Chapter 18. The Cardiovascular System: The Heart

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Chapter 18. The Cardiovascular System The Heart

• Part I Anatomy and Circulation

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Overview of Circulatory System

• Three components heart, vessels, lymphatic
  system
• General circulation arteries, capillaries,
  veins, (lymphatic vessels)
• Function transport, regulation of temperature,
  protection

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Now the Heart Function Location

• Simply put, the heart is nothing more than a
  transport-system pump.
• Located in the mediastinum
• The base is superior and the apex inferior
• Well protected

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Coverings

• Enclosed by a double-walled sac called the
  pericardium
• Superficial part is the fibrous pericardium
  (dense connective tissue)
• Deep part is the serous pericardium

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Serous pericardium

• Connected to the fibrous pericardium is the
  parietal layer
• The visceral layer forms the external surface of
  the heart itself
• Between is the pericardial cavity filled with
  serous fluid
• Pericarditis is an inflammation of the
  pericardium that hinders fluid production

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Heart wall layers

• Epicardium is the visceral layer of the serous
  pericardium
• Myocardium is the thick muscle layer (cardiac
  muscle fibrous skeleton)
• Endocardium is the inside of the heart (squamous
  epithelium and areolar tissue)

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Chambers external anatomy

• Superior are the two atria (sing. atrium)
• Inferior are the two ventricles
• Atrioventricular grooves (sulci)
• Interventricular sulci

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Atria

• Receiving chambers
• Auricles are small protruding appendages
• Separated by the interatrial septum
• Posterior wall is smooth
• Anterior wall contains muscle bundles called
  pectinate muscles

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More

• (Right) interatrial septum houses the fossa
  ovalis
• Right atrium receives blood from the inferior and
  superior vena cava
• Left atrium receives blood from the (4) pulmonary
  veins

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Ventricles

• Discarding chambers
• Walls contain muscles bundles called trabeculae
  carneae
• Also house cone-shaped muscles called papillary
  muscles

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More

• Left ventricle empties into pulmonary trunk,
  which leads to pulmonary arteries
• Right ventricle empties into the aorta
• Compare thickness of ventricles to atria and
  right to left ventricle

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General circulation

• Right side of heart contributes to pulmonary
  circuit
• Left side contributes to systemic circuit

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Coronary circulation

• Heart does not benefit from the blood inside its
  chambers
• Arterial supply is from R/L coronary arteries ?
  (R) anterior interventricular circumflex
  arteries
• ? (L) posterior interventricular
  marginal arteries

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Coronary veins

• Cardiac veins (great, middle, small, anterior
  cardiac)? coronary sinus ? right atrium
• Deficiency of blood to myocardium angina
  (pectoris)
• Prolonged blockage can cause myocardial
  infarction (MI)

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Heart valves

• Atrioventricular (AV) valves separate
  atria/ventricles
• Right valve is the tricuspid, left is the mitral
  (bicuspid)
• Collagen cords called chordae tendineae attach
  cusps to papillary muscles

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Heart valves (cont.)

• Ventricles separated from major vessels by aortic
  pulmonary semilunar (SL) valves
• Right atrium/venae cavae left atrium/pulmonary
  veins?

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Blood flow
Right atrium
Pulmonary Trunk/ Arteries
Venae cavae
Lungs
Tricuspid Valve
Right Ventricle
Pulmonary arteries
Pulmonary SL Valve
Mitral Valve
Left Ventricle
Left atrium
Aortic SL Valve
Ascending Aorta, etc.
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Valve defects

• Incompetent valves do not close properly and
  allow backflow
• Valvular stenosis is a stiffening of the valves
• Valve replacement

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Microscopic anatomy

• Striated and involuntary
• Acts on sliding filament mechanism
• Calcium initiates contraction
• Similar de/repolarization events
• Contains T-tubules and SR

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Unlike skeletal muscle cells

• Cells connected by intercalated disc
• Cells contract as a whole unit
• More larger mitochondria
• No triads/simpler T-tubules layout
• Some cells are self-depolarizing
• Absolute refractory period is much longer
• Cardiac muscle more adaptable in switching
  nutrient supply