Human Anatomy Part 1 - K. A. Dubenko, A. K. Kolomiysev, Yu. B. Chaykovsky 2002

Special Part
Myology, myologia [the study of muscles] - General Overview
Accessory apparatus of muscles

Auxiliary Muscle apparatuses include: fasciae, fibrous and synovial tendon sheaths, synovial bursae, muscular pulleys, and sesamoid bones.

Fasciae, fascia (Latin fascia – bandage), are Cytology/practical/45.html">Dense Connective Tissue sheaths that envelop individual Muscles, muscle groups and their tendons, certain Organs, and neurovascular bundles. They act as specific extensions of the Skeletal System and serve as attachment sites for individual muscle bundles. Fasciae enclose all muscles except facial muscles, forming protective sheaths around them. They provide structural support for muscles, Blood Vessels, and nerves, keep muscles and tendons in proper alignment, separate muscle groups and organs, and bound fascial spaces. Fasciae form thickenings between muscle groups known as intermuscular septa (septum intermuscularе). Sometimes a muscle originates from or attaches to a fascia. Fasciae facilitate Muscle contraction in a specific direction and prevent lateral displacement. When a fascia is injured or underdeveloped, a muscle may herniate through the defect. Weakness or injury to the pelvic floor fasciae is a major factor contributing to rectal or uterine prolapse. During inflammatory processes, fasciae act as a biological barrier, preventing the spread of inflammatory exudate to adjacent muscles or areas. In surgery, fasciae are used as plastic graft material in joint and cranial Procedures. They are classified into subcutaneous or superficial fascia (fascia superficialis) and deep or proper fascia (fascia propria).

Tendon sheaths (Vagina tendinis) can be either fibrous or synovial. Fibrous or osteofibrous tendon sheaths are located in the distal PARTS OF THE limbs surrounding the most mobile segments of long tendons (e.g., the extensor Muscles of the fingers). Fibrous sheaths help keep tendons in close proximity to Bones and joints and guide their movement in a specific direction. Synovial tendon sheaths, much like fibrous ones, enclose tendons at sites subject to the greatest friction and contact with bones and joint capsules. Each synovial sheath of digits II–V consists of two synovial layers: an outer and an inner layer (Fig. 115). The inner visceral layer directly covers the tendon on all sides, leaving a narrow strip exposed on the posterior surface of the tendon. At the edges of this strip, the inner layer folds back to become the outer or parietal layer, which encloses the tendon over the inner layer. The transition zone where the visceral layer folds into the parietal layer forms a double fold of the synovial membrane known as the tendon mesentery (mesotendineum). It contains the blood Vessels and nerves that supply the tendon; damage to this mesentery can lead to tendon necrosis. The slit-like cavities of the digital synovial sheaths are flattened and laterally expanded, forming lateral recesses of the synovial sheaths. These cavities contain synovial fluid (synovia), which facilitates smooth, elastic gliding of the tendons.

¹ Sechenov, I. M. Selected Philosophical and Psychological Works. - M., 1947. - P. 385.

Synovial bursae (bursa synovialis) are located beneath muscles and tendons over bony prominences and areas subject to maximum friction. Synovial bursae are typically found near joints, often communicating with the joint cavity, and are filled with synovial fluid.

Muscular pulleys (trochlea muscularis) are found in areas where muscles change their direction of pull by looping over bony or fibrous structures.

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Fig. 115. Diagram of The Structure of a synovial sheath (after Benninghoff): A – cross-section; B – longitudinal section

Synovial bursae are located between muscle tendons and pulleys to reduce friction. Muscular pulleys increase the angle of tendon insertion onto bones.

Sesamoid bones (ossa sesamoidea) are located within the tendons of certain muscles near their insertion onto bones, as well as in the region of the metatarsophalangeal joints (constantly present at the 1st digit) and the interphalangeal joint of the 1st digit. Sesamoid bones increase the angle of tendon attachment to bones, thereby enhancing the mechanical leverage of the muscle. These include the Patella and the pisiform bone (os pisiforme).