Cardiovascular System

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Cardiovascular System
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Basic Overview of Blood Vessels

• MAIN FUNCTION Transport O2, CO2, and nutrients
  around the body
• Arteries and arterioles (carry blood away from
  the heart)
• Veins and venules (carry blood towards the heart)
• Capillaries (where nutrients and O2 diffuse into
  your body tissues and cells)

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The Chambers of the Heart

• Consists of 4 chambers
• Pumping chambers are the ventricles
• - Right ventricle pumps blood to lungs
• - Left vent. pumps blood to rest of body
• Receiving chambers are the atria
• -right atrium receives O2
• poor blood from the body
• - left atrium receives O2 rich
• blood from lungs

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The Valves of the Heart

• Consists of 4 main valves to prevent the backflow
  of blood
• Semi-lunar valves are where blood is pumped out
  of the heart into major arteries
• - Pulmonary semilunar valve (right side)
• - Aortic semilunar valve (left side)
• AV valves between atria and ventricles (tricuspid
  on right, mitral (aka bicuspid) on the left)

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Coronary Blood Vessels

• Coronary arteries supply myocardium (heart
  muscle) with oxygen and nutrients
• Heart attacks occur when a blockage occurs in a
  coronary artery

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Anatomy of Blood Vessels

• Contain three layers (tunics)
• Tunica interna (intima) - inner layer in contact
  with blood which contains the endothelium that
  lines the interior of all vessels
• Tunica media - muscular layer (smooth)
  responsible for vasodilation and vasoconstriction
• Tunica externa (adventitia) - mostly collagen
  (also elastin) to reinforce vessel (nerves and
  lymphatic vessels also invade this layer)

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Blood Pressure

• Definition The force exerted on a vessel wall
  by the bloodstream.
• Usually refers to pressure in arteries closest to
  the heart
• Pressure is higher during systole (contraction of
  ventricles) and lower during diastole (relexation
  of ventricles)
• Typical pressure 120/80 (systolic/diastolic)

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Some Factors Affecting Blood Pressure

• Cardiac Output amount of blood pumped from the
  ventricles per minute
• Peripheral Resistance opposition to blood flow
  in blood vessels away from the heart (blood
  viscosity, blood vessel length and diameter
  affect resistance)
• Blood volume amount of fluid in the blood
  stream at any given time
• Baroreceptors (sensory neurons) in arterial
  walls monitor blood pressure and send signals to
  the vasomotor centers in the medulla to regulate
  changes in BP (see figure 19.8 on pg. 727)

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Hypertension (high blood pressure)

• Why is it dangerous?
• Heart must work harder to pump against a greater
  resistance (can lead to heart failure - weakening
  of the left ventricle)
• More peripheral resistance damages endothelium
  (inner walls) of arteries and can damage small
  blood vessels in many organs (kidneys, eyes for
  ex.)
• Chronic HBP 140/90 or greater

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Atherosclerosis

• Disease of the arterial wall caused by the
  formation of plaques
• Cholesterol is deposited by LDL particles in
  areas of damaged endothelium (1st step in plaque
  formation)
• When plaques rupture, blood clots form leading to
  blockage of small arteries

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Lipoproteins and Cholesterol

• Lipoproteins are molecules that carry cholesterol
  to and from tissues (are produced in the liver)
• LDL (low density - BAD) particles carry
  cholesterol to the tissues (excess cholesterol
  ends up in arterial walls forming plaque)
• HDL (high density - GOOD) particles take
  cholesterol from tissues and blood vessels and
  bring it to the liver for disposal

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Conduction System of Heart

• SA node (pacemaker of heart) in right atrium
• Sends signals to AV node (also in right atrial
  wall)
• Signals travel down septum of heart via Bundle of
  His
• Signal then travels to ventricular walls via
  Purkinje fibers

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ECG (electrocardiogram) a.k.a EKG

• Shows electrical excitation of cardiac conduction
  system
• P wave - atrial depolarization
• QRS wave - ventricular depolarization
• T wave - ventricular repolarization

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The Blood
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Blood Composition

• Blood consists of
• Plasma - mostly water, soluble proteins
• Erythrocytes (red blood cells)
• Buffy coat (Leukocytes (white blood cells),
  platelets)

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The Three Formed Elements

• Erythrocytes (Red Blood Cells) - transports O2
  and CO2 in the blood
• Leukocytes (White Blood Cells) - help to defend
  the body against foreign invaders and cancer
  cells
• Platelets - function in hemostasis (coagulation
  or clotting of blood)
• All are produced during hematopoiesis in red
  bone marrow

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Erythrocytes (RBC)

• Carry respiratory gases (oxygen and CO2) in the
  blood
• Hemoglobin protein binds O2 (see figure 17.4)
• Live about 120 days - old RBCs are broken down in
  liver, spleen and bone marrow
• Contribute to blood viscosity (more RBC means
  thicker blood)
• Erythropoietin (hormone released by kidneys)
  stimulates RBC production or erythropoiesis (see
  figure 17.6 in book)

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Blood antigens and antibodies

• Antigens (also called agglutinogens) are proteins
  on cell membranes that identify the cell as
  belonging to that person
• Antibodies, or agglutinins (proteins that can
  attach to antigens) also circulate in the blood
• A, B, and Rh antigens are used in blood typing
  and transfusions
• Transfusion of the wrong blood type results in
  agglutination (clumping of blood cells as they
  are attacked by antibodies) and hemolysis
  (destruction of erythrocytes)

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Table 17.4 pg 668
Universal donor
Universal recipient