The Human Heart 

Introducation-

  • The Heart is the main pumping organ of the circulatory system.
  • It is reddish brown in colour, hollow and muscular organ.
  • Its average weight is about 300gm in males and 250gm in female.
  • It is conical in shape and lies in mediastenum i.e. the space between two lungs.
  • It is broader at upper and conical at lower end (apex).
  • Conical end is slightly tilted to left side and rests above the diaphragm.
  • Heart is enclosed in a membranous sac called pericardium.
  • Pericardium is formed form two main layers- outer fibrous pericardium and inner serous pericardium.
  • Serous pericardium is soft, moist and elastic.
  • It is formed of squamous epithelium and is further divisible into two layers as parietal and visceral layer.
  • Parietal and visceral sublayers of serous pericardium are separated by a pericardial space.
  • This space is filled with pericardial fluid which acts as a shock absorber and protects the heart from mechanical injuries.
  • It also keeps the heart moist and acts as lubricant.

The Heart wall :-

  • The heart is mesodermal in origin.
  • Its wall is formed of three layers, Outer epicardium, middle myocardium and inner endocardium.
  • Epicardium is thin and formed of a single layer of flat squamous epithelium resting on basement membrane.
  • Myocardium is the middle thick layer formed of cardiac muscle.
  • Endocardium is a single thin layer formed of squamous epithelium.
  • The epicardium and endocardium are protective in function whereas myocardium is responsible for contraction and relaxation of heart. 






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