Mucosa - Mucus membrane composed of epithelium, connective tissue, and smooth muscle
Epithelium - Three main types of epithelium are found throughout the digestive tract. Stratified squamous epithelium which is found in the mouth, esophagus, pharynx, and anal canal for a protective function. Columnar epithelium found in the stomach and intestines to secrete and absorb. Exocrine/endocrine cells to secrete enzymes, hormones, etc...
Connective tissue - Contains blood and lymphatic cells as well as mucosa associated lymphatic tissue (MALT) that protects the digestive system against diseases.
Smooth muscle - A thin layer of smooth muscle that can contract to fold the mucosa to form valleys and ridges.
Submucosa - More connective tissue that binds the mucosa to the muscularis. It contains blood and lymphatic vessels to receive and transport absorbed nutrients.
Muscularis - As a muscle, it controls a lot of the muscle contractions within the digestive system. In the mouth, pharynx, and anal sphincter, it controls the voluntary actions of swallowing and defecation. In the rest of the digestive tract, its contractions produce peristalsis and segmentation.
Serosa - The most superficial layer of the tract, also called the visceral peritoneum.