Circulatory System 03

This is a section of umbilical cord showing portions of a vein (left) and artery (right). These vessels are surrounded by the mesenchymal connective tissue (Wharton's jelly) of the umbilical cord and carry blood from/to the fetus; hence the arterial oxygen pressure is lower than that of the vein. Note that while the wall of the vein is rather thick (nearly comparable to that of the artery), its media is much thinner than that of the artery. Furthermore, the elastic content of the walls of these vessels is different from their counterparts elsewhere; in particular, while the artery lacks an internal elastic lamina, the vein has a fairly obvious one.

Slide K-3, field M-8 of finder slide A, 2.5X objective.