Up Testes Female system Fertilisation & implant Placenta HIstology Placental Products Labour Pelvis Contraception

HISTOLOGY OF THE PLACENTA

 

FUNCTION OF THE PLACENTA

            Mother has oxygen and nutrients

Placenta provides viral interface, discriminatory barrier acting as the fetal liver and lungs

Fetus has waste metabolites including carbon dioxide

 

MATURE PLACENTA

            Disc shaped with a flat cap appearance

Weight 500g

Diameter 20cm

Surface area of 10sq m

 

TERMS

 

Chorion outer embrionic membrane ie: trophoblast cells of wall of blastocyst

Syncytiotrophoblast outermost layer of placenta formed by fusion of cytotrophoblast cells

Cytotrophoblast continuously divides to produce syncytiotrophoblast

Chorionic villi tongue like fronds composed of trophoblast and invading blood vessels

Decidua endometrium of pregnant uterus ( the decidua basalis forms the maternal part of the placenta and is lost)

Primary chorionic Villi cytotrophoblast cells grow into the syncytiotrophoblast. Therefore in cross section they are inner core of cytotrophoblast with outer sysncitial layer

Secondary Chorionic Villi Gains mesodermal core with angioblasts making their own blood cells

Tertiary chorionic villi now has endothelial lining due to capillaries being present

 

Anchoring villi (not free floating in the lacunae) The column of cytotrophoblast cells continue to grow through the endometrium and anchor to the innermost layer of the endometrium

 

SECOND TRIMESTER

            In the second trimester aborization of villi takes place with the tertiary villi branching to form  stem and intermediate villi

 

THIRD TRIMESTER

            Terminal villi form blood vessels undergo elaboration and form long capillary loops which bulge out pushing the trophoblast layers aside

            In cross-section the inner core has a dilated capillary lumen with close apposition between the capillary endothelium and syncytiotrophoblast minimal diffusion distance.

 

EXTRUSION OF EXCESS NUCLEI

            Nuclei of cytotrophoblast cells fuse with syncytiotrophoblast aggregate and package in areas away from the diffusion zone. Syncytial knots

            Periodically these nuclei appear to be shed into maternal circulation ? a form of apoptosis?

 

PLACENTAL INSUFFICIENCY

  1. Incomplete implantation - eg female circ. Impaired

  2. Restricted angiogenesis eg smoking, Intra uterine growth retardation (IUGR), fetal alcohol syndrome, pre-eclampsia

  3. INCREASED angiogenesis in high altitude and well controlled diabetics

  4. BM thickening diabetes mellitus

  5. Impaired permeability gestational diabetes, diabetes, pre eclampsia

 

UMBILICAL CORD

30-90CM LONG THEREFORE CAN CAUSE OBSTETRIC PROBLEMS

coiling around fetus

true knots forming

If only one artery present could be a marker for fetal cardiac abnormalities

 

etc etc I cant be bothered to type any more yippee! Im off to Rhodes this evening for week