillaries to venae cavae)
arteries (20 cm2)
If total cross-sectional area
then velocity
(aorta to capillaries)
capillaries
(2500 cm2)
aorta (2.5 cm2)
Blood flow (ml/min)
Perfusion (ml/min/g)
Blood flow velocity
(mm/sec)
Cross-sectional area (cm2)
Flow α ∆Pressure
Resistance
Blood Pressure
1. What is blood pressure?
2. direct determinants of BP
a. cardiac output
b. blood volume
c. peripheral resistance
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)
Resistance (Opposition to Flow)
1. blood viscosity
2. total blood vessel length
3. blood vessel radius
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 = 1
flow = 1 mm/sec
r = 2 mm r4 = 24 = 16
flow = 16 mm/sec
r = 3 mm r4 = 34 = 81
flow = 81 mm/sec
b. Therefore, a 3-fold change in resistance exerts
an 81-fold change in velocity.
Mechanisms of Venous Return
1.
2.
3.
4.
decreasing x-sec area
venous valves
muscle pumps
respiratory pump
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
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
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)
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
sensory fibers in c.n. IX
carotid sinus baroreceptors
cerebrum
aortic sinus baroreceptors
hypothalamus
cardiovascular center
in medulla
SA node
AV node
spinal cord
parasympathetic fibers in c.n. X
sympathetic fibers in spinal nerves
Baroreceptor Reflex
Chemoreceptor Reflex
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
CONTROL CENTER
1. increased sympathetic output via
cardioacceleratory center
2. decreased parasympathetic output
from cardioinhibitory center
EFFECTORS
1.
2.
contractility =
stroke volume
heart rate
therefore cardiac output
3.
vasoconstriction =
resistance
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
potent vasoconstrictor  increased resistance  increased BP
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
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
Summary of Blood Pressure Control
decreased blood pressure
leads to
decreased activity of baroreceptors in carotid and aortic sinuses
increased activity
leads to
decreased nervous input to cardioinhibitory center
increased activity
leads to
increased activity of the:
1.cardioacceleratory center
2.vasomotor center
decreased activity
leads to
increased sympathetic output from spinal cord
norepinephrine secretion causes
increased heart rate
increased stroke volume
leads to
leads to
increased cardiac output
leads to
negative feedback
increased blood pressure
increased vasoconstriction
leads to
increased resistance
leads to
Blood Vessel Routes
(see Handout)
Beginning of the Aorta
Arterial Supply Head and Neck
Arterial Circle of the Brain- Circle
of Willis
Arterial Supply to the Upper Arm
Arterial Supply to the Thorax
Arterial Supply to the Abdomen
Arterial Supply to the Pelvic
Region and Lower Limb