Figure 10.

Time line of the appearance of layering in the gut wall of human embryos. The histological sections show the absence (left) and presence (right) of the layered gut wall. The layered gut wall appears first in oesophagus, stomach and proximal small intestine at CS17, in the middle portion of the small intestine at CS18, in the distal small intestine and distal hindgut (just cranial to cloaca) at CS20, and in the rest of the colon (ascending limb and hindgut) at CS22 [Colour figure can be viewed at wileyonlinelibrary.com]