Sinus venosus

Sinus venosus is a large quadrangular cavity which precedes the atrium on the venous side of the chordate heart. In mammals, it exists distinctly only in the embryonic heart where it is found between the two venae cavae. As development proceeds, it becomes incorporated into the wall of the right atrium to form a smooth part called the sinus venarum, which is separated from the rest of the atrium by a ridge of fibres called the crista terminalis.

Structure

The sinus venosus receives blood from the vena cava and the pulmonary veins. It is initially a paired structure, but the left sinus venosus disappears during development. The right sinus venosus forms the sinus venarum of the right atrium and the coronary sinus. The sinus venosus also forms the sinoatrial node, the natural pacemaker of the heart.

Development

In the developing heart, the sinus venosus connects to the embryonic atrium and eventually becomes incorporated into the right atrium. The left sinus venosus forms the coronary sinus and the oblique vein of the left atrium. The right sinus venosus forms the smooth part of the right atrium known as the sinus venarum.

Clinical significance

The sinus venosus can be involved in congenital heart defects, known as sinus venosus atrial septal defects. These are a type of atrial septal defect where the defect involves the venous inflow of either the superior vena cava or the inferior vena cava.

See also

• Heart
• Atrium (heart)
• Vena cava
• Pulmonary veins
• Coronary sinus
• Sinoatrial node

References

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