The Placenta And Umbilical Cord Flashcards
What is fetal portion made from
Formed by chorion frondosum
What is maternal portion made from
Decidua basalis
How is placenta developed
During fourth and fifth months the decidua forms a number of decidual septa which project in to intervillous spaces but do not reach the chorionic plate, as a result of this septum formation the placenta is divided in to cotyledons
What are the dimensions of the placenta at full term
15-25 cm in diameter
3 cm thick
Weighs 500-600 g
Why is the fetal surface of the placenta whitish and smooth
As its covered by amnion
Describe maternal circulation
Cotyledons receive their blood through 80-100 spiral arteries that pierce the decidual plate and enter the intervillous spaces
O2 and nutrients from maternal blood passes through placental barrier in to umbilical vein and to fetus
At the same time CO2 and waste passes from umbilical artery of fetus to placenta
Describe fetal circulation
The 2 umbilical arteries carry fetal blood containing CO2 and waste products which passes to placenta through placental barrier
At the same time O2 and nutrients pass from maternal blood in to umbilical vein to fetus
What are the functions of the placenta
Nutrition
Excretion
Respiration
Prevents toxins and drugs as well as microorganisms from passing from mother to fetus
Production of hormones like progesterone, estrogen and HCG
What is a placental barrier
They are structures separating fetal blood from maternal blood(wall of tertiary villi)
They prevent mixing of fetal and maternal blood while allowing exchange of gasses and passage of nutrients and waste products
Describe the structure of the placental membrane
Composed of 4 layers a)endothelial lining of fetal vessels
b) primary mesoderm
c) Cytotrophoblast
d) Syncytiotrophoblast
How can permeability decrease in placental membrane
Fibrinoid material is deposited on outer surface
What are the dimensions of the umbilical cord
2 cm in diameter
50-60 cm long
Describe the development of the primitive umbilical cord
Formed during folding and contains;
▪️Body stalk containing allantois and umbilical blood vessels
▪️Yolk stalk and vitelline blood vessels
▪️Remaining part of extra embryonic coelom
Describe the development of the definitive umbilical cord
Extra embryonic ceolom and allantois obliterate and yolk stalk degenerates
So it will contain umbilical blood vessles and wharton’s jelly covered by amniotic membrane
What are abnormalities concerning the placenta
▪️bilobed or trilobed placenta
▪️accessory placenta
▪️placenta previa which may be:
Centralis
Marginals
Parietalis which leads to antepartum hemorrhage so must be c section
▪️attachment of placenta: marginal attachment or insertion in to the chorionic membranes outside the placenta
