Anatomy OINAS (UNIT 2)

Trapezius Origin

Superior nuchal line; external occipital protuberance; nuchal ligament; spinous process of T/S

Trapezius Insertion

Distal clavicle; acromion + spine of scapula

Trapezius Innervation

Spinal accessory nerve (CN XI) (motor fibers) ; C3-C4 (pain and proprioceptive fibers)

Trapezius Action

Extends neck; ipsilaterally laterally flexes neck; contralaterally rotates neck

Latissimus Dorsi Origin

Thoracolumbar fascia + iliac crest

Latissimus Dorsi Insertion

Floor of intertubercular groove

Latissimus Dorsi Innervation

Thoracodorsal nerve (C6-C8)

Latissimus Dorsi Action

Adduct + extend + internally rotate shoulder; raises body to arm during climbing; assists with respiration

Levator Scapulae Origin

Posterior tubercles of transverse processes of upper C/S

Levator Scapulae Insertion

Superior angle of scapula

Levator Scapulae Innervation

Dorsal scapular (C4-C5) and cervical (C3-C4) nerves

Levator Scapulae Action

Ipsilaterally laterally flexes neck; extends neck

Splenius Capitis Origin

Nuchal ligament; SP C7 + upper T/S

Splenius Capitis Insertion

Mastoid process + superior nuchal line of occipital bone

Splenius Capitis Innervation

Posterior rami of spinal nerves

Splenius Capitis Action

Acting unilaterally: laterally flexes the neck and ipsilaterally rotates neck

Acting bilaterally: extends the head and neck

Splenius cervicis Origin

Nuchal ligament; SP C7 + upper T/S

Splenius cervicis Insertion

Tubercles of transverse processes of upper C/S

Splenius cervicis Innervation

Posterior rami of spinal nerves

Splenius cervicis Action

Acting unilaterally: laterally flexes the neck and ipsilaterally rotates neck 

Acting bilaterally: extends the head and neck

Iliocostalis lumborum Origin

Middle crest sacrum; iliac crests; TP T11-L5; sacrotuberous ligament; posterior SI ligament; thoracolumbar fascia

Iliocostalis lumborum Insertion

Angles of lower ribs

Iliocostalis lumborum Innervation

Posterior rami of spinal nerves

Iliocostalis lumborum Action

Acting bilaterally: extends vertebral column and head

Acting unilaterally: laterally flexes vertebral column; ipsilaterally rotates

Iliocostalis thoracis Origin

Angles of lower ribs

Iliocostalis thoracis Insertion

Angles of upper ribs; TP C7

Iliocostalis thoracis Innervation

Posterior rami of spinal nerves

Iliocostalis thoracis Action

Acting bilaterally: extends vertebral column and head

Acting unilaterally: laterally flexes vertebral column; ipsilaterally rotates

Iliocostalis cervicis Origin

Angles of upper ribs

Iliocostalis cervicis Insertion

Posterior tubercles of TP of lower C/S

Iliocostalis cervicis Innervation

Posterior rami of spinal nerves

Iliocostalis cervicis Action

Acting bilaterally: extends vertebral column and head

Acting unilaterally: laterally flexes vertebral column; ipsilaterally rotates

Longissimus thoracis Origin

TP L/S; thoracolumbar fascia

Longissimus thoracis Insertion

TP T/S; most ribs (between angle and tubercle)

Longissimus thoracis Innervation

Posterior rami of spinal nerves

Longissimus thoracis Action

Acting bilaterally: extends vertebral column and head; as back is flexed controls movement via eccentric contraction 

Acting unilaterally: laterally flexes vertebral column

Longissimus cervicis Origin

TPs upper T/S

Longissimus cervicis Insertion

Posterior tubercles of TPs of lower C/S

Longissimus cervicis Innervation

Posterior rami of spinal nerves

Longissimus cervicis Action

Acting bilaterally: extends vertebral column and head; as back is flexed controls movement via eccentric contraction

Acting unilaterally: laterally flexes vertebral column

Longissimus capitis Origin

TP upper T/S; articular processes of lower C/S

Longissimus capitis Insertion

Mastoid process

Longissimus capitis Innervation

Posterior rami of spinal nerves

Longissimus capitis Action

Acting bilaterally: extends vertebral column and head; as back is flexed controls movement via eccentric contraction

Acting unilaterally: laterally flexes vertebral column

Spinalis thoracis Origin

SP lower T/S and upper L/S

Spinalis thoracis Insertion

SP mid T/S

Spinalis thoracis Innervation

Posterior rami of spinal nerves

Spinalis thoracis Action

Acting bilaterally: extends vertebral column and head; as back is flexed controls movement via eccentric contraction 

Acting unilaterally: laterally flexes vertebral column

Spinalis cervicis Origin

Nuchal ligament; SP upper T/S

Spinalis cervicis Insertion

SP mid C/S

Spinalis cervicis Innervation

Posterior rami of spinal nerves

Spinalis cervicis Action

Acting bilaterally: extends vertebral column and head; as back is flexed controls movement via eccentric contraction 

Acting unilaterally: laterally flexes vertebral column

Spinalis capitis Origin

Blends with semispinalis capitis (semispinalis capitis pictured)

Spinalis capitis Insertion

Medial to semispinalis capitis (semispinalis capitis pictured)

Spinalis capitis Innervation

Posterior rami of spinal nerves (semispinalis capitis pictured)

Spinalis capitis Action

Acting bilaterally: extends vertebral column and head; as back is flexed controls movement via eccentric contraction

Acting unilaterally: laterally flexes vertebral column

Semispinalis Origin

TP of lower C/S and all T/S

Semispinalis Insertion

Spanning 4-6 segments

Semispinalis Innervation

Posterior rami of spinal nerves

Semispinalis Action

Acting unilaterally: contralaterally rotates

Acting bilaterally: extension

Multifidus Origin

Posterior sacrum; PSIS; aponeurosis of erector spine; SI ligaments; mammillary processes of L/S; TP upper T/S; articular process lower C/S

Multifidus Insertion

Spanning 2-4 segments

Multifidus Innervation

Posterior rami of spinal nerves

Multifidus Action

Acting unilaterally: contralaterally rotates

Acting bilaterally: stabilizes vertebrae during local movements of vertebral column

Rotatores Origin

TP of all vertebrae; can only be see in in T/S region (best developed)

Rotatores Insertion

Brevis: Spans 1 segment immediately superior
Longus: Spans 2 segments

Rotatores Innervation

Posterior rami of spinal nerves

Rotatores Action

Stabilizes vertebrae; assists with extension + rotation; maybe proprioception

Levator costarum Origin

Tips of TP C7-T11

Levator costarum Insertion

Pass inferolaterally to rib between angle and tubercle

Levator costarum Innervation

Posterior rami C8-T11

Levator costarum Action

Elevates ribs (assisting with respiration); assist lateral flexion of vertebral column

External intercostal Origin

Inferior border of ribs

External intercostal Insertion

Superior border of rib below

External intercostal Innervation

Intercostal nerves

External intercostal Action

Supports intercostal space during respiration; elevates ribs during forced inspiration

Internal intercostal Origin

Inferior border of ribs

Internal intercostal Insertion

Superior border of rib below

Internal intercostal Innervation

Intercostal nerves

Internal intercostal Action

Supports intercostal space during respiration 

Interosseous part: depresses ribs 

Interchondral part: elevates ribs

Innermost intercostal Origin

Inferior border of ribs

Innermost intercostal Insertion

Superior border of rib below

Innermost intercostal Innervation

Intercostal nerves

Innermost intercostal Action

Supports intercostal space during respiration 

Interosseous part: depresses ribs 

Interchondral part: elevates ribs

Subcostal Origin

Internal surface of lower ribs near their angles

Subcostal Insertion

Superior borders of 2nd + 3rd ribs below

Subcostal Innervation

Intercostal nerves

Subcostal Action

Similar to internal intercostal muscles
(During forced respiration:
Interosseous: depresses ribs
Interchondral: elevates ribs)

Transversus thoracis Origin

Posterior surface of lower sternum

Transversus thoracis Insertion

Internal surface of costal cartilages 2-6

Transversus thoracis Innervation

Intercostal nerves

Transversus thoracis Action

Weakly depresses ribs; some proprioception

Diaphragm Origin

Sternal part: posterior xiphoid process

Costal part: internal lower costal cartilages and ribs 7-12

Lumbar part: medial + lateral arcuate ligaments (lumbocostal arches); bodies + discs of L1-L3; anterior longitudinal ligament

Diaphragm Insertion

Central tendon of diaphragm

Diaphragm Innervation

Phrenic nerve (C3-C5)

Diaphragm Action

Depresses costal cartilages; domes flatten during inspiration; primary muscle of breathing

Rectus capitis posterior major Origin

SP C2

Rectus capitis posterior major Insertion

Lateral inferior nuchal line of occipital bone

Rectus capitis posterior major Innervation

PPR C1 (suboccipital nerve)

Rectus capitis posterior major Action

Proprioception; ipsilaterally rotates C1-C2; extends Atlanto-occipital joint