169 Ch 21_lecture_presentation

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PowerPoint® Lecture Presentations prepared byJason LaPresLone Star College—North Harris

21Blood Vessels and Circulation


An Introduction to Blood Vessels and Circulation

• Learning Outcomes

• 21-1 Distinguish among the types of blood vessels based on their structure and function, and

describe how and where fluid and dissolved materials enter and leave the cardiovascular system.

• 21-2 Explain the mechanisms that regulate blood flow through vessels, describe the factors

that influence blood pressure, and discuss the mechanisms that regulate

movement of fluids between capillaries and interstitial spaces.




• 21-3 Describe the control mechanisms that regulate blood flow and pressure in tissues, and explain how the activities of the cardiac, vasomotor, and respiratory centers are coordinated to control blood flow through the tissues.

• 21-4 Explain the cardiovascular system’s homeostatic response to exercise and hemorrhaging, and identify the principal blood vessels and functional characteristics of the special circulation to the brain, heart, and lungs.




• 21-5 Describe the three general functional patterns seen in the pulmonary and systemic

circuits of the cardiovascular system.

• 21-6 Identify the major arteries and veins of the pulmonary circuit.

• 21-7 Identify the major arteries and veins of the systemic circuit.




• 21-8 Identify the differences between fetal and adult circulation patterns, and describe the

changes in the patterns of blood flow that occur at birth.

• 21-9 Discuss the effects of aging on the cardiovascular system, and give

examples of interactions between the cardiovascular system and other organ systems.



• Blood Vessels

• Are classified by size and histological organization

• Are instrumental in overall cardiovascular regulation


21-1 Classes of Blood Vessels

• Arteries

• Carry blood away from heart

• Arterioles

• Are smallest branches of arteries

• Capillaries

• Are smallest blood vessels

• Location of exchange between blood and interstitial fluid

• Venules

• Collect blood from capillaries

• Veins

• Return blood to heart


21-1 Blood Vessels

• The Largest Blood Vessels

• Attach to heart

• Pulmonary trunk

• Carries blood from right ventricle

• To pulmonary circulation

• Aorta

• Carries blood from left ventricle

• To systemic circulation


21-1 Blood Vessels

• The Smallest Blood Vessels

• Capillaries

• Have small diameter and thin walls

• Chemicals and gases diffuse across walls


21-1 Blood Vessels

• The Structure of Vessel Walls

• Walls have three layers

1. Tunica intima

2. Tunica media

3. Tunica externa


21-1 Blood Vessels

• The Tunica Intima (Inner Layer)

• Includes:

• The endothelial lining

• Connective tissue layer

• Internal elastic membrane

• In arteries, is a layer of elastic fibers in outer margin of

tunica intima


21-1 Blood Vessels

• The Tunica Media (Middle Layer)

• Contains concentric sheets of smooth muscle in loose

connective tissue

• Binds to inner and outer layers

• External elastic membrane of the tunica media

• Separates tunica media from tunica externa


21-1 Blood Vessels

• The Tunica Externa (Outer Layer)

• Anchors vessel to adjacent tissues in arteries

• Contains collagen fibers

• Elastic fibers

• In veins

• Contains elastic fibers

• Smooth muscle cells

• Vasa vasorum (“vessels of vessels”)

• Small arteries and veins

• In walls of large arteries and veins

• Supply cells of tunica media and tunica externa


Figure 21-1 Comparisons of a Typical Artery and a Typical Vein

Tunica externa

Tunica media

Tunica intima

Smooth muscle

Internal elasticmembrane

External elastic membrane

Endothelium

ARTERY

Elastic fiber

Lumenof vein

Lumenof artery

Artery and vein LM 60


Figure 21-1 Comparisons of a Typical Artery and a Typical Vein

Lumenof vein

Lumenof artery

Artery and vein LM 60

Tunica media

Tunica intima

Smoothmuscle

Endothelium

Tunica externa

VEIN


Table 21-1 Key Terms and Relationships Pertaining to Blood Circulation






21-1 Blood Vessels

• Differences between Arteries and Veins

• Arteries and veins run side by side

• Arteries have thicker walls and higher blood pressure

• Collapsed artery has small, round lumen (internal space)

• Vein has a large, flat lumen

• Vein lining contracts, artery lining does not

• Artery lining folds

• Arteries more elastic

• Veins have valves


21-1 Structure and Function of Arteries

• Arteries

• Elasticity allows arteries to absorb pressure waves that come with each heartbeat

• Contractility

• Arteries change diameter

• Controlled by sympathetic division of ANS

• Vasoconstriction

• The contraction of arterial smooth muscle by the ANS

• Vasodilation

• The relaxation of arterial smooth muscle

• Enlarging the lumen



• Vasoconstriction and Vasodilation

• Affect:

1. Afterload on heart

2. Peripheral blood pressure

3. Capillary blood flow



• Arteries

• From heart to capillaries, arteries change

• From elastic arteries

• To muscular arteries

• To arterioles



• Elastic Arteries

• Also called conducting arteries

• Large vessels (e.g., pulmonary trunk and aorta)

• Tunica media has many elastic fibers and few muscle

cells

• Elasticity evens out pulse force



• Muscular Arteries

• Also called distribution arteries

• Are medium sized (most arteries)

• Tunica media has many muscle cells



• Arterioles

• Are small

• Have little or no tunica externa

• Have thin or incomplete tunica media



• Artery Diameter

• Small muscular arteries and arterioles

• Change with sympathetic or endocrine stimulation

• Constricted arteries oppose blood flow

• Resistance (R)

• Resistance vessels - arterioles



• Aneurysm

• A bulge in an arterial wall

• Is caused by weak spot in elastic fibers

• Pressure may rupture vessel


Figure 21-2 Histological Structure of Blood Vessels

Large Vein

Medium-Sized Vein

Venule Arteriole

Muscular Artery

Elastic Artery

Fenestrated Capillary Capillaries Continuous Capillary

Pores

Endothelial cells

Basement membrane Basement membrane

Endothelial cells

Tunica externa

Endothelium

Tunica externa

Tunica media

Endothelium

Tunica intima

Tunica externa

Tunica media

Endothelium

Tunica intima

Internal elasticlayer

Endothelium

Tunicaintima

Tunica media

Tunica externa

Tunica externa

Tunica media

Endothelium

Tunica intima

Smooth muscle cells(Media)

Endothelium

Basement membrane



Large Vein

Medium-Sized Vein

Venule

Tunica externa

Endothelium

Tunica externa

Tunica media

Endothelium

Tunica intima

Tunica externa

Tunica media

Endothelium

Tunica intima



Arteriole

Muscular Artery

Elastic Artery

Internal elasticlayerEndothelium

Tunicaintima

Tunica media

Tunica externa

Tunica externa

Tunica media

Endothelium

Tunica intima

Smooth muscle cells(Media)

Endothelium

Basement membrane



Fenestrated Capillary Capillaries Continuous Capillary

Pores

Endothelial cells

Basement membrane Basement membrane

Endothelial cells


Figure 21-3a A Plaque within an Artery

Tunica externa

Lipid deposits(plaque)

Tunica media

Coronary artery

A cross-sectional viewof a large plaque

LM 6


Figure 21-3b A Plaque within an Artery

Plaque depositin vessel wall

A section of a coronaryartery narrowed by plaqueformation


21-1 Structure and Function of Capillaries

• Capillaries

• Are smallest vessels with thin walls

• Microscopic capillary networks permeate all active

tissues

• Capillary function

• Location of all exchange functions of cardiovascular

system

• Materials diffuse between blood and interstitial fluid



• Capillary Structure

• Endothelial tube, inside thin basement membrane

• No tunica media

• No tunica externa

• Diameter is similar to red blood cell



• Continuous Capillaries

• Have complete endothelial lining

• Are found in all tissues except epithelia and cartilage

• Functions of continuous capillaries

• Permit diffusion of water, small solutes, and lipid-

soluble materials

• Block blood cells and plasma proteins



• Specialized Continuous Capillaries

• Are in CNS and thymus

• Have very restricted permeability

• For example, the blood–brain barrier



• Fenestrated Capillaries

• Have pores in endothelial lining

• Permit rapid exchange of water and larger solutes

between plasma and interstitial fluid

• Are found in:

• Choroid plexus

• Endocrine organs

• Kidneys

• Intestinal tract



• Sinusoids (Sinusoidal Capillaries)

• Have gaps between adjacent endothelial cells

• Liver

• Spleen

• Bone marrow

• Endocrine organs

• Permit free exchange

• Of water and large plasma proteins

• Between blood and interstitial fluid

• Phagocytic cells monitor blood at sinusoids


Figure 21-4 Capillary Structure

Basementmembrane

Nucleus

Endothelial cell

Endosomes

Boundarybetween

endothelialcells

Fenestrations,or pores

Boundarybetween

endothelialcells

Basementmembrane

Endosomes

Basementmembrane

Gap betweenadjacent cells

SinusoidFenestrated capillaryContinuous capillary


Figure 21-4a Capillary Structure

Basementmembrane

Nucleus

Endothelial cell

Boundarybetween

endothelialcells

Endosomes

Basementmembrane

Continuous capillary


Figure 21-4b Capillary Structure

Basementmembrane

Nucleus

Endothelial cell

Endosomes

Boundarybetween

endothelialcells

Fenestrations,or pores

Basementmembrane

Fenestrated capillary


Figure 21-4c Capillary Structure

Gap betweenadjacent cells

Sinusoid



• Capillary Beds (Capillary Plexus)

• Connect one arteriole and one venule

• Precapillary Sphincter

• Guards entrance to each capillary

• Opens and closes, causing capillary blood to flow in

pulses


Figure 21-5a The Organization of a Capillary Bed

Smoothmuscle cells

Collateralarteries

Arteriole

Metarterioles

Thoroughfarechannel

Vein

Venule

Capillaries

Section ofprecapillary

sphincter

Precapillarysphincters

Arteriovenousanastomosis

A typical capillary bed. Solid arrows indicateconsistant blood flow; dashed arrows indicatevariable or pulsating blood flow.

Smallvenule

KEYConsistentblood flowVariableblood flow


Figure 21-5b The Organization of a Capillary Bed

Capillary bed LM 125

A micrograph of a number of capillary beds.

Capillary beds

Metarterioles

Arteriole

Smallartery



• Thoroughfare Channels

• Direct capillary connections between arterioles and

venules

• Controlled by smooth muscle segments

(metarterioles)



• Collaterals

• Multiple arteries that contribute to one capillary bed

• Allow circulation if one artery is blocked

• Arterial anastomosis

• Fusion of two collateral arteries

• Arteriovenous anastomoses

• Direct connections between arterioles and venules

• Bypass the capillary bed



• Angiogenesis

• Formation of new blood vessels

• Vascular endothelial growth factor (VEGF)

• Occurs in the embryo as tissues and organs develop

• Occurs in response to factors released by cells that are

hypoxic, or oxygen-starved

• Most important in cardiac muscle, where it takes place in

response to a chronically constricted or occluded vessel



• Vasomotion

• Contraction and relaxation cycle of capillary

sphincters

• Causes blood flow in capillary beds to constantly

change routes


21-1 Structure and Function of Veins

• Veins

• Collect blood from capillaries in tissues and organs

• Return blood to heart

• Are larger in diameter than arteries

• Have thinner walls than arteries

• Have lower blood pressure



• Venules

• Very small veins

• Collect blood from capillaries

• Medium-sized veins

• Thin tunica media and few smooth muscle cells

• Tunica externa with longitudinal bundles of elastic

fibers



• Large Veins

• Have all three tunica layers

• Thick tunica externa

• Thin tunica media

• Venous Valves

• Folds of tunica intima

• Prevent blood from flowing backward

• Compression pushes blood toward heart


Figure 21-6 The Function of Valves in the Venous System

Valve closed

Valve closed

Valve opens abovecontracting muscle

Valve closes belowcontracting muscle


21-1 Blood Vessels

• The Distribution of Blood

• Heart, arteries, and capillaries

• 30–35% of blood volume

• Venous system

• 60–65%

• 1/3 of venous blood is in the large venous networks

of the liver, bone marrow, and skin


Figure 21-7 The Distribution of Blood in the Cardiovascular System

Pulm

onar

y ar

terie

s 3%

Large venousnetworks (liver,

bone marrow, skin)21%

Venules andmedium-sized veins

25%

Pulmonary

circuit 9%H

eart 7%

Syste

mic

Pulmonary

capillarie

s 2%

Pulmonary veins 4%

Heart 7%

Aorta 2%Elastic arteries 4%S

ystemic capillaries 7%

Muscular arteries 5%

Arterioles 2%

Large veins18%

Systemic

capillaries 7%

arte

rial

syst

em13

%

Sys

tem

icve

no

us

syst

em64

%


21-1 Blood Vessels

• Capacitance of a Blood Vessel

• The ability to stretch

• Relationship between blood volume and blood

pressure

• Veins (capacitance vessels) stretch more than

arteries


21-1 Blood Vessels

• Venous Response to Blood Loss

• Vasomotor centers stimulate sympathetic nerves

1. Systemic veins constrict (venoconstriction)

2. Veins in liver, skin, and lungs redistribute venous

reserve


21-2 Pressure and Resistance

• Total Capillary Blood Flow

• Equals cardiac output

• Is determined by:

• Pressure (P) and resistance (R) in the

cardiovascular system


Figure 21-8 An Overview of Cardiovascular Physiology

Cardiac Output

Venous Return

Regulation(Neural and Hormonal)

VenousPressure

Arterial BloodPressure

PeripheralResistance

Capillary Pressure

Capillary exchange

Interstitial fluid



• Pressure (P)

• The heart generates P to overcome resistance

• Absolute pressure is less important than pressure

gradient

• The Pressure Gradient (P)

• Circulatory pressure

• The difference between:

• Pressure at the heart

• And pressure at peripheral capillary beds



• Flow (F)

• Is proportional to the pressure difference (P)

• Divided by R



• Measuring Pressure

1. Blood pressure (BP)

• Arterial pressure (mm Hg)

2. Capillary hydrostatic pressure (CHP)

• Pressure within the capillary beds

3. Venous pressure

• Pressure in the venous system



• Circulatory Pressure

• ∆P across the systemic circuit (about 100 mm Hg)

• Circulatory pressure must overcome total peripheral

resistance

• R of entire cardiovascular system



• Total Peripheral Resistance

• Vascular resistance

• Blood viscosity

• Turbulence



• Vascular Resistance

• Due to friction between blood and vessel walls

• Depends on vessel length and vessel diameter

• Adult vessel length is constant

• Vessel diameter varies by vasodilation and

vasoconstriction

• R increases exponentially as vessel diameter

decreases



• Viscosity

• R caused by molecules and suspended materials

in a liquid

• Whole blood viscosity is about four times that of

water



• Turbulence

• Swirling action that disturbs smooth flow of liquid

• Occurs in heart chambers and great vessels

• Atherosclerotic plaques cause abnormal turbulence


Figure 21-9 Factors Affecting Friction and Vascular ResistanceFriction and Vessel Length

Friction and Vessel Diameter

Vessel Length versus Vessel Diameter

Factors Affecting Vascular Resistance

Internal surfacearea 1

Internal surface area 2

Resistance to flow 1Flow 1

Resistance to flow 2

Flow 21/

Greatest resistance,slowest flow near surfaces

Leastresistance,greatest flowat center

Diameter 2 cm

Diameter 1 cm



Plaque deposit Turbulence

Turbulence









• An Overview of Cardiovascular Pressures

• Vessel diameters

• Total cross-sectional areas

• Pressures

• Velocity of blood flow


Figure 21-10a Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit

Vesseldiameter

(cm)

Vessel diameter


Figure 21-10b Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit

Total cross-sectional area of vessels

Cross-sectional

area(cm2)


Figure 21-10c Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit

Average blood pressure

Averageblood

pressure(mm Hg)


Figure 21-10d Relationships among Vessel Diameter, Cross-Sectional Area, Blood Pressure, and Blood Velocity within the Systemic Circuit

Velocity of blood flow

Velocityof blood

flow(cm/sec)



• Arterial Blood Pressure

• Systolic pressure

• Peak arterial pressure during ventricular systole

• Diastolic pressure

• Minimum arterial pressure during diastole



• Arterial Blood Pressure

• Pulse pressure

• Difference between systolic pressure and diastolic

pressure

• Mean arterial pressure (MAP)

• MAP = diastolic pressure + 1/3 pulse pressure



• Abnormal Blood Pressure

• Normal = 120/80

• Hypertension

• Abnormally high blood pressure

• Greater than 140/90

• Hypotension

• Abnormally low blood pressure



• Elastic Rebound

• Arterial walls

• Stretch during systole

• Rebound (recoil to original shape) during diastole

• Keep blood moving during diastole



• Pressures in Small Arteries and Arterioles

• Pressure and distance

• MAP and pulse pressure decrease with distance from

heart

• Blood pressure decreases with friction

• Pulse pressure decreases due to elastic rebound


Figure 21-11 Pressures within the Systemic Circuit

Systolic

Pulsepressure

Diastolic

mm Hg

Mean arterialpressure



• Venous Pressure and Venous Return

• Determines the amount of blood arriving at right atrium

each minute

• Low effective pressure in venous system



• Venous Pressure and Venous Return

• Low venous resistance is assisted by:

• Muscular compression of peripheral veins

• Compression of skeletal muscles pushes blood

toward heart (one-way valves)

• The respiratory pump

• Thoracic cavity action

• Inhaling decreases thoracic pressure

• Exhaling raises thoracic pressure



• Capillary Pressures and Capillary Exchange

• Vital to homeostasis

• Moves materials across capillary walls by:

• Diffusion

• Filtration

• Reabsorption



• Diffusion

• Movement of ions or molecules

• From high concentration

• To lower concentration

• Along the concentration gradient



• Diffusion Routes

1. Water, ions, and small molecules such as glucose

• Diffuse between adjacent endothelial cells

• Or through fenestrated capillaries

2. Some ions (Na, K, Ca2, Cl)

• Diffuse through channels in plasma membranes



• Diffusion Routes

3. Large, water-soluble compounds

• Pass through fenestrated capillaries

4. Lipids and lipid-soluble materials such as O2 and

CO2

• Diffuse through endothelial plasma membranes

5. Plasma proteins

• Cross endothelial lining in sinusoids



• Filtration

• Driven by hydrostatic pressure

• Water and small solutes forced through capillary wall

• Leaves larger solutes in bloodstream



• Reabsorption

• The result of osmotic pressure (OP)

• Blood colloid osmotic pressure (BCOP)

• Equals pressure required to prevent osmosis

• Caused by suspended blood proteins that are too large

to cross capillary walls


Figure 21-12 Capillary Filtration

Capillaryhydrostatic

pressure(CHP) Amino acid

Blood protein

Glucose

Ions

Interstitialfluid

Hydrogenbond

Watermolecule

Small solutes

Endothelialcell 2

Endothelialcell 1



• Interplay between Filtration and Reabsorption

1. Ensures that plasma and interstitial fluid are in

constant communication and mutual exchange

2. Accelerates distribution of:

• Nutrients, hormones, and dissolved gases

throughout tissues




3. Assists in the transport of:

• Insoluble lipids and tissue proteins that cannot

enter bloodstream by crossing capillary walls

4. Has a flushing action that carries bacterial toxins and

other chemical stimuli to:

• Lymphatic tissues and organs responsible for

providing immunity to disease




• Net hydrostatic pressure

• Forces water out of solution

• Net osmotic pressure

• Forces water into solution

• Both control filtration and reabsorption through

capillaries



• Factors that Contribute to Net Hydrostatic

Pressure

1. Capillary hydrostatic pressure (CHP)

2. Interstitial fluid hydrostatic pressure (IHP)

• Net capillary hydrostatic pressure tends to push water

and solutes:

• Out of capillaries

• Into interstitial fluid



• Net Capillary Colloid Osmotic Pressure

• Is the difference between:

1. Blood colloid osmotic pressure (BCOP)

2. Interstitial fluid colloid osmotic pressure (ICOP)

• Pulls water and solutes:

• Into a capillary

• From interstitial fluid



• Net Filtration Pressure (NFP)

• The difference between:

• Net hydrostatic pressure

• Net osmotic pressure

NFP = (CHP – IHP) – (BCOP – ICOP)



• Capillary Exchange

• At arterial end of capillary:

• Fluid moves out of capillary

• Into interstitial fluid

• At venous end of capillary:

• Fluid moves into capillary

• Out of interstitial fluid



• Capillary Exchange

• Transition point between filtration and reabsorption

• Is closer to venous end than arterial end

• Capillaries filter more than they reabsorb

• Excess fluid enters lymphatic vessels


Figure 21-13 Forces Acting across Capillary Walls

KEY

Arteriole

Filtration

CHP (Capillaryhydrostatic pressure)

Venule

BCOP (Blood colloidosmotic pressure)

NFP (Net filtrationpressure)

24 L/day 20.4 L/dayNo net fluidmovement

Reabsorption

35mmHg

25mmHg

25mmHg

25mmHg

25mmHg

18mmHg

NFP 10 mm Hg NFP 0 NFP 7 mm Hg

CHP BCOPFluid forced

out of capillary

CHP BCOPNo net

movementof fluid

BCOP CHPFluid movesinto capillary



• Capillary Dynamics

• Hemorrhaging

• Reduces CHP and NFP

• Increases reabsorption of interstitial fluid (recall of fluids)

• Dehydration

• Increases BCOP

• Accelerates reabsorption

• Increase in CHP or BCOP

• Fluid moves out of blood

• Builds up in peripheral tissues (edema)


21-3 Cardiovascular Regulation

• Tissue Perfusion

• Blood flow through the tissues

• Carries O2 and nutrients to tissues and organs

• Carries CO2 and wastes away

• Is affected by:

1. Cardiac output

2. Peripheral resistance

3. Blood pressure



• Cardiovascular Regulation Changes Blood

Flow to a Specific Area

1. At an appropriate time

2. In the right area

3. Without changing blood pressure and blood flow

to vital organs



• Controlling Cardiac Output and Blood Pressure

• Autoregulation

• Causes immediate, localized homeostatic adjustments

• Neural mechanisms

• Respond quickly to changes at specific sites

• Endocrine mechanisms

• Direct long-term changes


Figure 21-14 Short-Term and Long-Term Cardiovascular Responses

Autoregulation

Local vasodilatorsreleased

HOMEOSTASISRESTORED

HOMEOSTASIS DISTURBED

HOMEOSTASIS

Local decreasein resistanceand increase inblood flow

Inadequatelocal bloodpressure andblood flow

Normalblood pressure

and volume

• Physical stress (trauma, high temperature)• Chemical changes (decreased O2 or pH, increased CO2 or prostaglandins)• Increased tissue activity

Autoregulation is dueto opening and closing precapillary sphinctersdue to local release ofvasodilator or vasoconstrictorchemicals from the tissue.

Start


Figure 21-14 Short-Term and Long-Term Cardiovascular Responses

Central Regulation

Stimulation ofreceptors sensitiveto changes insystemic bloodpressure orchemistry

Endocrine mechanisms

HOMEOSTASISRESTORED

Neuralmechanisms

Activation ofcardiovascularcenters

Stimulationof endocrineresponse

Long-term increasein blood volumeand blood pressure

Short-term elevation of blood pressure bysympatheticstimulation of theheart and peripheralvasoconstriction

Central regulation involves neuroendocrine mechanisms that control the total systemic circulation. This regulation involves both the cardiovascular centers and the vasomotor centers.

If autoregulation is ineffective



• Autoregulation of Blood Flow within Tissues

• Adjusted by peripheral resistance while cardiac output stays the same

• Local vasodilators accelerate blood flow at tissue level

• Low O2 or high CO2 levels

• Low pH (acids)

• Nitric oxide (NO)

• High K+ or H+ concentrations

• Chemicals released by inflammation (histamine)

• Elevated local temperature



• Autoregulation of Blood Flow within Tissues

• Adjusted by peripheral resistance while cardiac output

stays the same

• Local vasoconstrictors

• Examples: prostaglandins and thromboxanes

• Released by damaged tissues

• Constrict precapillary sphincters

• Affect a single capillary bed



• Neural Mechanisms

• Cardiovascular (CV) centers of the medulla oblongata

• Cardiac centers

• Cardioacceleratory center increases cardiac

output

• Cardioinhibitory center reduces cardiac output



• Vasomotor Center

1. Control of vasoconstriction • Controlled by adrenergic nerves (NE)

• Stimulates smooth muscle contraction in arteriole walls

2. Control of vasodilation• Controlled by cholinergic nerves (NO)

• Relaxes smooth muscle

• Vasomotor Tone

• Produced by constant action of sympathetic

vasoconstrictor nerves



• Reflex Control of Cardiovascular Function

• Cardiovascular centers monitor arterial blood

• Baroreceptor reflexes

• Respond to changes in blood pressure

• Chemoreceptor reflexes

• Respond to changes in chemical composition,

particularly pH and dissolved gases



• Baroreceptor Reflexes

• Stretch receptors in walls of:

1. Carotid sinuses (maintain blood flow to brain)

2. Aortic sinuses (monitor start of systemic circuit)

3. Right atrium (monitors end of systemic circuit)



• Baroreceptor Reflexes

• When blood pressure rises, CV centers:

1. Decrease cardiac output

2. Cause peripheral vasodilation

• When blood pressure falls, CV centers:

1. Increase cardiac output

2. Cause peripheral vasoconstriction


Figure 21-15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses

Responses to IncreasedBaroreceptor Stimulation

Baroreceptorsstimulated

HOMEOSTASISDISTURBED

Rising bloodpressure

Cardioinhibitorycenters stimulated

Cardioacceleratorycenters inhibited

Vasomotor centersinhibited

Decreasedcardiacoutput

Vasodilationoccurs

HOMEOSTASISRESTORED

Blood pressuredeclines

HOMEOSTASIS

Normal rangeof bloodpressure

Start


Figure 21-15 Baroreceptor Reflexes of the Carotid and Aortic Sinuses

HOMEOSTASIS

Normal rangeof bloodpressure


HOMEOSTASISRESTORED

Falling bloodpressure

Blood pressurerises

Baroreceptorsinhibited

Vasoconstrictionoccurs

Increasedcardiacoutput

Vasomotor centersstimulated

Cardioacceleratorycenters stimulated

Cardioinhibitorycenters inhibited

Responses to DecreasedBaroreceptor Stimulation

Start



• Chemoreceptor Reflexes

• Peripheral chemoreceptors in carotid bodies and

aortic bodies monitor blood

• Central chemoreceptors below medulla oblongata:

• Monitor cerebrospinal fluid

• Control respiratory function

• Control blood flow to brain



• Chemoreceptor Reflexes

• Changes in pH, O2, and CO2 concentrations

• Produced by coordinating cardiovascular and

respiratory activities


Figure 21-16 The Chemoreceptor Reflexes

Increasing CO2 levels,

decreasing pHand O2 levels

Respiratory centers inthe medulla oblongatastimulated

Respiratory rateincreases

Increased cardiacoutput and bloodpressure

Cardioacceleratorycenters stimulated

Cardioinhibitorycenters inhibited

Respiratory Response

CardiovascularResponses

Effects onCardiovascular Centers

Vasomotor centersstimulated

Vasoconstrictionoccurs

Normal pH, O2,

and CO2 levels in

blood and CSF

HOMEOSTASIS

Elevated CO2 levels,

decreased pH and O2

levels in blood and CSF


Start

Decreased CO2 levels,

increased pH and O2

levels in blood and CSF

HOMEOSTASISRESTORED

Reflex Response

Chemoreceptorsstimulated



• CNS Activities and the Cardiovascular

Centers

• Thought processes and emotional states can

elevate blood pressure by:

• Cardiac stimulation and vasoconstriction



• Hormones and Cardiovascular Regulation

• Hormones have short-term and long-term effects

on cardiovascular regulation

• For example, E and NE from adrenal medullae

stimulate cardiac output and peripheral

vasoconstriction



• Antidiuretic Hormone (ADH)

• Released by neurohypophysis (posterior lobe of pituitary)

• Elevates blood pressure

• Reduces water loss at kidneys

• ADH responds to:

• Low blood volume

• High plasma osmotic concentration

• Circulating angiotensin II



• Angiotensin II

• Responds to fall in renal blood pressure

• Stimulates:

1. Aldosterone production

2. ADH production

3. Thirst

4. Cardiac output and peripheral vasoconstriction



• Erythropoietin (EPO)

• Released at kidneys

• Responds to low blood pressure, low O2 content in

blood

• Stimulates red blood cell production


Figure 21-17a The Hormonal Regulation of Blood Pressure and Blood Volume

HOMEOSTASIS

Factors that compensate fordecreased blood pressure andvolume

Increased red bloodcell formation

Thirst stimulated

Antidiuretic hormonereleased

Angiotensin II Effects

Combined Short-Termand Long-Term Effects

Endocrine Responseof Kidneys

Renin release leadsto angiotensin IIactivation

Erythropoietin (EPO)is released

Increased cardiacoutput andperipheralvasoconstriction

Sympathetic activationand release of adrenalhormones E and NE

Long-term

Short-term

Increasedbloodpressure

Increasedbloodvolume

Decreasing bloodpressure and

volume

StartBlood pressureand volume fall

HOMEOSTASISDISTURBED HOMEOSTASIS

RESTORED

Normal bloodpressure and

volume

Blood pressureand volume rise

Aldosterone secreted

Angiotensin II



• Natriuretic Peptides

• Atrial natriuretic peptide (ANP)

• Produced by cells in right atrium

• Brain natriuretic peptide (BNP)

• Produced by ventricular muscle cells

• Respond to excessive diastolic stretching

• Lower blood volume and blood pressure

• Reduce stress on heart


Figure 21-17b The Hormonal Regulation of Blood Pressure and Blood Volume

HOMEOSTASIS

Factors that compensate forincreased blood pressure andvolume

Increasing bloodpressure and

volume

HOMEOSTASISRESTORED

Declining bloodpressure and

volume

Normalblood pressure

and volume


Rising bloodpressure and

volume

Natriureticpeptides releasedby the heart

Increased water loss inurine

Reduced thirst

Inhibition of ADH,aldosterone, epinephrine,and norepinephrinerelease

Peripheral vasodilation

Reduced bloodvolume

CombinedEffects

Increased Na loss inurine

Responses to ANPand BNP


21-4 Cardiovascular Adaptation

• Blood, Heart, and Cardiovascular System

• Work together as unit

• Respond to physical and physiological changes (for

example, exercise and blood loss)

• Maintain homeostasis



• The Cardiovascular Response to Exercise

• Light Exercise

• Extensive vasodilation occurs increasing

circulation

• Venous return increases with muscle contractions

• Cardiac output rises

1. Venous return (Frank–Starling principle)

2. Atrial stretching



• The Cardiovascular Response to Exercise

• Heavy Exercise

• Activates sympathetic nervous system

• Cardiac output increases to maximum

• About four times resting level

• Restricts blood flow to “nonessential” organs (e.g., digestive system)

• Redirects blood flow to skeletal muscles, lungs, and heart

• Blood supply to brain is unaffected


Table 21-2 Changes in Blood Distribution during Exercise



• Exercise, Cardiovascular Fitness, and Health

• Regular moderate exercise

• Lowers total blood cholesterol levels

• Intense exercise

• Can cause severe physiological stress



Table 21-3 Effects of Training on Cardiovascular Performance

Subject Heart Weight (g)

Stroke Volume (mL)

Heart Rate (BPM)

Cardiac Output (L/min)

Blood Pressure (systolic/ diastolic)

Nonathlete (rest) 300 60 83 5.0 120/80

Nonathlete (maximum)

104 192 19.9 187/75

Trained athlete (rest)

500 100 53 5.3 120/80

Trained athlete (maximum)

167 182 30.4 200/90*

*Diastolic pressures of athletes during maximum activity have not been accurately measured.



• The Cardiovascular Response to Hemorrhaging

• Entire cardiovascular system adjusts to:

• Maintain blood pressure

• Restore blood volume



• Short-Term Elevation of Blood Pressure

• Carotid and aortic reflexes

• Increase cardiac output (increasing heart rate)

• Cause peripheral vasoconstriction

• Sympathetic nervous system

• Triggers hypothalamus

• Further constricts arterioles

• Venoconstriction improves venous return



• Short-Term Elevation of Blood Pressure

• Hormonal effects

• Increase cardiac output

• Increase peripheral vasoconstriction (E, NE, ADH,

angiotensin II)



• Shock

• Short-term responses compensate after blood losses

of up to 20% of total blood volume

• Failure to restore blood pressure results in shock



• Long-Term Restoration of Blood Volume

• Recall of fluids from interstitial spaces

• Aldosterone and ADH promote fluid retention and

reabsorption

• Thirst increases

• Erythropoietin stimulates red blood cell production


Figure 21-18 Cardiovascular Responses to Hemorrhaging and Blood Loss

Normal bloodpressure and

volume

Extensive bleedingreduces bloodpressure andvolume


Responsescoordinated by theendocrine system

Responsesdirected by thenervous system

Falling bloodpressure and

volume

Long-Term Hormonal Response

ADH, angiotensin II, aldosterone,and EPO released

Blood pressureand volume rise

HOMEOSTASISRESTORED

Cardiovascular Responses

Peripheralvasoconstriction;mobilization ofvenous reserve

Increasedcardiacoutput

Elevationof bloodvolume

Stimulation ofbaroreceptors andchemoreceptorsPain, stress,

anxiety, fear

Higher Centers

Stimulation ofcardiovascularcenters

Generalsympatheticactivation

HOMEOSTASIS



• Vascular Supply to Special Regions

• Through organs with separate mechanisms to control

blood flow

• Three important examples

1. Brain

2. Heart

3. Lungs



• Blood Flow to the Brain

• Is top priority

• Brain has high oxygen demand

• When peripheral vessels constrict, cerebral vessels

dilate, normalizing blood flow



• Stroke

• Also called cerebrovascular accident (CVA)

• Blockage or rupture in a cerebral artery

• Stops blood flow



• Blood Flow to the Heart

• Through coronary arteries

• Oxygen demand increases with activity

• Lactic acid and low O2 levels

• Dilate coronary vessels

• Increase coronary blood flow



• Blood Flow to the Heart

• Epinephrine

• Dilates coronary vessels

• Increases heart rate

• Strengthens contractions



• Heart Attack

• A blockage of coronary blood flow

• Can cause:

• Angina (chest pain)

• Tissue damage

• Heart failure

• Death



• Blood Flow to the Lungs

• Regulated by O2 levels in alveoli

• High O2 content

• Vessels dilate

• Low O2 content

• Vessels constrict


21-5 Pulmonary and Systemic Patterns

• Three General Functional Patterns

1. Peripheral artery and vein distribution is the same on

right and left, except near the heart

2. The same vessel may have different names in

different locations

3. Tissues and organs usually have multiple arteries

and veins

• Vessels may be interconnected with anastomoses


Figure 21-19 A Schematic Overview of the Pattern of Circulation

Brain

Upper limbs

Lungs

Pulmonarycircuit(veins)

LA

Leftventricle

Systemiccircuit

(arteries)

Kidneys

Spleen

Digestive organs

Gonads

Lower limbs

Liver


Figure 21-19 A Schematic Overview of the Pattern of Circulation

Brain

Upper limbs

Lungs

Pulmonarycircuit

(arteries)

RA

Rightventricle

Systemiccircuit(veins)

Kidneys

Liver Digestive

organs

Gonads

Lower limbs


21-6 The Pulmonary Circuit

• Deoxygenated Blood Arrives at Heart from Systemic Circuit

• Passes through right atrium and right ventricle

• Enters pulmonary trunk

• At the lungs

• CO2 is removed

• O2 is added

• Oxygenated blood

• Returns to the heart

• Is distributed to systemic circuit



• Pulmonary Vessels

• Pulmonary arteries

• Carry deoxygenated blood

• Pulmonary trunk

• Branches to left and right pulmonary arteries

• Pulmonary arteries

• Branch into pulmonary arterioles

• Pulmonary arterioles

• Branch into capillary networks that surround alveoli



• Pulmonary Vessels

• Pulmonary veins

• Carry oxygenated blood

• Capillary networks around alveoli

• Join to form venules

• Venules

• Join to form four pulmonary veins

• Pulmonary veins

• Empty into left atrium


Figure 21-20 The Pulmonary Circuit

Ascending aorta

Superior vena cava

Right lung

Right pulmonaryarteries

Right pulmonaryveins

Inferior vena cava

Descending aorta


Figure 21-20 The Pulmonary Circuit

Aortic arch

Pulmonary trunk

Left lung

Left pulmonaryarteriesLeft pulmonaryveins

Alveolus

Capillary

CO2

O2


21-7 The Systemic Circuit

• The Systemic Circuit

• Contains 84% of blood volume

• Supplies entire body

• Except for pulmonary circuit



• Systemic Arteries

• Blood moves from left ventricle

• Into ascending aorta

• Coronary arteries

• Branch from aortic sinus


Figure 21-21 An Overview of the Major Systemic Arteries

Vertebral

Right subclavian

Brachiocephalictrunk

Ascendingaorta

Aortic arch

Celiac trunkBrachial

Right common carotid

Left common carotid

Left subclavian

Axillary

Pulmonary trunkDescending aorta

Diaphragm

Renal

Superior mesenteric

Gonadal

Inferior mesenteric

Common iliac

Internal iliac

Radial

UlnarExternal

iliac

Femoral

Palmararches Deep

femoral


Figure 21-21 An Overview of the Major Systemic Arteries

Femoral

Popliteal

Posterior tibial

Anterior tibial

Fibular

Plantar arch

Descendinggenicular

Dorsalis pedis



• The Aorta

• The ascending aorta

• Rises from the left ventricle

• Curves to form aortic arch

• Turns downward to become descending aorta


Figure 21-22a Arteries of the Chest and Upper Limb

SuprascapularThyrocervical trunk

Right subclavian

Axillary

Lateral thoracicAnterior humeral

circumflex

Posterior humeralcircumflex

Subscapular

Deep brachial

Intercostal arteries

Brachial

Ulnar recurrent arteries

Right common carotidLeft common carotidVertebral

Brachiocephalic trunk

Left subclavian

Aortic arch

Ascending aorta

Thoracic aorta

Heart

Internal thoracic

Abdominal aortaUlnar collateral arteries

Thoracoacromial

Arteries of the chest and upperlimb, a diagrammatic view


Figure 21-22b Arteries of the Chest and Upper Limb

Right vertebral Rightcommoncarotid

Leftcommoncarotid

Leftvertebral

Leftthyrocervical

trunkLeftsubclavian


Right thyrocervicaltrunk

Rightsubclavian

Right axillary

Right internalthoracic

Leftinternalthoracic Left

axillary

AORTICARCH

ASCENDINGAORTA

THORACICAORTA

(see Fig. 2125)

Leftbrachial

Leftulnar

Leftradial

ABDOMINALAORTA

(see Fig. 2126)

LEFTVENTRICLE

Right brachial

Right radial Right ulnar

Connected by anastomosesof palmar arches that supply

digital arteries

To structures of thearm

Forearm,radial side

Forearm,ulnar side

Muscles of the rightpectoral region andaxilla

Skin and muscles ofchest and abdomen,mammary gland (rightside), pericardium

Spinal cord, cervical vertebrae(right side); fuses with left vertebral,forming basilar artery after enteringcranium via foramen magnum

Muscles, skin, tissues of neck, thyroid gland, shoulders, and upper back (right side)

A flowchart of the arteries of the chest and upper limb



• Branches of the Aortic Arch

• Deliver blood to head, neck, shoulders, and upper

limbs

1. Brachiocephalic trunk

2. Left common carotid artery

3. Left subclavian artery



• The Subclavian Arteries

• Leaving the thoracic cavity:

• Become axillary artery in arm

• And brachial artery distally



SuprascapularThyrocervical trunk

Right subclavian

Axillary

Lateral thoracicAnterior humeral

circumflex

Posterior humeralcircumflex

Subscapular

Deep brachial


Brachial

Ulnar recurrent arteries

Right common carotidLeft common carotidVertebral

Brachiocephalic trunk

Left subclavian

Aortic arch

Ascending aorta

Thoracic aorta

Heart

Internal thoracic

Abdominal aortaUlnar collateral arteries

Thoracoacromial




• The Brachial Artery

• Divides at coronoid fossa of humerus

• Into radial artery and ulnar artery

• Fuse at wrist to form:

• Superficial and deep palmar arches

• Which supply digital arteries




Radial

Anterior cruralinterosseous

Ulnar

Deep palmararchSuperficialpalmar arch

Digital arteries



• The Common Carotid Arteries

• Each common carotid divides into:

• External carotid artery - supplies blood to structures of the

neck, lower jaw, and face

• Internal carotid artery - enters skull and delivers blood to brain

• Divides into three branches

1. Ophthalmic artery

2. Anterior cerebral artery

3. Middle cerebral artery


Figure 21-23 Arteries of the Neck and Head

Second rib

Internal thoracicAxillary

Subclavian

SuprascapularTransverse cervical

Thyrocervicaltrunk

Carotid sinusVertebral

Internal carotid

Inferior thyroid

Basilar

Posterior cerebral

Carotid canal

Cerebral arterial circle

OphthalmicMiddle cerebral

Anterior cerebral

ClavicleFirst rib


Figure 21-23 Arteries of the Neck and Head

Branches of theExternal CarotidSuperficialtemporal

Maxillary

Occipital

Facial

LingualExternalcarotid

Common carotid


ClavicleFirst rib



• The Vertebral Arteries

• Also supply brain with blood

• Left and right vertebral arteries

• Arise from subclavian arteries

• Enter cranium through foramen magnum

• Fuse to form basilar artery

• Branches to form posterior cerebral arteries

• Posterior cerebral arteries

• Become posterior communicating arteries



• Anastomoses

• The cerebral arterial circle (or circle of Willis)

interconnects:

• The internal carotid arteries

• And the basilar artery


Figure 21-24a Arteries of the Brain

Anteriorcerebral

Ophthalmic

Internalcarotid (cut)

Middlecerebral

Pituitarygland

Posteriorcerebral

Cerebellar

Anterior communicating

Cerebral Arterial Circle

Anterior cerebral

PosteriorcommunicatingPosterior cerebral

Basilar

Vertebral

Inferior surface


Figure 21-24b Arteries of the Brain

Middlecerebral

Anteriorcerebral

OphthalmicCerebral arterialcircle

Internal carotid

Lateral view

Posteriorcerebral

Basilar

Vertebral



• The Descending Aorta

• Thoracic aorta

• Supplies organs of the chest

• Bronchial arteries

• Pericardial arteries

• Esophageal arteries

• Mediastinal arteries

• Supplies chest wall

• Intercostal arteries

• Superior phrenic arteries


Figure 21-25a Major Arteries of the Trunk

Aortic arch

Internal thoracic

Thoracic aorta

Somatic Branches ofthe Thoracic Aorta


Superior phrenic

Inferior phrenic

A diagrammatic view, with most of the thoracic and abdominal organs removed



Visceral Branches ofthe Thoracic Aorta

Bronchial arteries

Esophageal arteries

Mediastinal arteries

Pericardial arteries




• The Descending Aorta

• Abdominal Aorta

• Divides at terminal segment of the aorta into:

• Left common iliac artery

• Right common iliac artery

• Unpaired branches

• Major branches to visceral organs

• Paired branches

• To body wall

• Kidneys

• Urinary bladder

• Structures outside abdominopelvic cavity




Diaphragm

Adrenal

Renal

Gonadal

Lumbar

Terminal segmentof the aorta

Common iliac

Median sacral



Celiac Trunk

Left gastric

Splenic

Common hepatic

Superior mesenteric

Abdominal aorta

Inferior mesenteric



Figure 21-26 Arteries Supplying the Abdominopelvic Organs

Branches of theCommon Hepatic Artery

Hepatic artery proper (liver)

Gastroduodenal (stomachand duodenum)

Cystic (gallbladder)

Right gastric (stomach)

Right gastroepiploid(stomach and duodenum)

Superior pancreatico-duodenal (duodenum)

Ascending colon

Superior MesentericArtery

Inferior pancreatico-duodenal (pancreas and

duodenum)Middle colic (cut)

(large intestine)Right colic (large intestine)

Ileocolic (large intestine)

Intestinal arteries (small intestine)

Liver

Pancreas

Small intestine

Rectum


Figure 21-26 Arteries Supplying the Abdominopelvic Organs

Stomach

The Celiac Trunk

Common hepatic

Left gastric

Splenic

Spleen

Branches of theSplenic Artery

Left gastroepiploic(stomach)

Pancreatic(pancreas)

Inferior MesentericArtery

Left colic (colon)

Sigmoid (colon)

Rectal (rectum)

Sigmoid colon

Rectum

Small intestine

Pancreas



• Arteries of the Pelvis and Lower Limbs

• Femoral artery

• Deep femoral artery

• Becomes popliteal artery

• Posterior to knee

• Branches to form:

• Posterior and anterior tibial arteries

• Posterior gives rise to fibular artery


Figure 21-25b Major Arteries of the Trunk

A flowchart showing major arteries of the trunk

Leftcommoniliac

Pelvis andleft lowerlimb

Pelvis and rightlowerlimb

Right commoniliac

Right externaliliac

Leftinternaliliac

Left externaliliac

Rightinternaliliac

Superiorgluteal

Obturator

Internalpudendal

Lateralsacral

Lateral rotators ofhip; rectum, anus,perineal muscles,external genitaliaIlium, hip

and thighmuscles, hipjoint andfemoral head

Hip muscles,hip joint

Pelvic muscles, skin,viscera of pelvis (urinaryand reproductive organs),perineum, gluteal region,and medial thigh

Skin andmuscles ofsacrum


Figure 21-27a Arteries of the Lower Limb

Commoniliac

Externaliliac

Superiorgluteal

Inguinalligament

Deepfemoral

Lateralfemoral

circumflex

Medialfemoralcircumflex

Femoral

InternaliliacLateralsacral

Internalpudendal

Obturator

Descendinggenicular

Anterior view


Figure 21-27a Arteries of the Lower Limb

Anterior view

Popliteal

Anterior tibial

Posteriortibial

Fibular

Dorsalis pedis

Medial plantar

Lateral plantarDorsal arch

Plantar arch


Figure 21-27b Arteries of the Lower Limb

Posterior view

Medialfemoral

circumflex

Femoral

Internalpudendal

Obturator

Superior gluteal

Right externaliliac

Deep femoral

Lateral femoralcircumflex

Descendinggenicular


Figure 21-27b Arteries of the Lower Limb

Posterior view

Popliteal

Anterior tibial

Posteriortibial

Fibular


Figure 21-27c Arteries of the Lower Limb

Deepfemoral

Femoral

Descendinggenicular

Popliteal

Fibular Posteriortibial

Anteriortibial

Medialfemoral

circumflex

Lateralfemoral

circumflex

Thigh

Hip joint, femoral head, deepmuscles of the thigh

Skin of leg,knee joint

Leg andfootQuadriceps

musclesAdductor muscles,obturator muscles,hip joint

Connected by anastomoses ofdorsalis pedis, dorsal arch, andplantar arch, which supply distalportions of the foot and the toes

EXTERNAL ILIAC

A flowchart of blood flow to a lower limb



• Systemic Veins

• Complementary Arteries and Veins

• Run side by side

• Branching patterns of peripheral veins are more variable

• In neck and limbs

• One set of arteries (deep)

• Two sets of veins (one deep, one superficial)

• Venous system controls body temperature


Figure 21-28 An Overview of the Major Systemic Veins

VertebralExternal jugular Internal jugular

Brachiocephalic

Superior vena cava

Intercostal veins

Inferior vena cavaRenalGonadal

Subclavian

Axillary

Brachial

Basilic

Hepatic veins

Median cubital

Radial

Ulnar

Median antebrachial

Palmar venous arches

Digital veins

Lumbar veins

Left and rightcommon iliac

External iliacInternal iliac

Deepfemoral

Femoral

Superficial veinsDeep veins

KEY


Figure 21-28 An Overview of the Major Systemic Veins

Superficial veinsDeep veins

KEY

Femoral

Posterior tibial

Anterior tibial

Great saphenous

Popliteal

Small saphenous

Fibular

Plantar venous archDorsal venous arch



• The Superior Vena Cava (SVC)

• Receives blood from the tissues and organs of:

• Head

• Neck

• Chest

• Shoulders

• Upper limbs


Figure 21-29c Major Veins of the Head, Neck, and Brain

Superior sagittal sinus

Superficial cerebral veins

Inferior sagittal sinus

Great cerebralStraight sinus

Petrosal sinusesRight transverse sinus

Occipital sinus

Sigmoid sinus

Occipital

TemporalDeep cerebral

Cavernous sinusMaxillary

Facial

Vertebral

External jugular

Right subclavian

Axillary

Clavicle

First rib

Veins draining the brain and the superficialand deep portions of the head and neck.

Internal jugular

Right brachiocephalic

Left brachiocephalic

Superior vena cavaInternal thoracic



• The Dural Sinuses

• Superficial cerebral veins and small veins of the brain

stem

• Empty into network of dural sinuses

• Superior and inferior sagittal sinuses

• Petrosal sinuses

• Occipital sinus

• Left and right transverse sinuses

• Straight sinus


Figure 21-29b Major Veins of the Head, Neck, and Brain

Straightsinus

Occipitalsinus

Right transversesinus Right

sigmoid sinus

Inferior sagittalsinus

Superior sagittalsinus

Greatcerebral

vein

Cavernoussinus

Petrosal sinusesInternal jugularVertebral vein

A lateral view of the brainshowing the venousdistribution.



• Cerebral Veins

• Great cerebral vein

• Drains to straight sinus

• Other cerebral veins

• Drain to cavernous sinus

• Which drains to petrosal sinus

• Vertebral Veins

• Empty into brachiocephalic veins of chest


Figure 21-29a Major Veins of the Head, Neck, and Brain

An inferior view of the brain, showing the venous distribution.

Occipital sinus

Straight sinus

Transverse sinus

Cerebellar veins

Sigmoid sinus

Internal jugular

Cerebral veins

Cavernous sinus

Petrosal sinus

Superior sagittal,sinus (cut)



• Superficial Veins of the Head and Neck

• Converge to form:

• Temporal, facial, and maxillary veins

• Temporal and maxillary veins

• Drain to external jugular vein

• Facial vein

• Drains to internal jugular vein


Figure 21-29c Major Veins of the Head, Neck, and Brain

Superior sagittal sinus

Superficial cerebral veins

Inferior sagittal sinus

Great cerebralStraight sinus

Petrosal sinusesRight transverse sinus

Occipital sinus

Sigmoid sinus

Occipital

TemporalDeep cerebral

Cavernous sinusMaxillary

Facial

Vertebral

External jugular

Right subclavian

Axillary

Clavicle

First rib

Veins draining the brain and the superficialand deep portions of the head and neck.

Internal jugular

Right brachiocephalic


Superior vena cavaInternal thoracic



• Veins of the Hand

• Digital veins

• Empty into superficial and deep palmar veins

• Which interconnect to form palmar venous arches



• Veins of the Hand

• Superficial arch empties into:

• Cephalic vein

• Median antebrachial vein

• Basilic vein

• Median cubital vein

• Deep palmar veins drain into:

• Radial and ulnar veins

• Which fuse above elbow to form brachial vein


Figure 21-30 The Venous Drainage of the Abdomen and Chest

Palmar venousarches

Digital veins

Ulnar

Median antebrachialRadial

Cephalic

Anterior crural interosseous

Basilic

Median cubital

Deep veins

Superficial veinsKEY



• The Brachial Vein

• Merges with basilic vein

• To become axillary vein

• Cephalic vein joins axillary vein

• To form subclavian vein

• Merges with external and internal jugular veins

• To form brachiocephalic vein

• Which enters thoracic cavity



Deep veins

Superficial veinsKEY

Adrenal veinsPhrenic veins

Basilic

INFERIOR VENA CAVA

Intercostal veins

HemiazygosAccessory hemiazygos

CephalicAxillaryBrachiocephalicHighest intercostalSubclavian

External jugularInternal jugularVertebral

Brachial



• Veins of the Thoracic Cavity

• Brachiocephalic vein receives blood from:

• Vertebral vein

• Internal thoracic vein

• The Left and Right Brachiocephalic Veins

• Merge to form the superior vena cava (SVC)



• Tributaries of the Superior Vena Cava

• Azygos vein and hemiazygos vein, which receive

blood from:

1. Intercostal veins

2. Esophageal veins

3. Veins of other mediastinal structures



Medial sacralDeep veinsSuperficial veins

KEY External iliacInternal iliac

Common iliac

Lumbarveins

Gonadalveins

Renal veins

Hepaticveins

Internalthoracic

Azygos

Esophagealveins

Mediastinalveins

SUPERIORVENA CAVA


Figure 21-31a Flowcharts of Circulation to the Superior and Inferior Venae Cavae

Tributaries of the superior vena cava

Rightvertebral

Collect bloodfrom vertebraeand body wall

Left intercostalveins

Hemiazygos


Collects blood from cranium, face,and neck

Collect blood from structuresof anteriorthoracic wall

Left internal jugular

Right internal jugular

Left andright internalthoracicveins

Esophagealveins

Azygos

Collect blood from the mediastinum

Right external jugular

Rightsubclavian

Rightaxillary

Mediastinalveins

Rightbrachiocephalic

Veins of theright upper

limb

Rightintercostalveins

Collect blood from vertebraeand body wall

Collect blood from theeophagus

KEYSuperficial veinsDeep veins

SUPERIORVENA CAVA

RIGHTATRIUM

Collects blood from cranium, spinalcord, vertebrae

Leftvertebral

Through highestintercostal vein


Figure 21-31a Flowcharts of Circulation to the Superior and Inferior Venae Cavae

Tributaries of the superior vena cava


Venous networkof wrist and hand

Left cephalic Left basilic

Left axillary

Left brachial

Left subclavian


Left external jugular

Leftulnar

Leftradial

Radialside offorearm

Ulnarside offorearm

Collects bloodfrom lateral surfaceof upper limb

Collects bloodfrom medial surfaceof upper limb

Collects blood from forearm, wrist, and hand

Collects blood from neck, face, salivaryglands, scalp

Interconnected by mediancubital vein and median

antebrachial network



• The Inferior Vena Cava (IVC)

• Collects blood from organs inferior to the

diaphragm



• Veins of the Foot

• Capillaries of the sole

• Drain into a network of plantar veins

• Which supply the plantar venous arch

• Drain into deep veins of leg:

• Anterior tibial vein

• Posterior tibial vein

• Fibular vein

• All three join to become popliteal vein



• The Dorsal Venous Arch

• Collects blood from:

• Superior surface of foot

• Digital veins

• Drains into two superficial veins

1. Great saphenous vein (drains into femoral vein)

2. Small saphenous vein (drains into popliteal vein)



• The Popliteal Vein

• Becomes the femoral vein

• Before entering abdominal wall, receives blood from:

• Great saphenous vein

• Deep femoral vein

• Femoral circumflex vein

• Inside the pelvic cavity

• Becomes the external iliac vein



• The External Iliac Veins

• Are joined by internal iliac veins

• To form right and left common iliac veins

• The right and left common iliac veins

• Merge to form the inferior vena cava


Figure 21-32a Venous Drainage from the Lower Limb

External iliacCommon iliacInternal iliac

GlutealInternal pudendal

Lateral sacralObturatorFemoral

Femoral circumflex

Deep femoral

Femoral

Great saphenous

Popliteal

Smallsaphenous

Anterior tibial

Posterior tibial

Fibular

Dorsal venous arch

Plantar venous archDigital

An anterior view


Figure 21-32b Venous Drainage from the Lower Limb

External iliac

Gluteal

Internal pudendal

ObturatorFemoral

Femoral circumflex

Deep femoral

Femoral

Great saphenous

Popliteal

Smallsaphenous

Anterior tibial

Posterior tibial

Fibular

A posterior view


Figure 21-32c Venous Drainage from the Lower Limb

EXTERNAL ILIAC

Smallsaphenous

Femoral

Popliteal

FibularPosterior

tibialAnterior

tibial

Extensive anastomoses interconnectveins of the ankle and foot

Greatsaphenous


Collects bloodfrom thesuperficial veinsof the lower limb

Collects bloodfrom the thigh

Collects bloodfrom superficialveins of the legand foot

A flowchart of venous circulation from a lower limb

Deepfemoral



• Major Tributaries of the Abdominal Inferior Vena

Cava

1. Lumbar veins

2. Gonadal veins

3. Hepatic veins

4. Renal veins

5. Adrenal veins

6. Phrenic veins



• The Hepatic Portal System

• Connects two capillary beds

• Delivers nutrient-laden blood

• From capillaries of digestive organs

• To liver sinusoids for processing



Tributaries of the Hepatic Portal Vein

1. Inferior mesenteric vein

• Drains part of large intestine

2. Splenic vein

• Drains spleen, part of stomach, and pancreas

3. Superior mesenteric vein

• Drains part of stomach, small intestine, and part of large intestine

4. Left and right gastric veins

• Drain part of stomach

• Cystic vein

• Drains gallbladder



• Blood Processed in Liver

• After processing in liver sinusoids (exchange

vessels):

• Blood collects in hepatic veins and empties into

inferior vena cava


Figure 21-33 The Hepatic Portal System

Inferior vena cava

Hepatic

Cystic

Hepatic portal

Pancreaticoduodenal

Superior MesentericVein and Its Tributaries

Middle colic (fromtransverse colon)

Right colic (ascendingcolon)

Ileocolic (Ileum andascending colon)

Intestinal (small intestine)

Pancreas

Liver


Figure 21-33 The Hepatic Portal System

Left gastric

Right gastric

Stomach

Spleen

Pancreas

Left gastroepiploic(stomach)Right gastroepiploic(stomach)Pancreatic

Descending colon

Splenic Vein and ItsTributaries

Inferior MesentericVein and Its Tributaries

Left colic (descendingcolon)Sigmoid(sigmoid colon)

Superior rectal (rectum)


Figure 21-31b Flowcharts of Circulation to the Superior and Inferior Venae Cavae

Tributaries of the inferior vena cava

Superiorglutealveins

Internalpudendal

veins

Obturatorveins

Lateralsacralveins

Blood fromveins in leftlower limb

Leftexternal

iliacLeft internal

iliac

Rightexternal

iliacRight internal

iliac

Blood fromveins in right

lower limb

Rightcommon

iliac

Leftcommon

iliac

Collect blood from the pelvic muscles,skin, urinary and reproductive organsof pelvic cavity

Collect blood fromthe kidneys

Collect blood fromthe diaphragm

Collect blood fromthe adrenalglands

Collect blood fromthe spinal cordand body wall

Collect blood fromthe liver

Collect blood fromthe gonads (testesor ovaries)

Hepaticveins

Gonadalveins

Lumbarveins

Phrenicveins

Adrenalveins

Renalveins

RIGHTATRIUM

INFERIORVENA CAVA



21-8 Fetal and Maternal Circulation

• Fetal and Maternal Cardiovascular Systems

Promote the Exchange of Materials

• Embryonic lungs and digestive tract nonfunctional

• Respiratory functions and nutrition provided by

placenta



• Placental Blood Supply

• Blood flows to the placenta

• Through a pair of umbilical arteries that arise from internal

iliac arteries

• Enters umbilical cord

• Blood returns from placenta

• In a single umbilical vein that drains into ductus venosus

• Ductus venosus

• Empties into inferior vena cava



• Before Birth

• Fetal lungs are collapsed

• O2 provided by placental circulation



• Fetal Pulmonary Circulation Bypasses

• Foramen ovale

• Interatrial opening

• Covered by valve-like flap

• Directs blood from right to left atrium

• Ductus arteriosus

• Short vessel

• Connects pulmonary and aortic trunks



• Cardiovascular Changes at Birth

• Newborn breathes air

• Lungs expand

• Pulmonary vessels expand

• Reduced resistance allows blood flow

• Rising O2 causes ductus arteriosus constriction

• Rising left atrium pressure closes foramen ovale

• Pulmonary circulation provides O2


Figure 21-34a Fetal Circulation

Placenta

AortaForamen ovale (open)

Ductus arteriosus (open)

Pulmonary trunk

Liver Inferiorvena cavaDuctusvenosus

Umbilicalvein

Umbilical cord

Blood flow to and from the placenta in full-term fetus (before birth)

Umbilicalarteries


Figure 21-34b Fetal Circulation

Blood flow through theneonatal (newborn) heartafter delivery

Inferiorvena cava

Right ventricle

Left ventricle

Right atrium

Foramen ovale(closed)

Left atrium

Pulmonary trunk

Ductus arteriosus(closed)


Figure 21-35 Congenital Heart Problems

Normal Heart StructureMost heart problems reflect deviations from the normal formation of the heart and its connections to the great vessels.



• Patent Foramen Ovale and Patent Ductus Arteriosus

• In patent (open) foramen ovale blood recirculates through pulmonary circuit instead of entering left ventricle

• The movement, driven by relatively high systemic pressure, is a “left-to-right shunt”

• Arterial oxygen content is normal, but left ventricle must work much harder than usual to provide adequate blood flow through systemic circuit



• Patent Foramen Ovale and Patent Ductus Arteriosus

• Pressures rise in the pulmonary circuit

• If pulmonary pressures rise enough, they may force blood into systemic circuit through ductus arteriosus

• A patent ductus arteriosus creates a “right-to-left shunt”

• Because circulating blood is not adequately oxygenated, it develops deep red color

• Skin develops blue tones typical of cyanosis and infant is known as a “blue baby”



Patent Foramen Ovale and Patent Ductus ArteriosusIf the foramen ovale remains open, or patent,blood recirculates through the pulmonary circuit instead of entering the left ventricle. Themovement, driven by the relatively highsystemic pressure, is called a “left-to-right shunt.” Arterial oxygen content is normal, but the left ventricle must work much harder than usual to provide adequate blood flow through

the systemic circuit. Hence, pressures rise in the pulmonary circuit. If the pulmonary pressures rise enough, they may force blood into the systemic circuit through the ductus arteriosus. This condition—a patent ductus arteriosus—creates a “right-to-left shunt.” Because the circulating blood is not adequately oxygenated, it develops a deep red color. The skin then develops the blue tones typical of cyanosis and the infant is known as a “blue baby.”

Patent ductusarteriosus

Patentforamen

ovale



• Tetralogy of Fallot

• Complex group of heart and circulatory defects that affect 0.10 percent of newborn infants

1. Pulmonary trunk is abnormally narrow (pulmonary stenosis)

2. Interventricular septum is incomplete

3. Aorta originates where interventricular septum normally ends

4. Right ventricle is enlarged and both ventricles thicken in response to increased workload



Tetralogy of Fallotventricle is enlarged and both ventricles thicken in response to the increased workload.

The tetralogy of Fallot (fa-LO) is a complexgroup of heart and circulatory defects thataffect 0.10 percent of newborn infants. In thiscondition, (1) the pulmonary trunk is abnor-mally narrow (pulmonary stenosis), (2) the interventricular septum is incomplete, (3) the aorta originates where the interventricularseptum normally ends, and (4) the right

¯Patent ductus

arteriosusPulmonary

stenosisVentricular

septal defectEnlarged

right ventricle



• Ventricular Septal Defect

• Openings in interventricular septum that separate right and left ventricles

• The most common congenital heart problems, affecting 0.12 percent of newborns

• Opening between the two ventricles has an effect similar to a connection between the atria

• When more powerful left ventricle beats, it ejects blood into right ventricle and pulmonary circuit



Ventricular Septal DefectVentricular septal defects are openings in the inter-ventricular septum that separate the right and left ven-tricles. These defects are the most common congenital heart problems, affecting 0.12 percent of newborns. The opening between the two ventricles has an effect simi-lar to a connection between the atria: When the more powerful left ventricle beats, it ejects blood into the right ventricle and pulmonary circuit.

Ventricularseptal defect

Ventricularseptum



• Atrioventricular Septal Defect

• Both the atria and ventricles are incompletely separated

• Results are quite variable, depending on extent of defect and effects on atrioventricular valves

• This type of defect most commonly affects infants with Down’s syndrome, a disorder caused by the presence of an extra copy of chromosome 21



In an atriovenricular septal defect, both the atria andventricles are incompletely separated. The results arequite variable, depending on the extent of the defectand the effects on the atrioventricular valves. This type of defect most commonly affects infants with Down’s syndrome, a disorder caused by the presence of an extra copy of chromosome 21.

Atrioventricular Septal Defect

Atrialdefect

Ventriculardefect



• Transposition of Great Vessels

• The aorta is connected to right ventricle instead of to left ventricle

• The pulmonary artery is connected to left ventricle instead of right ventricle

• This malformation affects 0.05 percent of newborn infants



In the transposition of great vessels, theaorta is connected to the right ventricleinstead of to the left ventricle, and thepulmonary artery is connected to the leftventricle instead of the right ventricle. This malformation affects 0.05 percent ofnewborn infants.

Transposition of the Great VesselsPatent ductus

arteriosusAorta

Pulmonarytrunk


21-9 Effects of Aging and the Cardiovascular System

• Cardiovascular Capabilities Decline with Age

• Age-related changes occur in:

• Blood

• Heart

• Blood vessels



• Three Age-Related Changes in Blood

1. Decreased hematocrit

2. Peripheral blockage by blood clot (thrombus)

3. Pooling of blood in legs

• Due to venous valve deterioration



• Five Age-Related Changes in the Heart

1. Reduced maximum cardiac output

2. Changes in nodal and conducting cells

3. Reduced elasticity of cardiac (fibrous) skeleton

4. Progressive atherosclerosis

5. Replacement of damaged cardiac muscle cells by

scar tissue



• Three Age-Related Changes in Blood Vessels

1. Arteries become less elastic

• Pressure change can cause aneurysm

2. Calcium deposits on vessel walls

• Can cause stroke or infarction

3. Thrombi can form

• At atherosclerotic plaques


21-9 Cardiovascular System Integration

• Many Categories of Cardiovascular Disorders

• Disorders may:

• Affect all cells and systems

• Be structural or functional

• Result from disease or trauma


Figure 21-36 System Integrator: The Cardiovascular System

S Y S T E M I N T E G R A T O RBody System Cardiovascular System Body SystemCardiovascular System

Inte

gu

men

tary

Ske

leta

lM

usc

ula

rN

ervo

us

En

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crin

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Inte

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Ske

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ervo

us

En

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age

165

Pag

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5P

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369

Pag

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632

The section on vesseldistribution demonstrated theextent of the anatomicalconnections between thecardiovascular system and otherorgan systems. This figuresummarizes some of the physiologicalrelationships involved.

The most extensive communicationoccurs between the cardiovascular andlymphatic systems. Not only are the twosystems physically interconnected, butcells of the lymphatic system also movefrom one part of the body to anotherwithin the vessels of the cardiovascularsystem. We examine the lymphaticsystem in detail, including its role in theimmune response, in the next chapter.

The CARDIOVASCULAR System

Stimulation of mast cells produceslocalized changes in blood flow andcapillary permeability

Provides calcium needed for normalcardiac muscle contraction; protectsblood cells developing in red bonemarrow

Skeletal muscle contractions assist inmoving blood through veins; protectssuperficial blood vessels, especiallyin neck and limbs

Controls patterns of circulation in peripheral tissues; modifies heartrate and regulates blood pressure;releases ADH

Erythropoietin regulates productionof RBCs; several hormones elevateblood pressure; epinephrinestimulates cardiac muscle, elevatingheart rate and contractile force

Distributes hormones throughoutthe body; heart secretes ANP andBNP

Endothelial cells maintainblood—brain barrier; helpsgenerate CSF

Delivers oxygen and nutrients,removes carbon dioxide, lacticacid, and heat during skeletalmuscle activity

Transports calcium and phosphatefor bone deposition; delivers EPO tored bone marrow, parathyroidhormone, and calcitonin toosteoblasts and osteoclasts

Delivers immune system cells toinjury sites; clotting response sealsbreaks in skin surface; carries awaytoxins from sites of infection;provides heat

Lym

ph

atic

Pag

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7

Res

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ato

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857

Dig

esti

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910

Uri

nar

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992

Rep

rod

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Pag

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72

169 Ch 21_lecture_presentation

Health & Medicine

rib veins

superior vena

29c major

endothelial

25a major

commonly affects

subclavian

cardiac output