Tubules, 30 nm in diameter, are a conspicuous feature of all Golgi apparatus (Fig. 4.1). Their function, however, has remained elusive. Tubules may extend for considerable distances from the stack. The total surface area of the tubules and associated fenestrae is equivalent to or greater than that of the flattened portions of cisternae. Thus the tubules appear to contribute significantly to Golgi apparatus mass.
The tubules are continuous with the peripheries of the stacked cisternae (Figs. 4.1 to 4.4). Cisternae from the exterior faces of the stack consist almost entirely of tubules with much reduced central plate-like structures (Fig. 4.3). Cisternae near the middle of the stacks often begin to anastomose close to their edges and then blend gradually into the resultant fenestrae (Fig. 4.2). When fenestrae are absent, tubules may emerge directly from the peripheries of the flattened saccules (Fig. 4.3). These features are illustrated in the model and diagram of Fig. 4.5.
KeywordsGolgi Apparatus Rough Endoplasmic Reticulum Secretory Vesicle Smooth Endoplasmic Reticulum Peripheral Route
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