Fig. 3

Tendril formation in the oviducal gland after P4 implantation. Day 1 (A–D), day 2 (E–H), and day 5 (I–L) of P4 implantation. A, E, I The whole view from the oviducal gland (OG) to the upper (uOD) and lower (lOD) oviducts. The oviducal gland and the lower oviduct were cut longitudinally to expose formed tendrils. Black arrowheads, black arrows, and white arrowhead represent the initial thin portion, the middle thick portion, and the posterior thin portion of the formed tendrils (insets in E and I) (B, F, J) Magnified view of the oviducal gland. Tendrils (arrowheads) were extended from the middle portion of oviducal glands. C, G, K Stereomicroscope images of the formed tendrils (arrowheads). D, H, L Observation of the formed tendrils (arrowheads) using a scanning electron microscope. Note that the diameter of tendrils considerably increased on day 2 (H), and then decreased on day 5 (L). Scale bars, 5 cm (A, E, I), 1 cm (B, F, J), 1 mm (C, G, K) and 300 µm (D, H, L)