Applied anatomy and kinesiology; the mechanism of muscular movement . 140shows how it is protruded when the diaphragm contracts in taking a full breath. STERNOCLEroOMASTOID. A pair of muscles forming a letter V down the front and sides ofthe neck. Origin.—^The mastoid process of the skull. SCALENI 235 Insertion.—^The front of the sternum and the inner fourth of theposterior border of the clavicle. Structure.—Parallel fibers, dividing into two parts below its middle. Action.—As a breathing muscle, it lifts the sternum, both musclesof the pair acting together, while the head is held rigidly upri
Applied anatomy and kinesiology; the mechanism of muscular movement . 140shows how it is protruded when the diaphragm contracts in taking a full breath. STERNOCLEroOMASTOID. A pair of muscles forming a letter V down the front and sides ofthe neck. Origin.—^The mastoid process of the skull. SCALENI 235 Insertion.—^The front of the sternum and the inner fourth of theposterior border of the clavicle. Structure.—Parallel fibers, dividing into two parts below its middle. Action.—As a breathing muscle, it lifts the sternum, both musclesof the pair acting together, while the head is held rigidly the lower end is the fixed point, which is more usual, one ofthe pair rotates the face to the opposite side and the two flex theneck. The sternocleidomastoid is an important muscle of respiration,acting in labored breathing in such exercises as running or in makinga deep inhalation for any purpose. It is able to assist greatly incases where some of the other muscles of breathing are lost. The lower portion of this muscle is shown well in Fig. Fig. 141.—The scaleni. (Gray.) SCALENI. Three muscles named the anterior, middle, and posterior scalenifrom their relative positions and their triangular form as a group(Fig. 141). 236 BREATHING Origin.—The transverse processes of the cervical vertebrae. Insertion.—The anterior and middle scaleni, on the upper surfaceof the first rib; the posterior on the second rib. Structure.—Longitudinal fibers, tendinous at each end. Action.—^The scaleni are in a position to support the upper ribswhen the intercostals contract and to lift them by strong contrac-tion, providing the neck is held firmly erect. The presence of thebrachial plexus of nerves makes it difficult to secure satisfactoryisolated action of the scaleni, but under the mild stimulus that canbe given them, the elevation of the first ribs and sternum has beenseen. The inability of the scaleni to sustain and lift the chest whenthe neck is not held up is th
Size: 1264px × 1976px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, booksu, booksubjectphysicaleducationandtraining
