Secretory Mechanisms
The secretory cells can release their secretory
products by one of three mechanisms.
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Merocrine
secretion
corresponds to
the process of exocytosis. Vesicles open onto the surface of the cell, and
the secretory product is discharged from the cell without any further loss of
cell substance.
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Apocrine secretion
designates a
mechanism in which part of the apical cytoplasm of the cells is lost together
with the secretory product. The continuity of the plasma membrane is restored
by the fusion of the broken edges of the membrane, and the cell is able to accumulate
the secretory product anew. This mechanism is used by apocrine sweat glands,
the mammary glands and the prostate.
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Holocrine
secretion designates the breakdown and discharge of
the entire secretory cell. It is only seen in the sebaceous glands of the
skin.
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There are two additional
mechanisms by which secretory cells can release their products. Lipid soluble
substances may diffuse out of the secretory cell (e.g. steroid
hormone-producing endocrine cells). Transporters (membrane proteins) may
actively move the secretory product across the plasma membrane (e.g. the acid
producing parietal cells of the gastric glands). These secretory mechanisms may
not involve any light microscopically visible specialisations of the cell.
![thumbnail]( "Secretory Mechanisms")
Title:
Secretory Mechanisms
by:
om
at
2013-02-15T02:48:00+07:00
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Secretory Mechanisms