Syncytiotrophoblast

Syncytiotrophoblast
Primary chorionic villi. Diagrammatic.
Secondary chorionic villi. Diagrammatic.
Latin	syncitiotrophoblastus
Gray's	subject #6 47
Carnegie stage	5a
Days	8
Code	TE E6.0.1.1.4.0.2
MeSH	Syncytiotrophoblasts

Syncytiotrophoblast is the epithelial covering of the placenta villous tree. It is a unique tissue in that it is a multi-nucleated, terminally differentiated syncytium, extending to 13m². It lacks proliferative capacity and instead is maintained by fusion of underlying cytotrophoblast cells.

It is the outer syncytial layer of the trophoblasts and actively invades the uterine wall.

They form the outermost fetal component of the placenta (also known as 'syntrophoblast') and massively increase the surface area available for nutrient exchange between the mother and the fetus.

The syncytiotrophoblast secretes progesterone in addition to human chorionic gonadotropin (hCG) and human placental lactogen (HPL); hCG prevents degeneration of the corpus luteum. Progesterone serves to maintain the integrity of the uterine lining and, until the syncytiotrophoblast is mature enough to secrete enough progesterone to support pregnancy (in the fourth month of embryonic development), it is aided by the corpus luteum graviditatis.

Additional images

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  Section through embryonic area of Vespertilio murinus to show the formation of the amniotic cavity.

See also

• Syncytium
• Cytotrophoblast
• Intermediate trophoblast

External links

• Histology at BU 19908loa - "Female Reproductive System: placental villi"
• Nature (Journal) Diagram
• Musicki B, Pepe G, Albrecht E (1997). "Functional differentiation of placental syncytiotrophoblasts during baboon pregnancy: developmental expression of chorionic somatomammotropin messenger ribonucleic acid and protein levels.". J Clin Endocrinol Metab 82 (12): 4105–10. doi:10.1210/jc.82.12.4105. PMID 9398722.  Article
• Diagram at McGill
• Syncytiotrophoblast at eMedicine Dictionary