Sinus Venosus Development
Right and left sinus horns drain blood into the sinus venosus. Three important veins drain blood into each horn:
1) The vitelline vein
2) The umbilical vein
3) The common cardinal vein
The right umbilical vein, the left vitelline vein and left common cardinal vein are obliterated. The remainder of the left sinus horn forms the oblique vein of the left atrium and the coronary sinus. As a result of left-to- right shunts of blood, the right sinus horn and veins enlarge and forms the only communication with the atrium.
** The right sinus horn is incorporated into the right atrium to form the smooth-walled part of the right atrium.
In the right atrium, sinuatrial orifice is surrounded by two folds, the right and the left venous valves. Dorsally, the valves fuse and form the septum spurium.
> The left valve and septum spurium fuse with the developing atrial septum.
> The superior portion of the right valve disappears, whereas the inferior portion develops into:
a) The valve of the inferior vena cava
b) The valve of the coronary sinus
1) The vitelline vein
2) The umbilical vein
3) The common cardinal vein
The right umbilical vein, the left vitelline vein and left common cardinal vein are obliterated. The remainder of the left sinus horn forms the oblique vein of the left atrium and the coronary sinus. As a result of left-to- right shunts of blood, the right sinus horn and veins enlarge and forms the only communication with the atrium.
** The right sinus horn is incorporated into the right atrium to form the smooth-walled part of the right atrium.
In the right atrium, sinuatrial orifice is surrounded by two folds, the right and the left venous valves. Dorsally, the valves fuse and form the septum spurium.
> The left valve and septum spurium fuse with the developing atrial septum.
> The superior portion of the right valve disappears, whereas the inferior portion develops into:
a) The valve of the inferior vena cava
b) The valve of the coronary sinus
Dorsal view of differient stages in the development of the sinus venosus. A. 24 days, B. 35 days, C & D final stage of development. Broken line, the entrance of the sinus venousus into the atrial cavity. ACV, anterior cardinal vein; PCV, posterior cardinal vein; UV, umbilical vein; VIT V, vitelline vein; CCV, common cardinal vein.