Table 1.

Key stages and pivotal developmental events that occur throughout quail intestine development

E1.9 (HH12)	E2.2 (HH16)	E3.5 (HH21)	E4 (HH23)	E5 (HH27)	E6 (HH29)
Continuous outer basement membrane Narrow mesenchymal space Single layered endothelial plexus Open gut tube (GT)	Dispersed outer basement membrane Scattered mesenchymal cells Single endothelial plexus Open GT	Continuous outer basement membrane Multilayered mesenchyme Peak in mesenchymal width Stratified outer epithelium Anterior and posterior closure of GT	Continuous outer basement membrane Contraction of mesenchymal width Single layered outer epithelium	Dispersed outer basement membrane Increased mesenchymal width Cytokeratin-positive outer epithelium	Continuous outer basement membrane Decreased mesenchymal width Mesothelium Completely closed GT Endothelial plexus splits into two layers Outer circular muscle layer Length: 6mm
E10	E11	E12	E14	E16
Villi present Outer longitudinal muscle layer Absence of SMA-negative submesothelial mesenchyme Length: 42mm	Large surface blood vessels	Sharp increase in mesenchymal area Length: 72mm	Endothelial cells in base of villi Myofibroblasts in lamina propria Inner circular muscle layer Single layer of vascular smooth muscle Length: 85mm	Endodermal basement membrane dispersed Endothelial cells in tips of villi Inner longitudinal muscle layer Multilayered vascular media Limited submucosal mesenchyme Length: 110mm