The heart is a muscular organ responsible for pumping blood through the blood vessels by repeated, rhythmic contractions. The term cardiac (as in cardiology) means "related to the heart" and comes from the Greek καρδιά, kardia, for "heart."
The average human heart, beating at 72 beats per minute, will beat approximately 2.5 billion times during a lifetime (about 66 years). It weighs on average 250 g to 300 g in females and 300 g to 350 g in males.
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The heart is mesodermal in origin and is formed from splanchnopleuric mesoderm. It is first seen in the form of right and left endothelial heart tubes which soon fuse to form a single tube. This tube has an arterial end and a venous end and shows a series of dilatations which are:
  • Bulbus cordis
  • Ventricle
  • Atrium
  • Sinus venosus


The Heart can be divided into two Right heart and Left heart.

Right heart

Right heart is a term used to refer collectively to the right atrium and right ventricle of the heart; occasionally, this term is intended to reference the right atrium, right ventricle, and the pulmonary trunk collectively.
The right atrium receives deoxygenated systemic blood from the superior and inferior vena cavae. The blood is then pumped through the tricuspid valve into the right ventricle, which in turn pumps the blood through the pulmonary valve into the pulmonary artery.

Right Atrium

It is one of four chambers in the human heart. It receives de-oxygenated blood from the superior and inferior vena cavae and the coronary sinus, and pumps it into the right ventricle through the tricuspid valve. Right auricular appendix (right auricula, right auricle) is a small conical muscular pouch attached to the right atrium of the heart. Its margins present a dentated edge. It projects from the upper and front part of the sinus forward and toward the left side, overlapping the root of the aorta.

Venae cavae

The superior and inferior vena cava are collectively called the venae cavae. They are the veins that return de-oxygenated blood from the body into the heart. They both empty into the right atrium.

The superior vena cava (or anterior) is above the heart, and forms from a convergence of the left and right brachiocephalic veins that contain blood from the head and the arms. The vena cavae carry deoxygenated blood from the body to the right atrium of the heart. The venae cavae is the largest blood vessel in the heart.

The inferior vena cava (or posterior vena cava) travels up alongside the abdominal aorta with blood from the lower part of the body.

Coronary Sinus

It is a collection of veins joined together to form a large vessel that collects blood from the myocardium of the heart. It is present in humans and other animals.


It is located between the left atrium and ventricle on the posterior surface of the heart.
It runs transversely in the groove between the left atrium and ventricle on the posterior surface of the heart.
The coronary sinus orifice (opening) is just superior to the septal leaflet of the tricuspid valve. The coronary sinus orifice is also known as the ostium of the coronary sinus.


The valve of the coronary sinus (Thebesian valve) is a semicircular fold of the lining membrane of the atrium, at the orifice of the coronary sinus. The valve may vary in size, or be completely absent.
It may prevent the regurgitation of blood into the sinus during the contraction of the atrium.
This valve may be double or it may be cribriform.

Right Ventricle

Tricuspid valve

It is on the right side of the heart, between the right atrium and the right ventricle. The normal tricuspid valve usually has three leaflets and three papillary muscles. The largest cusp is interposed between the atrioventricular orifice and the conus arteriosus and is termed the anterior or infundibular cusp.
A second, the posterior or marginal cusp, is in relation to the right margin of the ventricle.
A third, the medial or septal cusp, to the ventricular septum.
The tricuspid valve prevents the blood from returning to the right atrium when the right ventricle contracts

Conduction system

The heartbeat originates in a specialized cardiac conduction system and spreads via this system to all parts of the heart muscle. The structures that form the conducting system are the sinoatrial node (SA node); anterior, middle and posterior internodal tracts; the atrioventricular node (AV node); the bundle of His; right and left bundle branches; anterior-superior and posterior-inferior brances of the left bundle; and the Purkinje network.

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