Final answer:
Merocrine, apocrine, and holocrine are types of exocrine gland secretions. Merocrine glands release secretions by exocytosis, apocrine glands lose the cell's apical part, and holocrine glands release contents by cell rupture.
Step-by-step explanation:
Types of Glandular Secretions
Exocrine glands exhibit different modes of secretion, mainly merocrine, apocrine, and holocrine. Merocrine glands release their secretions in vesicles by exocytosis without causing any damage to the glandular cells. Examples include the salivary glands and pancreas. The eccrine sweat glands are also merocrine and are involved in thermoregulation. In contrast, apocrine glands lose a small portion of their cell body during secretion, as seen in mammary glands during breast milk production. Holocrine glands accumulate secretory products within their cells, which then rupture, releasing the contents and resulting in the destruction of the cells. Sebaceous glands, which secrete oils for hair and skin, are an example of holocrine glands.