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trapezius

• superficial

• origin: C7-T12

• insertion: clavicle, scapula/scapular spine

• elevation, depression, retraction, upward rotation

latissimus dorsi

• Location: Large superficial muscle of lower back

• Position: Inferior to trapezius, covers lower thoracic and lumbar regions

• Origin: Spinous processes T7-L5, sacrum, iliac crest, lower 3-4 ribs

• Insertion: Intertubercular groove of humerus

• Action: Extends, adducts, and medially rotates arm

rhomboid major

• Location: Deep to trapezius, between scapulae

• Position: Inferior to rhomboid minor

• Origin: Spinous processes T2-T5

• Insertion: Medial border of scapula (below spine)

• Action: Retracts and elevates scapula, rotates scapula downward

rhomboid minor

• Location: Deep to trapezius, between scapulae

• Position: Superior to rhomboid major

• Origin: Spinous processes C7-T1, nuchal ligament

• Insertion: Medial border of scapula (at spine level)

• Action: Retracts and elevates scapula, rotates scapula downward

levator scapula

• Location: Deep to trapezius, posterior-lateral neck

• Position: Medial to posterior scalenes, deep to sternocleidomastoid

• Origin: Transverse processes C1-C4

• Insertion: Superior angle of scapula and medial border

• Action: Elevates scapula, rotates scapula downward

posterior deltoid

• Location: Superficial muscle of shoulder

• Position: Posterior aspect of shoulder, lateral to infraspinatus

• Origin: Spine of scapula

• Insertion: Deltoid tuberosity of humerus

• Action: Extends and laterally rotates arm

supraspinatus

• Location: Deep muscle of shoulder

• Position: Sits in supraspinous fossa, deep to trapezius

• Origin: Supraspinous fossa of scapula

• Insertion: Greater tubercle of humerus (superior facet)

• Action: Abducts arm (initiates abduction), stabilizes shoulder joint

subscapularis

infraspinatus

• Location: Deep muscle of shoulder

• Position: Sits in infraspinous fossa, deep to trapezius and deltoid

• Origin: Infraspinous fossa of scapula

• Insertion: Greater tubercle of humerus (middle facet)

• Action: Laterally rotates arm, stabilizes shoulder joint

subscapularis

• Location: Deep muscle of shoulder (anterior scapula)

• Position: Sits in subscapular fossa, on anterior/costal surface of scapula

• Origin: Subscapular fossa

• Insertion: Lesser tubercle of humerus

• Action: Medially rotates arm, stabilizes shoulder joint

teres major

• Location: Deep muscle of shoulder

• Position: Inferior to teres minor, along inferior lateral border of scapula

• Origin: Inferior angle and lower lateral border of scapula

• Insertion: Intertubercular groove of humerus (medial lip)

• Action: Extends, adducts, and medially rotates arm

teres minor

• Location: Deep muscle of shoulder

• Position: Superior to teres major, inferior to infraspinatus

• Origin: Upper lateral border of scapula

• Insertion: Greater tubercle of humerus (inferior facet)

• Action: Laterally rotates arm, stabilizes shoulder joint

splenius capitis

• Location: Deep muscle of posterior neck

• Position: Deep to trapezius, superficial to semispinalis capitis

• Origin: Nuchal ligament (C7), spinous processes C7-T3/T4

• Insertion: Mastoid process and lateral occipital bone

• Action: Bilaterally: extends head/neck; Unilaterally: laterally flexes and rotates head to same side

splenius cervicis

• Location: Deep muscle of posterior neck

• Position: Deep to trapezius, medial and deep to levator scapulae

• Origin: Spinous processes T3-T6

• Insertion: Transverse processes C1-C3

• Action: Bilaterally: extends neck; Unilaterally: laterally flexes and rotates neck to same side

semispinalis capitis

• Location: Deep muscle of posterior neck

• Position: Deep to splenius capitis, part of transversospinalis group

• Origin: Transverse processes C7-T6

• Insertion: Between superior and inferior nuchal lines of occipital bone

• Action: Bilaterally: extends head/neck; Unilaterally: laterally flexes and rotates head to opposite side

semispinalis cervicis

• Location: Deep muscle of neck

• Position: Deep to semispinalis capitis, part of transversospinalis group

• Origin: Transverse processes T1-T6

• Insertion: Spinous processes C2-C5

• Action: Bilaterally: extends neck; Unilaterally: laterally flexes and rotates neck to opposite side

spinalis group

• Location: Deep intrinsic back muscles

• Position: Most medial column of erector spinae, along spinous processes

• Origin: Spinous processes of lower vertebrae (varies by region)

• Insertion: Spinous processes of superior vertebrae

• Action: Bilaterally: extends vertebral column; Unilaterally: laterally flexes trunk

longissimus group

• Location: Deep intrinsic back muscles

• Position: Middle column of erector spinae, between spinalis and iliocostalis

• Origin: Transverse processes of lower vertebrae, sacrum

• Insertion: Transverse processes of superior vertebrae, ribs, mastoid process

• Action: Bilaterally: extends vertebral column; Unilaterally: laterally flexes trunk

iliocostalis group

• Location: Deep intrinsic back muscles

• Position: Most lateral column of erector spinae, along angles of ribs

• Origin: Iliac crest, sacrum, lower ribs

• Insertion: Ribs and transverse processes of cervical vertebrae

• Action: Bilaterally: extends vertebral column; Unilaterally: laterally flexes trunk

serratus posterior superior

• Location: Intermediate layer, deep to rhomboids

• Position: Superior back, deep to rhomboids, superficial to erector spinae

• Origin: Nuchal ligament, spinous processes C7-T3

• Insertion: Ribs 2-5 (lateral to angles)

• Action: Elevates ribs (assists inspiration)

serratus posterior inferior

• Location: Intermediate layer, deep to latissimus dorsi

• Position: Inferior back, deep to latissimus, superficial to erector spinae

• Origin: Spinous processes T11-L2/L3

• Insertion: Ribs 9-12 (lateral to angles)

• Action: Depresses ribs (assists expiration)

vertebral foramen

• Location: Central opening in vertebra

• Function: Houses and protects spinal cord

• Structures passing through: Spinal cord, meninges, epidural space with blood vessels and fat

intervertebral foramen

• Location: Opening between adjacent vertebrae (formed by superior and inferior vertebral notches)

• Function: Allows passage of spinal nerves

• Structures passing through: Spinal nerve, blood vessels

spinous process

• Location: Posterior projection from vertebral arch

• Function: Attachment site for muscles and ligaments, lever for movement

• Nearby structures: Erector spinae, multifidus, interspinous ligaments

transverse process

• Location: Lateral projections from vertebral arch

• Function: Attachment site for muscles and ligaments

• Nearby structures: Erector spinae, rotator muscles, intertransverse ligaments

superior articular process

• Location: Projects superiorly from vertebral arch

• Function: Forms facet joint with inferior articular process of vertebra above

• Nearby structures: Joint capsule, synovial fluid, facet joint

inferior articular process

• Location: Projects inferiorly from vertebral arch

• Function: Forms facet joint with superior articular process of vertebra below

• Nearby structures: Joint capsule, synovial fluid, facet joint

vertebral body

• Location: Anterior weight-bearing portion

• Function: Main weight-bearing structure, supports intervertebral discs

• Nearby structures: Intervertebral discs, anterior/posterior longitudinal ligaments

pedicle

• Location: Connects vertebral body to transverse processes

• Function: Forms walls of vertebral foramen, creates vertebral notches

• Nearby structures: Spinal nerves (vertebral notches form intervertebral foramen)

lamina

• Location: Connects transverse processes to spinous process

• Function: Forms posterior wall of vertebral foramen

• Nearby structures: Ligamentum flavum attaches here

intervetebral disc

• Location: Between vertebral bodies

• Function: Shock absorption, allows movement, separates vertebrae

• Components: Nucleus pulposus (inner gel), annulus fibrosus (outer rings)

anterior longitudinal ligament

• Location: Runs along anterior surface of vertebral bodies

• Function: Prevents hyperextension, stabilizes spine

• Attachment: Skull to sacrum

posterior longitudinal ligament

• Location: Runs along posterior surface of vertebral bodies (inside vertebral canal)

• Function: Prevents hyperflexion, limits disc herniation posteriorly

• Attachment: Axis (C2) to sacrum

ligamentum flavum

• Location: Connects laminae of adjacent vertebrae

• Function: Maintains upright posture, prevents sudden flexion, elastic

• Special feature: Yellow elastic connective tissue

interspinous ligament

• Location: Connects adjacent spinous processes

• Function: Limits flexion

• Nearby structures: Continues posteriorly as supraspinous ligament

transverse foramen

• Location: Only in cervical vertebrae (C1-C7)

• Function: Passage for vertebral arteries (except C7)

• Found in: Transverse processes of cervical vertebrae

transverse costal facet

• Location: On transverse processes of thoracic vertebrae

• Function: Articulation point for tubercle of rib

• Found in: T1-T10 (sometimes T11-T12)

superior costal facet

• Location: Superior portion of vertebral body (thoracic)

• Function: Articulation with head of rib (of same number)

• Found in: Thoracic vertebrae

inferior costal facet

• Location: Inferior portion of vertebral body (thoracic)

• Function: Articulation with head of rib (one number below)

• Found in: Most thoracic vertebrae (T1-T9)

dens

• Location: Projects superiorly from body of C2 (axis)

• Function: Pivot point for rotation of C1 (atlas) and skull

• Special feature: Embryologically represents body of C1

sacral canal

• Location: Continuation of vertebral canal through fused sacral vertebrae

• Function: Contains cauda equina (nerve roots)

• Opens at: Sacral hiatus

sacral foramina

• Location: Anterior (pelvic) and posterior (dorsal) surfaces

• Function: Passage for sacral spinal nerves

• Number: 4 pairs on each surface

ala

• Location: Lateral masses of sacrum

• Function: Articulation with ilium (sacroiliac joint), weight transmission

• Formed from: Fused transverse processes

sacrum

scapula

superior angle (scapula)

• Location: Superomedial corner of scapula

• Muscle attachment: Levator scapulae inserts here

• Level: Approximately T2 vertebra

inferior angle (scapula)

• Location: Inferomedial corner of scapula

• Muscle attachment: Teres major, latissimus dorsi, serratus anterior

• Level: Approximately T7 vertebra

lateral angle (scapula)

• Location: Thickened lateral corner

• Contains: Glenoid cavity

• Function: Forms shoulder joint

vertebral border (scapula)

• Location: Medial edge closest to vertebral column

• Muscle attachments: Rhomboids, serratus anterior, levator scapulae

axillary border (scapula)

• Location: Lateral edge toward axilla

• Muscle attachments: Teres major, teres minor, long head of triceps

superior border (scapula)

• Location: Superior edge of scapula

• Contains: Suprascapular notch

• Muscle attachment: Omohyoid

scapula spine

• Location: Prominent ridge on posterior surface

• Function: Divides posterior scapula into supraspinous and infraspinous fossae

• Muscle attachments: Trapezius, deltoid

acromion

• Location: Lateral end of scapular spine

• Function: Articulates with clavicle (AC joint)

• Muscle attachments: Deltoid, trapezius

coracoid process

• Location: Anterior projection from superior lateral scapula

• Function: Attachment point for muscles and ligaments

• Muscle attachments: Pectoralis minor, coracobrachialis, short head of biceps

glenoid cavity

• Location: Lateral angle of scapula

• Function: Articulates with head of humerus (glenohumeral joint)

• Features: Shallow socket

suprascapular notch

• Location: Superior border medial to coracoid process

• Function: Passage for suprascapular nerve

• Nearby structures: Suprascapular artery passes over (not through)

infraspinous fossa

• Location: Posterior surface below spine

• Muscle: Infraspinatus originates here

• Larger than: Supraspinous fossa

supraspinous fossa

• Location: Posterior surface above spine

• Muscle: Supraspinatus originates here

• Smaller than: Infraspinous fossa

subscapular fossa

• Location: Posterior surface above spine

• Muscle: Supraspinatus originates here

• Smaller than: Infraspinous fossa

flexion

Bending forward (anteriorly)

extension

Bending backward (posteriorly)

lateral flexion

Bending to the side

rotation

Twisting left or right