Cardiovascular System

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Cardiovascular System

• Blood Vessels

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Anatomy of Blood Vessels

• Arteries carry blood from the heart to the tissues

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Anatomy of Blood Vessels

• Arterioles are small arteries that connect to
  capillaries

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Anatomy of Blood Vessels

• Capillaries are the site of substance exchange
  between the blood and body tissues

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Anatomy of Blood Vessels

• Venules connect capillaries to larger veins

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Anatomy of Blood Vessels

• Veins convey blood from the tissues back to the
  heart.

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Arteries

• Tunica interna (intima) innermost
• Tunica media middle layer
• Tunica externa outer layer

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Tunica Intima

• Composed of
• simple squamous epithelium (endothelium)
• Internal elastic membrane

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Tunica Media

• Rich in smooth muscle and elastic fibers

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Tunica Media

• Maintains elasticity and contractility

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Tunica Externa

• Rich in elastic and collagen fibers

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Functional Properties of Arteries

• Elasticity
• Contractility

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Elasticity

• Due to the elastic tissue in the tunica intima
  and media

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Elasticity

• Allows arteries to accept blood under great
  pressure from the contraction of the ventricles

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Contractility

• Due to the smooth muscle in the tunica media

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Contractility

• Allows arteries to increase or decrease lumen size

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Contractility

• Sympathetic stimulation of alpha 1 receptors on
  cutaneous arteries causes vasoconstriction

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Contractility

• Sympathetic stimulation of beta 2 receptors on
  arteries supplying skeletal muscle causes
  vasodilation

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Elastic Arteries

• Elastic Arteries Large arteries with more
  elastic fibers and less smooth muscle

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Elastic Arteries

• Example aorta, sublcavian, and pulmonary arteries

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Elastic Arteries

• Also called conducting arteries because they
  conduct blood from the heart to medium sized
  arteries

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Muscular or distributing arteries

• Medium sized and have a large amount of smooth
  muscle and distribute blood to various parts of
  the body

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Muscular or distributing arteries

• Examples brachial, femoral, and popliteal
  arteries

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Arterioles

• Very small arteries that deliver blood to
  capillaries

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Capillaries

• Connect arterioles and venules

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Capillaries

• Microcirculation flow of blood through the
  capillaries

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Capillaries

• Capillaries are found near almost every cell in
  the body

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Capillaries

• Function Permit the exchange of nutrients and
  wastes between the blood and tissue cells

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Capillaries

• Composed of a single layer of cells (endothelium)
  and a basement membrane

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Capillaries

• Two types
• Continuous
• Fenestrated

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Capillaries

• Continuous composed of endothelial cells that
  form a continuous tube that contains gaps between
  cells called intercellular clefts

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Capillaries

• Fenestrated capillaries plasma membrane
  contains small pores

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Capillaries

• Materials can cross the blood capillary walls in
  four ways

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Capillaries

• Four Ways
• Intercellular clefts
• Trancytosis using pinocytic vesicles
• Diffusion
• Fenestrations

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Intercellular clefts

• Open in response to histamine (released during
  inflamation) making capillaries more leaky

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Intercellular clefts

• This allows fluid and wbc, and antibodies to go
  from the bloodstream to the site of infection

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Pinocytosis

• Large fats cross via pinocytosis

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Diffusion

• Water, CO2, and O2 cross capillaries by diffusion

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Fenestrations

• Allow small molecules such as water and
  electrolytes to get into the urine

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Fenestrations

• Prevent large proteins and red cells from getting
  into the urine

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Sinusoids

• Discontinuous capillaries

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Sinusoids

• Present in the liver

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Sinusoids

• Allow large molecules such as protein and
  bilirubin to get from the bloodstream into
  hepatocytes

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Venules

• They are small vessels that are formed from the
  union of several capillaries

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Venules

• Merges to form veins

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Venules

• Drain blood from capillaries into veins

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Veins

• Contain 60 of our blood volume

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Veins

• Consist of the same three tunics as arteries

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Veins

• Have a thinner tunica intima and media

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Veins

• Thicker tunica externa

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Veins

• Thinner walled than arteries due to less elastic
  tissue and smooth muscle

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Veins

• Low pressure systems

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Veins

• Contain valves to prevent backflow

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Veins

• Squeezing of the veins by muscles and inspiration
  promote venous return

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Venous Return

• The volume of blood returning back to the heart
  from the systemic veins

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Veins

• Vascular sinuses veins with very thin walls
  with no smooth muscle to alter their diameter
• Example Coronary sinus

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Anastomoses

• Union of the branches of two or more arteries
  supplying the same region

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Anastomoses

• Provide alternate routes for blood to reach a
  tissue or organ

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Anastomoses

• Collateral circulation is the alternate flow of
  blood to a body part through an anastomosis

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Anastomoses

• What is the importance of arteries that
  anastomose?

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Anastomoses

• Occlusion of an end artery interrupts the blood
  supply to a whole segment of an organ, producing
  necrosis of that segment

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Blood Pressure

• Pressure exerted on the walls of a blood vessel

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Blood Pressure

• In a clinical sense, it refers to pressure in
  arteries

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Blood Pressure

• BPCO X TPR

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Blood Pressure

• Systolic and Diastolic fluctuations in the
  pressure are only seen in the arteries and
  arterioles

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Systolic Pressure

• Peak pressure in the arteries with each cardiac
  cycle during ventricular contraction

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Systolic Pressure

• Due to the stroke volume being ejected into the
  aorta

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Diastolic Pressure

• Lowest pressure in the arteries with each cardiac
  cycle

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Diastolic Pressure

• Force of blood recorded during ventricular
  relaxation

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Blood Pressure

• Young adult male 120/80 mm Hg (8-10 mm Hg less
  in a young adult female)

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Resistance

• Depends on three variables
• Blood viscosity
• Vessel length
• Blood Vessel Radius

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Blood Viscosity

• Increased viscosity increases resistance

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Vessel length

• Increased length increases resistance

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Blood Vessel Radius

• Increased radius decreases resistance

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Systemic vascular resistance

• Total peripheral resistance (TPR)

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Systemic vascular resistance

• All of the vascular resistance offered by
  systemic blood vessels

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Mean Arterial Pressure

• MAP Diastolic Pressure X 1/3(systolic pressure
  diastolic pressure)

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Mean Arterial Pressure

• MAP CO X TPR

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Mean Arterial Pressure

• Factors that increase BP
• increase SV
• increase HR
• constrict the blood vessels (increases
  resistance)

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Mean Arterial Pressure

• Factors that decrease BP
• Decrease CO
• Dilate the arteries

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Cardiovascular Center

• A group of neurons in the medulla that regulate
  heart rate, contractility, and blood vessel
  diameter

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Cardiovascular Center

• CV receives input from higher brain regions and
  sensory receptors (baroreceptors and
  chemoreceptors)

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Cardiovascular Center

• Sympathetic impulses along cardioaccelerator
  nerves increase heart rate and contractility

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Cardiovascular Center

• Parasympathetic impulse along vagus nerves
  decrease heart rate

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Cardiovascular Center

• The sympathetic division also continually sends
  impulses to smooth muscle in blood vessel walls
  via vasomoter nerves resulting in a moderate
  state of tonic vasoconstriction

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Neural Regulation of Blood Pressure

• Baroreceptors
• Chemoreceptors

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Baroreceptors

• Pressure-sensitive sensory neurons that monitor
  stretching of the walls of blood vessels

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Baroreceptors

• If blood pressure falls, the baroreceptor
  reflexes
• accelerate heart rate
• increase force of contraction
• promote vasoconstriction

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Baroreceptors

• If pressure increases above normal, the reflexes
  cause
• decrease in sympathetic tone
• increase in parasympathetic tone

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Hormonal Regulation

• Renin leads to the formation of angiotensin II

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Hormonal Regulation

• Angiotensin II causes
• Vasoconstriction
• Secretion of aldosterone, which leads to sodium
  and water retention

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Hormonal Regulation

• Epinephrine and norepinephrine increase CO and
  cause vasoconstriction

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Hormonal Regulation

• ADH causes water retention and a little
  vasoconstriction

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Hormonal Regulation

• Nitric oxide from the endothelial cells causes
  vasodilation

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Hormonal Regulation

• Cortisol keep our arteries sensitive to
  vasoconstricting hormones

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Shock

• Is an inadequate CO that results in failure of
  the CV system to deliver adequate amounts of O2
  and nutrients to meet the metabolic needs of body
  cells

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Shock

• Could result in
• dysfunction of cellular membranes
• abnormal cellular metabolism
• cellular death

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Types of Shock

• 5 main types

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Hypovolemic Shock

• Due to decreased blood volume

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Cardiogenic Shock

• Due to poor heart function

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Vascular Shock

• Due to inappropriate vasodilation

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Obstructive Shock

• Due to obstruction of blood flow

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Neurogenic shock

• Due to decreased sympathetic outflow

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Homeostatic Response

• Activation of renin-angiotensin-aldosterone system

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Homeostatic Response

• Secretion of ADH

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Homeostatic Response

• Activation of the sympathetic division of the ANS

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Circulatory Routes

• Systemic
• Pulmonary
• Hepatic Portal
• Fetal

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Hepatic Portal Circulation

• Collects blood from the veins of the pancreas,
  spleen, stomach, intestines and gallbladder and
  directs it into the hepatic portal vein of the
  liver before it returns to the heart

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Hepatic Portal Circulation

• Enables nutrient utilization and blood
  detoxification by the liver