Back Muscles

Trapezius Origin

Occipital Bone (superior nuchal line, external occipital protuberance)

C1-C6 (nuchal ligament)

C7-T12 (spinous process)

Trapezius Insertion

Clavicle (lateral third), Acromion, Scapular Spine

Trapezius Innervation

Spinal accessory (Cranial 6) nerve - motor

Cervical nerves (C3-C4) - sensory

Trapezius Action

**Rotates the scapula superiorly

Descending Part: elevates scapula

Transverse Part: retracts scapula

Ascending Part: depresses scapula

Deltoid Origin

Clavicular Part: Clavicle (lateral third)

Acromial Part: Scapula (acromion)

Spinal Part: Scapula (spine of scapula)

Deltoid Insertion

Humerus (deltoid tuberosity)

Deltoid Innervation

Axillary Nerve (C5-C6)

Deltoid Action

Clavicular Part: flexes and medially rotates arm

Acromial Part: abducts arm

Spinal Part: extends and laterally rotates arm

Latissimus Dorsi Origin

T7-T12 (spinous processes)

L1-L5 (thoracolumbar fascia)

Ilium (iliac crest)

9th-12th Ribs

Scapula (inferior angle)

Latissimus Dorsi Insertion

Humerus (intertubercular sulcus)

Latissimus Dorsi Innervation

Thoracodorsal nerve (C6-C8)

Latissimus Dorsi Action

Extends, Adducts, and Medially Rotates Arm

Rhomboid Minor Origin

Nuchal Ligament

C7-T1 (spinous processes)

Rhomboid Minor Insertion

Scapula (medial border)

Rhomboid Minor Innervation

Dorsal Scapular Nerve (C4-C5)

Rhomboid Minor Action

Retracts, Elevates, and Rotates the scapula

Fixes scapula to thoracic wall

Rhomboid Major Origin

T2-T5 (spinous processes)

Rhomboid Major Insertion

Scapula (medial border)

Rhomboid Major Innervation

Dorsal Scapular Nerve (C4-C5)

Rhomboid Major Action

Retracts, Elevates, and Rotates the scapula

Fixes scapula to thoracic wall

Supraspinatus Origin

Scapula (supraspinatus fossa)

Supraspinatus Insertion

Humerus (greater tubercle, superior facet)

Supraspinatus Innervation

Suprascapular Nerve (C4-C6)

Supraspinatus Action

Initiates arm abduction

Infraspinatus Origin

Scapula

Infraspinatus Insertion

Humerus (greater tubercle, middle facet)

Infraspinatus Innervation

Suprascapular Nerve (C4-C6)

Infraspinatus Action

Laterally rotates arm

Levator Scapulae Origin

C1-C4 (transverse processes)

Levator Scapulae Insertion

Scapula (superior angle)

Levator Scapulae Innervation

Cervical (C3-C4) and Dorsal Scapular (C5) Nerves

Levator Scapulae Action

Elevates scapula medially

Rotates scapula tilting glenoid cavity inferiorly

Serratus Posterior Superior Origin

Nuchal Ligament

C7-T3 (spinous processes)

Serratus Posterior Superior Insertion

2nd - 4th Ribs (superior borders)

Serratus Posterior Superior Innervation

Ventral rami of upper thoracic nerves (T1-T4)

Serratus Posterior Superior Action

Elevates upper ribs

Serratus Posterior Inferior Origin

T11-L2 (spinous processes)

Serratus Posterior Inferior Insertion

9th - 12th Ribs (Inferior border near angles)

Serratus Posterior Inferior Innervation

Anterior rami of lower thoracic nerves (T9-T12)

Serratus Posterior Inferior Action

Depresses lower ribs

Iliocostalis Cervicis Origin

3rd-7th Ribs

Iliocostalis Cervicis Insertion

C4-C6 (transverse processes)

Iliocostalis Cervicis Innervation

Lateral branches of dorsal rami of spinal nerves (C8-L1)

Iliocostalis Cervicis Action

Extends and laterally bends the spine

Iliocostalis Thoracis Origin

7th-12th Ribs

Iliocostalis Thoracis Insertion

1st-6th Ribs (angles)

C7 (transverse process)

Iliocostalis Thoracis Innervation

Lateral branches of dorsal rami of spinal nerves (C8-L1)

Iliocostalis Thoracis Action

Extends and laterally bends the spine

Iliocostalis Lumborum Origin

Sacrum

Ilium (iliac crest)

Iliocostalis Lumborum Insertion

6th - 12th Ribs (angles)

Iliocostalis Lumborum Innervation

Lateral branches of dorsal rami of spinal nerves(C8-L1)

Iliocostalis Lumborum Action

Extends and laterally bends the spine

External Oblique Origin

5th - 12th Ribs (external surfaces)

External Oblique Insertion

Ilium (iliac crest - anterior half)

Pubis (pubic tubercle)

Linea Alba

Xiphoid Process

External Oblique Innervation

Intercostal Nerves (T5-T12)

Subcostal Nerve

Iliohypogastric Nerve

External Oblique Action

Flexes and rotates trunk

Supports and compresses abdominal viscera

Teres Minor Origin

Scapula (lateral boarder)

Teres Minor Insertion

Humerus (greater tubercle - inferior facet)

Teres Minor Innervation

Axillary Nerve (C5-C6)

Teres Minor Action

Laterally rotates arm, Helps to hold head of humerus in the glenoid cavity

Teres Major Origin

Scapula (inferior angle - posterior surface)

Teres Major Insertion

Humerus (crest of the lesser tubercle)

Teres Major Innervation

Lower Subscapular Nerve (C6-C7)

Teres Major Action

Adducts and medially rotates arm

Longissimus Cervicis Origin

T1-T6 (transverse processes)

Longissimus Cervicis Insertion

C2-C5 (transverses processes)

Longissimus Cervicis Innervation

Posterior rami of spinal nerves (C1-L5)

Longissimus Cervicis Action

Extends and Laterally bends the spine

Longissimus Thoracis Origin

Ilium (iliac crest)

Sacrum

Lumbar Vertebrae (spinous processes)

Longissimus Thoracis Insertion

Lumbar Vertebrae (costal and accessory processes)

T1-T12 (transverse processes)

2nd - 12th Ribs

Longissimus Thoracis Innervation

Posterior rami of spinal nerves (C1-L5)

Longissimus Thoracis Action

Extends and laterally bends the spine

Internal Oblique Origin

Thoracolumbar Fascia

Ilium (iliac crest)

Lateral half of the inguinal ligament

Internal Oblique Insertion

10th - 12th Ribs (inferior borders)

Pubis (pectineal line)

Linea Alba

Internal Oblique Innervation

Intercostal Nerves (T8-T12)

Subcostal Nerve

First Lumbar Nerve

Iliohypogastic Nerve

Ilioinguinal Nerve

Internal Oblique Action

Flexes and Rotates trunk

Supports and Compresses abdominal viscera

Splenius Capitis Origin

C3-T3 (spinous processes)

Splenius Capitis Insertion

Temporal Bone (mastoid process)

Occipital Bone (lateral third of superior nuchal line)

Splenius Capitis Innervation

Dorsal rami of middle cervical nerves

Splenius Capitis Action

Extends and Laterally bends the head

Rotates it to the same side

Splenius Cervicis Origin

T3-T6 (spinous processes)

Splenius Cervicis Insertion

C1-C3 (transverse processes)

Splenius Cervicis Innervation

Dorsal rami of lower cervical nerves

Splenius Cervicis Action

Extends and Laterally bends the cervical spine

Rotates it to the same side

Posterior Scalene Origin

C4-C6 (posterior tubercles)

Posterior Scalene Insertion

2nd Rib (outer surface)

Posterior Scalene Innervation

Anterior rami of cervical nerves

Posterior Scalene Action

Elevates 2nd Rib

Laterally flexes neck (unilateral contraction)

Flexes neck (bilateral contraction)

Serratus Anterior Origin

1st-9th Ribs

Serratus Anterior Insertion

Scapula (medial border - from superior angle to inferior angle)

Serratus Anterior Innervation

Long Thoracic Nerve (C5-C7)

Serratus Anterior Action

Draws forward and Rotates the scapula (hold it against thoracic wal)

Semispinalis Capitis Origin

C3-T6 (transverse processes)

Semispinalis Capitis Insertion

Occipital Bone (between nuchal lines)

Semispinalis Capitis Innervation

Dorsal rami of spinal nerves

Semispinalis Capitis Action

Extends and laterally bends the head

Rotates it to the opposite side

Semispinalis Thoracis Origin

T7-T12 (transverse processes)

Semispinalis Thoracis Insertion

C6-T6 (spinous processes)

Semispinalis Thoracis Innervation

Dorsal rami of spinal nerves

Semispinalis Thoracis Action

Extends and laterally bends the thoracic spine

Rotates it to the opposite side