The Intestinal Goblet Cell

Most secretory cells produce a product which is a complex of both proteins and carbohydrates. These cells include parotid acinar cells, chondrocytes, epididymis epithelial cells, and mucous cells of the alimentary and respiratory tracts. The complex carbohydrate secretions 

From the above considerations, it appears that the Golgi complex serves three main functions in the elaboration of secretory products (1) it provides a cellular site for the complexing of certain moieties to secretory precursors which are derived from the cisternae of the RER (2) it is involved in the final concentration of secretory material and (3) it provides a vehicle for the net transport of intracellular secretory material to the extracellular space. A fourth function of the Golgi complex involves the formation of primary lysosomes. Since the lysosome is a product retained intracellularly rather than secreted to the extracellular environment, it will not be included in the ensuing discussion of cellular secretory mechanisms. The reader, therefore, is referred to an excellent and thorough review of lysosomes edited by Dingle and Fell (1969a,b). 

The above Golgi functions, particularly the first and third, raise two important questions. Since the Golgi complex is not known to have the machinery for protein synthesis, what is the origin of the enzymes required for the covalent linkage of carbohydrates and other moieties to the secretory precursors, and how do they enter the Golgi complex The second question involves the use of intracellular membranes, particularly those of Golgi vacuoles, in the transport of secretory products. 

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