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 [bur´sah] (pl. bur´sae) (L.)
a small fluid-filled sac or saclike cavity situated in places in tissues where friction would otherwise occur. adj., adj bur´sal. Bursae function to facilitate the gliding of muscles or tendons over bony or ligamentous surfaces. They are numerous and are found throughout the body; the most important are located at the shoulder, elbow, knee, and hip. Inflammation of a bursa is known as bursitis.
bursa of Fabricius an epithelial outgrowth of the cloaca in chick embryos, which develops in a manner similar to that of the thymus in mammals, atrophying after 5 or 6 months and persisting as a fibrous remnant in sexually mature birds. It contains lymphoid follicles, and before involution is a site of formation of B-lymphocytes associated with humoral immunity.
bursa muco´sa (mucous bursa) (synovial bursa) a closed synovial sac interposed between surfaces that glide upon each other; it may be subcutaneous, submuscular, subfascial, or subtendinous in location.
subacromial bursa one between the acromion and the insertion of the supraspinatus muscle, extending between the deltoid and the greater tubercle of the humerus. See illustration.
Subacromial bursa, lying between the acromion and supraspinatus tendon and extending between the deltoid and greater tubercle. From Dorland's, 2000.


[bur′sə] pl. bursae
Etymology: Gk, byrsa, wineskin
1 a fibrous sac between certain tendons and the bones beneath them. Lined with a synovial membrane that secretes synovial fluid, the bursa acts as a small cushion that allows the tendon to move over the bone as it contracts and relaxes. See also adventitious bursa,bursa of Achilles,olecranon bursa,prepatellar bursa.
2 a sac or closed cavity. See also omental bursa,pharyngeal bursa. bursal, adj.


Plural of bursa.


A closed sac lined with a synovial membrane and filled with fluid, usually found in areas subject to friction, such as where a tendon passes over a bone.
Mentioned in: Joint Fluid Analysis

bursae (burˑ·sā),

n.pl membrane-lined sacs containing synovial fluid, usually found in and around joints. Bursae provide protective cushioning and lubrication.