Primary chorionic villi. Diagrammatic.
Secondary chorionic villi. Diagrammatic.
Syncytiotrophoblast (from the Greek 'syn'- "together"; 'cytio'- "of cells"; 'tropho'- "nutrition"; 'blast'- "bud") is the epithelial covering of the highly vascular embryonic placental villi, which invades the wall of the uterus to establish nutrient circulation between the embryo and the mother. 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, rupturing maternal capillaries and thus establishing an interface between maternal blood and embryonic extracellular fluid, facilitating passive exchange of material between the mother and the embryo.
The syncytiotrophoblast secretes progesterone and leptin 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.
- Langman's Medical Embryology, 10th Edition. T.W. Sadler. p. 34
- BU Histology Learning System: 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
|This developmental biology article is a stub. You can help Wikipedia by expanding it.|