Back Muscles prep 2025

splenius capitis origin

Ligamentum nuchae and spinous processes of C7-T4

splenius capitis insertion

mastoid process and occipital bone

splenius capitis action

extends and rotates neck

Splenius capitis innervation

posterior rami of C3 and C4 cervical nerves

splenius cervicis origin

Spinous processes of T3-T6

splenius cervicis insertion

Transverse process of C1-C3

splenius cervicis action

extend head and neck

splenius cervicis innervation

posterior rami of spinal nerves C2-C6

levator scapulae origin

transverse processes of C1-C4

levator scapulae insertion

superior part of the medial border of scapula

levator scapulae action

elevates and adducts scapula

levator scapulae innervation

dorsal scapular nerve (C5)

Rhomboid Minor origin

spinous processes of C7-T1

Rhomboid minor insertion

medial border of scapula

Rhomboid minor action

retraction of scapula, downward rotation of scapula

Rhomboid minor innervation

Dorsal scapular nerve (C4, C5)

Serratus posterior inferior origin

Spinous processes of T11-L2

Serratus posterior inferior insertion

Lower border of ribs 9-12

serratus posterior inferior action

depress ribs during exhalation

Serratus posterior inferior innervation

Ventral rami of T9-T12

Trapezius Origin

occipital bone

Trapezius insertion

scapula and clavicle

trapezius action

stabilizes, raises, retracts, and rotates scapula

Trapezius Innervation

Accessory nerve (CN XI)

spine of scapula origin

posterior deltoid

Spine of scapula insertion

Trapezius

Spine of Scapula action

serves as an attachment point for several muscles of the scapular region

Spine of Scapula innervation

N/A

Deltoid origin

clavicle, acromion, spine of scapula

Deltoid insertion

deltoid tuberosity of humerus

Deltoid action

abducts arm (humerus)

Deltoid innervation

Axillary nerve (C5, C6)

infraspinatus origin

infraspinous fossa of scapula

infraspinatus insertion

greater tubercle of humerus

infraspinatus action

lateral rotation of arm (humerus)

infraspinatus innervation

Suprascapular nerve (C5, C6)

Teres minor origin

upper 2/3 of lateral border of scapula

teres minor insertion

Inferior facet of greater tubercle of humerus

teres minor action

laterally rotates arm

teres minor innervation

Axillary nerve (C5, C6)

Teres major origin

Posterior surface of inferior angle of scapula

Teres major insertion

intertubercular groove of humerus

Teres major action

extends, adducts, and medially rotates arm

Teres major innervation

lower subscapular nerve

Latissimus dorsi origin

thoracic and lumbar vertebrae, the thoracolumbar fascia, the lower ribs, and iliac crest. (sometimes the inferior angle of the scapula)

Latissimus Dorsi insertion

intertubercular groove of humerus

Latissimus dorsi action

extends, adducts, and medially rotates humerus

Latissimus dorsi innervation

Thoracodorsal nerve (C6-C8)

Thoracolumbar fascia origin

From sacrum and iliac bones with attachments as high as the superior nuchal line

Thoracolumbar fascia insertion

Lumbar Spinous and Transverse Processes, Sacrum, Iliac Crest

Thoracolumbar fascia action

Provides integrity to the posterior anatomical wall

Acts like a corset around trunk to provide stability

thoracolumbar fascia innervation

sensory free nerve ending originating from the dorsal rami of spinal nerves

External oblique origin

ribs 5-12

External oblique insertion

linea alba and iliac crest

External oblique action

flexes and rotates vertebral column

External oblique innervation

intercostal nerves T7-T12

Internal oblique origin

thoracolumbar fascia, iliac crest, inguinal ligament

Internal oblique insertion

lower ribs and linea alba

internal oblique action

flexes and rotates trunk

internal oblique innervation

anterior rami of T7-T12 and L1

Gluteus medius origin

lateral surface of ilium

Gluteus medius insertion

greater trochanter of femur

gluteus medius action

abducts and medially rotates thigh

gluteus medius innervation

Superior gluteal nerve (L5, S1)

rhomboid major origin

spinous processes of T2-T5

rhomboid major insertion

medial border of scapula

rhomboid major action

retraction of scapula, downward rotation of scapula

rhomboid major innervation

dorsal scapular nerve