Topic 3: Myology of the Back and Suboccipital Region

Vocabulary practice flashcards covering the extrinsic, intermediate, and intrinsic back musculature, thoracolumbar fascia, and suboccipital muscles and nerves from Topic 3.

Origin (proximal insertion / head)

The termination of a muscle that attaches to the immobile bone.

Insertion (distal insertion)

The muscle termination attached to the bone that exhibits increased movement during contraction.

Muscle Belly

The wider fleshy portion of a muscle located between its origin and insertion.

Homolateral Movement

A movement produced toward the same side of the body as the contracting muscle.

Contralateral Movement

A movement produced toward the opposite side of the body relative to the contracting muscle.

Extrinsic Muscles of the Back (Thoraco-brachial muscles)

The most superficial group of back muscles (trapezius, latissimus dorsi, rhomboids, and levator scapulae) that connect and fix the upper limb to the trunk.

Intermediate Muscles of the Back (Respiratory group)

Two thin muscle sheets (serratus posterior superior and serratus posterior inferior) situated immediately deep to the superficial group, running obliquely from the spine to the ribs to assist in respiration.

Intrinsic Muscles of the Back

Deep back muscles fixed directly to the vertebrae and/or ribs that produce spinal movements, arranged in superficial, intermediate, and deep layers.

Trapezius

An extrinsic back muscle originating from the superior nuchal line, external occipital protuberance, ligamentum nuchae, and spinous processes of CVII to TXII, inserting into the lateral third of the clavicle, acromion, and spine of the scapula.

Trapezius Innervation and Action

Innervated by the accessory nerve (CN XI) for motor function and C3–C4 for proprioception; elevates (upper fibers), adducts (middle fibers), and depresses (lower fibers) the scapula, and rotates the scapula during humeral abduction above the horizontal.

Latissimus Dorsi

An extrinsic back muscle originating from the spinous processes of TVII to LV, sacrum, iliac crest, and ribs X to XII, inserting into the floor of the intertubercular sulcus of the humerus; innervated by the thoracodorsal nerve (C6–C8) to extend, adduct, and medially rotate the humerus.

Levator Scapulae

An extrinsic back muscle originating from the transverse processes of CI to CIV and inserting onto the upper medial border of the scapula; innervated by C3–C4 and the dorsal scapular nerve (C4, C5) to elevate the scapula.

Rhomboid Major

An extrinsic back muscle originating from the spinous processes of TII to TV and inserting into the medial border of the scapula between the spine and inferior angle; innervated by the dorsal scapular nerve (C4, C5) to retract (adduct) and elevate the scapula.

Rhomboid Minor

An extrinsic back muscle originating from the lower portion of the ligamentum nuchae and spinous processes of CVII and TI, inserting onto the medial border at the spine of the scapula; innervated by the dorsal scapular nerve (C4, C5) to retract and elevate the scapula.

Serratus Posterior Superior

An intermediate back muscle originating from the lower ligamentum nuchae, spinous processes of CVII to TIII, and supraspinous ligaments, inserting into the upper border of ribs II to V lateral to their angles; innervated by anterior rami of T2 to T5 to elevate ribs II to V.

Serratus Posterior Inferior

An intermediate back muscle originating from the spinous processes of TXI to LIII and supraspinous ligaments, inserting into the lower border of ribs IX to XII lateral to their angles; innervated by anterior rami of T9 to T12 to depress ribs IX to XII and prevent lower rib elevation during diaphragm contraction.

Thoracolumbar Fascia

A dense fascia coating the muscles of the vertebral canals in the thoracic and lumbar regions; in the lumbar region it consists of three layers (anterior, middle, and posterior), with the posterior layer covering the erector spinae and serving as an attachment for the latissimus dorsi.

Splenius Capitis

A superficial intrinsic back muscle originating from the lower half of the ligamentum nuchae and spinous processes of CVII to TIV, inserting into the mastoid process and skull below the lateral third of the superior nuchal line; innervated by posterior rami of middle cervical nerves to extend the head/neck (bilaterally) and rotate the head to the same side (unilaterally).

Splenius Cervicis

A superficial intrinsic back muscle originating from the spinous processes of TIII to TVI, inserting into the transverse processes of CI to CIII; innervated by posterior rami of lower cervical nerves to extend the neck (bilaterally) and rotate the head to the same side (unilaterally).

Erector Spinae Group

The intermediate layer of intrinsic back muscles and main spinal extensor, organized into three fasciculated columns from lateral to medial: iliocostalis, longissimus, and spinalis.

Common Mass of Erector Spinae

The shared inferior tendinous origin of the erector spinae muscles anchored to the posterior superior iliac spine (PSIS), iliac crest, iliac tuberosity, median sacral crest, and lumbar spinous processes.

Iliocostalis

The most lateral column of the erector spinae group, divided into lumborum, thoracis, and cervicis parts; provides the most effective leverage for lateral flexion of the spine.

Longissimus

The intermediate and most developed column of the erector spinae group, running from the common mass to the mastoid process of the skull; divided into thoracis, cervicis, and capitis parts.

Spinalis

The most medial and least developed column of the erector spinae group, primarily prominent in the thoracic region (spinalis thoracis) and running between spinous processes; its cranial fibers typically blend with semispinalis capitis.

Transversospinal Group (Transverse-spinatus)

A deep group of intrinsic back muscles that run obliquely upward and medially from vertebral transverse processes to the laminae or spinous processes of overlying vertebrae, comprising the rotatores, multifidus, and semispinalis.

Rotatores (Brevis and Longus)

The deepest, shortest transversospinal muscles, most developed in the thoracic region; rotator brevis crosses 1 intervertebral junction to the adjacent lamina, while rotator longus crosses 2 intervertebral junctions.

Multifidus

Intermediate-depth transversospinal muscles that arise from transverse processes and insert into the base of spinous processes 2 to 4 vertebral levels above (crossing 2–4 intervertebral junctions).

Semispinalis

The most superficial and longest transversospinal group (divided into thoracis, cervicis, and capitis), arising from transverse processes and crossing 6 to 8 intervertebral junctions to attach to spinous processes or the occipital bone.

Interspinales

Short paired intrinsic postural muscles positioned on either side of the interspinous ligament between adjacent spinous processes; they stabilize the spine and aid in extension, but are replaced by connective tissue in the thoracic region.

Intertransversarii

Short segmental intrinsic muscles connecting the transverse processes of adjacent vertebrae, innervated by anterior rami of spinal nerves to provide fine motor sensory feedback, spinal stabilization, and lateral tilt.

Levatores Costarum

Segmental muscles arising from the transverse processes of CVII to TXI that pass inferolaterally to insert near the tubercle of the rib below (brevis crosses 1 level, longus crosses 2 levels) to elevate the ribs.

Rectus Capitis Posterior Major

A suboccipital muscle originating from the spinous process of the axis (CII) and inserting into the lateral portion of the occipital bone below the inferior nuchal line; innervated by the posterior ramus of C1 to extend the head and rotate the face to the same side.

Rectus Capitis Posterior Minor

A suboccipital muscle originating from the posterior tubercle of the atlas (CI) and inserting into the medial portion of the occipital bone below the inferior nuchal line; innervated by the posterior ramus of C1 to extend the head.

Obliquus Capitis Superior

A suboccipital muscle originating from the transverse process of the atlas (CI) and inserting into the occipital bone between the superior and inferior nuchal lines; innervated by the posterior ramus of C1 to extend the head and bend it homolaterally.

Obliquus Capitis Inferior

A suboccipital muscle originating from the spinous process of the axis (CII) and inserting into the transverse process of the atlas (CI); innervated by the posterior ramus of C1 to rotate the face to the same side.

Suboccipital Nerve

The posterior ramus of the C1 spinal nerve, emerging above the posterior arch of the atlas to provide motor innervation to the suboccipital muscles.

Greater Occipital Nerve (Arnold's Nerve)

The primary sensory posterior ramus (medial branch) of the C2 spinal nerve, emerging inferior to the obliquus capitis inferior to innervate the posterior scalp.