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Respiratory Muscles

RESPIRATORY PHYSIOLOGY

Muscles of Inspiration

_A

Muscles of Expiration

_A_

Principal

Accessory

Sternodeido-mastoid ——-(elevates Sternum) Scalenus anterior -— middle ^ posterior (elevate and fix uppcr ribs)

Quiet

breathing

Expiration results from passive recoil of lungs

Active

breathing

External intercostafs — (elevate ribs)

■ Internal intercostals, except interchondral part

Interchondral part ot internal intercostals (also elevates ribs)

Abdominal

muscles

(depress lowcr

ribs, compres

Diaphragm (domes descend. inereasing longitudinal dimension of chest and elevating lower ribs).

abdominal eon ten ts)

Rectus

abdominis

Extemal

oblique

obliąue

Transversus

abdominis

Ficure 5.5 Respiratory Muscles_

During quiet respiration, contraclion of Ihe diaphragm alone accounts (icipate in inspiration and assist the diaphragm, espedally during acti\ *■ for about 75% ot inspiration. Muscles of the thoradc wali (intercostal breathing (e.g., during exercise). muscles) and selecled musdes of the neck and abdomen also can par-

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