NUR1 324 Lecture : digestion.doc
Document Summary
Main role in homeostasis: provide appropriate amount and type of nutrients to body. Main properties: tubular nature, communication with external environment: The lumen is considered as being part of the external environment. 2 types of evolutionary development: growth, differentiation: In length (the human git is 3x the height of an average man) Growth of the internal surface (inner surface is 600x larger than the outer surface because of convolutions). The git is not a simple structure; it is a sequence of interconnected organs. However, if you take a cross section anywhere, you will get the same 4 typical layers making the wall of the git. 4 layers of the gut wall (from outside to lumen): serosa: thin but though layer of tissue, muscularis externa: Longitudinal layer: muscles fibers parallel to the tube responsible for the shortening of the. Circular layer: muscle fibers at right angle with the long axis of the gut.
