Exocrine Glands: Types of Secretions

Exocrine glands can be serous, mucous, or mixed depending on the nature of their secretory products.

Serous glands produce thin aqueous secretions that are rich in glycoproteins and enzymes.

For example, the parotid salivary glands are serous glands positioned in front of the ears. They produce saliva, rich in amylase that helps break down starchy food.  

Mucous glands consist of cells whose cytoplasm is filled with mucin-rich secretory vesicles, giving them a frothy appearance.

A good example of mucous glands are sublingual glands that lie below the tongue at the floor of the mouth. These glands secrete mucin that dissolves in water, forming a thick, slimy mucus coat that lubricates the oral cavity and helps make food easier to swallow.

Mixed exocrine glands are composed of serous secretory units intermixed with mucous secretory units and can produce both serous and mucous secretions.

The submandibular salivary glands are mixed glands located towards the back of the mouth that discharge saliva through the submandibular duct.