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The thyroid follicles can also be considered of acinar formation but in this case the follicles, being part of an endocrine gland, act as a hormonal deposit rather than to facilitate secretion. Mucous acini usually stain pale, while serous acini usually stain dark.
Mucoserous acini (singular acinus) or mixed acini are mainly present in submandibular and sublingual glands. They are formed by mucous cells with some serous cells interspersed each other. Both cells pour their secretion directly in the lumen. Layer of mucous cells and serous demilune of serous cells superficial to mucous cells
They contain serous acini, a grouping of serous cells that secrete serous fluid, isotonic with blood plasma, that contains enzymes such as alpha-amylase. Serous glands are most common in the parotid gland and lacrimal gland but are also present in the submandibular gland and, to a far lesser extent, the sublingual gland.
Each acinus consists of a single layer of cuboidal epithelial cells surrounding a lumen, a central opening where the saliva is deposited after being produced by the secretory cells. The three forms of acini are classified in terms of the type of epithelial cell present and the secretory product being produced - serous, mucoserous, and mucous.
The mucous salivary glands are similar in structure to the buccal and labial glands. They are found especially at the back part behind the vallate papillae, but are also present at the apex and marginal parts. In this connection, the anterior lingual glands require special notice.
Merocrine glands – cells secrete their substances by exocytosis. (e.g. mucous and serous glands; also called "eccrine", e.g. major sweat glands of humans, goblet cells, salivary gland, tear gland and intestinal glands) Apocrine glands – a portion of the secreting cell's body is lost during secretion.
Submucosal means that the actual gland resides in the connecting tissue below the mucosa. The submucosa is the tissue that connects the mucosa to the muscle outside the tube. The glands themselves are quite complex. The mucus factory is at the bottom, in the submucosa, it is composed of many little sacs (acini) where the mucus originates.
Further, because the secretory cells are of both serous and mucous types, the submandibular gland is a mixed gland, and though most of the cells are serous, the exudate is chiefly mucous. It has long striated ducts and short intercalated ducts. [7] The secretory acinar cells of the submandibular gland have distinct functions.