Electron micrographs of an eccrine sweat gland, a. This micrograph shows myoepithelial cells (My) and two distinctive gland cell types, dark cells (D) and clear cells (C). The apical portion of the dark cell is broad; it faces the lumen (L) of the gland and contains numerous secretory granules. The dashed line marks the boundary of one dark cell. The clear cell is more removed from the lumen of the gland. Its base rests on the myoepithelial cells or directly on the basal lamina. Most of the free surface of the clear cell faces an intercellular canaliculus (IC). Clear cells contain numerous mitochondria, extensive Infoldings of the plasma membrane, and large numbers of electron-dense glycogen inclusions, x 5,600. (Courtesy of Dr. John A. Terzakis.) b. At higher magnification, dark cells display rER (arrow) and a Golgi apparatus (G) in addition to secretory granules. Clear cells show large amounts of folded membrane, mitochondria, and glycogen. The myoepithelial cells (My) contain large numbers of contractile actin filaments. Short stubby arrows (upper right) mark the boundary of a clear cell, x 17,500. (Courtesy of Dr. John A. Terzakis.)
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