U4 anatomy - muscle of thoracic wall

external intercostals

internal intercostals

innermost intercostals

red arrow

separated from internal intercostals by AVN

subcostales

transversus thoracis

posterior side of anterior thoracic wall

inferior margin of rib above

external intercostal origin

superior margin of rib below

external intercostal insertion

intercostal n

innervation of external intercostal, internal intercostals, innermost intercostals, transversus thoracis, subcostales

move the ribs superiorly

most active during inspiration, supports intercostal space

external intercostal function

lateral edge of costal groove of rib above

internal intercostal origin

superior margin of rib below

-deep to attachment of external intercostal

internal intercostal insertion

move ribs inferiorly

-more active during expiration

-supports intercostal space

internal intercostal function

medial edge of costal groove of rib above

innermost intercostal origin

internal aspect of superior margin of rib below

innermost intercostal insertion

acts with internal intercostals

innermost intercostal function

internal surface of lower ribs near angle

subcostales origin

internal surface of second or third rib below

subcostales insertion

depresses ribs

subcostales function

-xiphoid process

-inferior aspect of deep surface of sternum

-costal cartilages 4-7

transversus thoracis origin

inferior margins and internal surface of costal cartilages of 2nd-6th ribs

transversus thoracis insertion

depress costal cartilages

transversus thoracis function