Fig. 14.

Choriocapillaris ultrastructure at 11 WG in periphery (A), equator (B), and posterior pole (C). Undifferentiated angioblasts (pericyte and endothelial cell precursors) in peripheral choroid had dense chromatin and formed loosely arranged aggregates with slit-like lumens (L). At the equator (B) immature endothelial cells had numerous mitochondria (M) with some tight junctions present (J). Complex membranous infoldings resembling filopodia extended into the developing lumen (F). Immature erythrocytes (E) were present in the lumen and their membranes appeared to fuse with the filopodia. (C) Pericyte-like cells were observed in posterior pole where they appeared more differentiated, with dispersed chromatin in their nuclei (PN) and numerous mitochondria (M) in close proximity with rough endoplasmic reticulum (RER) and Golgi (arrowhead). Endothelial cells had condensed chromatin in their nuclei (EN), made tight junctions with one another (J). In the posterior pole, Bruch’s membrane (BMb) was starting to form posterior to the RPE. (Scale bar in A & B 2 μm, and C 1 μm) (Fig. 2 from Baba et al., Invest. Ophthalmol. Vis. Sci. 50:3506, 2009, with permission).