page_title: Cytotrophoblast
section_title: Invasive lineage
hierarchical_section_title: Cytotrophoblast / Invasive lineage
caption_attribution_description: English: Histopathology of a tubal pregnancy, including a chorionic villus. There is some hemorrhage in the intervillous space. H&amp;E stain. Reference: &#32;(2019).&#32;"Development of the human placenta". Development&#32;146&#32;(22): dev163428. DOI:10.1242/dev.163428. ISSN 0950-1991.
context_page_description: The cytotrophoblast is the inner layer of the trophoblast. It is interior to the syncytiotrophoblast and external to the wall of the blastocyst in a developing embryo.
  The cytotrophoblast is considered to be the trophoblastic stem cell because the layer surrounding the blastocyst remains while daughter cells differentiate and proliferate to function in multiple roles. There are two lineages that cytotrophoblastic cells may differentiate through: fusion and invasive. The fusion lineage yields syncytiotrophoblast and the invasive lineage yields interstitial cytotrophoblast cells.
  Cytotrophoblastic cells play an important role in the implantation of an embryo in the uterus.
context_section_description: The invasive lineage creates cytotrophoblasts that are essential in the process of implantation and forming a fully functional placenta. An undifferentiated cytotrophoblastic stem cell will differentiate into an extravillous cytotrophoblast intermediate and then into an interstitial cytotrophoblast. An interstitial cytotrophoblast may then further differentiate into an endovascular cytotrophoblast or form a syncytium.
caption: Histopathology of a chorionic villus, in a tubal pregnancy.
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