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The Circulatory System

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					The Circulatory System:

 Blood Vessels and Circulation




                                 20-1
Blood Vessels and Circulation
•   General anatomy of blood vessels
•   Blood pressure, resistance and flow
•   Capillary exchange
•   Venous return and circulatory shock
•   Special circulatory routes
•   Anatomy of
    – pulmonary circuit
    – systemic arteries and veins
                                          20-2
    Anatomy of Blood Vessels




• Arteries carry blood _______________________
• Veins ___________________________________
• _____________ connect smallest arteries to veins
                                                 20-3
Vessel Wall
• __________________ (intima)
  – smooth inner layer
     • repels blood cells and platelets
  – simple squamous ___________
• Tunica media
  – middle layer
  – usually thickest; smooth
    muscle, collagen, some elastic
  – ____________________ for
    vasomotion
• __________________ (tunica
  adventitia)
  – outermost layer
  – loose connective tissue with
    vasa vasorum                          20-4
Large
Vessels




          20-5
                         Arteries
• _______________________ arteries - largest
  – pulmonary, aorta and common carotid
  – tunica media
     • elastic tissue, alternating with layers of smooth muscle,
       collagen and elastic fibers
  – ____________ during systole, recoil during diastole;
    lessens fluctuations in BP
• Distributing (______________-) arteries
  – carries blood to specific organs; femoral and splenic
  – smooth muscle layers makes up 3/4 of wall thickness



                                                                   20-6
 Arteries and Metarterioles
• Resistance (small) arteries/arterioles
  – control amount of blood to tissues
• ______________________-
  – short vessels connect arterioles to
    capillaries
  – ______________________________
    ______________________________




                                           20-7
            Arterial Sense Organs
• Major arteries above heart
• Carotid sinuses
   – walls of internal carotid artery
   – _______________  signals
     brainstem
• _______________________
   – oval bodies near carotids
   – monitor blood chemistry
      • adjust respiratory rate to
        stabilize pH, CO2, and O2
• _______________________
   – walls of aorta
   – same function as carotid
     bodies
                                        20-8
 Types of Capillaries
• only 1/4 of the capillaries
  are open at a given time
• Continuous in most tissues
   – endothelial cells have
     tight junctions with clefts
     to allow passage of
     solutes
• _______________ - kidneys,
  small intestine
   – _____________________
     absorption or filtration
   – filtration pores – allow
     passage of only small
     molecules                     20-9
Types of Capillaries (cont.)
• _______________ - liver,
  bone marrow, spleen
   – irregular blood-filled
     spaces; some have
     extra large
     fenestrations, allow
     proteins and blood
     cells to enter




                               20-10
Veins
• Veins
   – lower blood pressure: 10mmHg with little fluctuation
   – thinner walls, less muscular and elastic tissue
   – expand easily, have high capacitance
   – _________________________________________________
• ________________________
   – venules more porous than capillaries
   – muscular venules have tunica media
• __________________________
                                                           20-11
   – veins with thin walls, large lumens, no smooth muscle
• Artery

• Vein

• Vessel with
  thickest
  tunica media




                 20-12
         Circulatory Routes
• Most common route
   – heart  arteries 
    ______________ 
    capillaries 
    venules  veins
• ___________________
   – blood flows through
    two capillary
    networks before
    returning to heart
     • kidneys
     • between ________
       _______________        20-13
                Anastomoses
• Where 2 blood vessels
  merge
• ____________________
  – artery flows directly into
    vein
• ____________________
  – most common, blockage
    less serious
  – ____________________
    ____________________
• Arterial anastomosis
  – _____________________
                                 20-14
    (coronary)
     Principles of Blood Flow
• ____________________:
  – amt of blood flowing through a tissue in a
    given time (ml/min)
• ____________________:
  – rate of blood flow per given mass of tissue
    (ml/min/g)
• ____________________:
  – physical principles of blood flow based on
    pressure and resistance


                                                  20-15
               Blood Pressure
• _________________________________________
• Measured at brachial artery of arm
• Systolic pressure
  – BP during ___________________________
• Diastolic pressure
  – BP during ___________________________
• Normal value, young adult: ________ mm Hg
• ___________________________
  – systolic - diastolic
  – measure of stress exerted on small arteries
• Mean arterial pressure (MAP):
  – measurements taken at intervals of cardiac cycle, best
    estimate: _________________________________
  – varies with gravity: standing; 62 - head, 180 - ankle 20-16
             Blood Pressure
• Arterial elasticity
   – expansion and recoil
     maintains steady flow,
     smoothes out pressure
     fluctuations and 
     stress on small
     arteries
• BP _________ with age:
  arteries less distensible
• BP determined by ______
  _____________________
  _____________________
  _____________________
                              20-17
Abnormalities of Blood Pressure
• ___________________
  – chronic resting BP > 140/90
  – consequences
    • can weaken small arteries and cause aneurysms
• ___________________
  – chronic low resting BP
  – caused by ______________________________



                                                      20-18
                           • Chronic low BP
• Mean arterial pressure   • physical principles of
                             blood flow based on
• Systolic pressure          pressure and
                             resistance
• Pulse pressure           • diastolic pressure +
                             (1/3 of pulse pressure)
                           • Pressure during
• Hypotension                ventricular
                             contraction
• Perfusion                • systolic – diastolic
                           • rate of blood flow per
• Hemodynamics               given mass of tissue
                             (ml/min/g)
                                                 20-19
       Peripheral Resistance
• Blood viscosity (RBC’s & albumin)
  – ______________________________________
  –  viscosity with polycythemia , dehydration
• ______________________________
  – pressure and flow  with distance (friction)
• Vessel radius - influences flow
  – most adjustable variable, controls resistance
    quickly
  – vasomotion: change in vessel radius
    • vasoconstriction, vasodilation               20-20
       Peripheral Resistance
• Vessel radius (cont.)
  – laminar flow - flows in layers,
    faster in center
  – blood flow (F) proportional to
    the fourth power of radius (r),
    F  r4




                                      20-21
Regulation of BP and Flow

• _______________
• Neural control
• _______________




                            20-22
 Local Control of BP and Flow
• Metabolic theory of ________________
  –  oxygen in tissues or  wastes = vasodilation
• Vasoactive chemicals
  – stimulate vasomotion; histamine, bradykinin
• _________________________
  – blood supply cut off then restored
• _________________ - growth of new
  vessels
  – regrowth of uterine lining, around
    obstructions, exercise, malignant tumors
  – controlled by growth factors and inhibitors   20-23
 Neural Control of BP and Flow
• Vasomotor center of __________________:
  – sympathetic control stimulates vessels to
    constrict
    • but dilates vessels in skeletal and cardiac muscle
  – Integrates, baroreflexes, chemoreflexes,
   medullary ischemic reflex




                                                       20-24
  Neural Control: Chemoreflex
• ______________ in aortic bodies, carotid
  bodies, aortic arch, subclavian arteries,
  external carotid arteries
• Autonomic response to changes in blood
  chemistry
  – _____________________
  – primary role: _____________________
  – secondary role: vasomotion
    • hypoxemia, hypercapnia and acidosis stimulate
      chemoreceptors, instruct vasomotor center to
      cause vasoconstriction,  BP,  lung perfusion and
      gas exchange
                                                      20-25
 Other Inputs to Vasomotor Center

• _______________________
  – inadequate perfusion of ___________
    • cardiac and vasomotor centers send sympathetic
      signals to heart and blood vessels
    •  cardiac output and causes widespread
      vasoconstriction
    •  BP
• Other brain centers
  – stress, anger, arousal can also  BP

                                                       20-26
Hormonal Control of BP and Flow
• ____________________ (prohormone produced
 by liver)

       ______________ (kidney enzyme released
 by low BP)
• Angiotensin I

       ______ (angiotensin-converting enzyme in
 lungs)
             ACE inhibitors block this enzyme lowering BP
• ______________________________
  – very potent ________________________
                                                        20-27
Hormonal Control of BP and Flow
• ________________________
  – promotes Na+ and water retention by kidneys
  – increases blood volume and pressure
• ________________________               ( urinary sodium excretion)
  – generalized vasodilation
• ___________________ (water retention)
  – pathologically high concentrations, vasoconstriction
• Epinephrine and norepinephrine effects
  – most blood vessels
     • binds to -adrenergic receptors, vasoconstriction
  – skeletal and cardiac muscle blood vessels
     • binds to -adrenergic receptors, vasodilation              20-28
        Blood Flow in Response to Needs




• Arterioles shift blood flow with changing priorities
• During exercise
   –  perfusion of lungs, myocardium and skeletal muscles    20-29
     perfusion of kidneys and digestive tract
       Capillary Exchange -
   Filtration and Reabsorption
• Opposing forces
  – blood (________________) pressure drives
    fluid out of capillary
  – ____________________ (COP) draws fluid in
    • plasma proteins (albumin)- more in blood
    • oncotic pressure = net COP (blood COP - tissue COP)
• __________________pressure
  – physical force exerted against a surface by a
    liquid, (BP is an example)

                                                            20-30
Capillary Filtration and Reabsorption
• Capillary filtration at arterial end
• Capillary reabsorption at venous end




                                         20-31
                              • converts angiotensinogen 
• Angiogenesis                  angiotensin

                              • Pressure of fluid through
• Atrial natriuretic factor     vessels


• Renin                       • Hormone produced by heart

                              • Increases Na+ absorption,
• Aldosterone                   blood volume, blood pressure

• Hydrostatic pressure        • Potent vasoconstrictor formed
                                from precursor

• Colloid osmotic pressure    • Pressure of fluid attracted to
                                dissolved compounds
• Angiotensin II
                              • Growth of new vessels       20-32
       Causes of ____________
•  Capillary filtration ( capillary BP or permeability)
   – poor venous return
      • congestive heart failure - pulmonary edema
      • insufficient muscular activity
   – kidney failure (water retention, hypertension)
   – histamine makes capillaries more permeable
•  Capillary reabsorption
   – hypoproteinemia (oncotic pressure  blood albumin)
     cirrhosis, famine, burns, kidney disease
• Obstructed ______________________

                                                            20-33
     Consequences of Edema
• Tissue necrosis
  – oxygen delivery and waste removal impaired
• Pulmonary edema
  – ____________________
• Cerebral edema
  – __________________________________
• ____________________
  – excess fluid in tissue spaces causes low
    blood volume and low BP
                                                 20-34
  Mechanisms of Venous Return
• Pressure gradient
• Gravity drains blood from head
  and neck
• ______________________ in the
  limbs
• _______________________
  – inhale - thoracic cavity expands
    (pressure ) abdominal pressure ,
    forcing blood upward
  – central venous pressure fluctuates
     • blood flows faster with inhalation
• Cardiac suction of expanding
  atrial space

                                            20-35
Venous Return and Physical Activity
• Exercise  venous
  –   heart beats faster, harder -  CO and BP
  –   vessels dilate  flow
  –    respiratory rate  action of thoracic pump
  –    skeletal muscle pump
• __________________________
  – venous pressure not enough force blood upward
  – with prolonged standing, CO may be low enough to
    cause dizziness or syncope
       • prevented by tensing leg muscles, activate skeletal m. pump
  – jet pilots wear pressure suits
                                                                   20-36
             Circulatory Shock
•   Cardiac output insufficient to meet
    metabolic needs
    – ____________________ - inadequate
      pumping of heart (MI)
    – low venous return (LVR) shock - 3 principle
      forms
      1. ________________________ shock - most
         common
         – loss of blood volume: trauma, burns, dehydration
      2. obstructed venous return shock
         – __________________________________
      3. venous pooling (vascular) shock
                                                              20-37
                    LVR Shock
• Venous pooling (vascular) shock
  – long periods of standing, sitting or widespread
    vasodilation
  – ________________ shock - loss of vasomotor tone,
    vasodilation
     • causes from emotional shock to brainstem injury
• ___________________ shock
  – bacterial toxins trigger vasodilation and  capillary
    permeability
• ____________________ shock
  – severe immune reaction to antigen, histamine release,
    generalized vasodilation,  capillary permeability
                                                            20-38
Special Circulatory Routes- Brain
• Total perfusion kept constant
  – seconds of deprivation causes loss of consciousness
  – 4-5 minutes  _______________________________
  – flow shifts from one region to another
• Responds to changes in BP and chemistry
  – cerebral arteries: dilate as BP , constrict as BP rises
  – main chemical stimulus: pH
     • CO2 + H2O  H2 CO3  H+ + (HCO3)-
     • _______________ (CO2 ) in brain, pH , triggers
       vasodilation
     • _______________________,  pH, vasoconstriction
        – occurs with hyperventilation, may lead to
          ischemia, dizziness and sometimes syncope 20-39
               TIA’s and CVA’s
• ________________________________________
  – dizziness, loss of vision, weakness, paralysis,
    headache or aphasia; lasts from a moment to a few
    hours, often early warning of impending stroke
• _______________________________________
  – brain infarction caused by ____________________
     • atherosclerosis, thrombosis, ruptured aneurysm
  – effects range from unnoticeable to fatal
     • blindness, paralysis, loss of sensation, loss of speech
       common
  – recovery depends on surrounding neurons, collateral
    circulation
                                                                 20-40
  Special Circulatory Routes -
             Lungs
• Low pulmonary blood pressure
  – flow slower, more time for gas exchange
  – capillary fluid absorption
    • oncotic pressure overrides hydrostatic pressure
• Unique response to hypoxia
  – pulmonary arteries constrict, redirects flow to
    better ventilated region



                                                        20-41
                         • Bacterial toxins

                         • Suffocation
• Hypovolemic shock
• cerebral vascular      • Loss of blood
  accident (stroke)
• Septic shock
                         • Inadequate heart
• Venous pooling shock     action
• Pulmonary edema
• Cardiogenic shock      • Brain infarction

                         • Vasodilation
                           associated with long
                           periods of inaction
                                              20-42
       Pulmonary Circulation
• Pulmonary trunk to
  pulmonary arteries to
  lungs
  – lobar branches for each lobe
    (3 right, 2 left)
• Pulmonary veins return to
  left atrium
  – increased O2 and reduced
    CO2 levels
• Basketlike capillary beds
  surround alveoli
• Exchange of gases with air
  at alveoli
                                   20-43
   Major Systemic Arteries
• Supplies oxygen and nutrients to all organs




                                                20-44
      Arterial Supply of Brain
• Paired vertebral aa. combine to form______________
  artery on pons
• _________________ on base of brain formed from
  anastomosis of basilar and internal carotid aa
• Supplies brain, internal ear and orbital structures




                                                        20-45
     _____________________
• Major arteries
  close to surface -
  - allows palpation
  for pulse and
  serve as
  pressure points
  to reduce arterial
  bleeding


                             20-46
  Major Systemic Veins
• Deep veins run
  ______________
  to arteries while
  superficial veins
  have many
  anastomoses




                         20-47
 Deep Veins of Head and Neck


• Large, thin-walled dural
  sinuses form in
  between layers of dura
  mater (drain brain to
  internal jugular vein)




                               20-48
 Veins of _____________ System

• Drains blood from
  viscera (stomach,
  spleen and
  intestines) to liver
  so that nutrients
  are absorbed



                             20-49

				
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