10.4 The physiology of the placenta:
Role of the placenta in the feto-maternal exchange processes

• Mechanisms of the feto-maternal exchanges
• Breathing function
• Nutritive and excretory functions
• Placenta and the immunological barrier
• Protein transfer
• Protective function
• Endocrinal function

Endocrinal function

The placenta and especially the syncytiotrophoblast can be seen as a large endocrine gland.

Before implantation hormone production is ensured through ovarian and hypophysial hormones.

At the beginning of the pregnancy the synthesis of estrogen and progesterone is ensured by the corpus luteum graviditatis that is maintained by the human chorion-gonadotropin (HCG), a product of the trophoblast. The activity of the corpus luteum decreases progressively with the beginning of the 8th week in order to be entirely replaced by the placenta at the end of the 1st trimester.

During the pregnancy the hormone concentration in the maternal blood is regulated by the cooperation of the placental, hypophysial and fetal suprarenal hormones as well as hormones from the gonads

Fig. 40
At the beginning of the pregnancy the syncytiotrophoblast produces the HCG that has effects at both the level of the infantile suprarenal glands (induces DHEA) and the maternal corpus luteum (induced secretion of E2 and P).