tubercle

Tubercle is a term used in anatomy and pathology to describe a small, rounded eminence on a bone or a small nodular lesion. The word comes from Latin tuberculum meaning a little swelling.

In anatomy, a tubercle is a projection on a bone that serves as an attachment site for muscles or ligaments. The humerus, for example, has the greater tubercle and the lesser tubercle, which provide attachment points for the rotator cuff muscles. Other bones may bear tubercles that function as attachment sites or articulation points, contributing to muscle leverage and joint mechanics. The term can also describe small rounded nodules occurring on other structures, such as ribs or vertebrae, where they influence joint or tendon relationships.

In pathology, a tubercle refers to a granulomatous lesion associated with infection by Mycobacterium tuberculosis. A classic tubercle consists of a central area of caseous necrosis surrounded by macrophages, epithelioid cells, Langhans giant cells, and a rim of lymphocytes. This organized structure reflects a localized immune response and can calcify over time. In pulmonary tuberculosis, tubercles may coalesce and develop into cavities, contributing to disease progression and transmission.

Throughout medical usage, tubercle denotes a small, rounded feature whether it is a bony projection or a specific type of granulomatous lesion. The context—anatomical anatomy versus infectious pathology—clarifies which meaning is intended.