UNSW Embryology
|
|
Placenta- Molecular
Development
|
Embryology Home
Page
|
|
|
|
|
Page
Links Introduction
Development
Overview ReferencesAbout
Notes
|
Page
2 | Abnormalities
| OMIM
| Questions
| Medline
Page
3 | Pig
Stage 13/14
Page
4 | Human
(Stage22) | Selected
Human highpower
Text only
page | WWW
Links
|
Introduction
The placenta (Gk. plakuos= flat cake)
is a mateno-fetal organ which begins
developing at implantation of the
blastocyst and is delivered with the fetus
at birth. During that 9 month period it
provides nutrition, gas exchange, waste
removal, endocrine and immune support for
the developing fetus. There is a developmental
overview on this current page.
|
Transverse section
through Human Placental Cord (3
month).
|
|
|
|
|
|
|
Development
of the Placenta
- Placenta
- embryonic/maternal organ
- villous chorion/decidua basalis
- continuous with amniotic and chorionic
sacks
- Dimensions
- discoid up to 20cm diameter and 3 cm
thick (term)
- weighs 500-600 gm
- Shapes
- accessory placenta, bidiscoid, diffuse,
horseshoe
- maternal and embryonic surface
- delivered at parturition
- retention may cause uterine hemorrhage
- Maternal Surface
- Cotyledons
- form cobblestone appearance
- originally placental septa formed
grooves
- covered with maternal decidua
basalis
- Fetal Surface
- umbilical cord attachment
- cord 1-2 cm diameter, 30-90cm long
- covered with amniotic attached to
chorionic plate
- umbilical vessels branch into chorionic
vessels
- which anastomose
- Chorionic Villi-Primary Villi
- week 2
- trophoblastic shell cells
- syncitiotrophoblasts,
cytotrophoblasts
- frorm finger-like extensions
- Chorionic Villi- Secondary Villi
- week 3
- extraembryonic mesoderm grows into
villi
- covers entire surface of chorionic
sac
- Chorionic Villi- Tertiary Villi
- mesenchyme differentiates into blood
vessels and cells
- forms arteriocapillary network
- fuse with placental vessels
- developing in connecting stalk
- Chorionic Villi
- Stem
- or anchoring villi
- cytotrophoblast cells attached to
maternal tissue
- Branched
- or terminal villi
- grow from sides of stem villi
- region of main exchange
- surrounded by maternal blood in
intervillous spaces
- maternal sinusoids
- Chorionoic Villi
- originally cover entire chorionic
surface
- become restricted to decidua basalis
region
- Frondosum
- Capsularis
- Maternal Decidua basalis reaction
- deposition of glycogen
- proliferation of blood vessels
- Placental- Histology
- Placental- Histology UNSW Histology-
slide 96
- Placental Function
- 4 layers separate maternal and fetal
blood
- syncitiotrophoblast
- cytotrophoblast
- villi connective tissue
- fetal capillary endothelium
- 3 main functions
- metabolism
- transport
- endocrine
- Placental Metabolism
- synthesizes
- glycogen
- cholesterol
- fatty acids
- provides nutrient and energy
- Placental Transport
- gases and nutrition
- oxygen, carbon dioxide, carbon
monoxide
- water, glucose, vitamins
- hormones, mainly steroid not protein
- electrolytes
- maternal antibodies
- waste products
- urea, uric acid, bilirubin
- drugs and their metabolites
- infectious agents
- cytomegalovirus, rubella, measles,
microorganisms
- Placental Endocrine
- Human chorionic gonadotrophin (hCG)
- like leutenizing hormone, supports
corpus luteum
- Human chorionic somatommotropin (hCS)
- or placental lactogen
- stimulate mammary development
- Human chorionic thyrotropin (hCT)
- Human chorionic corticotropin
(hCACTH)
- progesterone and estrogens
- support maternal endometrium
- relaxin
|
|
|
|
|
|
|
|
References
- Selected Lists of References from PubMed
March 1999 search results are available for
School of Anatomy computers without internet
access. Computers with internet access can
search from either Page
2 or PubMed
Internet Access
- Selected Research Articles and
Reviews
|
Search
Pubmed Now
By clicking on the listed keywords below (used
to search the database) the most current references
on Medline will be displayed.
|
|
About Notes
- Notes from the Embryology Program compiled and
written by Dr Mark Hill.
- Note Links to OMIM Entries are copies of originals
for computers without internet access. Computers with
internet access can directly access the database.
|
|
|
m.hill@unsw.edu.au
Date Last Modified: 11/10/99
This site maintained by Dr M. Hill
|
|