FIGURE 4.

Xenopus laevis, patterns of mucosal vessels of the urinary bladder as seen from the mucosal side. (a) Distended bladder. Most mesh capillaries (c) are straight, a few capillaries only undulate. A maximum of three layers of vessels (capillaries, venules or small veins, arterioles, or small arteries) is seen. A local convolution of small vesical arteries (sva) is shown (encircled area). Arrow points at a bifurcation of a vesical artery with daughter vessels laying close aside. (b) Similar to (a), but less distended bladder displaying more undulating capillaries (c) and postcapillary venules (asterisks). Note small (short arrow) and large branching angles (long arrow) of a vesical artery (va). (c) Contracted (empty) bladder. Note strong undulating capillaries (c) and postcapillary venules (asterisks). (d) Strongly contracted bladder displaying narrow spaced mesh capillaries of dome‐shaped mucosal folds (d). svv small vesical vein, vvv vesical venule