placenta

Question 1

what is the placenta

Answer 1

The placenta is a fusion between the fetal chorion and the maternal endometrium tissue for the purpose of physiological exchange. The placenta is an organ which is transient, vital, and changing. Its usually 2-3 cm thick and 15-20 cm wide, and 500-600 mg with lots of surface area. .

Question 2

Differentiation of the trophoblast (essential for implantation of the blastocyst)

Answer 2

Syncytiotrophoblast mediates implantation. more cyto trophoblast attaching to endometrium causes more syncytiotrophoblast to be made. As the sycytiotrophoblast is made the uteroplacental circulation is established, the embryo is completely embedded by day 12-14.

Question 3

Expanding trophoblastic tissue has two faces

Answer 3

chorionic plate: the chorion adjacent to the embryo

Cytotrophoblastic Shell: the trophoblast adjacent to the decidua basalis

Question 4

Decidua Regions are named in reference to the embryo

Answer 4

decidua basalis: at site of implantation
decidua capsularis: the dicidua capsularis- decidua surrounding the embryo
decidua parietalis: remainder of deciduating endometrium

Question 5

Chorionic Villi

Answer 5

Form from the chorion (trophoblast=cytoand syncytio trophoblast + EEM

Formation of chorionic vili:
Primary villi (Day 14) are extensions of the cyto and syncytiotrophoblast

Secondary villi (Day 16) acquire a core of EEM

Tertiary villi (Day20) are secondary plus Blood vessels

As tertiary villi grow, distinct regions can be identified Stem, intermediate and terminal villi

Question 6

Villi branches

Answer 6

stem (core) villi provide the central core of support for the villous tree. A Solid extension of cytotrophoblast and trophoblast cell column, extends distally thru syncytiotrophoblast and expands to the dicidua and contributes to the cytotrophoblastic shell, with central veins and arteries

Branches of the stem villi are called intermediate or floating villi- and float in the intervillous space and carry the arterioles and venules with capillaries loops

Terminal villi are sinusoids with large capillary beds

Question 7

How the placenta disattaches

Answer 7

a juctional (separation) zone is established

Basal plate: the functional zone of endometrium and the chorionic tissue , the basal plate separates with the placenta at birth

Placental base: the basal zone of the endometrium in decidua basalis area, and remains in the uterus after birth

Question 8

Further development changes names of the chorion

Answer 8

D capsularis- chorion looses villi and is the Chorion leave and is smooth

D-basalis- chorion frondosum (villous chorion)

together they make up the placenta

Codyledon or lobe is a hypertrophied villi

Question 9

changes in placental membrane as development proceeds

Answer 9

initial placental membrane: syncytiotrophoblast, cytotrophoblast, basement membrane, EEM, capillary endothelium

After month 4: there is loss of the cytotrophoblast, there is thinning syncytiotrophoblast, decrease in size of chorionic villi

normally not very much blood mixing

Question 10

Functions of the placenta

Answer 10

mediates transport and metabolism of nutrients and wastes

secretes essential proteins and hormones

Protects the embryo/fetus from immunological attack

Material cross the placenta by diffusion, endocytosis, exocytosis

Question 11

placenta previa and accreta and abrupto

Answer 11

implantation at cervix, premie detachment and hemorrhaging

Accreta: implantation in to basal zone, doesnt leave the body

Abrupto: detachment could be due to environmtnetl toxins

Question 12

Molar pregnancy

Answer 12

trophoblast development without embryo, increased hcg, complete molar (only paternal), incomplete (maternal and paternal)