capsula

Capsula is a term of Latin origin that appears in several scientific disciplines to denote a capsule-like container or covering. In practice, it is most often encountered in two broad contexts: biology and medicine, and botany, with occasional use in anatomy and zoology.

In microbiology, a bacterial capsule refers to a gelatinous layer that surrounds some bacteria, situated outside the cell wall. This capsule is typically composed of polysaccharides or, less commonly, polypeptides. It serves protective functions, helping bacteria resist desiccation and evade host immune responses, including phagocytosis. The presence and characteristics of a capsule can influence a bacterium’s virulence and its interaction with vaccines that target capsule polysaccharides.

In pharmaceutics, a capsule is a small, cylindrical container used for oral dosage forms. There are hard capsules, usually made of two-piece shells and filled with powders, pellets, or granules, and soft capsules, which are typically one-piece and filled with liquids. Capsule shells are commonly made from gelatin or plant-derived polymers such as hydroxypropyl methylcellulose. Capsules are designed to dissolve in the gastrointestinal tract, releasing their contents for absorption.

In botany, a capsule refers to a dry, dehiscent fruit that splits open to release seeds. Capsule fruits are found in many plant families and can dehisce along one or more seams, depending on the species. This fruit type is a standard term in botanical descriptions and helps distinguish it from other fruit types such as legumes or follicles.

In anatomy, the Latin term capsula appears in phrases such as capsula interna, where it denotes a small, capsule-like structure, typically translated as internal capsule. The usage is primarily historical or descriptive within Latinized anatomical nomenclature.