Merocrine

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405 Modes of Secretion by Glands Merocine

Histology of paneth cells, annotated

Merocrine is a term used in histology and cell biology to describe a type of exocrine secretion where the secretory cells excrete their substances by exocytosis without causing any damage to the cell or its membrane. This process allows cells to release their contents (e.g., enzymes, sweat, or saliva) directly into the extracellular environment. Merocrine secretion is one of the three main types of exocrine secretion mechanisms, the other two being apocrine and holocrine secretion.

Mechanism

In merocrine secretion, secretory vesicles within the cell transport the substance to the cell membrane. These vesicles are formed in the Golgi apparatus of the cell. Once the vesicles reach the cell membrane, they fuse with it and release their contents into the extracellular space. This process is facilitated by various proteins, including SNAREs (soluble N-ethylmaleimide-sensitive factor attachment protein receptors), which help in the docking and fusion of vesicles with the cell membrane.

Examples

One of the most well-known examples of merocrine glands are the eccrine sweat glands, which are found throughout the human body and play a key role in thermoregulation by secreting sweat. Another example is the salivary glands, which release saliva into the mouth to aid in digestion and maintain oral hygiene.

Comparison with Other Secretion Types

- Apocrine secretion involves the loss of part of the cell's cytoplasm along with the secretory product. This type of secretion is seen in the mammary glands during milk production. - Holocrine secretion involves the entire cell disintegrating to release its contents. This is observed in the sebaceous glands of the skin, where cells filled with sebum (a lipid-rich substance) burst and are replaced by new cells.

Significance

Merocrine secretion is crucial for various physiological processes, including digestion, respiration, and thermoregulation. It allows for the continuous secretion of substances without significant loss of cell mass or function, making it an efficient and sustainable mechanism for maintaining homeostasis in the body.

See Also

• Exocrine gland
• Endocrine gland
• Secretion
• Cell biology