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Blood Vessels and Circulation

Chapter 21

Five General Classes of Blood Vessels

• Arteries, which carry blood away from the heart

• Aterioles, the smallest arterial branches, that communicate with

• Capillaries, where diffusion (exchange) between blood and interstitial fluids occurs

• Venules, which carry blood from the capillary beds

• Veins, larger vessels that return blood to the heart

Anatomy of Blood Vessels• The walls of arteries and veins contain 3

distinct layers– The tunica intima, or tunica interna, consists of the

innermost endothelial layer and an underlying layer of connective tissuey

– The tunica media, contains concentric sheets of smooth muscle in a framework of loose connective tissues, commonly the thickest layer in arteries

– Tunica externa, or tunica adventitia, is the outermost layer and forms a connective tissue sheath around the vessel, that stabilizes and anchors the blood vessel

Differences between Arteries and Veins

• In general, the walls of arteries are thicker than those of veins, principally due to the thickness of the smooth muscle and elastic fibers in the tunica media

• When not opposed by blood pressure, the walls of pp y parteries constrict the lumen to a narrow diameter. Veins, on the other hand, tend to collapse and appear flattened in cross section

• The endothelial lining of an artery folds when an artery contracts, veins do not form folds

Arteries

• The contractile nature of the arterial wall gives arteries the ability to actively change diameter

• These changes in diameter are primarily under the control of the sympathetic division of the autonomic y pnervous system

• Vasoconstriction is the process by which the smooth muscle in arteries contract when stimulated and the diameter of the blood vessel decreases

• Vasodilation increases the diameter of the lumen and results from relaxation of the smooth muscle layer

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Arteries• Vasoconstriction and vasodilation affect

– The afterload of the heart

– Peripheral blood pressure

– & capillary bloodflow

• Arteries are classified, based on size, as either; elasticArteries are classified, based on size, as either; elastic (aka conducting), up to 2.5cm in diameter, or muscular (aka distribution or medium sized arteries) with a diameter of 0.5 to 4.0 mm

• Small arteries (generally with an internal diameter of 30 µm or less) are called arterioles

• See fig 21-2 on p711

• Structurally capillaries are an endothelial tube inside a basal lamina

• Capillaries are the only blood vessels permitting exchange between blood and surrounding tissues

Capillaries

• Because of this capillaries:– Surround muscle fibers

– Radiate through connective tissue

– & weave throughout all active tissues

• There are two major types of capillaries– Continuous capillaries with a complete endothelial

lining

– Fenestrated capillaries which contain pores spanning the endothelial lining

Capillaries

the endothelial lining• These pores (fenestrations) allow for much more rapid

movement of water and solutes between blood plasma and the interstitial fluids

• Sinusoids are a type of fenestrated capillary with flattened and irregular gaps between endothelial cells permitting a free exchange of water and solutes as large as plasma proteins

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

• Capillary beds are an interconnected network of vessels consisting of– The collateral arteries feeding an arteriole

M t t i l ( bl f t ti )

Capillary Beds

– Metarterioles (capable of contraction)

– Capillaries

– Arteriovenous anastomoses (joining of artery & vein)

– Venules

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• Each capillary bed – connects one arteriole to one venule

– & contains precapillary sphincters that regulates blood flow through the bed

Capillary Beds

blood flow through the bed

Veins

• Veins collect blood from all tissues and organs and return it to the heart

• Veins are also classified according to size V l ll t f ill b d– Venules - collect from capillary beds

– Medium-sized veins

– Large veins

• Venules and medium-sized veins contain valves which prevent the backflow of blood

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

Valve closed

Valve opens abovecontracting muscle

Valve closed

Valve closes belowcontracting muscle

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The Distribution of Blood

• Our blood volume is unevenly distributed among arteries, veins, and capillaries

• The heart, arteries, and capillaries normally contain about 30-35% of the blood volumeTh i h• The venous system contains the rest

• Veins, with their thinner walls, are much more distensible than arteries, as a result veins act as reservoir for blood volume and are termed capacitance vessels (arteries, with their contractile muscular walls are considered a reserve of pressure)

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

Large venousnetworks (liver,

bone marrow, skin)21%

Large veins18%

Venules andmedium-sized veins

25%

Cardiovascular Physiology

Cardiovascular Physiology

• The goal of cardiovascular regulation is the maintenance of adequate blood flow through the capillary beds in peripheral tissues and organs

• Under normal circumstances, this means that blood flow is equal to cardiac output

• When cardiac output increases, so does blood flow through the capillary beds…and vice versa

• Factors affecting blood flow and cardiac output fall under the broad topic: cardiovascular physiology

Blood flow

• Blood flow is determined by the interplay between pressure (P) and resistance (R) in the cardiovascular network.

• In order for blood to flow the heart must generate sufficient pressure to overcome the peripheral resistance in the pulmonary and systemic circuits

• As pressure (P) increases flow increases and as resistance (R) decreases flow increases

Blood flow

• Absolute pressure (the size of the number) is less important than the pressure gradient – the difference in pressure from one end of the vessel to the other.

• In other words, blood will flow as long as the gpressure is greater at one end of the vessel versus the other.

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Cardiovascular Physiology

• In order to understand cardiovascular physiology we must understand circulatory pressure and resistance, as well as the mechanisms of capillary exchange thatmechanisms of capillary exchange that ultimately provide part of the feedback that regulates pressure and resistance.

Circulatory Pressure

• Circulatory pressure can be divided into three components

• Blood pressure (BP), really arterial pressure, around 100mm Hg at aorta to 35mm ataround 100mm Hg at aorta to 35mm at capillary bed

• Capillary hydrostatic pressure, pressure within the capillary beds 35-18 mm Hg

• Venous pressure around 18 mm Hg

• Resistance of the cardiovascular system opposes the movement of blood

• For blood to flow, the circulatory pressure must t t l i h l i t th

Resistance (R)

overcome total peripheral resistance; the resistance of the entire cardiovascular system

Peripheral Resistance

• Peripheral resistance has three major components– Vascular resistance: the resistance of the blood

vessels is the largest component of peripheral resistance, it is dependent upon the length and diameter of the blood vessels

– Viscosity is resistance to flow caused by blood components, blood viscosity is generally stable excepting specific disorders

– Turbulence seldom occurs in the smallest vessels and has little affect on resistance in larger vessels

Figure 21-9 Factors Affecting Friction and Vascular Resistance p719Friction and Vessel Length

Friction and Vessel Diameter

V l L th V l Di t

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

Vessel Length versus Vessel Diameter

Factors Affecting Vascular Resistance

Diameter 2 cm

Diameter 1 cm

Resistance to flow 1

Resistance to flow 16

Plaque deposit Turbulence

Turbulence

Plaque deposit Turbulence

Turbulence

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• Arterial blood pressure– Maintains blood flow through capillary beds

– Rises during ventricular systole and falls during ventricular diastole

P l i h h i ill i h

Arterial blood pressure

• Pulse is a rhythmic pressure oscillation that accompanies each heartbeat– Pulse pressure = difference between systolic and

diastolic pressures

• Mean Arterial Pressure (MAP) is a weighted average of pulse pressure and diastolic pressure

Figure 21-11 Pressures within the Systemic Circuit

Systolic

Pulsepressure

Diastolic

Mean arterialpressure

mm Hg

Venous Pressure and Venous Return

• Venous pressure, though low, determines venous return

• Venous pressures in the vena cavae are around 2mm Hg2mm Hg

• Both muscular compression and the respiratory pump assist in propelling blood toward the heart

Muscular Compression

• The contraction of skeletal muscles near a vein compress it, helping push blood toward the heart

• Valves in the veins insure that blood flows in• Valves in the veins insure that blood flows in one direction only

• Normal standing and walking causes cycles of muscle contraction that assist venous return

Respiratory Pump

• As you inhale, the increase in thoracic cavity volume decreases pressure within the pleural cavity and pulls air into the lungs and also blood into the inferior vena cava and right atrium

• As you exhale, the increasing pressure pushes blood into the right atrium from the vena cavae

• This respiratory pump is important during heavy exercise when respiration is deep and frequent

Capillary Exchange

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Capillary Exchange

• Capillary exchange is the flow of water and solutes from capillaries to interstitial space

• Most of this material is reabsorbed, but some enters the lymphatic system which thenenters the lymphatic system, which then returns it to the bloodstream

• The most important processes that move materials across capillary walls are diffusion, filtration, and reabsorption

Diffusion

• Diffusion is the passive movement of ions or compounds from a region of high concentration to a region of low concentration

• Water, ions, and small organic molecules , , greadily diffuse across capillary boundaries

• Plasma proteins and blood cells are normally unable to cross the capillary boundaries except at sinusoids, where large gaps exist

Filtration• Filtration is the removal of solutes as a

solution flows across a porous membrane (fenestrated capillaries).

• The driving force in filtration is Capillary Hydrostatic Pressure (CHP) which forcesHydrostatic Pressure (CHP) which forces water and small ions across the capillary walls

• This leaves larger solutes, blood cells, and plasma proteins behind within the vessel where they maintain the osmotic potential (blood colloidal osmotic pressure) to drive reabsorption

Figure 21-12 Capillary Filtration

Capillaryhydrostatic

pressure(CHP) Amino acid

Blood protein

Glucose

Ions

Interstitialfluid

Small solutes

Hydrogenbond

Watermolecule

Endothelialcell 2

Endothelialcell 1

Reabsorption

• Reabsorption occurs as a result of blood colloidal osmotic pressure which draws water back into the capillaries via osmosis

• Remember:– hydrostatic pressure forces water and solutes out

of the blood vessel via filtration– Reabsorption pulls water back into the blood

vessel driven by the osmotic pressure of blood cells and plasma proteins remaining in the blood vessel

In Summary

• Blood entering the capillary bed has a capillary hydrostatic pressure (CHP) of 35 mm Hg

• the blood colloid osmotic pressure (pulling water back into the blood vessel) is a constantwater back into the blood vessel) is a constant across the capillary bed at 25 mm Hg

• Blood leaving capillary bed has a CHP of 18

• So what does that all mean?

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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

Cardiovascular Regulation

• Homeostatic mechanisms regulate cardiovascular activity to ensure that blood flow through tissues (perfusion) meets the demands for oxygen and nutrientsdemands for oxygen and nutrients

• Regulation of cardiovascular function is accomplished via autoregulation, neural mechanisms, and endocrine mechanisms

• Section 20.4 in openstax, Figure 21-12 in Martini (section 21-3)

Autoregulation

• The pattern of blood flow within capillary beds changes in response to chemical changes in interstitial fluids

• Autoregulation causes immediate localized• Autoregulation causes immediate, localized homeostatic adjustments

• If autoregulation fails to return the system to homeostasis, neural and endocrine factors are activated

Neural Mechanisms

• Neural mechanisms respond to changes in arterial pressure (baroreceptors) or blood gas levels (chemoreceptors) at specific sites

• Cardiovascular centers of the autonomic• Cardiovascular centers of the autonomic nervous system adjust cardiac output and peripheral resistance to maintain blood pressure and ensure adequate bloodflow

Endocrine Mechanisms

• Endocrine mechanisms cause the release of hormones to enhance short term adjustments or direct long-term changes

• E NE ADH Angiotensin II Erythropoetin• E, NE, ADH, Angiotensin II, Erythropoetin, and atrial natriuretic peptide are important in cardiovascular regulation

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

Central Regulation

Autoregulation

Stimulation ofreceptors sensitiveto changes insystemic bloodpressure orchemistry

Endocrine mechanisms

If autoregulation is ineffective

Neuralmechanisms

Activation ofcardiovascularcenters

Stimulationof endocrineresponse

Long-term increasein blood volumeand blood pressure

Short-term elevationof blood pressure bysympatheticstimulation of theheart and peripheralvasoconstriction

Central regulation involves bothneural and endocrine mechanisms.Activation of the cardiovascularcenters involves both thecardioacceleratory centers (whichstimulate the heart) and the vasomotorcenters (which control the degree ofperipheral vasoconstriction). Neuralmechanisms elevate cardiac outputand reduce blood flow to nonessentialor inactive tissues. The primaryvasoconstrictor involved in neuralregulation is norepinephrine (NE).Endocrine mechanisms involvelong-term increases in blood volumeand blood pressure.

Local vasodilatorsreleased

HOMEOSTASISRESTORED

HOMEOSTASIS DISTURBED

HOMEOSTASIS

HOMEOSTASISRESTORED

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 orprostaglandins)

• Increased tissue activity

Start

Autoregulation involveschanges in the patten ofblood flow within capillarybeds as precapillarysphincters open and close inresponse to chemicalchanges in the interstitialfluid. Factors that promotethe dilation of blood vesselsare called vasodilators.Local vasodilators such aslactate accelerate blood flowthrough their tissue of origin.

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Patterns of Cardiovascular Responsee s o C d ov scu espo se

• Light exercise results in– Extensive vasodilation as oxygen consumption

increases– Increased venous return through the action of muscle

Exercise and the Cardiovascular System

gcontraction and respiratory pump

– A rise in cardiac output in response to increased venous return and atrial pressure

• Heavy exercise results in– Increased blood flow to skeletal muscles– Restriction of blood flow to nonessential organs

• Trained athletes have bigger hearts and greater stroke volumes than non-athletes

• An athletes cardiac output can be half again that of a non-athlete during exercise

• Regular moderate exercise can cut the risk of heart attack in half

• Only around 8% of US adults exercise at recommended levels

Cardiovascular response to hemorrhaging: short term

• Carotid and aortic reflexes increase cardiac ouput and peripheral vasoconstriction

• Sympathetic nervous system elevates blood• Sympathetic nervous system elevates blood pressure

• E and NE increase cardiac output and ADH enhances vasoconstriction

Cardiovascular response to hemorrhaging: long term

• Decline in capillary blood pressure recalls fluids from interstitial spaces

• Aldosterone and ADH promote fluid retentionp

• Increased thirst promotes water absorption across the digestive tract

• Erythropoietin ultimately increases blood volume and improves O2 delivery

Figure 21-18 Cardiovascular Responses to Hemorrhaging and Blood Loss

Normal bloodpressure and

volume

Extensive bleedingreduces bloodpressure andvolume

HOMEOSTASISDISTURBED

Responsescoordinated by theendocrine system

R

Falling bloodpressure and

volume

Blood pressureand volume rise

HOMEOSTASISRESTORED

Elevationof bloodvolume

HOMEOSTASIS

Responsesdirected by thenervous system Long-Term Hormonal Response

ADH, angiotensin II, aldosterone,and EPO released

Cardiovascular Responses

Peripheralvasoconstriction;mobilization ofvenous reserve

Increasedcardiacoutput

Stimulation ofbaroreceptors andchemoreceptorsPain, stress,

anxiety, fear

Higher Centers

Stimulation ofcardiovascularcenters

Generalsympatheticactivation

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Circulatory Shock

• Circulatory shock is marked by low blood pressure and inadequate peripheral bloodflow

• Symptoms appear after a loss of about 30% of total blood volume

• In mild cases, homeostatic mechanisms can cope withIn mild cases, homeostatic mechanisms can cope with the situation

• When blood volume drops by more than 35% homeostatic mechanisms cannot cope and low cardiac output results in damage to the myocardium

• In the absence of treatment, damage becomes irreversible and death ensues

• The brain – The brain has a very high oxygen demand and normally

receives about 12% of Cardiac output– Four arteries anastomose inside the cranium insuring constant

blood flow

Special circulation

• The heart – Coronary arteries arise from the ascending aorta

• The lungs – Pulmonary circuit, regulated by local responses to O2 levels

within the alveoli– The pulmonary circuit responds differently than other tissues

in that a decline in O2 levels causes vasoconstriction in the lung tissues and blood is shunted to the alveoli)

The distribution of blood: General functional patterns

• Peripheral distribution of arteries and veins is generally symmetrical, except near the heart where the largest vessels connect to the atria or ventriclesventricles

• Single vessels may have several names as they cross anatomical boundaries

• Arteries and corresponding veins usually travel together

Pulmonary circuit consists of pulmonary vessels

• The pulmonary trunk gives rise to the right and left pulmonary arteries which deliver blood to the lungs

• Capillary networks in the lungs surround alveoli where gas exchange occurs

• Four pulmonary veins, two from each lung deliver blood to the left atrium

The Systemic Circuit

• The systemic circuit supplies and drains the capillary beds in parts of the body not serviced by the pulmonary circuit

• The systemic circuit begins at the left• The systemic circuit begins at the left ventricle and ends at the right atrium

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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 trunk

Descending aorta

Diaphragm

Renal

Superior mesenteric

Gonadal

Inferior mesenteric

Common iliac

Internal iliac

Radial

UlnarExternal

iliac

Femoral

Palmararches Deep

femoral

Popliteal

Posterior tibial

Anterior tibial

Fibular

Plantar arch

Descendinggenicular

Dorsalis pedis

Ascending Aorta And Aortic Arch

• The right and left coronary arteries originate from base of aortic sinus at the base of the aortic arch

• The aortic arch connects the ascending and descending aortasg

• Three elastic arteries branch from the aortic arch; the brachiocephalic, left common carotid, and left subclavian

• The brachiocephalic ascends then branches to form the right subclavian and right common carotid arteries

Figure 21-22a Arteries of the Chest and Upper Limb (Part 1 of 2)

SuprascapularThyrocervical trunk

Right subclavian

Axillary

Lateral thoracicAnterior humeral

circumflex

Posterior humeralcircumflex

Subscapular

Deep brachial

Right common carotidLeft common carotidVertebral

Brachiocephalic trunk

Left subclavian

Aortic arch

Ascending aorta

Thoracic aorta

Heart

Thoracoacromial

Deep brachial

Intercostal arteries

Brachial

Ulnar recurrent arteries

Internal thoracic

Abdominal aortaUlnar collateral arteries

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

Brachiocephalictrunk

Right thyrocervicaltrunk

Rightsubclavian

Right axillary

Right internalthoracic

Leftinternalthoracic Left

axillary

AORTICARCHMuscles of the right

pectoral region and

Skin and muscles ofchest and abdomen,mammary gland (right

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)

axillary

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

axilla side), pericardium

A flowchart of the arteries of the chest and upper limb

Figure 21-23 Arteries of the Neck and Head

Branches of theExternal Carotid

Superficialtemporal

Maxillary

Occipital

Facial

LingualI t l tid

Basilar

Posterior cerebral

Carotid canal

Cerebral arterial circle

OphthalmicMiddle cerebral

Anterior cerebral

gExternalcarotid

Common carotid

Brachiocephalictrunk

Second rib

Internal thoracicAxillary

Subclavian

SuprascapularTransverse cervical

Thyrocervicaltrunk

Carotid sinusVertebral

Internal carotid

Inferior thyroid

Descending Aorta

• The descending aorta is continuous with the aortic arch and is divided into the superior thoracic aorta and inferior abdominal aorta by the diaphragmthe diaphragm

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Figure 21-25a Major Arteries of the Trunk

Aortic arch

Internal thoracic

Thoracic aorta

Somatic Branches ofthe Thoracic Aorta

Intercostal arteries

Superior phrenic

Inferior phrenic

Diaphragm

Visceral Branches ofthe Thoracic Aorta

Bronchial arteries

Esophageal arteries

Mediastinal arteries

Pericardial arteries

Adrenal

Renal

Gonadal

Lumbar

Terminal segmentof the aorta

Common iliac

Median sacral

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

Celiac Trunk

Left gastric

Splenic

Common hepatic

Superior mesenteric

Abdominal aorta

Inferior mesenteric

Figure 21-27 Arteries of the Lower LimbCommon

iliac

Externaliliac

Superiorgluteal

Inguinalligament

Deepfemoral

Lateralfemoral

circumflex

Medialfemoral

circumflex

Femoral

Internaliliac

Lateralsacral

Internalpudendal

Obturator

Descendinggenicular

Superior gluteal

Right externaliliac

Deep femoral

Lateral femoralcircumflex

EXTERNAL ILIAC

Popliteal

Anterior tibial

Posteriortibial

Fibular

Dorsalis pedis

Medial plantar

Lateral plantar

Dorsal arch

Plantar arch

Anterior view Posterior view A flowchart of blood flow to a 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 andfoot

Quadricepsmuscles

Adductor muscles,obturator muscles,hip joint

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

• The superior vena cava drains blood from the head and neck

• The inferior vena cava drains blood from the remainder of the body

Systemic Veins

remainder of the body

Figure 21-28 An Overview of the Major Systemic Veins

VertebralExternal jugular Internal jugular

Brachiocephalic

Superior vena cava

Intercostal veins

Inferior vena cavaRenal

Gonadal

Subclavian

AxillaryCephalicBrachial

Basilic

Hepatic veins

Median cubital

Radial

Ulnar

Median antebrachial

Lumbar veins

Left and rightcommon iliac

External iliacInternal iliacPalmar venous arches

Digital veins

Internal iliac

Deepfemoral

Femoral

Posterior tibial

Anterior tibial

Great saphenous

Popliteal

Small saphenous

Fibular

Plantar venous archDorsal venous arch

Superficial veins

Deep veins

KEY

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

Cerebral veins

Cavernous sinus

P t l i

Superior sagittal,sinus (cut)

An inferior view of the brain, showing the venous distribution. For the relationship of these veins to meningeal layers, see Figure 14-3, p. 453.

Occipital sinus

Straight sinus

Transverse sinus

Cerebellar veins

Sigmoid sinus

Internal jugular

Petrosal sinus

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

Occipital

Vertebral

External jugular

Right subclavian

Axillary

Clavicle

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

Internal jugular

Right brachiocephalic

Left brachiocephalic

Superior vena cavaInternal thoracic

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

M di bi l

Adrenal veinsPhrenic veins

Basilic

INFERIOR VENA CAVA

Intercostal veins

HemiazygosAccessory hemiazygos

CephalicAxillaryBrachiocephalicHighest intercostalSubclavian

External jugularInternal jugularVertebral

Lumbar

Gonadalveins

Renal veins

Hepaticveins

Internalthoracic

Azygos

Esophagealveins

Mediastinalveins

SUPERIORVENA CAVA

Brachial

Palmar venousarches

Digital veins

Ulnar

Median antebrachial

Radial

Cephalic

Anterior cruralinterosseous

Medialsacral

Basilic

Median cubital

Deep veins

Superficial veinsKEY

External iliac

Internal iliac

Common iliac

Lumbarveins

Figure 21-32 Venous Drainage from the Lower Limb External iliacCommon iliac

Internal iliacGluteal

Internal pudendal

Lateral sacral

ObturatorFemoral

Femoral circumflex

Deep femoral

Femoral

Great saphenous

Popliteal

Smallsaphenous

Anterior tibial

Posterior tibial

Fibular

Dorsal venous arch

Plantar venous archDigital

An anterior view A posterior view

EXTERNAL ILIAC

Smallsaphenous

Femoral

Popliteal

FibularPosterior

tibialAnterior

tibial

Extensive anastomoses interconnectveins of the ankle and foot

Greatsaphenous

KEYSuperficial veins

Deep veins

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

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The Hepatic Portal System

• Blood leaving capillaries supplied by the celiac, superior, and inferior mesenteric arteries flows into the hepatic portal system

• This blood contains substances absorbed by the stomach and intestinesstomach and intestines

• At the liver these compounds are stored, metabolized into other compounds or excreted

• After flowing through the sinusoids of the liver, blood collects in the hepatic portal vein and is discharged into the 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)

Left gastric

Right gastric

Stomach

Spleen

Pancreas

Left gastroepiploic(stomach)

Right gastroepiploic(stomach)

Pancreatic

Descending colon

Splenic Vein and ItsTributaries

Inferior Mesenteric

Liver

transverse colon)

Right colic (ascendingcolon)

Ileocolic (Ileum andascending colon)

Intestinal (small intestine)

Vein and Its Tributaries

Left colic (descendingcolon)

Sigmoid(sigmoid colon)

Superior rectal (rectum)

• Fetal blood flow to the placenta is supplied via paired umbilical arteries

• A single umbilical vein drains from the placenta t th d t hi h ll t bl d f

Fetal Bloodflow

to the ductus venosus, which collects blood from both the umbilical vein and liver and empties into the inferior vena cava

Fetal Circulation of the Heart and Great Vessels

• There is no need for pulmonary function in the fetus

• Two shunts bypass the pulmonary circuit – Foramen ovale or interatrial opening allows blood to

flow from the right to left atrium

– Ductus arteriosus connects the pulmonary and aortic trunks

Cardiovascular Changes at Birth

• At birth the lungs and pulmonary vessels expand

• The ductus arteriosus constricts and becomes ligamentum arteriosum

• A valvular flap closes the foramen ovale

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Figure 21-34a Fetal Circulation

AortaForamen ovale (open)

Ductus arteriosus (open)

Pulmonary trunk

Li

Placenta

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

Right atrium

Foramen ovale(closed)

Left atrium

Pulmonary trunk

Ductus arteriosus(closed)

Blood flow through theneonatal (newborn) heartafter delivery

Inferiorvena cava

Right ventricle

Left ventricle