Secretory Mechanisms
The secretory cells can release their secretory products by one of three mechanisms.
| | 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. |
| 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. | |
| | Holocrine secretion designates the breakdown and discharge of the entire secretory cell. It is only seen in the sebaceous glands of the skin. |
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.
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