Cells Tissues and Development: Formation of the Placenta

What are the two main regions of the chorion? (outer most membrane of the embryo/fetus ) and give the features of both.

Smooth chorion= chorion laeve. - no villi - Associated with decidua capsularis Villus chorion= chorion frondosum - Large, branched villi. - Associated with decidua basalis.

How is the chorion attached to the decidua?

- Stem/anchoring villi that form cytotropohoblastic shell at the site of attachment.

What is the maternal contribution to the placenta?

decidua basalis, underlying tissue of the placenta that contains spiral arterioles for maternal blood delivery. Takes place in placenta formation.

What is the fetal contribution to the placenta?

villous chorion (chorion frondosum), which contains fetal blood vessels in the chorionic plate.

Where do chorionic villi arise from?

- Arise from the chorionic plate. - These villi project into lacunae and are bathed directly by maternal blood from within the placenta.

What is contained within the chorionic plate?

- Blood vessels arising from the umbilical cord. - Covered with amniotic epithelium.

What is the function of the decidua capsularis?

- Covers the site of implantation and is in contact with the chorion (outer membrane of embryo).

What occurs during decidualisation in the decidua basalis?

- Formation of decidual cells form from endometrial stromal cells. - These cells are rich in lipids and glycogen.

What is the origin of the placenta?

- Formed from the lacunar networks that develop from the trophoblast layer of the blastocyst upon full implantation into the uterine wall. ( primitive uteroplacental circulation).

What is the function of the decidua parietalis?

- Forms remaining endometrium not in direct contact with embryo or fetus.

What can be readily transferred through the placenta from mother to fetus?

- Nutrients - Antibodies - harmful substances.

What are the functions of decidual cells in the decidua basalis?

- Restrict trophoblast invasion. - Provide some nourishment for the embryo and fetus. - Create a separation layer at parturition. - Secrete relaxin.

What are the endocrine activities of the placenta?

- Secretes hCG early in pregnancy which prolongs the life of the corpus luteum. - Progesterone and oestrogen are produced by the placenta later in pregnancy to maintain placental function and prevent the premature rejection of placenta by the mother.

What is the placental barrier composed of?

- syncitiotrophoblast - cytotrophoblast - villous CT and wall.

What is chorionic villi composed of?

- syncitiotrophoblast. - cytotrophoblast. - extraembryonic mesoderm. - villous blood fessels of a fetal origin.

What can be readily transferred through the placenta from the fetus to the mother?

- waste products e.g. CO2. - RBC antigens