Divided attention

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 

powerful.Pericardium:double membrane 

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.