muscles of the thorax, ribs, and back

muscles attached to the ribs

• external intercostals

• internal intercostals

• innermost intercostals

• subcostals

• transversus thoracis

external intercostals

O: inferior borders of 1-11th rib

I: superior borders of 1-11th rib

A: slightly elevate ribs at costovertebral joints

internal intercostals

O: 1st rib(deep to external)

I: 11th rib

A: slightly depress ribs at costovertebral joints

innermost intercostals

O: 1st rib (deepest)

I: 11th rib

A: elevate ribs at costovertebral joints

subcostals

O: 7th rib

I: 9th rib

A: depress ribs

transversus thoracis

O: postolateral aspects of body and xiphoid process of sternum

I: internal surfaces of 2-6th costal cartilages and costal ends of adjacent ribs

A: depress ribs and costal cartilages

muscle attached to diaphragm

costal diaphragm

costal diaphragm

O: rib 7-12 and their cartilages, L1-L3 (crus)

I: central tendon

A: inspiration

deep muscles of the thorax

• longissimus

• spinalis

• semispinalis

• serratus posterior inferior

• serratus posterior superior

longissimus

O: TVP of C4-T6 vertebrae, spinous processes of L1-L5 vertebrae, dorsal surface of sacrum and iliac crest

I: mastoid process of temporal bone, posterior tubercles of TVP C2-C6, TVP of L and T vertebrae, 2-12th ribs

A: extends, rotates and laterally flexes head - laterally flexes neck and thorax

spinalis

O: nuchal ligament, SP of C7-T2 and T11-L3

I: SP C2-C4, T2-T8

A: extends and laterally flexes neck and trunk

semispinalis

O: intermediate between spinalis and longissimus, superior articular processes of C4-C7, TVP T1-T11

I: between S/I nuchal lines of occipital bone, SP: C2-T4

A: extends and laterally rotates head, neck and trunk

serratus posterior inferior

O: SP T11-T12

I: external surfaces of 9th-12th ribs

A: depress ribs at costovertebral joints

serratus posterior superior

O: nuchal ligament, SP C7-T3

I: external surface of 2nd-5th ribs

A: elevates ribs at costovertebral joints

muscles attached to back

iliocostalis

quadratus lumborum

intertransversarii

interspinales

multifidus

rotatores

iliocostalis

O: SP L1-L5, dorsal surface of sacrum and iliac crest

I: TVP of lumbar and thoracic vertebrae, 2-12th ribs

A: elevates ribs at costovertebral joints

quadratus lumborum

O: posterior iliac crest

I: TVP L1-L4, inferior border of 12th rib

A: lateral flexion/extends trunk, stabilizes 12th rib

intertransverserarii

originate and insert to TVP of adjacent vertebrae

1. colli - lateral flexion neck

2. thoracis - lateral flexion trunk

3. lumborum - lateral flexion trunk

interspinales

O: SP - C3-T12, L2-L5

I: SP C2-T11, L1-L4

A: extends neck and trunk

multifidus

O: posterior, superior iliac spine, dorsal surface of sacrum, mammillary process of L vertebrae, TVP: of thoracic vertebrae, articular process of C4-C7

I: SP: lumbar, thoracic, and cervical vertebrae

A: lateral flexion and rotation, extend spine

rotatores thoracis

O: TVP of thoracic vertebrae

I: laminae and SP of thoracic vertebra and ½ segments above

A: extends and rotates trunk

middle layer of thoracic muscles (scapula and shoulder)

• rhomboideus major

• rhomboideus minor

• serratus anterior

• pectoralis minor

• subclavius

rhomboideus major

O: SP T2-T5

I: medial border/inferior spine of scapula

A: retraction and downwardly rotates pectoral girdle @ acromioclavicular and sternoclavicular joints

rhombodieus minor

O: nuchal ligament, SP: C7-T1

I: medial border of scapula

A: retraction and downwardly rotates pectoral girdle @ acromioclavicular and sternoclavicular joints

serratus anterior

O: 1st-9th ribs (laterally, externally)
I: medial border of scapula (posterior)

A: protraction and upwardly rotates pectoral girdle @ acromioclavicular and sternoclavicular joints

pectoralis minor

O: anterior ends of 3-5th ribs

I: coracoid process of scapula

A: protraction and downwardly rotates pectoral girdle @ acromioclavicular and sternoclavicular joints

subclavius

O: superior surface of costal end of 1st rib, adjacent first costal cartilage

I: inferior surface of middle 1/3 clavicle

A: stabilizes clavicle

superficial layers of thoracic muscles

• pectoralis major

• levator scapula

• latissimus dorsi

pectoralis major

O: clavicular head, clavicle, sternocostal head, manubrium, sternal body, true ribs, external abdominal oblique aponeurosis

I: crest of greater tubercle of humerus

A:adducts, medially rotates, @ glenohumeral joint

• depresses, pectoral girdle, @ acromioclavicular and sternoclavicular joints

levator scapula

O: TVP C1-C2, posterior tubercles of TVP of C3-C4

I: superior angle of scapula

A: elevates, downwardly rotates pectoral girdle at @ acromioclavicular and sternoclavicular joints

• extends and laterally flexes neck at cervical vertebrae

latissimus dorsi

O: SP T7-T12, L1-L5, 9th-12th ribs

I: intertubercular sulcus of humerus

A: adducts, medially rotates and extends arm at shoulder joint

erector spinae group

• spinalis

• longissimus

• iliocostalis

A: responsible for straightening vertebral column, movements of head, neck and trunk

muscles attached to neck

scalenes (anterior, medius, and posterior)

sternocleidomastoid