Demilunes

Demilunes are a histological feature of certain salivary glands, referring to serous demilunes: crescent- or half-moon-shaped caps of serous secretory cells that overlay mucous-producing acini in mixed glands. The name reflects their curved, crescent appearance.

In many humans, mucous tubules of submandibular and some sublingual glands are surrounded by a layer of serous cells, forming a cap that gives the impression of a half-moon on microscopy. Pure mucous glands lack these serous caps; thus demilunes are characteristic of mixed mucous-serous glands rather than all salivary tissues.

Functionally, the mucous cells produce mucins, while the serous demilune cells secrete a watery, enzyme-rich fluid. The serous component contributes to the enzymatic aspect of saliva, including proteolytic or amylolytic enzymes, depending on species and gland type. The overall saliva reflects both mucous and serous secretions.

Histology and visualization of demilunes depend on staining and tissue preparation. In routine sections, demilunes appear as crescent-shaped serous tissue at the periphery of mucous tubules. They may be more or less prominent depending on the gland and individual variation. Special stains, such as mucicarmine, can help distinguish mucous from serous components.

Clinically, demilunes are considered a normal architectural feature of certain salivary glands and are described in microscopic reports to characterize gland structure. They are not specific indicators of disease when encountered in typical anatomy, though their appearance helps delineate mucous-serous gland organization.