The Circulatory System:

1
The Circulatory System

• Blood Vessels and Circulation

2
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

3
Anatomy of Blood Vessels

• Arteries carry blood _______________________
• Veins ___________________________________
• _____________ connect smallest arteries to veins

4
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

5
Large Vessels
6
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

7
Arteries and Metarterioles

• Resistance (small) arteries/arterioles
• control amount of blood to tissues
• ______________________-
• short vessels connect arterioles to capillaries
• ______________________________ ___________________
  ___________

8
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

9
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

10
Types of Capillaries (cont.)

• _______________ - liver, bone marrow, spleen
• irregular blood-filled spaces some have extra
  large fenestrations, allow proteins and blood
  cells to enter

11
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
• __________________________
• veins with thin walls, large lumens, no smooth
  muscle

12

• Artery
• Vein
• Vessel with thickest tunica media

13
Circulatory Routes

• Most common route
• heart ? arteries ? ______________ ? capillaries
  ? venules ? veins
• ___________________
• blood flows through two capillary networks
  before returning to heart
• kidneys
• between ________ _______________

14
Anastomoses

• Where 2 blood vessels merge
• ____________________
• artery flows directly into vein
• ____________________
• most common, blockage less serious
• ____________________ ____________________
• Arterial anastomosis
• _____________________ (coronary)

15
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

16
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

17
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 ______ _____________________
  _____________________ _____________________

18
Abnormalities of Blood Pressure

• ___________________
• chronic resting BP gt 140/90
• consequences
• can weaken small arteries and cause aneurysms
• ___________________
• chronic low resting BP
• caused by ______________________________

19

• Chronic low BP
• physical principles of blood flow based on
  pressure and resistance
• diastolic pressure (1/3 of pulse pressure)
• Pressure during ventricular contraction
• systolic diastolic
• rate of blood flow per given mass of tissue
  (ml/min/g)

• Mean arterial pressure
• Systolic pressure
• Pulse pressure
• Hypotension
• Perfusion
• Hemodynamics

20
Peripheral Resistance

• Blood viscosity (RBCs 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

21
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

22
Regulation of BP and Flow

• _______________
• Neural control
• _______________

23
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

24
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

25
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

26
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

27
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 ________________________

28
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

29
Blood Flow in Response to Needs

• Arterioles shift blood flow with changing
  priorities
• During exercise
• ? perfusion of lungs, myocardium and skeletal
  muscles ? perfusion of kidneys and digestive
  tract

30
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)

31
Capillary Filtration and Reabsorption

• Capillary filtration at arterial end
• Capillary reabsorption at venous end

32

• converts angiotensinogen ? angiotensin
• Pressure of fluid through vessels
• Hormone produced by heart
• Increases Na absorption, blood volume, blood
  pressure
• Potent vasoconstrictor formed from precursor
• Pressure of fluid attracted to dissolved
  compounds
• Growth of new vessels

• Angiogenesis
• Atrial natriuretic factor
• Renin
• Aldosterone
• Hydrostatic pressure
• Colloid osmotic pressure
• Angiotensin II

33
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 ______________________

34
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

35
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

36
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

37
Circulatory Shock

• Cardiac output insufficient to meet metabolic
  needs
• ____________________ - inadequate pumping of
  heart (MI)
• low venous return (LVR) shock - 3 principle forms
• ________________________ shock - most common
• loss of blood volume trauma, burns, dehydration
• obstructed venous return shock
• __________________________________
• venous pooling (vascular) shock

38
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

39
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

40
TIAs and CVAs

• ________________________________________
• 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

41
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

42

• Bacterial toxins
• Suffocation
• Loss of blood
• Inadequate heart action
• Brain infarction
• Vasodilation associated with long periods of
  inaction

• Hypovolemic shock
• cerebral vascular accident (stroke)
• Septic shock
• Venous pooling shock
• Pulmonary edema
• Cardiogenic shock

43
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

44
Major Systemic Arteries

• Supplies oxygen and nutrients to all organs

45
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

46
_____________________

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

47
Major Systemic Veins

• Deep veins run ______________ to arteries while
  superficial veins have many anastomoses

48
Deep Veins of Head and Neck

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

49
Veins of _____________ System

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