Anatomy and Physiology of Children and Adolescents - M. R. Sapin 2007

Musculoskeletal System
Muscular System
Accessory Structures of Muscles

Muscles perform their Functions with the aid of accessory structures, which include fasciae, fibrous and osteofibrous canals, synovial sheaths and synovial (mucous) bursae, as well as pulleys (trochleae).

Fasciae are Connective Tissue sheaths that enclose muscles. They partition muscles by forming intermuscular septa and prevent friction between adjacent muscles (Fig. 31). In cases of Hemorrhage or the spread of abscesses toward the muscles, fasciae restrict the dissemination of Blood and pus beyond the fascial sheath. They are classified into superficial, deep, and proper (investing) fasciae.

Proper fasciae form a distinct connective tissue sheath around each individual Muscle. Superficial fasciae overlie muscle groups, whereas deep fasciae lie between deep and superficial muscle layers, separating them from one another.

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Fig. 31. Osteofibrous sheaths of the muscles in the lower third of the right thigh:

1 — fascia lata of the thigh; 2 — fascial Sheath of the flexor muscles; 3 — Femur; 4 — sciatic nerve; 5 — femoral artery and vein; 6 — fascial sheath of the sartorius muscle; 7 — medial intermuscular septum of the thigh; 8 — osteofibrous sheath of the extensor muscles; 9 — lateral intermuscular septum of the thigh

In regions subject to intensive mechanical stress and powerful muscular activity, fasciae acquire a tendinous Structure, resembling the aponeuroses of broad muscles.

Fibrous and osteofibrous canals are found in areas where tendons span multiple joints (such as the hand and FOOT). These canals serve to hold tendons in a fixed position During Muscle contraction. The walls of fibrous canals are composed of dense Fibrous connective tissue, while bones participate in The formation of osteofibrous canals. Within these fibrous canals lie synovial sheaths, which eliminate friction between the tendon and the canal walls.

Synovial sheaths are formed by a synovial membrane, one layer of which lines the walls of the canal, while the other envelops and fuses with the tendon. Both layers merge at their ends to form a closed, narrow cavity containing a small amount of synovial fluid, which lubricates the sliding synovial surfaces.

Synovial (mucous) bursae perform a function similar to that of synovial sheaths. These bursae are closed, fluid- or mucus-filled sacs located in regions where a tendon passes over a bony prominence or across the tendon of another muscle.

Pulleys refer to bony prominences (condyles, epicondyles) over which a muscle tendon is reflected. As a result, the angle of tendon attachment to the bone increases, thereby enhancing the mechanical force exerted by the muscle on the bone.