Myology

The tendons are tough, whitish cords, varying in length and thickness, and devoid of elasticity. They consist almost entirely of white- fibrous tissue, the fibrils of which have an undulating course parallel with each other and are firmly united together. They are very sparingly supplied with blood-vessels, the smaller tendons having in their interior no trace of them. Nerves supplying tendons end in what are known as neurotendinous spindles or organs of Golgi these axe described with the organs of the senses.

The aponeuroses are flattened or expanded tendons, of a pearly-white color, iridescent and often glistening; they are only sparingly supplied with blood vessels.

The tendons and aponeuroses connect the muscles with the structures to be moved, such as the bones and cartilages, Where the end of a muscle is continued directly into a tendon, the line of junction between the two is usually well defined, but where the muscle meets the tendon obliquely, bundles of tendon fibers generally run for a variable distance into the substance of the muscle, so that the line of junction is irregular. Microscopic examination shows that, in either case, the tendon is subdivided into small bundles; corresponding in size and number with the fibers of the muscle. Each muscular fiber ends in a more or less rounded extremity covered with sarcolemma, and the fibers of each tendon bundle are intimately united with the sarcolemma covering the end of the muscular fiber. The mode of union is well shown when the muscle fiber has shrunk inside its sarcolemma.

The fasciae are fibro-areolar, membranous laminae, of variable thickness and strength, found in all regions of the body, investing the softer and more delicate organs. During the process of development many of the cells of the mesoderm are differentiated into bones, muscles, vessels, etc.; the cells of the mesoderm which are not so utilized form an investment for these structures and are differentiated into the true skin and the fasciae of the body. The fasciae are subdivided into superficial and deep.

The superficial fascia is found immediately beneath the skin over the entire surface of the body. It connects the skin to the subjacent parts, and consists of fibro-areolar tissue, containing in its meshes pellicles of fat in varying quantity. It varies in thickness in different parts of the body; in the groin it is so thick that it may be subdivided into several laminae. It facilitates the movement of the skin, serves as a soft bed for the passage of vessels and nerves to the skin, and retains the warmth of the body, since fat is a bad conductor of heat. Beneath the fatty layer there is generally another layer of superficial fascia, almost devoid of adipose tissue, in which the trunks of the subcutaneous vessels and nerves and the superficial lymph-glands are found. Certain cutaneous muscles are situated in the superficial fascia, e.g. the Platysma and the muscles of the face. The superficial fascia is most distinct at the louver part of the abdomen, in the perineum, and in the limbs; it is very thin oil the dorsal aspects of the hands and feet, on the side of the neck, in the face, and around the anus. It is very dense in the scalp, palms of the hands, and soles of the feet, forming a fibro-fatty layer, which binds the skin firmly to the underlying structures.

The deep fascia is a dense, inelastic membrane, forming sheaths for the muscles, and in some cases affording them broad surfaces for attachment. It consists of bundles of white fibrous tissue, placed parallel with one another and connected together by other fibers disposed in a rectilinear manner. It forms a strong investment which not only binds down collectively the muscles in each region, but may give a separate sheath to each, and to the vessels and nerves as well. It assists the muscles in their actions by the degree of tension and pressure it makes upon their surfaces, in certain situations the degree of tension and pressure is regulated by muscles inserted into it, as, for instance, by the Tensor fasciae latae and Gluteus maximus in the thigh, and the Palmaris longus in the hand. In the limbs, the fascia not only invests the limb, but gives off septa, which separate the various muscles, and are attached to the periosteum these prolongations of fasciae are usually spoken of as intermuscular septa.

The fasciae and muscles may be grouped into those of the head and neck; of the trunk; of the upper limb; and of the lower limb.

Figure 41
Skeletal muscle longitudinal section - Figure 041
Figure 42
Skeletal muscle magnified - Figure 042
Figure 43
Sarcomere - Figure 043

 


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