digestive and respiratory system derived from primitive gut /foregut /midgut /hindgut ---epi. of digestive and respiratory system derived from endoderm ---CT and MT of digestive and respiratory system derived from splanchnic or visceral mesoderm
1. General features: (1) small number of cells and large amount of extracellular ground substance (2) extracellular is composed of fibers and amorphous ground substance-matrix (3) all of them originate from mesenchymeembryonal CT (4) have functions of connection, supporting, protecting, nutrition, defence and repairing
5 separate events must occur: -O must be successfully transported from bulk solution(mass transport) -O must adsorb transiently onto electrode surface (non-faradaic) CT must occur between electrode and (faradaic)