Cardiovascular System

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Cardiovascular System
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Cardiovascular System

• Helps maintain homeostasis by
• Circulating blood to the lungs (the pulmonary
  circuit) and then to the other tissues of the
  body (systemic circuit)

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Cardiovascular System

• Heart
• Blood vessels
• Arteries
• Capillaries
• Veins

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Closed Circuit

• Two capillary beds where gas exchange occurs
• Lungs O2 in, CO2 out
• Tissues O2 out, CO2 in
• Really two pumps
• Right heart pulmonary circuit pump
• Left heart systemic circuit pump

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Closed Circuit
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Closed Circuit

• Where is the hydrostatic pressure high?
• Where is the pressure low?
• Where is the partial pressure of oxygen high?
• Where is there less oxygen?

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Pericardium

• Visceral pericardium layer next to cardiac
  muscle
• Parietal pericardium layer around the outside
• Pericardial cavity between the visceral and
  parietal layers
• contains 10 to 20 mL of lubricating fluid

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Visceral Pericardium

• Also called the epicardium
• Composed of a simple squamous epithelium (a
  serous membrane that produces pericardial fluid)
  and a thin layer of areolar connective tissue

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Parietal Pericardium

• Fibrous pericardium outside, composed of dense
  irregular CT (pericardial sac)
• Serous pericardium inside (produces pericardial
  fluid), a simple squamous epithelium plus a layer
  of areolar tissue

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Heart External Anatomy

• Atria upper chambers (have expandable flaps
  called auricles)
• Ventricles lower chambers
• Coronary sulcus groove separating atria from
  ventricles
• Interventricular sulcus separates left and
  right ventricles

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Heart Wall

• Epicardium (visceral pericardium)
• Myocardium cardiac muscle tissue
• Thin in L and R atria
• Medium thickness in R ventricle
• Thickest in L ventricle
• Endocardium simple squamous epithelium plus
  areolar CT
• Folds in endocardium form cardiac valves

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Chambers

• Four chambers
• Right atrium
• Right ventricle
• Left atrium
• Left ventricle

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Atria

• Relatively thin myocardium, ridges called
  pectinate muscles
• L and R atria separated by interatrial septum
• Atrial myocardium forms a single functional unit
  called the atrial syncytium (depolarization
  spreads throughout all myocardial cells)

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Ventricles

• Trabeculae carneae muscular ridges found on
  inner surface of ventricles (helps ensure mixing
  of blood?)
• Left ventricle inverted cone shape
• Right ventricle shaped like a pouch
• Ventricular syncytium, interventricular septum

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Heart Valves

• 4 valves, located in fibrous skeleton between
  atria and ventricles
• 2 atrioventricular valves (AV valves)
• Right AV valve tricuspid valve
• Left AV valve bicuspid v. mitral v.
• 2 semilunar valves
• Pulmonary semilunar valve
• Aortic semilunar valve

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AV Valves

• Atrioventricular valves, prevent blood flowing
  back into atria during ventricular contraction
• Tricuspid valve right AV valve
• Bicuspid valve mitral valve left AV valve

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AV Valves

• Attached to edges of AV valves are chordae
  tendineae (dense regular CT)
• Papillary muscles pull on chordae tendineae
  during ventricular contraction to hold valve
  closed against the high pressure in the ventricles

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Semilunar Valves

• Between ventricles and the large blood vessels
  that leave the ventricles (pulmonary trunk,
  aorta)
• 3 flaps each, no chordae tendineae or papillary
  muscles needed

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Direction of Blood Flow

• Blood enters the right atrium from
• Superior and inferior vena cavae
• Coronary sinus
• To right ventricle through tricuspid valve
• Through pulmonary semilunar valve into pulmonary
  trunk and on to the lungs

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Direction of Blood Flow

• From lungs, blood enters left atrium through
  pulmonary veins
• Through bicuspid valve to left ventricle
• Though aortic semilunar valve into aorta
• Aorta branches into arteries supplying systemic
  circuit

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Blood Supply to the Heart

• Left and right coronary arteries originate at
  base of aorta, behind 2 of the 3 flaps of the
  aortic semilunar valve
• Blood returns through great cardiac vein, which
  empties through coronary sinus into right atrium

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Cardiac Muscle Function

• Adjacent cardiac muscle cells connected by
  intercalated discs
• Forms atrial and ventricular syncytia, action
  potential spreads throughout myocardium so atria
  contract as a single unit, ventricles contract as
  a single unit (a fraction of a second later)

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Cardiac Muscle Function

• Myogenic cardiac muscle cells can contract
  without direct stimulation from CNS
• Neurogenic autonomic nervous system can change
  heart rate

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Cardiac Muscle Function

• Action potential
• Rapid depolarization (fast Na channels)
• Plateau phase (slow Ca2 channels)
• Repolarization (slow K channels)plateau phase
  makes action potential in cardiac muscle much
  longer (300 msec) than action potential in
  skeletal muscle (100 msec)

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Conducting System

• Composed of specialized cardiac muscle cells that
  carry electrical impulses but do not contract
• Sinoatrial node (SA node)
• Internodal pathways
• Atrioventricular node (AV node)
• Atrioventricular bundle (AV bundle, bundle of
  His)
• Bundle branches, Purkinje fibers

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Conducting System

• Slow sodium leak (prepotential or pacemaker
  potential) causes cells to gradually depolarize
  until reaching threshold
• First cell to reach threshold is usually in the
  SA node (posterior wall of R atrium)
• Delay at AV node ensures atria finish contraction
  before ventricles begin contraction

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Conducting System

• SA node sodium leak determines heart rate (HR)
• Normal rate would be around 90 to 100
  beats/minute (bpm), except
• Parasympathetic stimulation (vagus nerve) slows
  normal resting HR to 70 bpm
• AV node can support HR around 40 to 60 bpm if SA
  node not functioning

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Electrocardiogram

• A recording of the electrical activity of the
  cardiac muscle
• Electrocardiograph the machine
• Electrocardiogram the recording produced by the
  machine
• Also called EKG or ECG

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Electrocardiogram

• P wave depolarization of atria
• QRS complex depolarization of ventricles
• T wave repolarization of ventricles
• Timing between waves (segments and intervals) and
  size of waves indicate the health of cardiac
  muscle

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Abnormal ECG

• Enlarged P wave enlarged atria, or atrial
  hypertrophy
• Enlarged QRS complex ventricular hypertrophy
  (congestive heart failure?)
• Elevated ST segment hypoxia due to acute
  myocardial infarction?
• Premature ventricular contraction (PVC, also
  called ectopic heartbeat)

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Abnormal Heart Rate

• Arrhythmia any abnormal conduction
• Bradycardia HR lt 60 bpm
• Tachycardia HR gt 100 bpm
• Flutter organized, coordinated contractions gt
  200 bpm
• Fibrillation disorganized, uncoordinated
  contractions that cannot pump blood

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Abnormal Heart Rate

• Atrial flutter and atrial fibrillation usually
  survivable, as ventricles can fill to 70 of
  capacity even if atria not functioning
• Ventricular fibrillation fatal if not corrected
  (defibrillation)

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Cardiac Cycle

• From the end of one heart contraction to the end
  of the next contraction
• Systole contraction
• Diastole relaxation
• First 100 msec atrial systole
• 100 to 375 msec ventricular systole
• 375 to 800 msec both in diastole

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Heart Sounds

• Lubb dup sound represents heartvalves closing
• 1st heart sound (lubb) AV valves closing during
  ventricular contraction
• 2nd heart sound (dup) semilunar valves closing

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Heart Murmurs

• Turbulent blood flow through damaged valves leads
  to a blowing or vibrating sound
• Valvular insufficiency valves not closing
  completely
• Valvular prolapse flaps go past closed
• Valvular stenosis valves too narrow

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Cardiac Output

• The most important single factor in
  cardiovascular physiology is the question, How
  much blood does the heart pump?
• SV EDV - ESV
• CO HR x SV

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Cardiac Output

• ExampleHR 70 bpmEDV 130 mLESV 50 mL

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Regulation of CO

• Heart rate
• Cardioacceleratory (CA) center and
  cardioinhibitory (CI) center (both in medulla
  oblongata)
• Atrial reflex (Bainbridge reflex) right atrium
  stretching signals CA center to increase heart
  rate
• Aortic reflex stretching of aorta signals CI
  center to decrease heart rate
• Carotid sinus reflex similar to aortic reflex
• Drugs, hormones, temperature, age, etc.

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Regulation of CO

• End diastolic volume
• Filling time how long the ventricle is able to
  fill with blood before next contraction
• Venous return how much blood per minute is
  returning through the right atrium

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Regulation of CO

• End systolic volume
• Preload how stretched are the cardiac muscle
  fibers in the ventricle at the end of diastole
• Contractility how much force can be produced
  during contraction
• Afterload how hard is it to open the semilunar
  valve

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Frank-Starling Principle

• Two dead guys Otto Frank and Ernest Starling
• Relationship between ventricular stretching and
  contractile force
• Not too much, not too little, just right

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Cardiac Reserve

• How much additional blood can you move if youre
  running away from a tiger?
• Cardiac reserve (CR) maximum CO minus resting
  CO
• Regular aerobic exercise can dramatically
  increase cardiac reserve

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Congestive Heart Failure

• Also called CHF
• Left heart failure inadequate blood flow to
  systemic circuit, leads to pulmonary edema
• Right heart failure inadequate blood flow to
  pulmonary circuit, leads to systemic edema

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Lymphatic System
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Lymphatic System

• Helps maintain homeostasis by
• Production, maintenance, and distribution of
  lymphocytes
• Return of fluid and solutes from peripheral
  tissues to the blood
• Distribution of some hormones, nutrients, and
  waste products

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Lymphatic System

• Lymph
• Lymphatic vessels
• Lymphocytes
• Lymphoid tissues and organs

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Lymphatic Vessels

• Lymphatic capillaries
• Originate as blind pockets, larger in diameter
  than blood capillaries
• Small lymphatic vessels
• Similar to veins, but contain more valves
• Major lymphatic vessels
• Thoracic duct
• Right lymphatic duct

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Lymphatic Vessels

• Why not just dump the lymph directly into the
  nearest vein?
• Hydrostatic pressure in the vein still too high,
  gradient points the wrong way
• Have to carry the lymph back to the subclavian
  veins, where the pressure is lower

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Lymphoid Organs

• Lymph nodes
• Lymph enters node through afferent lymphatics
• Lymph leaves node through efferent lymphatics
• Filters and purifies lymph before it enters
  venous circulation
• Removes 99 of antigens
• Fixed macrophages and B lymphocytes

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Lymphoid Organs

• Thymus
• Processes lymphocytes, produces thymosins
• Spleen
• Largest lymphoid organ
• Removes old and abnormal blood cells
• Stores iron
• Initiates immune reaction by B and T cells in
  response to antigens in circulating blood

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