Back Anatomy – Muscles, Osteology & Ligaments

Vocabulary flashcards covering major muscles, osteological landmarks, ligaments, and clinical spaces discussed in the back‐anatomy lecture.

Trapezius

Origin—external occipital protuberance, nuchal ligament, C7–T12 spines; Insertion—lateral ⅓ clavicle, acromion, spine of scapula; Innervation—spinal accessory n. (CN XI) with C3-C4 sensory; Action—elevates, retracts, depresses scapula; Blood—superficial transverse cervical a.

Latissimus dorsi

Origin—T7–L5 spines, thoracolumbar fascia, iliac crest, lower ribs; Insertion—intertubercular sulcus of humerus; Innervation—thoracodorsal n. (C6-C8); Action—extends, adducts, medially rotates humerus; Blood—thoracodorsal a.

Levator scapulae

Origin—transverse processes C1-C4; Insertion—superior angle & medial border of scapula; Innervation—dorsal scapular n. (C5); Action—elevates scapula, tilts glenoid inferiorly; Blood—deep transverse cervical a.

Rhomboid minor

Origin—nuchal ligament, C7–T1 spines; Insertion—medial scapular border at spine; Innervation—dorsal scapular n. (C5); Action—retracts & stabilizes scapula; Blood—dorsal scapular a.

Rhomboid major

Origin—T2–T5 spines; Insertion—medial scapular border below spine; Innervation—dorsal scapular n.; Action—retracts scapula, rotates to depress glenoid; Blood—dorsal scapular a.

Serratus posterior superior

Origin—nuchal ligament, C7–T3 spines; Insertion—ribs 2-5 (superior borders); Innervation—intercostal nn. T2-T5; Action—elevates ribs, aids inspiration.

Serratus posterior inferior

Origin—T11–L2 spines; Insertion—ribs 9-12 (inferior borders); Innervation—intercostal nn. T9-T12; Action—depresses ribs, aids expiration.

Iliocostalis (erector spinae)

Most lateral erector spinae column; Origin—posterior sacrum, iliac crest, sacrospinous ligament, lumbar & sacral spines; Insertion—angles of ribs & cervical transverse processes; Innervation—dorsal rami; Action—extends & laterally flexes vertebral column.

Longissimus (erector spinae)

Intermediate erector spinae; Origin—common erector spinae tendon; Insertion—ribs, transverse processes, mastoid process (capitis); Innervation—dorsal rami; Action—extension & lateral flexion of spine/head.

Spinalis (erector spinae)

Medial erector spinae column; Origin—common tendon & lower spine; Insertion—upper thoracic & cervical spinous processes; Innervation—dorsal rami; Action—spinal extension.

Splenius capitis

Origin—nuchal ligament, C7–T3 spines; Insertion—mastoid process & lateral nuchal line; Innervation—dorsal rami; Action—extends head/neck, ipsilateral rotation & lateral flexion.

Splenius cervicis

Origin—T3–T6 spines; Insertion—transverse processes C1-C4; Innervation—dorsal rami; Action—extends neck, ipsilateral rotation.

Semispinalis capitis

Origin—transverse processes C4–T12; Insertion—occipital bone; Innervation—dorsal rami; Action—extends head, contralateral rotation.

Semispinalis cervicis

Origin—upper thoracic transverse processes; Insertion—C2–C5 spinous processes; Innervation—dorsal rami; Action—extends neck, contralateral rotation.

Multifidus

Origin—sacrum, ilium, transverse processes; Insertion—spinous processes 2-4 segments superior; Innervation—dorsal rami; Action—stabilizes vertebrae during movement.

Levator costarum

Origin—transverse processes C7–T11; Insertion—rib below (brevis) or two below (longus); Innervation—dorsal rami C8-T11; Action—elevates ribs, assists respiration.

Rectus capitis posterior major

Origin—C2 spinous process; Insertion—inferior nuchal line (lateral); Innervation—suboccipital n. (C1 dorsal ramus); Action—extends & rotates head.

Rectus capitis posterior minor

Origin—posterior tubercle C1; Insertion—inferior nuchal line (medial); Innervation—suboccipital n.; Action—extends head.

Obliquus capitis superior

Origin—C1 transverse process; Insertion—occipital bone between nuchal lines; Innervation—suboccipital n.; Action—extends & laterally flexes head.

Obliquus capitis inferior

Origin—C2 spinous process; Insertion—C1 transverse process; Innervation—suboccipital n.; Action—rotates atlas to turn head.

Triangle of auscultation

Borders—medial trapezius, inferior latissimus dorsi, lateral scapular border; Floor—rhomboid major; Clinical—thin muscle layer allows clear lung auscultation.

Suboccipital triangle

Borders—rectus capitis posterior major (superomedial), obliquus capitis superior (superolateral), obliquus capitis inferior (inferolateral); Floor—posterior atlanto-occipital membrane; Roof—semispinalis capitis; Contents—vertebral artery & suboccipital nerve.

Vertebral column (overview)

33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, 4 coccygeal (partially fused).

Typical vertebra

Components—body (weight-bearing), pedicles, laminae, vertebral foramen (spinal cord), transverse & spinous processes, articular facets (zygapophyseal joints), vertebral notches forming intervertebral foramen (spinal nerves exit).

Cervical vertebrae (C3–C7)

Small body, large vertebral foramen, transverse foramina for vertebral vessels, bifid spinous process, uncinate processes.

Atlas (C1)

No body or spinous process; articulates with occipital condyles; part of atlanto-occipital joint enabling nodding.

Axis (C2)

Has dens (odontoid process) projecting superiorly; forms pivot of atlanto-axial joint enabling head rotation.

Vertebra prominens (C7)

Long, non-bifid spinous process palpable at base of neck.

Thoracic vertebrae

Heart-shaped bodies, long downward spinous processes, costal facets for rib articulation, smaller vertebral foramen; rigidity due to rib cage.

Lumbar vertebrae

Large kidney-shaped bodies, short blunt spinous processes, thick transverse processes, vertical articular facets; high load—common L4-L5 disc herniation.

Sacrum

Fusion of five vertebrae; forms posterior pelvic wall; features anterior/posterior sacral foramina for nerves & auricular surface for sacroiliac joint.

Coccyx

Tailbone of 3-5 fused rudimentary vertebrae; attachment for pelvic floor muscles such as coccygeus.

Anterior longitudinal ligament (ALL)

Runs along anterior vertebral bodies; limits extension; often torn in whiplash injuries.

Posterior longitudinal ligament (PLL)

Runs inside vertebral canal on posterior bodies; limits flexion; weaker than ALL—posterior disc herniations common.

Ligamentum flavum

Connects adjacent laminae; elastic fibers permit flexion & recoil; hypertrophy can cause spinal stenosis.

Interspinous ligament

Connects adjoining spinous processes along their length; stabilizes during flexion.

Supraspinous ligament

Runs along tips of spinous processes; continuous superiorly with nuchal ligament in cervical region.

External occipital protuberance

Midline bump on occipital bone; origin for trapezius.

Superior nuchal line

Ridge on occipital bone; insertion for trapezius, splenius capitis, occipitalis muscle.

Inferior nuchal line

Lower occipital ridge; insertion for rectus capitis posterior major & minor.

Iliac crest (L4 level)

Palpable superior border of ilium; landmark for lumbar puncture needle placement.

Mastoid process

Projection of temporal bone; insertion for sternocleidomastoid & splenius capitis.