Lesson 7
1. Describe the 3 anatomical layers of the artery.
Tunica intima
o Innermost endothelium
o Barrier between blood and vessel
Tunica media
o Smooth muscle
o Thickest layer
o Separated from other layers by elastic layers
Stretches during systole, recoils during diastole to propel blood
forward
Tunica externa (adventitia)
o Contains nourishing blood vessels, lymphatics and nerves
2. Discuss the functions of the endothelium, including functions of transport, anti-
coagulation, signaling and vessel size regulation.
Barrier to transfer of large molecules into interstitial space
Produces heparin, thrombomodulin and plasminogen activators to keep blood
from clotting as it slows
Releases nitric oxide and prostacyclin into circulation to relax vessel
Produce natriuretic hormone for volume control
o Natriuretic hormone is released during volume overload
Modulate the size of the vessel
Release chemokines (signals) for immune cells
3. Identify the functions of the tunica media, especially regulation of vessel diameter for
peripheral vascular resistance.
Smooth muscle
o Relax or constrict in response to endothelial signals
o Number of layers varies with size of vessel
Controls peripheral vascular resistance
o PVR = how much work LV has to do to deliver blood to periphery
Produces collagen, elastin and proteoglycans to repair itself
Produce interleukins and tumor necrosis factor to assist with inflammation
Atherosclerosis is a disease of the tunica media
4. Explain the terms: peripheral vascular resistance, capacitance, and laminar flow.
PVR
o Peripheral vascular resistance is the resistance in the circulatory system
that is used to create blood pressure, the flow of blood and is also a
component of cardiac function. When blood vessels constrict
(vasoconstriction) this leads to an increase in PVR.
Capacitance
o Vessels capable of holding and storing blood.
o Low pressure reservoirs of blood in venules
Laminar Flow
, o Flow in which blood travels smoothly or in regular paths, in contrast to
turbulent flow, in which blood undergoes irregular fluctuations and mixing
o Laminar Flow
Sluggish flow at walls of vessel
Smooth flow in the middle
o Turbulent Flow
Obstructions to flow, create turbulence
Like the rapids in a river
Resistance increased
Clotting risk increased
5. Use Poiseuille's law to describe the relationship of pressure and resistance in regulating
blood pressure.
Poiseuille’s law
o Resistance is inversely proportional to the radius of the vessel
The smaller the diameter the greater the resistance
The larger the diameter the lesser the resistance
o Vessels that are long have more resistance than several vessels in
parallel
Think about traffic flow on one highway versus many smaller
parallel roads
6. Identify how the baroreceptors regulate blood pressure through the sympathetic nervous
system.
Baroreceptors sense a change in tension in aortic arch (pressure of the blood
leaving the left ventricle)
o If low, epinephrine increases HR and norepinephrine to constrict
arterioles → increases BP
, o If high, vagus is stimulated through parasympathetic NS to slow HR and
relax blood vessels → decreases BP
7. Identify the hormonal regulation of blood pressure.
Antidiuretic hormone
o Prevents loss of fluid through kidneys
Aldosterone
o Retains sodium to retain water
Renin-angiotensin system (RAAS)
o Renin (from kidney) is stimulated by
Low renal artery pressures
Low levels of Na in blood at renal artery
Low serum potassium
o Opposed by the natriuretic peptides
Formed in the atria, ventricles, brain and endothelium
8. Explain the outcome of turbulent blood flow.
Resistance increased
Clotting risk increased
9. Explain the factors regulating blood pressure
Poiseuille’s law (explanation above)
Baroreceptors (explanation above)
Hormonal Factors (explanation above)
Chemoreceptors
o Sense a change in blood pH
Acidosis increases respiratory rate and depth to blow off CO2
Alkalosis inhibits stimulation of chemoreceptors
10. Define the term "shock".
Shock is inadequate delivery of oxygen and nutrients that are necessary for
cellular function
o Whenever cellular oxygen demand outweighs supply, both the cell and
the organism are in a state of shock
Not all tissues and organs will experience the same amount of
oxygen imbalance for a given clinical disturbance
o Prolonged shock states can lead to multiorgan system failure/multiple
organ dysfunction
11. Compare and contrast the 4 classifications of shock including the volume of blood lost
and signs and symptoms.
Class I
o <15% of blood volume
o Generally well tolerated, commonly seen after blood donation
o Treatment with oral rehydration or judicious use of IV fluids
Class II
o 15-30% volume loss
o S/S: tachycardia, anxiety, lowered urine output, thirst
o Treatment with IV crystalloids, control low BP to maintain MAP of 50-60
Class III
o 30-40% blood loss
o S/S: decreased BP, tachycardia, minimal urine output, confusion
, o Patient is unable to compensate for loss
o Treatment is control of bleeding and transfusion
Class IV
o >40% blood loss
o Rapidly fatal
o S/S: Profoundly hypotensive, cool extremities, minimal or no urine output,
minimally responsive to stimuli
o Treatment is control of bleeding and transfusion
12. Explain the pathophysiologic basis for tachycardia, low urine output, anxiety, confusion
and thirst seen with hemorrhage.
Tachycardia
o The body can quickly sense a fall in blood pressure through its arterial
and cardiopulmonary baroreceptors → activates the sympathetic nervous
system → increase heart rate/contractility and constrict blood vessels
(increase systemic vascular resistance). Cardiac output is redistributed
from less important organs to the brain and heart, both of which are
critical for survival.
Low urine output/thirst
o Kidneys release Renin following hemorrhage leading to increased
circulating levels of angiotensin II and aldosterone. This causes vascular
constriction, enhanced sympathetic activity, stimulation of vasopressin
release, activation of thirst mechanisms, and very importantly, increased
renal reabsorption of sodium and water to increase blood volume.
Anxiety/confusion
o Lack of oxygen to the brain → AMS
13. Describe how blood is diverted from or to organs of "communist" or "capitalist" nature.
Capitalist organs are the brain and heart
o You can live less than 2 minutes without them
o Blood flow is preferentially shunted to them to keep the body alive
Communist organs are all the rest
o You can live for minutes to hours to days without them
o Blood is preferentially shunted from them to the capitalists when in short
supply
Probably not intended to go on for hours
14. Relate the intended effects of the sympathetic nervous system and hormonal response
to blood loss.
Decreased cardiac filling → Decreased intraventricular pressures and volumes
→ Sympathetic NS stimulation → increase PVR and contractility of heart
o Loss of blood in “communist organs”
Hormonal release
o Cortisol and beta-endorphin
o ADH to reserve water
o Renin to increase aldosterone
15. Discuss how the chest, pelvis and abdomen can be sites of occult blood loss.
Internal bleeding – damage to organs not visible (occult blood loss)
1. Describe the 3 anatomical layers of the artery.
Tunica intima
o Innermost endothelium
o Barrier between blood and vessel
Tunica media
o Smooth muscle
o Thickest layer
o Separated from other layers by elastic layers
Stretches during systole, recoils during diastole to propel blood
forward
Tunica externa (adventitia)
o Contains nourishing blood vessels, lymphatics and nerves
2. Discuss the functions of the endothelium, including functions of transport, anti-
coagulation, signaling and vessel size regulation.
Barrier to transfer of large molecules into interstitial space
Produces heparin, thrombomodulin and plasminogen activators to keep blood
from clotting as it slows
Releases nitric oxide and prostacyclin into circulation to relax vessel
Produce natriuretic hormone for volume control
o Natriuretic hormone is released during volume overload
Modulate the size of the vessel
Release chemokines (signals) for immune cells
3. Identify the functions of the tunica media, especially regulation of vessel diameter for
peripheral vascular resistance.
Smooth muscle
o Relax or constrict in response to endothelial signals
o Number of layers varies with size of vessel
Controls peripheral vascular resistance
o PVR = how much work LV has to do to deliver blood to periphery
Produces collagen, elastin and proteoglycans to repair itself
Produce interleukins and tumor necrosis factor to assist with inflammation
Atherosclerosis is a disease of the tunica media
4. Explain the terms: peripheral vascular resistance, capacitance, and laminar flow.
PVR
o Peripheral vascular resistance is the resistance in the circulatory system
that is used to create blood pressure, the flow of blood and is also a
component of cardiac function. When blood vessels constrict
(vasoconstriction) this leads to an increase in PVR.
Capacitance
o Vessels capable of holding and storing blood.
o Low pressure reservoirs of blood in venules
Laminar Flow
, o Flow in which blood travels smoothly or in regular paths, in contrast to
turbulent flow, in which blood undergoes irregular fluctuations and mixing
o Laminar Flow
Sluggish flow at walls of vessel
Smooth flow in the middle
o Turbulent Flow
Obstructions to flow, create turbulence
Like the rapids in a river
Resistance increased
Clotting risk increased
5. Use Poiseuille's law to describe the relationship of pressure and resistance in regulating
blood pressure.
Poiseuille’s law
o Resistance is inversely proportional to the radius of the vessel
The smaller the diameter the greater the resistance
The larger the diameter the lesser the resistance
o Vessels that are long have more resistance than several vessels in
parallel
Think about traffic flow on one highway versus many smaller
parallel roads
6. Identify how the baroreceptors regulate blood pressure through the sympathetic nervous
system.
Baroreceptors sense a change in tension in aortic arch (pressure of the blood
leaving the left ventricle)
o If low, epinephrine increases HR and norepinephrine to constrict
arterioles → increases BP
, o If high, vagus is stimulated through parasympathetic NS to slow HR and
relax blood vessels → decreases BP
7. Identify the hormonal regulation of blood pressure.
Antidiuretic hormone
o Prevents loss of fluid through kidneys
Aldosterone
o Retains sodium to retain water
Renin-angiotensin system (RAAS)
o Renin (from kidney) is stimulated by
Low renal artery pressures
Low levels of Na in blood at renal artery
Low serum potassium
o Opposed by the natriuretic peptides
Formed in the atria, ventricles, brain and endothelium
8. Explain the outcome of turbulent blood flow.
Resistance increased
Clotting risk increased
9. Explain the factors regulating blood pressure
Poiseuille’s law (explanation above)
Baroreceptors (explanation above)
Hormonal Factors (explanation above)
Chemoreceptors
o Sense a change in blood pH
Acidosis increases respiratory rate and depth to blow off CO2
Alkalosis inhibits stimulation of chemoreceptors
10. Define the term "shock".
Shock is inadequate delivery of oxygen and nutrients that are necessary for
cellular function
o Whenever cellular oxygen demand outweighs supply, both the cell and
the organism are in a state of shock
Not all tissues and organs will experience the same amount of
oxygen imbalance for a given clinical disturbance
o Prolonged shock states can lead to multiorgan system failure/multiple
organ dysfunction
11. Compare and contrast the 4 classifications of shock including the volume of blood lost
and signs and symptoms.
Class I
o <15% of blood volume
o Generally well tolerated, commonly seen after blood donation
o Treatment with oral rehydration or judicious use of IV fluids
Class II
o 15-30% volume loss
o S/S: tachycardia, anxiety, lowered urine output, thirst
o Treatment with IV crystalloids, control low BP to maintain MAP of 50-60
Class III
o 30-40% blood loss
o S/S: decreased BP, tachycardia, minimal urine output, confusion
, o Patient is unable to compensate for loss
o Treatment is control of bleeding and transfusion
Class IV
o >40% blood loss
o Rapidly fatal
o S/S: Profoundly hypotensive, cool extremities, minimal or no urine output,
minimally responsive to stimuli
o Treatment is control of bleeding and transfusion
12. Explain the pathophysiologic basis for tachycardia, low urine output, anxiety, confusion
and thirst seen with hemorrhage.
Tachycardia
o The body can quickly sense a fall in blood pressure through its arterial
and cardiopulmonary baroreceptors → activates the sympathetic nervous
system → increase heart rate/contractility and constrict blood vessels
(increase systemic vascular resistance). Cardiac output is redistributed
from less important organs to the brain and heart, both of which are
critical for survival.
Low urine output/thirst
o Kidneys release Renin following hemorrhage leading to increased
circulating levels of angiotensin II and aldosterone. This causes vascular
constriction, enhanced sympathetic activity, stimulation of vasopressin
release, activation of thirst mechanisms, and very importantly, increased
renal reabsorption of sodium and water to increase blood volume.
Anxiety/confusion
o Lack of oxygen to the brain → AMS
13. Describe how blood is diverted from or to organs of "communist" or "capitalist" nature.
Capitalist organs are the brain and heart
o You can live less than 2 minutes without them
o Blood flow is preferentially shunted to them to keep the body alive
Communist organs are all the rest
o You can live for minutes to hours to days without them
o Blood is preferentially shunted from them to the capitalists when in short
supply
Probably not intended to go on for hours
14. Relate the intended effects of the sympathetic nervous system and hormonal response
to blood loss.
Decreased cardiac filling → Decreased intraventricular pressures and volumes
→ Sympathetic NS stimulation → increase PVR and contractility of heart
o Loss of blood in “communist organs”
Hormonal release
o Cortisol and beta-endorphin
o ADH to reserve water
o Renin to increase aldosterone
15. Discuss how the chest, pelvis and abdomen can be sites of occult blood loss.
Internal bleeding – damage to organs not visible (occult blood loss)
