Difference Between Chorion and Placenta

Chorion vs Placenta

Chorion and placenta are two important parts, which are developed during the embryo development. Fetus is important for the existence of both these parts.

What is Placenta?

Placenta is formed during the development of the embryo. It acts as a metabolic and endocrine organ located between the developing embryo and the endometrium of the uterus. Placenta is a discoid, oval shaped organ, which has an approximate diameter of 20 cm and thickness of 2-3 cm. Placenta exists only during the gestational period. Both fetal and maternal components contribute to form the placenta. Chorion is the fetal component, whereas uterine endometrium is the maternal component. The main function of the placenta is to act as a selective barrier, which mediates all fetomaternal and maternofetal transfers. It controls the exchange of water, oxygen, carbon dioxide and metabolic wastes between the fetus and the mother. The other main function is to act as an endocrine organ during the pregnancy. The most important hormones of placental origin include hCG, human placental lactogen (hPL) and steroid hormones like estradiol, estriol and progesterone. In addition, placenta secretes some important enzymes such as alkaline phosphatase, diamine oxidase and cysteine aminopeptidase.

What is Chorion?

Chorion is the fetal part of the placenta. It is composed of four layers; cellular layer (fibroblast), reticular layer, basement membrane and trophoblast. Chorion and chorionic villi are differentiated from the blastocyst during the implantation. During the fetal period, chorionic villi further develop and become a part of the placenta. The remaining part of the chorion, together with amnion forms the transparent fetal membranes.

What is the difference between Chorion and Placenta?

• Chorion is the fetal part of the placenta.


Further Reading:

  1. Difference Between Amnion and Chorion
  2. Difference Between Placenta and Umbilical Cord