Heart:is a hollow,muscular organ,It consist of:
Endocardium:a layer of epithelial tissuethat lines
the inside of the heart.It continue from the
endothelium that lines the blood vessels.
Myocardium:middle layer is the thickest part of
the heart.It is formed of cardiac muscle tissue.
themuscle fibres are long,striated and branched.
myocardial contractions are involuntary,fast and
surrounding the heart.The space between the two
membranes is called the pericardial space.
Structure of heart:Chambers :heart is divided in
four parts.Two uppers chambers(atria) and two
lower(ventricles).Atria:thin walls blood flows
from veins.Ventricles:thickest walls left ventricle
thicker than right,blood leave heart and flow into
arteries.The hear is separated by interventrcular
septum.Valves:atria and ventricles connected by
atrioventricular valves.Right(tricuspid valve)
Left(mitral valve).Semilunar valve preven the
blood flowing backwards into ventricles.