Anatomy - MOINA of the Thorax Muscles

origin of external intercostal muscle (11)

inferior border of rib

insertion of external intercostal muscle (11)

superior border of rib below

innervation of external intercostal muscle (11)

intercostal nerves

action of external intercostal muscle (11)

• stabilizes the rib cage

• with 1st rib fixed, they raise ribs during inspiration and thus increase AP and transverse diameters of thorax

orientation of fibers of external intercostal muscle

fibers pass downward and forward

origin of internal intercostal muscle (11)

inferior border of rib

insertion of internal intercostal muscle (11)

superior border of rib below

innervation of internal intercostal muscle (11)

intercostal nerves

action of internal intercostal muscle (11)

• stabilizes rib cage

• with last rib fixed by abdominal muscles, they lower ribs during expiration

orientation of fibers of internal intercostal muscle (11)

fibers pass downward and backward

origin of innermost intercostal muscle (incomplete layer)

adjacent ribs

insertion of innermost intercostal muscle (incomplete layer)

adjacent ribs

innervation of innermost intercostal muscle (incomplete layer)

intercostal nerves

action of innermost intercostal muscle (incomplete layer)

assists external and internal intercostal muscles

origin of diaphragm

• xiphoid process

• lower 6 costal cartilages

• first 3 lumbar vertebrae

insertion of diaphragm

central tendon

innervation of diaphragm

phrenic nerve

action of diaphragm

• most important muscle of inspiration

• increases vertical diameter of thorax by pulling central tendon downward

• assists in raising lower ribs

• also used in abdominal straining and weight lifting

origin of levatores costarum (12)

tip of transverse process of C7 and T1-T11 vertebrae

insertion of levatores costarum (12)

rib below

innervation of levatores costarum (12)

posterior rami of thoracic spinal nerves

action of levatores costarum (12)

• elevates ribs

• possibly proprioception

origin of serratus posterior superior (from thoracic wall chapter)

lower cervical and upper thoracic spines

insertion of serratus posterior superior (from thoracic wall chapter)

upper ribs

innervation of serratus posterior superior (from thoracic wall chapter)

intercostal nerves

action of serratus posterior superior (from thoracic wall chapter)

• proprioception

• possibly raises ribs and therefore an inspiratory muscle

origin of serratus posterior inferior (from thoracic wall chapter)

lower thoracic and upper lumbar spines

insertion of serratus posterior inferior (from thoracic wall chapter)

lower ribs

innervation of serratus posterior inferior (from thoracic wall chapter)

intercostal nerves

action of serratus posterior inferior (from thoracic wall chapter)

• proprioception

• possibly depresses ribs and therefore an expiratory muscle