Vaskuler Ch20

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    Chapter 20:

    Blood Vessels and Circulation

    Circulatory routes:

    Most common route

    heart arteries arterioles

    capillariesvenules veins

    Portal system

    blood flows throuh two

    consecutive capillary networ!sbefore returnin to heart

    hypothalamus " anterior pituitary

    found in !idneys

    between intestines " liver

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    Circulation #outes: $nastomoses

    $rteriovenous shunt

    artery directly to vein

    finers% toes% ears& heatloss% allows blood to bypass

    e'posed areas durin cold

    Venous anastomosis

    more common

    alternate drainae of orans

    $rterial anastomosis

    collateral circulation

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    (he Vessel )all

    (unica e'ternaoutermost layer

    loose connective tissue

    (unica mediamiddle layer

    usually thic!est& smooth muscle% collaen% some elastic

    smooth muscle for vasoconstriction and vasodilation

    (unica interna

    inner layer% e'posed to blood

    simple s*uamous endothelium

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    +are Vessels

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    $rteries

    Conductin ,elastic- arteries " larest

    pulmonary% aorta and common carotid

    tunica media consists of perforated sheets of elastic

    tissue% alternatin with thin layers of smooth muscle%collaen and elastic fibers

    e'pand durin systole% recoil durin diastole& lessens

    fluctuations in BP .istributin ,muscular- arteries

    distributes blood to specific orans& femoral and splenic

    smooth muscle layers constitute /1 of wall thic!ness

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    Medium Vessels

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    $rteries and Metarterioles

    #esistance ,small- arteries

    arterioles control amount of blood to various orans

    Metarterioles

    short vessels connect arterioles to capillaries

    muscle cells form a precapillary sphincter about

    entrance to capillary

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    mall Vessels

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    Capillaries

    (horouhfare channel " metarteriole continues

    throuh capillary bed to venule

    Precapillary sphincters control which beds are well

    perfused

    only 31 of the capillaries are open at a iven time

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    Control of Capillary Bed Perfusion

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    Control of Capillary Bed Perfusion

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    (ypes of Capillaries

    Continuous " occur in most tissues

    endothelial cells have tiht 4unctions with intercellular

    clefts ,allow passae of solutes-

    5enestrated " !idneys% small intestineorans that re*uire rapid absorption or filtration&

    endothelial cells have filtration pores ,fenestrations- "

    allow passae of small molecules inusoids " liver% bone marrow% spleen

    irreular blood"filled spaces& some have e'tra lare

    fenestrations% allow proteins and blood cells to enter

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    5enestrated Capillary

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    5enestrated 6ndothelial Cell

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    Veins

    Venulespro'imal venule is *uite porous% e'chanes fluid with

    tissues% li!e a capillary% at this point only

    Venous sinuses: veins with thin walls% lare lumens%no smooth muscle

    Veins have lower blood pressure: av77 30mm8

    with little fluctuationthinner walls% less muscular and elastic tissue

    e'pand easily% have hih capacitance

    venous valves aid s!eletal muscles in upward blood flow

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    Blood .istribution% #estin $dult

    High

    Capacitance

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    Principles of Blood 5low

    Blood flow: amountof blood flowin throuh a

    tissue in a iven time ,mlmin-

    Perfusion: rateof blood flow periven massof

    tissue ,mlmin-

    9mportant for delivery of nutrients and o'yen% and

    removal of metabolic wastes

    8emodynamics: physical principles of blood flow

    based on pressure and resistance

    5 P#% ,5 flow% P difference in pressure% #

    resistance to flow

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    Blood Pressure

    Measured at brachial artery of arm

    ystolic pressure: BP durin ventricular systole

    .iastolic pressure: BP durin ventricular diastole

    ;ormal value% youn adult: 320

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    Blood Pressure Chanes )ith .istance

    More pulsatile

    closer to heart

    More pulsatile

    closer to heart

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    $bnormalities of Blood Pressure

    8ypertension

    chronic restin BP A 3100

    can wea!en small arteries and cause aneurysms

    8ypotension

    chronic low restin BP

    causes: blood loss% dehydration% anemia

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    Blood Pressure 2

    9mportance of arterial elasticity

    e'pansion and recoil maintains steady flow of blood

    throuhout cardiac cycle% smoothes out pressure

    fluctuations and stress on small arteries BP rises with ae: arteries less distensible

    BP determined by cardiac output% blood volume

    and peripheral resistance

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    Peripheral #esistance

    Blood viscosity " by #BCs and albumin

    viscosity with anemia% hypoproteinemia

    viscosity with polycythemia % dehydration

    Vessel lenth

    pressure and flow decline with distance

    Vessel radius " very powerful influence over flow

    most ad4ustable variable% controls resistance *uic!ly

    vasomotion: chane in vessel radius

    vasoconstriction% vasodilation

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    +aminar 5low and Vessel #adius

    mall radius averae

    velocity of flow is low

    +are radius averae

    velocity of flow is hih

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    Peripheral #esistance

    Vessel radius ,cont7-

    laminar flow " flows in layers% faster in center

    blood flow ,5- proportional to the fourth power of

    radius ,r-% 5 r1 arterioles can constrict to 3/ of fully rela'ed radius

    if r / mm% 5 ,/1- @3 mmsec& if r 3 mm% 5

    3mmsec

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    5low at .ifferent Points

    5rom aorta to capillaries% flow for / reasonsreater distance traveled% more friction to flowsmaller radii of arterioles and capillaries

    farther from the heart% reater the total cross sectionalarea

    5rom capillaries to vena cava% flow aain

    lare amount of blood forced into smaller channelsnever reains velocity of lare arteries

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    #eulation of BP and 5low

    +ocal control

    ;eural control

    8ormonal control

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    +ocal Control of BP and 5low

    Metabolic theorytissue inade*uatelyperfused%wastesaccumulate

    vasodilation

    Vasoactive chemicalssubstances that stimulate vasomotion& histamine%

    brady!inin

    #eactive hyperemia

    blood supply cut off then restored $nioenesis " rowth of new vessels

    rerowthof uterine linin% around obstructions% e'ercise%malinant tumors

    controlled by rowth factors and inhibitors

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    ;eural Control of BP and 5low

    Vasomotor center of medulla oblonata:

    sympathetic control stimulates most vessels to constrict%

    but dilates vessels in s!eletal and cardiac muscle

    interates three autonomic refle'esbarorefle'es

    chemorefle'es

    medullary ischemic refle'

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    ;eural Control: Barorefle'

    Chanes in BP detected by stretch receptors%baroreceptors% in lare arteries above heart

    aortic arch

    aortic sinuses ,behind aortic valve cusps-

    carotid sinus ,base of each internal carotid artery-

    $utonomic negativefeedbac! response

    baroreceptors send constant sinals to brainstem

    BPcauses rate of sinals to rise% inhibitsvasomotorcenter% sympathetic tone% vasodilation causes BP

    BPcauses rate of sinals to drop% excitesvasomotor

    center% sympathetic tone% vasoconstriction and BP

    B fl

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    Barorefle'

    ;eative 5eedbac! #esponse

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    ;eural Control: Chemorefle'

    Chemoreceptors in aortic body and carotid bodieslocated in aortic arch% subclavian arteries% e'ternal

    carotid arteries

    $utonomic response to chanes in blood chemistryp8% D2% CD2

    primary role: ad4ust respiration

    secondary role: vasomotion hypo'emia% hypercapnia and acidosis stimulate

    chemoreceptors% instruct vasomotor center to cause

    vasoconstriction% BP% lun perfusion and as e'chane

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    Baroreceptors

    Carotid body

    Aortic bodyAortic body

    Chemoreceptors E

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    Dther 9nputs to Vasomotor Center

    Medullary ischemic refle'inade*uate perfusion of brainstem

    cardiac and vasomotor centers send sympathetic sinals to

    heart and blood vessels: cardiac output and BP Dther brain centers

    stress% aner% arousal can also BP

    8 l C l f BP d 5l

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    Angiotensinogen,prohormone produced by liver-

    #enin ,!idney enFyme " low BP-

    Angiotensin I

    $C6 ,aniotensin"convertin enFyme in luns-

    Angiotensin IIvery potent vasoconstrictor

    8ormonal Control of BP and 5low

    $niotensin 99

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    8ormonal Control of BP and 5low 2

    6pinephrine and norepinephrine effectsmost blood vessels

    binds to "adreneric receptors% vasoconstriction

    s!eletal and cardiac muscle blood vessels binds to "adreneric receptors% vasodilation

    $.8 ,water retention-

    patholoically hih concentrations% vasoconstriction $trial natriuretic factor ,urinary sodium e'cretion-

    eneraliFed vasodilation

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    #outin of Blood 5low

    +ocaliFed vasoconstrictionpressure downstream drops% pressure upstream rises

    enables routin blood to different orans as needed

    $rterioles " most control over peripheral resistance

    located on pro'imal side of capillary beds

    most numerous

    more muscular by diameter

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    Blood 5low in #esponse to ;eeds

    $rterioles shift blood flow with chanin priorities

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    Blood 5low Comparison

    .urin e'ercise

    perfusion of luns% myocardium and s!eletal musclesperfusion of !idneys and diestive tract

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    Capillary 6'chane

    Dnly occurs across capillary walls between bloodand surroundin tissues

    / routes across endothelial cells

    intercellular clefts

    fenestrations

    throuh cytoplasm

    Mechanisms involveddiffusion% transcytosis% filtration and reabsorption

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    Capillary 6'chane " .iffusion

    Most important mechanism

    +ipid soluble substances

    steroid hormones% D2and CD2diffuse easily

    9nsoluble substances

    lucose and electrolytes must pass throuh channels%

    fenestrations or intercellular clefts

    +are particles " proteins% held bac!

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    Capillary 6'chane " (ranscytosis

    Pinocytosis% transport vesicles across the cell% e'ocytosis

    9mportant for fatty acids% albumin and some hormones

    ,insulin-

    Capillary 6'chane

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    Capillary 6'chane "

    5iltration and #eabsorption

    Dpposin forcesblood ,hydrostatic- pressure drives fluid out of capillary

    highonarterial endof capillary% lowonvenous end

    colloid osmotic pressure ,CDP- draws fluid intocapillary ,same on both ends-

    results from plasma proteins ,albumin-" more in blood

    oncotic pressure net CDP ,blood CDP " tissue CDP-

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    Capillary 5iltration E #eabsorption

    7 in

    13 out

    Capillary filtration at arterial

    end

    Capillary reabsorption at

    venous end

    Variations

    location,lomeruli"filter%

    alveolar cap7" absorb-

    activity% trauma,filtration-

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    Causes of 6dema

    Capillary filtration ,capillary BP or permeability-poor venous return

    conestive heart failure " pulmonary edema

    insufficient muscular activity!idney failure ,water retention% hypertension-

    histamine ma!es capillaries more permeable

    Capillary reabsorptionhypoproteinemia ,oncotic pressure blood albumin-

    cirrhosis%famine%burns%!idneydisease

    Dbstructed lymphatic drainae

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    Conse*uences of 6dema

    Circulatory shoc!e'cess fluid in tissue spaces causes low blood volume

    and low BP

    (issue necrosiso'yen delivery and waste removal impaired

    Pulmonary edema

    suffocation

    Cerebral edema

    headaches% nausea% seiFures and coma

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    Mechanisms of Venous #eturn Pressure radient

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    !eletal Muscle Pump

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    Venous #eturn and Physical $ctivity

    6'ercise venous return in many waysheart beats faster% harder " CD and BPvesselsofs!eletalmuscles%lunsandheartdilateflow

    respiratory rate action of thoracic pump s!eletal muscle pump

    Venous poolin occurs with inactivity

    venous pressure not enouh force blood upward

    with proloned standin% CD may be low enouh to

    cause diFFiness or syncope

    prevented by tensin le muscles% activate s!eletal m7 pump

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    Circulatory hoc!

    $ny state where cardiac output insufficient to meetmetabolic needs

    cardioenic shoc! " inade*uate pumpin of heart ,M9-

    low venous return ,+V#- shoc! " / principle forms

    +V# shoc!

    hypovolemic shoc! " most common

    loss of blood volume: trauma% bleedin% burns% dehydration

    obstructed venous return shoc! " tumor or aneurysm

    ne't slide

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    +V# hoc! 2

    Venous poolin ,vascular- shoc!lon periods of standin% sittin or widespread

    vasodilation

    neuroenic shoc! " loss of vasomotor tone% vasodilation causes from emotional shoc! to brainstem in4ury

    eptic shoc!

    bacterial to'ins trier vasodilation and capillarypermeability

    $naphylactic shoc!

    severe immune reaction to antien% histamine release%

    eneraliFed vasodilation% capillary permeability

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    #esponses to hoc!

    Compensated shoc!homeostatic mechanisms may brin about recovery

    BP triers barorefle' and production of aniotensin

    99% both stimulate vasoconstrictionif person faints and falls to horiFontal position% ravity

    restores blood flow to brain& *uic!er if feet are raised

    .ecompensated shoc! ,above mechanisms fail-ne't slide

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    #esponses to hoc! 2

    .ecompensated shoc!,life threatenin positive feedbac! loops occur-

    CD myocardial ischemia and infarction CD

    slow circulation disseminated intravascularcoaulation slow circulation

    ischemia and acidosis of brainstem vasomotortone% vasodilation CD ischemia and acidosis of

    brainstem

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    pecial Circulatory #outes " Brain

    (otal perfusion !ept constantfew seconds of deprivation causes loss of consciousness

    1"= minutes causes irreversible brain damae

    flow can be shifted from one active reion to another

    #esponds to chanes in BP and chemistrycerebral arteries: dilate as BP % constrict as BP risesmain chemical stimulus: p8

    CD2 > 82D 82 CD/8>> ,8CD/-" if CD2,hypercapnia- in brain% p8 % triers vasodilation

    hypocapniap8%vasoconstriction%occurs withhyperventilation% may lead to ischemia% diFFiness and

    sometimes syncope

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    (9$s and CV$s

    (9$s " transient ischemic attac!sdiFFiness% loss of vision% wea!ness% paralysis% headache

    or aphasia& lasts from a moment to a few hours% often

    early warnin of impendin stro!e CV$ " cerebral vascular accident ,stro!e-

    brain infarction caused by ischemia

    atherosclerosis% thrombosis% ruptured aneurysm

    effects rane from unnoticeable to fatal

    blindness% paralysis% loss of sensation% loss of speech common

    recovery depends on surroundin neurons% collateral

    circulation

    pecial Circulatory #outes "

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    pecial Circulatory #outes

    !eletal Muscle

    8ihly variable flow

    $t rest

    arterioles constrict% total flow about 3+min

    .urin e'ercise

    arterioles dilate in response to epinephrine and

    sympathetic nerves

    precapillary sphincters dilate due to lactic acid% CD2blood flow can increase 300 fold

    Muscular contraction impedes flow

    isometric contraction causes fatiue faster than isotonic

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    pecial Circulatory #outes " +uns

    +ow pulmonary blood pressureflow slower% more time for as e'chane

    capillary fluid absorption

    oncotic pressure overrides hydrostatic pressure

    Ini*ue response to hypo'ia

    pulmonary arteries constrict% redirects flow to better

    ventilated reion

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    Pulmonary Circulation

    Pulmonary trun! to pulmonary arteries to each lun

    lobar branches for each lobe ,/ riht% 2 left-

    Pulmonary veins return to left atrium

    increased D2 and reduced CD2 levels

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    Pulmonary Capillaries ;ear $lveoli

    Bas!etli!ecapillary beds

    surround the

    alveoli 6'chane of

    ases with air at

    alveoli

    4 i i

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    Ma4or ystemic $rteries

    upplies o'yen and nutrients to all orans

    $ i l i

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    $rterial Pressure Points

    ome ma4or arteries close to surface "" allows palpation for

    pulse and serve as pressure points to reduce arterial bleedin

    M 4 B h f h $

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    Ma4or Branches of the $orta

    $scendin aortariht E left coronary arteries supply heart

    $ortic arch

    brachiocephalic riht common carotid supplyin riht side of head

    riht subclavian supplyin riht shoulder E upper limb

    left common carotid supplyin left side of headleft subclavian supplyin shoulder and upper limb

    .escendin aorta is thoracic aorta above

    diaphram and abdominal aorta below diaphram

    M 4 B h f h $

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    Ma4or Branches of the $orta

    $ i f h 8 d d ; !

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    $rteries of the 8ead and ;ec!

    Common carotid divides into internal E e'ternal carotids

    e'ternal carotid supplies most e'ternal head structures

    $ i l l f h B i

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    $rterial upply of the Brain

    Paired vertebral aa7 combine to form

    the basilar artery on the pons

    Circle of )illis on base of brain is

    formed from anastomosis of basilar

    E paired internal carotid aa

    upplies brain% internal ear and

    orbital structures

    anterior% middle Eposterior cerebral

    superior% anterior E

    posterior cerebellar

    $ t i f th I +i b

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    $rteries of the Ipper +imb

    ubclavian passes

    between clavicle E

    3st rib

    Vessel chanes names

    as passes to differentreions

    subclavian to a'illary

    to brachial to radial E

    ulnarbrachial used for BP

    and radial artery for

    pulse

    $ t i f th (h

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    $rteries of the (hora'

    (horacic aorta supplies viscera E body wallbronchial% esophaeal and mediastinal branches

    posterior intercostal and phrenic arteries

    9nternal thoracic% anterior intercostal E pericardiophrenic

    arise from subclavian artery

    M 4 B h f $bd i l $ t

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    Ma4or Branches of $bdominal $orta

    +ower limb+ower limb

    JidneyJidney

    H9H9

    H9H9

    H9H9

    C li ( ! B h

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    Celiac (run! Branches

    Branches of celiac trun! supply upper abdominal viscera ""

    stomach% spleen% liver E pancreas

    M t i $ t i

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    Mesenteric $rteries

    $ t i f th + +i b

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    $rteries of the +ower +imb

    Branches to the lower limb arise from e'ternal iliac

    branch of the common iliac artery

    M 4 t i V i

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    Ma4or ystemic Veins

    .eep veins run parallel to arteries while superficial

    veins have many anastomoses

    . V i f 8 d d ; !

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    .eep Veins of 8ead and ;ec!

    +are% thin"walled dural sinuses form in between layers of

    dura mater ,drain brain to internal 4uular vein-

    fi i l V i f 8 d E ; !

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    uperficial Veins of 8ead E ;ec!

    Branches of internal and e'ternal 4uular veins drain the

    e'ternal structures of the head

    Ipper limb is drained by subclavian vein

    e fi i l E .ee Vei f I e +i b

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    uperficial E .eep Veins of Ipper +imb

    9nferior Vena Cava E Branches

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    9nferior Vena Cava E Branches

    ;otice absence of veins drainin the viscera """

    stomach% spleen% pancreas and intestines

    +ower limb+ower limb

    JidneyJidney

    +iver+iver

    Veins of 8epatic Portal ystem

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    Veins of 8epatic Portal ystem

    .rains blood from viscera ,stomach% spleen and

    intestines- to liver so that nutrients are absorbed

    uperficial and .eep Veins of +ower +imb

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    uperficial and .eep Veins of +ower +imb