Question

How many walls does the human heart have?

Answer 1

The human heart arises from the mesoderm. This mesoderm gets differentiated into three distinct layers that make the wall of the heart. All three layers made the heart wall so thick so that it can pump blood to the distal end of the body.

Complete answer:
The heart is made up of three layers namely-
-Outer pericardium
-Middle myocardium
-Inner endocardium

Pericardium - It is the outermost covering of the heart. It is further divided into two layers -
-Outer parietal pericardium
-Inner visceral pericardium
The space between the two layers is called the pericardial cavity or pericardial space and it contains a thin film of fluid.

Outer parietal pericardium - it is a protective sac of the heart. Its main function is to keep the heart a
attached to the mediastinum. It is further divided into the outer fibrous layer and an inner serous layer.
Inner visceral pericardium - it lines the myocardium which lies beneath the pericardium.

Myocardium - it forms the middle layer of the heart and is made up of cardiac muscle fibers or cardiac myocytes. It is the thickest layer of the three and performs the pumping action of the heart. The myocardium has three types of fibers.
-Muscle fibers which form a contractile unit of the heart
-Muscle fibers that form pacemaker
-Muscle fibers that form a conductive system.

Endocardium - it is the innermost layer of the heart wall. It continues as the endothelium of the blood vessels.

Note: There are special properties of cardiac muscle that makes it unique -
-Excitability: The ability of a tissue to respond to stimulus
-Rhythmicity: The ability of a tissue to produce its own impulses regularly. It is also called autorhythmicity
-Conductivity: The heart has a special conductive which makes the impulses possible to reach every part of the heart.
-Contractility: The ability to shorten in length in response to a stimulus.