The External Intercostals

University:
Stanford University
Course:
MED 101 | Human Anatomy
Academic year:

2024
Views:

353

Pages:

2
Author:

larbi43100

‭The external intercostals‬ ‭ hese‬ ‭are‬ ‭muscles‬ ‭located‬ ‭between‬ ‭the‬ ‭ribs.‬ ‭They‬ ‭are‬ ‭therefore‬ T ‭responsible‬ ‭for‬ ‭the‬ ‭elevation‬ ‭of‬ ‭the‬ ‭ribs‬‭outward‬‭and‬‭the‬‭elevation‬‭of‬‭the‬ ‭sternum forward.‬ ‭During forced inspiration, three other muscles are used:‬ ‭●‬ ‭The small pectoral: which originates from the 3rd, 4th and 5th‬ ‭○‬ ‭ribs and ends on the coracoid process of the ulna.‬ ‭●‬ ‭The‬ ‭sternocleidomastoid‬ ‭muscle:‬ ‭originates‬ ‭at‬ ‭the‬ ‭level‬ ‭of‬ ‭the‬ ‭occipital‬ ‭line‬ ‭and‬ ‭the‬ ‭mastoid‬ ‭and‬ ‭ends‬ ‭at‬ ‭the‬ ‭level‬ ‭of‬ ‭the‬ ‭sternum‬ ‭and on the medial part of the clavicle.‬ ‭●‬ ‭The‬ ‭scalenes:‬ ‭three‬ ‭in‬ ‭number.‬ ‭They‬ ‭are‬ ‭stretched‬‭from‬‭the‬‭cervical‬ ‭vertebrae to the first two ribs.‬ ‭a.‬ ‭The anterior scalene: originates at the level of C3 to C6 and‬ ‭ends on the first rib.‬ ‭a.‬ ‭The middle scalene: takes its origin from C2 to C7 and ends‬ ‭behind the previous one.‬ ‭b.‬ ‭The posterior scalene: originates from C4 to C6 and ends on‬ ‭the second rib.‬ ‭Exhalation: a passive phenomenon.‬ ‭ xhalation‬ ‭is‬ ‭a‬ ‭passive‬ ‭phenomenon‬ ‭which‬ ‭results‬ ‭from‬ ‭the‬ ‭relaxation‬ ‭of‬ E ‭the‬‭inspiratory‬‭muscles‬‭and‬‭the‬‭elastic‬‭return‬‭of‬‭the‬‭lung‬‭tissue.‬‭Stretched‬ ‭during inspiration, the lung then returns to its basic position.‬ ‭ hen‬ ‭exhaling‬ ‭at‬ ‭rest,‬ ‭we‬ ‭therefore‬ ‭observe,‬ ‭thanks‬ ‭to‬ ‭the‬‭relaxation‬‭of‬ W ‭the‬ ‭inspiratory‬ ‭muscles,‬ ‭a‬ ‭reduction‬ ‭in‬ ‭volume‬ ‭inside‬ ‭the‬ ‭lung‬ ‭and‬ ‭therefore‬‭an‬‭increase‬‭in‬‭alveolar‬‭pressure.‬‭This‬‭leads‬‭to‬‭a‬‭reduction‬‭in‬‭the‬ ‭diameter of the lungs and bronchi.‬ ‭ he‬‭intra-alveolar‬‭pressure‬‭will‬‭become‬‭higher‬‭than‬‭atmospheric‬‭pressure.‬ T ‭This‬‭will‬‭therefore‬‭cause‬‭the‬‭air‬‭to‬‭escape‬‭from‬‭the‬‭lungs‬‭to‬‭the‬‭outside‬‭by‬ ‭a pressure gradient.‬ ‭ orced‬‭expiration‬‭is‬‭an‬‭active‬‭phenomenon.‬‭It‬‭involves‬‭the‬‭muscles‬‭of‬‭the‬ F ‭abdominal‬ ‭wall,‬ ‭notably‬ ‭the‬ ‭rectus‬ ‭abdominis‬ ‭and‬ ‭the‬ ‭internal‬ ‭obliques‬ ‭(abdominals).‬ ‭When‬ ‭these‬ ‭muscles‬ ‭contract,‬ ‭they‬ ‭push‬ ‭the‬ ‭diaphragm‬ ‭upward‬ ‭while‬ ‭the‬ ‭ribs‬ ‭are‬ ‭pushed‬ ‭inward‬ ‭and‬ ‭downward.‬ ‭This‬ ‭will‬ ‭therefore increase the intrapulmonary pressure and decrease the volume.‬