Respiratory Muscles

RESPIRATORY MUSCLES, muscles that increase and decrease the volume of the chest cavity during breathing. The main work of R. m. falls on the process of inhalation, since exhalation usually occurs to a significant extent passively and is performed mainly due to the weight of the chest walls, elasticity of the lungs, costal cartilages, and abdominal muscles. During quiet breathing, a small number of muscles participate, namely: the diaphragm (see), external intercostal and interchondral muscles. During enhanced, tense inhalation, the following participate: 1) muscles of the trunk: mm. scaleni, mm. serrati posterior et anterior, mm. pectorales major et minor, mm. sterno-cleido-mastoidei, mm. trapezii, mm. extensores columnae vertebra-lis, mm. rhomboidei, mm. levatores scapulae, mm. latissimi dorsi; 2) muscles of the larynx: mm. sterno-hyoidei, mm. sterno-thyreoidei, mm. crico-arytaenoidei postici, mm. thyreo-ary-taenoidei; 3) muscles of the palate and pharynx: m. levator veli palatini, m. azygos uvulae, mm. constrictores pharyngis; 4) muscles of the face: mm. dilatatores narium anterior et posterior, mm. levatores alae nasi. During enhanced, tense inhalation, the following participate: 5) mm. intercostales intend, mm. infracostales; 6) muscles of the abdominal press: m. triangularis sterni, mm. serrati posteriores inferiores, mm. quadrati lumborum. Basically, the action of R. m. comes down to the expansion and narrowing of the chest cavity. During inhalation, it increases in vertical size due to the descent of the diaphragm, and in the sagittal and frontal planes due to the elevation and divergence of the ribs. During enhanced exhalation, the reduction of the cavity is achieved by the action of the rib depressors and the abdominal press, which increases pressure in the abdominal cavity, as a result of which the diaphragm is pulled upward.