Cavity at the caudal end of the developing embryonic heart where intra- and extra-embryonic veins meet.
Note: The sinus venosus develops into the portion of the right
atrium in the
adult heart that receives blood from the
vena cava.
Source:
PAC, 2016, 88, 713. 'Glossary of terms used in developmental and reproductive toxicology (IUPAC Recommendations 2016)' on page 805 (https://doi.org/10.1515/pac-2015-1202)