Basal Plasmalemma Infolds Basal Labyrinth Basolateral Interdigitations

^ Epithelial cells, which are involved in an extensive transport of ions and liquids, have deep, often complex, vertical involutions of the basal plasmalemma. In earlier descriptions, they were known as the "basal labyrinth" [2. Involutions of the plasmalemma obviously serve to enlarge the basal cell surface area. Involutions exist in different variations. Separating curtains of membrane folds create high, narrow cytoplasmic spaces, which contain large, mostly oval crista-type mitochondria [3. Constituents of these plasma membrane involutions mediate transport functions. Involutions and the rows of mitochondria between them create the appearance of a basal stria-tion in light microscopy (see Figs. 89, 90, 92).

Part of an epithelial cell of the tubulus proximalis from a rat nephron.

1 Cell nucleus, pushed up to the apical cell region

2 Basal membrane involutions

3 Mitochondria

4 Basal lamina

5 Lumen of a peritubular capillary

6 Endothelial cell, region with nucleus

7 Fenestrated epithelium

8 Lysosomes

Electron microscopy; magnification: x 10 000

Interdigitations Electron Microscope

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oo Interdigitations [1 between cell processes in the epithelium of a secretory ID duct from the parotid gland. The tissue is cut parallel to the cell surface. The ^ interlocking digitations of neighboring plasmalemma are particularly impressive in this picture. They convey the impression of a labyrinth. As in other sections, the processes, which create the interdigitations, contain large mitochondria E .The shape of the mitochondria adjusts to the spacing within the cell processes.

The cells of the secretory duct of salivary glands have all the structural criteria of a transport epithelium (see Figs. 89, 90, 91, 96).

1 Interdigitizing cell processes

2 Mitochondria

3 Desmosomes

Electron microscopy; magnification: x 4000

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  • Faruz Medhane
    What is the basal and basolateral labyrinth?
    7 years ago

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