VASCULATURE, HEMODYNAMICS AND THEIR PATHOPHYSIOLOGY

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VASCULATURE, HEMODYNAMICS AND THEIR
PATHOPHYSIOLOGY
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Blood Flow

• Blood vessels arteries, veins
• Three tissue layers (inside to outside)
• Intima
• Epithelium connective tissue
• Media
• Smooth muscle elastic tissue
• Externa
• Connective elastic tissue

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Arteries

• Thick to thin
• Accommodate pressure changes
• Blood ejected as heart contracts
• Contraction/relaxation of arteriolar smooth
  muscle
• Controls lumen size
• Controls fluid pressure inside lumen
• REMEMBER closed circuit of tubes
• Fluid pressing against the walls fluid pressure
• If vessel clamped, inside opening now smaller,
  but contains same amount of fluid. What does
  this do to fluid pressure?

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Veins

• Relatively thin, less elastic
• Larger diameter
• Some w/ valves
• Flow toward heart assisted by skeletal muscle
  contraction

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Systemic circulation controlled neurally

• Sympathetic only
• NOTE One of the few sites w/out dual
  innervation
• Cardiovascular control center
• Baroreceptors, chemoreceptors in arterial walls
• Baroreceptors blood pressure changes
• Chemoreceptors blood levels O2, CO2 and H
• Signal cardiovascular control center

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Some characteristics

• Compliance increase in volume vessel can
  accommodate w/ increased pressure
• Depends on ratio elasticmuscle fibers in vessel
  walls
• Which types of vessels are most compliant?
• Why do they need to be?
• Determines vessel's response to changes in
  pressures
• Blood pressure (use mean arterial pressure (MAP))
• Depends on compliance of arteries and mean blood
  vol in arterial system
• If patient had hardening of the arteries
  would blood pressure be higher, lower or show no
  change?
• If patient had kidney problem and retains water
  would blood pressure be higher, lower or show no
  change?

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Lymphatic System

• Vascular system runs parallel to blood
  vasculature
• Similar to blood vasculature (closed system of
  tubes filled with fluid)
• Opens to blood vasculature at vena cava
• Lymph nodes
• Lie along lymphatic vessels
• Have cells, lymphocytes, wbcs
• Filter lymph (fluid)
• Break down microbes/damaged cells/toxins

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Lympatic system contd

• Lymph fluid filling lymphatic vessels.
• Mostly water, proteins
• Begins as ISF
• Drains to lymphatic capillaries ? lymphatic
  vessels ? lymph ducts ? veins
• REVIEW FROM EARLIER TOPICS
• What is ISF?
• What is it called when a disease or dysfunction ?
  incrd ISF?
• What would happen to the ISF if the lymphatic
  vessels were blocked?

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Diseases of the Veins

• Thrombus, embolism
• Thrombus blood clot attached to vessel wall
• Embolism obstruction of vessel by matter
  circulating in bloodstream
• Fat, air, infants cells (in pregnant women)
• Thromboembolism blood clot detached from the
  vessel wall that circulates

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A coronary thrombosis is seen microscopically
occluding the remaining small lumen of this
coronary artery.
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Venous Diseases contd

• Formation of thrombus
• Platelets adhere to vessel wall where
  irregularities
• Hypertension may harm vessel wall over time
• Other platelets stick to the first ? platelet
  aggregation and coagulation cascade
• Rbcs/wbcs also trapped where blood flow
  turbulent ? layers of rbcs, wbcs and platelets

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Venous Diseases contd

• Thrombus, etc.
• Causes
• Aging
• Immobilization cells may deposit when vessels
  not compressed with muscle contraction
• Injury to vessel endothelium
• Common in hypertension
• Increased clotting response

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Venous Diseases contd

• Effects of thrombi
• Decreased venous emptying
• Increased venous pressures
• Edema
• Pain
• Treatment
• Anticoagulants, fibrinolytics

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Diseases of the Arteries

• Arterial occlusions
• Arteriosclerosis
• Abnormal thickening, hardening of arterial vessel
  walls
• Smooth muscle and collagen stiffen vessel middle
  layer
• Lipids and cholesterol deposit on inner layer
• Atherosclerosis -- affects larger vessels
• Fat, fibrin deposit on the inner vessel walls ?
  atheroma
• Few symptoms unless 60 of the blood supply is
  blocked
• NOTE Atherosclerosis as sub-category of
  arteriosclerosis
• Arteries stiffen, harden, in response to chronic
  assault or dysfunction
• Atherosclerosis atheroma (or deposits) form,
  enlarge, further complicating blood flow

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This is a normal coronary artery with no
atherosclerosis and a widely patent lumen that
can carry as much blood as the myocardium
requires.
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The degree of atherosclerosis is much greater in
this coronary artery, and the lumen is narrowed
by half. A small area of calcification is seen in
the plaque at the right.
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Arterial Diseases contd

• Arterial occulsions contd
• Progressive over years
• Fatty streaks of lipid material appear as yellow
  streaks, spots
• Mainly in bends, branches of vessels
• Common in most older than about 20 years
• Atheromas when fatty deposits complicated further
  with calcium, cell debris
• ? Arterial wall degeneration
• Due to
• Injury response aging
• Repeated deposits of blood elements

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Here is occlusive coronary atherosclerosis. The
coronary at the left is narrowed by 60 to 70.
The coronary at the right is even worse with
evidence for previous thrombosis with
organization of the thrombus and recanalization
such that there are three small lumens remaining.
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Arterial Diseases contd

• Arterial occlusions contd
• Modifiable/nonmodifiable factors put some at risk
• Modifiable risk factors
• 1. Hyperlipidemia incrd plasma lipoproteins
• Caused by diet, disease, genetic defects
• Lipoproteins -- carrier proteins for fats in
  bloodstream

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Arterial Diseases contd

• Arterial occlusions contd
• Modifiable risk factors contd
• 2. Hypertension - may cause or exacerbate
  arteriosclerosis
• Causes trauma to arterial walls
• 3. Cigarette smoking STOP!!
• ? vascular damage
• Nicotine CNS effects ? incrd heart rate and
  incrd vasoconstriction ? incrd blood pressure
  (hypertension)
• Platelet adhesiveness incrd with tars, chemicals
  in cigarette smoke
• Decrd O2 in arterial blood of smokers (CO
  replaces O2 on Hb in rbcs)

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Arterial Diseases contd

• Arterial occlusions contd
• Modifiable risk factors contd
• 4. Diabetes (unrelieved especially adult-onset)
  
• ? incrd lipid levels, hypertension, obesity
• Chronic hyperglycemia affects blood and vascular
  wall cells
• Non-modifiable risk factors
• 1. Sex (males are at greater risk)
• 2. Age
• 3. Juvenile diabetes
• 4. Genetic predisposition

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Arterial Diseases contd

• Arterial occlusions contd
• Clinical
• Incrd blood pressure
• Decrd oxygen at tissues ? pain, wasting, etc.
• Treatment
• Reduce fat intake
• Drugs to decrease blood lipids
• Reduce risk factors (STOP SMOKING!! treat
  hypertension, etc.)

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Arterial Diseases contd

• Other arterial problems
• Aneurism - dilation arterial wall
• ? Incrd vessel wall tension/stress
• Layers of clot develop
• Stagnant blood flow at region of balloon
• Asymptomatic until rupture (often) then ?
  embolism may ? ? death
• Treatment by surgical repair

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Arterial Diseases contd

• Hypertension consistent increase in arterial
  blood pressure.
• ? Damage of vessel walls
• If arteries constrict over time and have incrd
  pressure within ? thickening of artery walls to
  withstand stress
• ? Narrowing of arterial lumen
• ? Inflammatory response

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Arterial Diseases contd

• Primary hypertension
• No specific cause identified
• Can happen with
• Retention of sodium and water ? incrd blood
  volume
• Secondary hypertension
• Some systemic disease ? incrd cardiac output or
  incrd vascular resistance
• So heart pumps more blood w/ every beat or
  vessels resist pressure
• Ex kidney dysfunctions or some endocrine
  disorders
• About 5-10 of all hypertension

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Arterial Diseases contd

• Complicated hypertension
• Sustained hypertension ? pathology at other sites
• Chronic pressures ? edema and tissue damage
• Most common organs effected heart, kidney,
  eyes, brain
• Treatment
• Modify lifestyle
• Drugs
• NOTE compliance difficult