BACK MUSCLES & MECHANICS
These three paravertebral columns—iliocostalis, longissimus, spinalis, arranged lateral to medial—provide gross extension and postural resistance to gravity.
What is the erector spinae?
A patient can't abduct beyond the first 15 degrees and has lateral shoulder numbness; the axillary nerve is compressed in this space bounded by teres minor, teres major, triceps long head, and the surgical neck.
What is the quadrangular space?
This single anterior vessel runs in the anterior median fissure and supplies the anterior two-thirds of the cord.
What is the anterior spinal artery?
This muscle is the roof of the suboccipital triangle and is reflected to expose the contents—not one of the three walls.
What is the semispinalis capitis?
A patient develops unilateral leg swelling after prolonged immobility with a negative DVT Doppler; the cause is loss of this pump-like mechanism that normally propels lymph.
What is skeletal muscle contraction?
A patient keeps gross range of motion but has segmental instability and poor fine control under complex loading; dysfunction of this deeper muscle group, not erector spinae, is the cause.
What is the transversospinalis (semispinalis, multifidus, rotatores)?
A midshaft humeral injury causes wrist drop because this nerve—with the profunda brachii artery—travels through the triangular interval.
What is the radial nerve?
A patient has bilateral motor loss and bilateral loss of pain and temperature but preserved vibration and proprioception; this vascular syndrome explains the sparing of the dorsal columns.
What is anterior spinal artery syndrome?
This is the only suboccipital muscle with no skull attachment, running C2 spinous process to C1 transverse process.
What is the obliquus capitis inferior?
Paracortex expansion in a node signals proliferation in this cell zone, classically seen with viral infection—not the B-cell cortex or the plasma-cell medulla.
What is the T-cell zone (paracortex)?
Unilateral contraction of transversospinalis produces rotation in this direction, predictable from its oblique fibers running from transverse processes to higher spinous processes.
What is contralateral (opposite-side) rotation?
This posterior shoulder space transmits the circumflex scapular artery only, so its compression is purely vascular with no named nerve deficit.
What is the triangular space?
Aortic surgery risks cord ischemia by compromising segmental reinforcement from this major radicular artery.
What is the artery of Adamkiewicz?v
Selective atrophy of all four suboccipital muscles with loss of fine upper-cervical control localizes to this nerve, not CN XI or the C2 ramus.
What is the C1 posterior ramus (suboccipital nerve)?
A DiGeorge patient has intact marrow precursors but severe T-cell deficiency because education fails in this superior-mediastinal primary lymphoid organ.
What is the thymus?
Nearly all intrinsic back muscles share this innervation, which distinguishes them from extrinsic muscles like latissimus, trapezius, and rhomboids supplied by anterior rami or cranial nerves.
What are the posterior (dorsal) rami?
The quadrangular space carries the axillary nerve alongside this artery, its named vascular companion.
What is the posterior circumflex humeral artery?
A prostate cancer patient has vertebral body metastases without early lung involvement; this valveless venous network allows the retrograde spread.
What is the Batson (vertebral venous) plexus?
This vessel loops posteromedially across the posterior arch of C1 after leaving the transverse foramen—the surgical exception that it doesn't stay anterior.
What is the vertebral artery (V3 segment)?
This structure drains roughly three-quarters of the body and empties at the left internal jugular–subclavian junction, so its laceration causes chylothorax.
What is the thoracic duct?
A stem gives horizontal muscle fibers and asks the mechanical role; naming this function follows the lecture's fiber-direction-predicts-action rule.
What is compression stabilization?
A humeral fracture spares elbow extension despite radial nerve involvement; this anatomical fact about the injury being distal to early triceps branches explains the preserved function.
What is the location of injury relative to the triceps motor branches (distal to them)?
An fMRI BOLD signal reflects the hemodynamic response, not neural firing directly; in the neurovascular unit, these cells couple synaptic activity to vessels via calcium signaling at endfeet.
What are astrocytes?
A stab wound deep to semispinalis capitis causes vertigo, ataxia, and diplopia; naming this circulation explains the deficit, and CT plus this study is the emphasized workup.
What is the posterior circulation (assessed with CT angiography)?
A vignette contrasts nodal basins: unlike scrotal skin draining to inguinal nodes, this parenchyma drains to para-aortic retroperitoneal nodes near L1–L2.
What is the testis (testicular parenchyma)?