There are many temporary organs in our body like thymus , pineal gland etc . but this one is special as it only develops in a gravid state in pregnant body .
- It is exclusively found in Eutherian mammals.
- It is an organ that forms after implantation of the blastocyst occurs.-
- it is discoid ( meaning disc-shaped ), Hemochorial ( meaning chorion is directly attached to the maternal blood vessels) it is about 15 - 20 cm and 3 mm in thickness ( at the center while the edges are thin )
- Placental weight is about one-sixth of the baby's weight at term .and covers approximately 30 percent of the uterine wall.
- Placenta - specialized part of the chorion
It is two surfaces and a circumferential margin:
A . Fetal Surface
- Smooth and glistening, covered by thing amnion that can be scrapped up easily
except at the attachment of an umbilical cord
-at terms, it consists of four-fifth of the entire placenta
B . Maternal Surface
- rough and spongy ( dull red color )
- a thin greyish layer of decidua basalis ( Compact and spongy part )
- 15 - 20 polygonal convex areas called Lobes / Cotyledons limited by fissures
-fissures occupied by a decidual septum ( derived from Basal Plate )
-Greyish spots saw which are degenerated calcified structure
- Intervillus space consists of Decidua basalis + Blood
Margin
- continuous with chorion leave + amnion
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