It is about heart structure.

1. THE HEART STUCURE
The human heart is a four-chambered muscular organ
that pumps blood throughout the body. It is located in
the center of the chest, between the lungs. The heart

2. is about the size of a fist and weighs about 10
ounces.
The heart is made up of three layers:
 The epicardium is the outermost layer. It is a thin,
serous membrane that covers the heart.
 The myocardium is the middle layer. It is the
thickest layer and is made of cardiac muscle. This
muscle contracts and relaxes to pump blood
through the heart.
 The endocardium is the innermost layer. It is a thin,
smooth membrane that lines the heart chambers.
The heart is divided into four chambers:
 The right atrium is the upper chamber on the right
side of the heart. It receives oxygen-poor blood
from the body.
 The right ventricle is the lower chamber on the
right side of the heart. It pumps oxygen-poor blood
to the lungs.
 The left atrium is the upper chamber on the left
side of the heart. It receives oxygen-rich blood
from the lungs.
 The left ventricle is the lower chamber on the left
side of the heart. It pumps oxygen-rich blood to the
body.
The heart also has four valves that control the flow of
blood through the heart. These valves are:
 The tricuspid valve is located between the right
atrium and the right ventricle. It prevents blood
from flowing back into the right atrium.

3.  The pulmonic valve is located between the right
ventricle and the pulmonary artery. It prevents
blood from flowing back into the right ventricle.
 The mitral valve is located between the left atrium
and the left ventricle. It prevents blood from flowing
back into the left atrium.
 The aortic valve is located between the left
ventricle and the aorta. It prevents blood from
flowing back into the left ventricle.
The heart is a complex organ that is essential for life. It
pumps blood throughout the body, providing oxygen and
nutrients to all of the tissues. The heart is also
responsible for removing waste products from the body.