Difference between Sinus Venosus and Conus Arteriosus

What is Sinus Venosus?

The sinus venosus is a large quadrangular cavity that is a thin-walled chamber (60-90 μm thick). It collects venous blood from all the organs of the body. It is present just before the right atrium. It is a structure that can be seen only in chordates heart on maturity. In mammals, it is only seen in the embryonic stage.

The sinus venosus develops as a paired structure, but eventually it shrinks on the left side to form coronary sinus and sinoatrial nodes, and fuses with the right atrium to form sinus venarum.

The tissue composition of the sinus venosus cavity includes connective tissues, with a bound inner endothelial layer and outer epicardial walls. The amount of cardiac walls in the structure differs in different organisms.

The main function of the sinus venosus is the initiation and control of heartbeat. In many fishes the structure serves the function of a pacemaker. It collects blood from the jugular veins, hepatic veins and secondary circulation, and delivers it to the atrium.

What is Conus Arteriosus?

Conus arteriosus is a conical pouch that is formed in the right ventricle. It is the site from where the pulmonary artery arises. It arises from the bulbus cordis, a structure found in embryos. It is also referred to as the infundibulum.

It is a muscular structure that forms a major part of the heart’s outflow tract (the outflow tract is the connection between the ventricles and the great arteries). Blockage in the ventricular outflow tract can cause tetralogy of Fallot. This condition leads to circulation of oxygen deficient blood in the body.

The walls of the conus arteriosus are smooth. Its major role is to form a passage for the flowing of blood from the right ventricle to the pulmonary trunk.

Sinus Venosus vs Conus Arteriosus

Sinus Venosus

Conus Arteriosus


Sinus venosus is a quadrangular thin-walled pouch present just before the right atrium.

Conus arteriosus is a conical pouch that is formed in the right ventricle.


It is a quadrangular pouch.

It is a conical pouch.


It precedes the right atrium.

It is present in the right ventricle.

Wall Type

The wall is thin.

The wall is smooth.


It collects venous blood from all the body organs.

It forms a transition between the right ventricle and pulmonary artery.


It is seen in adult as well as embryonic chordate hearts. In mammals it can be seen only in the embryonic stage.

It develops from the bulbus cordis structure in the embryo.

Blood Input

It inputs blood through three venous sources: cuverial ducts, hepatic veins and jugular veins.

It does not input blood into the pumping heart.

Explore BYJU’S Biology for more related topics.

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Frequently Asked Questions on Difference between Sinus Venosus and Conus Arteriosus

Where does the conus arteriosus lead to?

The conus arteriosus leads to the pulmonary arteries that leave the heart with deoxygenated blood.

What is the function of the conus arteriosus in a frog?

The conus arteriosus in a frog has a spiral valve that helps in regulating the flow of blood in the heart.

Does conus arteriosus carry oxygenated blood?

No, conus arteriosus carries deoxygenated blood.

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