Myology, Topography, and Neurovascular Organization of the Back and Axial Skeleton

Comprehensive vocabulary flashcards covering the superficial, intermediate, deep, and intersegmental musculature of the axial skeleton, vascular supply, spinal cord topography, and peripheral and autonomic neuroanatomy.

Endomysium

The innermost layer of connective tissue that surrounds individual skeletal muscle fibers and supports capillaries and fine nerve fibers.

Perimysium

The connective tissue sheath that encloses bundles of muscle fibers known as fascicles within a skeletal muscle.

Epimysium

The dense layer of deep fascia and connective tissue that surrounds an entire muscle, separating it from adjacent muscles and tissues.

Trapezius

A large superficial extrinsic back muscle originating from the medial superior nuchal line, external occipital protuberance, nuchal ligament, and spinous processes of $C7-T12$, inserting into the lateral third of the clavicle, acromion, and spine of the scapula; innervated by cranial nerve $XI$ (motor) and $C3-C4$ (sensory/proprioception).

Latissimus dorsi

A broad, fan-shaped superficial extrinsic muscle originating from spinous processes $T7-T12$, the thoracolumbar fascia, iliac crest, and ribs $9-12$, inserting into the crest of the lesser tubercle and floor of the intertubercular sulcus of the humerus, innervated by the thoracodorsal nerve ($C6-C8$).

Levator scapulae

A superficial extrinsic back muscle originating from the posterior tubercles of the transverse processes of $C1-C4$ and inserting onto the superior angle and superior medial border of the scapula; innervated by the dorsal scapular nerve ($C5$) and anterior rami of $C3-C4$.

Rhomboid minor

A small quadrilateral extrinsic back muscle originating from the nuchal ligament and spinous processes of $C7-T1$, inserting into the medial border of the scapula at the root of the spine, and innervated by the dorsal scapular nerve ($C4-C5$).

Rhomboid major

An extrinsic back muscle originating from the spinous processes of $T2-T5$ (or up to $T7$), inserting along the medial border of the scapula inferior to the root of the spine, and innervated by the dorsal scapular nerve ($C4-C5$).

Thoracolumbar fascia

A girdling structure composed of three aponeurotic and fascial layers (posterior, middle, anterior) that separates the paraspinal muscles from the posterior abdominal wall musculature, providing structural stability and muscle attachment.

Serratus posterior superior

A thin intermediate extrinsic back muscle originating from the nuchal ligament and spinous processes of $C7-T3$, inserting into the superior borders of ribs $2-5$ near their angles; innervated by anterior primary rami via intercostal nerves $T2-T5$.

Serratus posterior inferior

An intermediate extrinsic muscle occupying the thoracolumbar junction, originating from the spinous processes of $T11-L2$ via the thoracolumbar fascia and inserting into the inferior borders of ribs $9-12$ near their angles; innervated by intercostal nerves $T9-T12$.

Splenius capitis

The broad superficial intrinsic neck muscle originating from the inferior half of the nuchal ligament and spinous processes of $C7-T3/T4$, inserting onto the mastoid process and lateral third of the superior nuchal line, innervated by the posterior primary rami of middle cervical spinal nerves.

Splenius cervicis

A superficial intrinsic back muscle originating from the spinous processes of $T3-T6$ and inserting onto the posterior tubercles of the transverse processes of $C1-C3/C4$, innervated by the posterior primary rami of lower cervical spinal nerves.

Erector spinae common tendon

The broad, dense inferior aponeurotic origin of the erector spinae musculature that attaches to the posterior iliac crest, posterior sacrum, sacroiliac ligaments, sacral and lumbar spinous processes, and thoracolumbar fascia.

Iliocostalis

The most lateral longitudinal column of the erector spinae group, divided into lumborum, thoracis, and cervicis segments, which extends between the common tendon, the angles of the ribs, and the cervical transverse processes.

Longissimus thoracis

The intermediate column of the erector spinae within the thorax, originating from the common tendon and inserting into the transverse processes of all thoracic vertebrae and the angles of the lower $6$ ribs; innervated by posterior primary rami.

Longissimus cervicis

The intermediate column of the erector spinae in the cervical region, originating from the upper thoracic transverse processes and inserting into the transverse processes of $C2-C6$.

Longissimus capitis

The cranial extension of the intermediate erector spinae column, originating from the upper thoracic and lower cervical transverse processes and inserting onto the posterior margin of the mastoid process.

Spinalis thoracis

The most medial column of the erector spinae in the thoracic region, originating from the lower thoracic and upper lumbar spinous processes and inserting onto the upper thoracic spinous processes.

Spinalis cervicis

A medial column erector spinae muscle arising from the ligamentum nuchae and spinous process of $C7$, inserting into the spinous process of the axis ($C2$).

Transversospinalis group

The deep intrinsic group of back muscles lying deep to the erector spinae, comprising the semispinalis, multifidus, and rotatores, which run obliquely superiorly and medially from transverse processes to spinous processes.

Semispinalis capitis

A prominent transversospinalis muscle originating from the transverse processes of $C7-T6$ and articular processes of $C4-C6$, inserting on the occipital bone between the superior and inferior nuchal lines; acts in head extension and contralateral rotation.

Semispinalis cervicis

A deep intrinsic muscle originating from the transverse processes of $T1-T6$ and inserting into the spinous processes of $C2-C5$, serving as a primary extensor and contralateral rotator of the neck.

Multifidus

A major transversospinalis stabilizer originating from the sacrum, PSIS, sacroiliac ligaments, mammillary processes, transverse processes, and articular processes, spanning $2-4$ vertebral segments superiorly to insert onto spinous processes.

Rotatores

The deepest intrinsic transversospinalis muscles arising from transverse processes and inserting at the junction of the lamina and spinous process of superior vertebrae; divided into rotatores brevis (spanning $1$ vertebral segment) and rotatores longus (spanning $2$ segments).

Interspinales

Short, paired intersegmental intrinsic muscles that connect the superior surface of a spinous process to the inferior surface of the immediately superior spinous process, primarily developed in the cervical and lumbar regions.

Levatores costarum

Intersegmental muscles originating from the transverse processes of $C7-T11$ and inserting on the rib below between its tubercle and angle; categorized into breves (inserting on the immediate rib below) and longi (inserting on the second rib below).

Rectus capitis posterior major

A suboccipital muscle originating from the spinous process of the axis ($C2$) and inserting into the lateral portion of the inferior nuchal line of the occipital bone; forms the superomedial border of the suboccipital triangle.

Rectus capitis posterior minor

A suboccipital muscle arising from the posterior tubercle of the atlas ($C1$) and inserting into the medial portion of the inferior nuchal line; innervated by the suboccipital nerve ($C1$).

Obliquus capitis superior

A suboccipital muscle originating from the transverse process of the atlas ($C1$) and inserting onto the occipital bone between the superior and inferior nuchal lines; forms the superolateral boundary of the suboccipital triangle.

Obliquus capitis inferior

A suboccipital muscle originating from the spinous process of the axis ($C2$) and inserting onto the transverse process of the atlas ($C1$); forms the inferolateral boundary of the suboccipital triangle.

Suboccipital triangle

A deep posterior cervical triangle bounded by rectus capitis posterior major, obliquus capitis superior, and obliquus capitis inferior, roofed by semispinalis capitis, floored by the posterior atlanto-occipital membrane and posterior arch of atlas, containing the vertebral artery (V3 segment), suboccipital nerve ($C1$), and suboccipital venous plexus.

Suboccipital nerve

The posterior primary ramus of the $C1$ spinal nerve, emerging superior to the posterior arch of the atlas to provide pure motor innervation to the suboccipital muscles and portions of semispinalis capitis.

Greater occipital nerve

The large medial branch of the posterior primary ramus of $C2$ that pierces semispinalis capitis and trapezius to supply sensory innervation to the posterior scalp up to the vertex; a known generator of cervicogenic headaches.

Third occipital nerve

The medial branch of the posterior primary ramus of $C3$ that supplies cutaneous sensation to the lower occipital region and upper posterior neck, as well as articular branches to the $C2-C3$ zygapophyseal joint.

Rectus abdominis

A long, vertical anterior abdominal strap muscle originating from the pubic crest and pubic symphysis, inserting into the xiphoid process and costal cartilages $5-7$, innervated by thoracoabdominal nerves ($T7-T12$).

External abdominal oblique

The most superficial lateral abdominal wall muscle, originating from the external surfaces of ribs $5-12$ and inserting into the linea alba, pubic tubercle, and anterior iliac crest; acts in contralateral trunk rotation and abdominal compression.

Internal abdominal oblique

The intermediate lateral abdominal muscle arising from the thoracolumbar fascia, iliac crest, and lateral inguinal ligament, inserting into ribs $10-12$, the linea alba, and the pubis; produces ipsilateral trunk rotation.

Transversus abdominis

The deepest muscle layer of the anterolateral abdominal wall, originating from the thoracolumbar fascia, iliac crest, inguinal ligament, and lower $6$ costal cartilages, acting as an essential dynamic stabilizer of the spine and compressor of abdominal viscera.

Serratus anterior

A thoracic wall muscle originating from the external surfaces of ribs $1-8$ (or $1-9$) and inserting on the costal surface of the medial border of the scapula; innervated by the long thoracic nerve ($C5-C7$), with lesions causing scapular winging.

Scalene muscles

A group of lateral cervical muscles (anterior, middle, posterior) originating from the transverse processes of $C2-C7$ and inserting onto the first and second ribs; they laterally flex the neck, elevate the ribs during inspiration, and flank the interscalene space through which the brachial plexus and subclavian artery pass.

Artery of Adamkiewicz

The great anterior radiculomedullary artery, typically arising from a left lower intercostal or upper lumbar artery, which provides the dominant arterial blood supply to the lower two-thirds of the spinal cord.

Costocervical trunk

A branch arising from the second part of the subclavian artery (posterior/deep to anterior scalene) that divides into the deep cervical artery (supplying deep cervical muscles) and the highest (supreme) intercostal artery.

Diaphragmatic apertures

The three anatomical openings of the diaphragm: the caval hiatus at $T8$ (transmitting the inferior vena cava and right phrenic nerve), the esophageal hiatus at $T10$ (transmitting the esophagus and vagal trunks), and the aortic hiatus at $T12$ (transmitting the aorta, thoracic duct, and azygos vein).

Vertebra prominens

The palpable seventh cervical vertebra ($C7$), featuring an elongated, non-bifid spinous process that serves as a clinical surface landmark indicating the transition from the cervical to the thoracic spine.

Intercristal line

A transverse anatomical landmark drawn across the highest points of the iliac crests (cristal tubercles), which correlates reliably with the $L4-L5$ intervertebral disk space.

Lumbar triangle of Petit

A triangular area of potential weakness on the posterolateral abdominal wall bounded medially by the latissimus dorsi, laterally by the external abdominal oblique, and inferiorly by the iliac crest, with its floor formed by the internal abdominal oblique.

Triangle of auscultation

A thinning of the back musculature bounded medially by the trapezius, superiorly/laterally by rhomboid major, and inferiorly by latissimus dorsi, floored by the thoracic wall; used clinically to auscultate lung sounds with minimal muscular interference.

Conus medullaris

The tapered, cone-shaped inferior extremity of the spinal cord, situated at the vertebral level of $L1-L2$ in adults.

Filum terminale

A delicate, thread-like fibrous prolongation of the pia mater extending inferiorly from the apex of the conus medullaris to attach to the dorsum of the coccyx, anchoring the spinal cord longitudinally.

Denticulate ligaments

Twenty-one pairs of lateral, tooth-like triangular extensions of spinal pia mater that attach laterally to the arachnoid and dura mater, suspending the spinal cord within the dural sac.

Cauda equina

The collection of elongated posterior and anterior spinal nerve roots descending within the lumbar cistern below the conus medullaris to exit at their respective intervertebral foramina.

Bell-Magendie Law

The physiological anatomical principle establishing that sensory (afferent) nerve impulses enter the spinal cord via posterior (dorsal) roots, whereas motor (efferent) nerve impulses exit via anterior (ventral) roots.

Sinuvertebral nerve

Also called the recurrent meningeal nerve, this mixed nerve branches from the spinal nerve within the intervertebral foramen and re-enters the spinal canal to innervate the meninges, posterior longitudinal ligament, outer anulus fibrosus, and periosteum.

Dorsal rami distribution

The segmental divisions of spinal nerves providing motor innervation to epaxial (intrinsic) muscles, whose medial branches are muscular throughout and cutaneous above $T6$, and whose lateral branches are muscular throughout and cutaneous below $T7$.

Dermatome

A defined strip or region of skin whose sensory innervation is supplied by the cutaneous branches of a single specific spinal nerve, with all spinal nerves participating except $C1$.

Sympathetic division

The thoracolumbar arm of the autonomic nervous system, with preganglionic neuron cell bodies located in the lateral horns of spinal cord segments $T1-L2$, characterized by short preganglionic fibers and long postganglionic fibers.

Parasympathetic division

The craniosacral division of the autonomic nervous system, originating from cranial nerve nuclei ($CN\,III$, $CN\,VII$, $CN\,IX$, and $CN\,X$) and sacral segments $S2-S4$, characterized by long preganglionic fibers and short postganglionic fibers terminating in or near effector organs.