Which veins contribute to the formation of the superior vena cava in utero?

The correct choice referring to the formation of the superior vena cava in utero is the common cardinal veins. During embryonic development, the superior vena cava is formed from the merging of these veins, which are a key part of the embryonic venous system. The common cardinal veins are responsible for draining the blood from the anterior and posterior parts of the embryo into the heart.

Understanding the role of the common cardinal veins is essential for grasping the development of the fetal circulatory system. As the embryo develops, the common cardinal veins contribute to the systemic venous return. Over time, they undergo a series of changes and regressions, ultimately leading to the formation of the superior vena cava as we see in the mature cardiovascular system.

The other veins mentioned have different roles or fates during embryonic development. The subcardinal veins, for instance, contribute mainly to the formation of renal veins and may play a role in creating parts of the inferior vena cava. Supracardinal veins mostly contribute to the development of the azygos venous system. Gonadal veins primarily handle the drainage from the gonads and do not contribute to the formation of the superior vena cava directly. Thus, the common cardinal veins are uniquely positioned in the embryonic anatomy