The Heart is a vital organ in the human body that pumps blood and through the blood vessels transports oxygen and nutrients to the body, and carries carbon dioxide to the lungs.
It is approximately the size of a closed fist and is located between the lungs, its length is about 12 c.m., width- 9 c.m. and thickness is 6 c.m. and is weighing about 250-350 gm.
The human heart is situated in the mediastinum within the thoracic cavity. The heart is enclosed by a double membrane known as the pericardium. The wall of the heart is made up of three layers inner to outer- epicardium, myocardium, and endocardium.
Pericardium-
The pericardium is a sac that surrounds the heart. The outer surface of the pericardium is called the fibrous membrane, which is formed by inelastic, tough, dense irregular connective tissues. This is lined by a double inner membrane called the serous membrane. The part of the serous membrane attached to the fibrous membrane is the parietal pericardium, and the part of which attached to the heart is known as the visceral pericardium, in between the 2 layers the space that is pericardial space which contains the fluid that lubricates and reduces the friction between the linings.
Heart Wall-
The heart wall has three-layer – inner endocardium, middle myocardium, and outer epicardium. The innermost layer is the endocardium, It is made up of a simple squamous epithelium and covers heart chambers and valves. The middle layer is the myocardium, form from the cardiac muscle fibers, these are involuntary striated muscle tissue and are connected by intercalated discs which allow a rapid response to impulses of action potential and act as a single unit and contract. The outermost layer is the epicardium which is formed by the visceral pericardium of the serous lining.
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