G1ii: Anatomy of the heart, including valves, chambers and the pericardium

  • The heart is a muscular pump which propels blood to all parts of the body
  • Heart consists of 3 layers:
    1. Endocardium: thin internal epithelial layer
    2. Myocardium: thick middle layer of cardiac muscle
    3. Epicardium: thin external layer formed by visceral layer of pericardium

Fibrous Skeleton of Heart

  • Dense framework of collagen
  • Surrounds valve orifices
  • Anchors muscle fibres
  • Provides attachments for valves
  • Electrical insulation separating atrial & ventricular syncytium

Atria

  • Structure – thin walled, low P chambers
  • Coronary sinus opens into RA between AV orifice & IVC orifice
  • Four pulm. veins open into LA posterior wall
  • Function – reservoir. Adds 30% to ventricular filling

Ventricles

• Right Ventricle

  • Thin walled 2° lower pressure operation
  • Chordae tendinae connect AV valves to papillary muscles of ventricles

• Left Ventricle

  • Twice as thick cf. RV, does most of work
  • Larger papillary muscles → work harder

• Function

  • Papillary m. & chordae tendinae prevent bulging of AV valves into atra during systole
  • Ventricles propel blood towards outflow tract

Valves

• Structure

  • Endothelium covered in fibrous tissue
  • Firmly attached to fibrous rings of cardiac skeleton

• AV valves

  • Tricuspid & mitral valve

• SL valves

  • & aortic have 3 cusps
  • Behind valves are small outpockets k.a. Sinuses of Valsalva
  • Orifices of RCA & LCA are behind R & L cusps of Aorta

• Function

  • Unidirectional flow of blood through heart

Pericardium

• Structure

  • Double walled fibrous sac
  • Enclosing heart & great vessels

• Function

  • Lubrication for continuous contraction by pericardial fluid
  • Minimal distensibility → resists large & rapid ↑ cardiac size

→ keeps Starling curve on steep portion