New Insights into the Process of Placentation and the Role of Oxidative Uterine Microenvironment

Figure 2

Extravillous trophoblast invasion and spiral artery remodelling. Within the syncytium, lacunae (the primitive intervillous space) are formed and proliferative cytotrophoblast cells emanate until they contact the endometrium (anchoring villi). At the tips of the villi, cytotrophoblasts differentiate into invasive trophoblast cells that will leave the villi and migrate through the stroma until they reach maternal spiral arteries or the deep myometrium. Interstitial extravillous trophoblasts that reach spiral arteries disrupt the vascular smooth muscle cell layer and replace it by fibrinoid material, while endovascular trophoblasts destroy their lumen and occupy their endometrium, converting them into low-resistance vessels.