capsular

Capsular is an adjective relating to a capsule, a membranous envelope that encloses, covers, or separates an organ, a structure, or a cell. The term is used across biology, medicine, and related fields to describe tissues, diseases, or structures associated with a capsule.

In anatomy and medicine, capsular refers to the capsule surrounding an organ or joint. Examples include the joint capsule, the renal capsule surrounding the kidney, and Glisson's capsule around the liver, as well as the lens capsule of the eye. Clinically, the capsule can be involved in disease or procedures, such as adhesive capsulitis (frozen shoulder) involving the shoulder joint capsule, or capsular contraction around breast implants.

In microbiology, many bacteria are described as capsulated when they produce a capsule—a gelatinous layer outside the cell wall, typically composed of polysaccharides and sometimes proteins. The capsule helps protect bacteria from phagocytosis and can contribute to virulence and persistence. Species such as Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, and Bacillus anthracis have prominent capsules. Capsule polysaccharides are important serologic antigens and are used in vaccines, for example pneumococcal, Hib, and meningococcal vaccines that target capsular antigens.

Other uses include terms like capsular pattern in musculoskeletal examination and capsular contracture in plastic surgery, reflecting capsule-related phenomena in addition to the underlying tissue.