Starting from the lumen, the inner three layers form the tunica mucosa . The innermost layer is the lamina epithelialis , a layer of epithelium. Next is the lamina propria , a layer of connective tissue. In some organs, a layer of smooth muscle is present as the lamina muscularis . Below the mucosa is the tunica submucosa which is predominately connective tissue.
Muscular layers form the tunica muscularis .
On the outer surface of the organs which are surrounded by a body cavity, a tunica serosa comprised of mesothelium and a small amount of underlying connective tissue is present.