Page 91 - Atlas of Histology with Functional Correlations

FIGURE 2.6 ■ Basal region of an ion-transporting cell. ×16,600.

FUNCTIONAL CORRELATIONS 2.6 ■ Infolded

Basal Regions of the Cell

The deep infoldings of the basal and lateral cell membranes are seen only
with electron microscopy. These infoldings are found in certain cells of the

body, whose main function is to transport ions across the cell membrane. The
cells in the tubular portions of the kidney (proximal convoluted tubules and
distal convoluted tubules) selectively absorb useful or nutritious components

from the glomerular filtrate and retain them in the body. At the same time,
these cells eliminate toxic or nonuseful metabolic waste products such as
urea and drug metabolites.

Because these cells transport numerous ions across their membranes,
+
increased amounts of energy are needed, which is generated by Na /K +
ATPases (sodium pumps) embedded in the infolded basal and lateral cell
membranes. To perform these vital functions, numerous long mitochondria
that are located in these basal infoldings continually supply the cells with the

energy source (ATP) that operates these pumps for membrane transport.
Similar basal cell membrane infoldings are seen in the striated ducts of the
salivary glands. These glands produce saliva, which is then modified by

selective transport of various ions across the cell membrane as it moves
through these ducts to the larger excretory ducts.

FIGURE 2.7 | Cilia and Microvilli

This high-magnification electron micrograph illustrates the ultrastructural

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