Wall of the Alimentary Canal
													The alimentary canal consists of four layers. Listed from outside to inside: 1) the fibroserous outer covering; serous in most of GI tract, fibrous in esophagus.   2) the muscularis (externa), smooth muscle (except in upper esophagus) in two or three layers; 3) the submucosa, containing glands, nerves,  and blood vessels; 4) the mucosa, the epithelial secretory and absorptive lining, bounded by the muscularis mucosae (mm).
		4
									mm
				3
	2
											1