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Placenta - Anatomy & Physiology (view source)
Revision as of 19:36, 11 July 2011
, 19:36, 11 July 2011→Introduction
The formation of the placenta is referred to as the "second" or "embryonic" period of pregnancy and describes the establishment of a fully functional placenta. The placenta is an apposition of foetal and parental tissue for the purposes of physiological exchange. There is little mixing of maternal and foetal blood, and for most purposes the two can be considered as separate.
The formation of the placenta is referred to as the "second" or "embryonic" period of pregnancy and describes the establishment of a fully functional placenta. The placenta is an apposition of foetal and parental tissue for the purposes of physiological exchange. There is little mixing of maternal and foetal blood, and for most purposes the two can be considered as separate.
==Formation==
The placenta consists of a foetal portion formed by the chorion and a maternal portion formed by the decidua basalis. The uteroplacental circulatory system begins to develop from approximately day 9 via the formation of vascular spaces called "trophoblastic lacunae".
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Maternal sinusoids develop from capillaries of the maternal side which anastamose with these trophoblastic lacunae. The differential pressure between the arterial and venous channels that communicate with the lacunae establishes directional flow from the arteries into the veins resulting in a uteroplacental circulation.
== Exchange ==
== Exchange ==