the heart is a hollow four chambered muscular organ which sits inbetween the lungs.
the walls are mostly made of cardiac muscle.
[briefly explain the way de oxygenated blood is turned into oxygenated blood]
the heart has 4 chambers;
right atrium, left atrium, right ventricle, left ventricle
cardiac muscles are involantary
the cardiovascular system includes the heart,blood vessels and blood.
some main functions are;
transporting oxygen and nutrients
removing waste products
controlling body temperature