●       Heart is made up of specialized muscle cells know the Cardiac Muscle Cells. Cardiac Muscle cells are branched and striated muscle cells that are connected linearly to each other. They are cylindrical in shape like Skeletal Muscles but are also branched unlike them.

●       Heart is covered from outside by a membrane called Pericardium. Pericardium further consists of two parts. Outer Fibrous Pericardium and inner Serous Pericardium. It functions to protect the Heart from infections and trauma.

●       Heart is situated in the centre of Thorax in a cavity known as Mediastinum. It is slightly to the left of the median line (central body line) and points in inferolaterally to the left side.

●       Heart is further divided into two sides and four chambers (two on each side). Both sides are separated from each other through a septum.

• Right Side : Right sided Heart has an Atrium (superiorly) and a Ventricle (inferiorly). Right Atrium is connected to Venous system through Superior and Inferior Vena Cavae. It is also connected to Left Ventricle inferiorly through an opening guarded by a Tricuspid (three cusps) Valve. Right Side of the Heart is connected to the Lungs via Pulmonary Arteries. A Pulmonary Valve guards the connection between the Pulmonary Arteries and the Right Ventricle.

• Left Side : Left Side of the Heart also has an Atrium and a Ventricle like the Right Side. Left Atrium is connected to the Pulmonary Veins from the Lungs. It is also connected to the Left Ventricle through a Bicuspid (two cusps) Valve, inferiorly. Aorta leaves the Heart from its Left Ventricle through an Aortic Valve.

●     Heart is also divided into layers.

• Outer layer is called Epicardium. It is the inner part of the Serous Pericardium.

• Middle layer is the Myocardium. It is the main bulk of the Heart made up of Cardiac Muscles.

• Inner layer is called the Endocardium which is in contact with the blood inside Heart.

FUNCTION

●       Heart is a muscular organ which continues to work nonstop throughout life. It pumps blood through our whole body via blood vessels. With the blood vessels and the blood it constitutes the Circulatory System. Circulation can be divided into :

• Pulmonary Circulation : Right side of the Heart receives deoxygenated blood from whole body into Right Atrium through Vena Cavae. It is pumped into the Right Ventricle and then Pulmonary Vessels. From here it is taken to the lungs for Oxygenation.

• Systemic Circulation : Left Side of the Heart receives oxygenated from the Lungs through Pulmonary veins into Left Atrium. It is then pumped into the Left Ventricle. Left Ventricle pumps it forcefully into the Aorta through which it is transferred to the whole body.

●       Valves inside the Heart guard blood flow and maintain its direction. They prevent backflow to the Atrium from Ventricles, and from Aorta and Pulmonary Arteries to the Ventricles.