Alimentary Canal a tube that is about 8 meters long, a passageway from the mouth to anus that passes through thoracic and abdominalpelvic regions, the wall of which consists of 4 layers, from most internal to external, submucosa - a layer under the mucosa that has loose connective tissue, housing blood vessels, lymph vessels, nerves, glands, nourishes surrounding layers, and transports nutrients away, mucosa right on top of the submucosa, an inner mucous membrane surrounding the lumen of the alimentary canal, composed of epithelium, connective tissue, some smooth muscle tissue, it protects the tissue of the canal and also plays a role in secretion and absorption, including folds to increase surface area of absorption, muscularis composed of two layers of smooth muscle, inner circular and outer longitudinal layer, its purpose is to propel food through the canal (why it is so muscular), and finally, serosa, a serous layer, the outermost layer of the alimentary canal, it protects underlying tissues and secretes serous fluid to reduce friction
Movements of the tube can be divided into two different categories: mixing and propelling. Propelling movements of the alimentary canal include a motion called peristalsis, when a ring of contraction forms in a portion of one side of the tube with the other side being relaxed ahead allowing for the food to be propelled forward. Mixing movements of the alimentary canal are when the smooth muscles contract rhythmically in small sections of the tube.