ABSTRACT
The placenta is the first identifiable organ, and its development is a prerequisite for normal development of the embryo into a fetus. It combines in one tissue diverse activities and functions that are separate in the adult, including gas and nutrient transport, waste removal, and hormone biosynthesis. Accounts of early implantation draw on the studies of Hertig and Rock,1 whose specimens are housed in the Carnegie Collection of the Human Developmental Anatomy Center, Research Collections division of the National Museum of Health & Medicine, in Washington, DC. Human placental development was described in detail by Boyd and Hamilton in their classic book2 while Fox included information on placental development in a trenchant pathology text.3 Kaufmann and Benirschke’s Pathology of the Human Placenta4 contains much useful information on placental anatomy and development, as well as some molecular aspects. Placentation in diverse species is described elsewhere in Section VI; placental anatomy and transfer are fully discussed in Knobil and Neill’s Physiology of Reproduction.5,6 (See also https://medicine.ucsd.edu/cpa/homefs.html.) Studies of the genetic basis of placental development in the mouse are revealing genes that may well be of importance in human placental development7 (see Chapters 22 and 27). The present account of human placental development is a brief outline and these sources should be consulted for more detailed information.
