Placenta Development

Introduction

Human Placental Membranes

The placenta (Greek, plakuos = flat cake) named on the basis of this organs appearance. The placenta a mateno-fetal organ which begins developing at implantation of the blastocyst and is delivered with the fetus at birth.

During that 9 month period it provides nutrition, gas exchange, waste removal, endocrine and immune support for the developing fetus. (More? Placental Overview | Histology).

There are essentially 3 separate aortic/venous circulatory systems: umbilical, systemic and vitelline. The umbilical system is lost at birth, the vitelline contributes to the portal system and the systemic (embryonic) is extensively remodelled to fom the the cardiovascular system.

Historic Embryology - Placenta
1883 Embryonic Membranes \| 1907 Development Atlas \| 1909 \| 1910 Textbook \| 1917 Textbook \| 1921 Textbook \| 1921 Foetal Membranes \|1921 human \| 1921 Pig implantation \| 1922 Single placental artery \| 1923 Placenta Review \| 1939 umbilical cord \| 1943 human and monkey \| 1944 chorionic villus and decidua parietalis \| 1946 placenta ageing \| 1960 first trimester placenta \| 1960 monkey \| 1972 Placental circulation \| Historic Disclaimer

Reading

Human Embryology (2nd ed.) Larson Chapter 7 p151-188 Heart, Chapter 8 p189-228 Vasculature
The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 14: p304-349
Before we Are Born (5th ed.) Moore and Persaud Chapter 12; p241-254
Essentials of Human Embryology Larson Chapter 7 p97-122 Heart, Chapter 8 p123-146 Vasculature
Human Embryology Fitzgerald and Fitzgerald Chapter 13-17: p77-111

Placental Classification

Classification of placenta is on the basis of histological (microscopic) structural organization and layers between fetal and maternal circulation, giving 3 main groups:

Haemochorial - placenta where the chorion comes in direct contact with maternal blood (human)
Endotheliochorial - maternal endometrial blood vessels are bare to their endothelium and these comes in contact with the chorion. (dogs, cats)
Epitheliochorial - maternal epithelium of the uterus comes in contact with the chorion.considered as primitive (pigs, cows)

The presence of these three differing types of placenta have also been used to describe the pattern mammalian evolution. See also Placental Layers