The Cardiovascular System: Blood The Cardiovascular System: Blood Vessels and HemodynamicsVessels and Hemodynamics
A. Anatomy of blood vesselsA. Anatomy of blood vessels 1. Arteries1. Arteries a. Elastic (conducting) arteriesa. Elastic (conducting) arteries b. Muscular (distributing) b. Muscular (distributing) arteriesarteries c. Anastomosesc. Anastomoses 2. Arterioles2. Arterioles 3. Capillaries3. Capillaries 4. Venules4. Venules 5. Veins5. Veins 6. Blood distribution6. Blood distributionB. Capillary exchangeB. Capillary exchange a. Diffusiona. Diffusion b. Vesicular transportb. Vesicular transport c. Bulk flow (filtration and c. Bulk flow (filtration and reabsorption)reabsorption)
C. Hemodynamics: physiology of C. Hemodynamics: physiology of circulationcirculation 1. Velocity of blood flow1. Velocity of blood flow 2. Volume of blood flow2. Volume of blood flow a. Blood pressurea. Blood pressure b. Peripheral resistanceb. Peripheral resistance 3. Venous return3. Venous returnD. Control of blood pressure and blood D. Control of blood pressure and blood
flowflow 1. Cardiovascular center1. Cardiovascular center a. Input to cardiovascular centera. Input to cardiovascular center b. Output from cardiovascular b. Output from cardiovascular centercenter 2. Neural regulation2. Neural regulation a. Baroreceptorsa. Baroreceptors b. Chemoreceptorsb. Chemoreceptors 3. Hormonal regulation3. Hormonal regulation 4. Autoregulation (local control)4. Autoregulation (local control)E. Blood vessel routesE. Blood vessel routes
ArteriesArteries1. lumen1. lumen
2. tunica intima2. tunica intima
a. endotheliuma. endothelium
b. internal elastic laminab. internal elastic lamina
3. tunica media3. tunica media
4. tunica adventitia4. tunica adventitia
Arterial PropertiesArterial Properties
1. elasticity1. elasticity
2. contractility2. contractility
a. vasoconstrictiona. vasoconstriction
b. vasodilationb. vasodilation
Arterial TypesArterial Types1. elastic (conducting)1. elastic (conducting) a. elastina. elastin b. pressure reservoirsb. pressure reservoirs2. muscular (distributing)2. muscular (distributing) a. great contractilitya. great contractility b. blood shuntingb. blood shunting c. anastomosesc. anastomoses d. collateral circulationd. collateral circulation
Muscular Arteries
Muscular Arteries
Elasticarteries
ArteriolesArterioles
1. highest contractility1. highest contractility
2. blood shunting2. blood shunting
Routing of Blood FlowRouting of Blood Flow
CapillariesCapillaries
1. microscopic1. microscopic
2. distribution2. distribution
3. exchange3. exchange
4. simple squamous4. simple squamous
5. precapillary sphincters5. precapillary sphincters
6. vasomotion6. vasomotion
Endothelium basement membrane
Capillary TypesCapillary Types1. continuous1. continuous
2. fenestrated2. fenestrated
3. sinusoids3. sinusoids
Venules and VeinsVenules and Veins1. same basic tunics1. same basic tunics
2. larger lumen2. larger lumen
3. thinner tunica media3. thinner tunica media
4. very distensible4. very distensible
5. valves5. valves
Valve
Blood ReservoirsBlood Reservoirs
Skin, liver, andspleen
Capillary ExchangeCapillary Exchange
1. diffusion1. diffusion2. vesicular transport2. vesicular transport3. bulk flow3. bulk flow a. filtrationa. filtration b. reabsorptionb. reabsorption c. Starling's law of the capillariesc. Starling's law of the capillaries
What is vasomotion?What is vasomotion?
Bulk Flow is Dependent On Bulk Flow is Dependent On Four PressuresFour Pressures
1. blood hydrostatic pressure (BHP = 30 mm Hg-arterial)1. blood hydrostatic pressure (BHP = 30 mm Hg-arterial) (outward force) = 10 mm Hg-venous(outward force) = 10 mm Hg-venous
2. interstitial fluid hydrostatic pressure2. interstitial fluid hydrostatic pressure (IFHP = 0 to -3(suction) mm Hg) (inward force)(IFHP = 0 to -3(suction) mm Hg) (inward force)
3. blood colloid osmotic pressure3. blood colloid osmotic pressure (BCOP = 28 mm Hg) (inward force)(BCOP = 28 mm Hg) (inward force)
4. interstitital fluid osmotic pressure4. interstitital fluid osmotic pressure (IFOP = 8 mm Hg) (outward force)(IFOP = 8 mm Hg) (outward force)
Net Filtration Pressure Net Filtration Pressure (Arterial End)(Arterial End)
NFP = outward forces - inward forcesNFP = outward forces - inward forces = (BHP + IFOP) - (BCOP + IFHP)= (BHP + IFOP) - (BCOP + IFHP) = (30 + 8) - (28 + 0)= (30 + 8) - (28 + 0) = (38) - (28)= (38) - (28) = +10 mm Hg= +10 mm HgIf IFHP was (-3) then NFP = 13 mm HgIf IFHP was (-3) then NFP = 13 mm Hg
net flow of fluid is? out of the capillarynet flow of fluid is? out of the capillary (filtration)(filtration)
Net Filtration Pressure- Venous Net Filtration Pressure- Venous EndEnd
NFP = outward forces - inward forcesNFP = outward forces - inward forces = (BHP + IFOP) - (BCOP + IFHP)= (BHP + IFOP) - (BCOP + IFHP) = (10 + 8) - (28 + 0)= (10 + 8) - (28 + 0) = (18) - (28)= (18) - (28) = -10 mm Hg= -10 mm Hg
If IFHP was (-3) then NFP = -7 mm HgIf IFHP was (-3) then NFP = -7 mm Hg
net flow of fluid is? into of the capillarynet flow of fluid is? into of the capillary (reabsorption)(reabsorption)
The Forces of Capillary Filtration The Forces of Capillary Filtration and Absorptionand Absorption
Capillary ExchangeCapillary Exchange
Hemodynamics
Blood flow (ml/min)Perfusion (ml/min/g)Blood flow velocity (mm/sec)Cross-sectional area (cm2)
total cross sectional area
velocity
art
erio
les
(40
cm
2)
vein
s (
80
cm
2)
ven
ae
ca
vae
(8
cm
2 )
If total cross-sectional area then velocity (aorta to capillaries)
venu
les
(250
cm
2 )
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
Flow α ∆Pressure Resistance
art
erie
s (2
0 c
m2 )
capillaries (2500 cm2)
12
00
mm
/se
c
15
mm
/se
c
0.4
mm
/se
c
5 m
m/s
ec
80
mm
/se
c (I
VC
)
Blood PressureBlood Pressure
1. What is blood pressure?1. What is blood pressure?
2. direct determinants of BP2. direct determinants of BP
a. cardiac output a. cardiac output
b. blood volume b. blood volume
c. peripheral resistancec. peripheral resistance
Volume of Blood FlowVolume of Blood Flow
CO = SV x HRCO = SV x HR = 5.25 L/min (the volume of blood circulating= 5.25 L/min (the volume of blood circulating through systemic or pulmonary through systemic or pulmonary vessels each minute)vessels each minute)
Two other factors influence cardiac output:Two other factors influence cardiac output: 1) blood pressure1) blood pressure 2) resistance (opposition)2) resistance (opposition)
CO = CO = mean arterial blood pressure (MABP)mean arterial blood pressure (MABP) resistance (R)resistance (R)
Resistance (Opposition to Flow)Resistance (Opposition to Flow)
1. blood viscosity1. blood viscosity
2. total blood vessel length2. total blood vessel length
3. blood vessel radius3. blood vessel radius
Systemic vascular resistance (SVR)Systemic vascular resistance (SVR)(total peripheral resistance (TPR)(total peripheral resistance (TPR) 1. major function of arterioles1. major function of arterioles2. vasodilation 2. vasodilation vsvs vasocontriction vasocontriction a. Blood flow is proportional to the fourth power of a. Blood flow is proportional to the fourth power of vessel radius.vessel radius. r = 1 mm r4 = 1r = 1 mm r4 = 144 = 1 flow = 1 mm/sec = 1 flow = 1 mm/sec r = 2 mm r4 = 2r = 2 mm r4 = 244 = 16 flow = 16 mm/sec = 16 flow = 16 mm/sec r = 3 mm r4 = 3r = 3 mm r4 = 344 = 81 flow = 81 mm/sec = 81 flow = 81 mm/sec
b. Therefore, a 3-fold change in resistance exerts b. Therefore, a 3-fold change in resistance exerts an an 81-fold change in velocity.81-fold change in velocity.
Mechanisms of Venous ReturnMechanisms of Venous Return
1. decreasing x-sec area1. decreasing x-sec area
2. venous valves2. venous valves
3. muscle pumps3. muscle pumps
4. respiratory pump4. respiratory pump
Control of Blood Pressure and Control of Blood Pressure and Blood FlowBlood Flow
The cardiovascular center (CVC) consists The cardiovascular center (CVC) consists of three groups of neurons:of three groups of neurons:
1. cardioacceleratory neurons1. cardioacceleratory neurons
2. cardioinhibitory neurons2. cardioinhibitory neurons
3. vasomotor neurons3. vasomotor neurons
CVC Input CVC Input
1. input1. input
a. higher brain centersa. higher brain centers
b. baroreceptorsb. baroreceptors
c. chemoreceptorsc. chemoreceptors
Nervous Input to Medullary Nervous Input to Medullary Cardiovascular CenterCardiovascular Center
higher brain cerebral cortex limbic system hypothalamus
medullaoblongata
baroreceptors(blood pressure)
chemoreceptors (O2, H+, CO2)
CVC Output CVC Output
2. output2. output
a. vagus (X) nervea. vagus (X) nerve
b. sympathetic neuronsb. sympathetic neurons
(1) heart(1) heart
(2) arterioles(2) arterioles
Nervous Output From Medullary Nervous Output From Medullary Cardiovascular CenterCardiovascular Center
heart(decrease rate)
heart (increase rateand contractility)
Medulla oblongata
blood vessels (vasoconstriction and vasodilation)
cardiac accelerator nerves (sympathetic)
vasomotor nerves (sympathetic)
vagus nerve (X)
Neural Control of the Heart Reflexes
carotid sinus and aortic sinus reflexesright atrial (Bainbridge) reflex
Reflexes activate the Vasomotor center – results in vasoconstriction/vasodilation of arteriolesBaroreflexes and chemoreflexes
Medullary ischemic reflexcarotid sinus baroreceptorssensory fibers in c.n. IX
aortic sinus baroreceptors
SA nodeAV node
parasympathetic fibers in c.n. X
sympathetic fibers in spinal nerves
cerebrum
hypothalamus
cardiovascular center in medulla
spinal cord
Baroreceptor ReflexBaroreceptor Reflex
Chemoreceptor ReflexChemoreceptor Reflex
Negative Feedback of Neural Control
CONTROLLED CONDITION
a stimulus or stress disrupts homeostasis by causing a decrease in blood pressure
RECEPTOR
RETURN TO HOMEOSTASIS
EFFECTORS
CONTROL CENTER
baroreceptors in carotid and aortic sinuses are stretched less, resulting in decreased
rate of nerve impulses to the cardiovascular center
1. increased sympathetic output via cardioacceleratory center2. decreased parasympathetic output from cardioinhibitory center
1. contractility = stroke volume2. heart rate therefore cardiac output
3. vasoconstriction = resistance
increased blood pressure
Hormonal RegulationHormonal Regulation1. epinephrine and norepinephrine1. epinephrine and norepinephrinepotent vasoconstrictor increased resistance increased BPincreased HR + increased SV = increased CO increased BP
2. antidiuretic hormone2. antidiuretic hormoneincreases water retention by kidneys increased blood volume increased BP
3. angiotensin II3. angiotensin IIpotent vasoconstrictor increased resistance increased BP
4. aldosterone4. aldosteronepromotes sodium retention by kidneysincreased water retention increased blood volume increased BP
5. atrial natriuretic peptide5. atrial natriuretic peptidedecreases sodium retention by kidneysdecreased water retention decreased blood volume decreased BP
AutoregulationAutoregulationAbility of tissues to regulate their own blood supplyMetabolic theory of autoregulation
Inadequate perfusion =A. Decreased O2 vasodilationB. 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 Controldecreased blood pressure
leads to
decreased activity of baroreceptors in carotid and aortic sinuses
leads to
decreased nervous input to cardioinhibitory center
leads to
increased activity of the:1.cardioacceleratory center2.vasomotor center
leads to
increased sympathetic output from spinal cord
norepinephrine secretion causes
increased blood pressure
increased stroke volumeincreased heart rate
leads to leads to
increased vasoconstriction
leads to
increased cardiac output
leads to
increased resistance
leads to
negative feedback
increased activity
increased activity
decreased activity
Blood Vessel Routes Blood Vessel Routes (see Handout)(see Handout)
Beginning of the AortaBeginning of the Aorta
Arterial Supply Head and NeckArterial Supply Head and Neck
Arterial Circle of the Brain- Circle Arterial Circle of the Brain- Circle of Willisof Willis
Arterial Supply to the Upper ArmArterial Supply to the Upper Arm
Arterial Supply to the ThoraxArterial Supply to the Thorax
Arterial Supply to the AbdomenArterial Supply to the Abdomen
Arterial Supply to the Pelvic Arterial Supply to the Pelvic Region and Lower LimbRegion and Lower Limb
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