Spinal Cord-External Features PDF

Spinal Cord- External Features AN5203 Dr. Moira Jenkins SPINAL CORD ◼ GENERAL FUNCTIONS – Integrates and modulates input for motor responses – Transmits information to/from brain Spinal Nerve ◼ Afferent neuron cell bodies (pseudounipolar) are in the DRG ◼ Ventral root (M)and dorsal root (S)com...

Spinal Cord- External Features AN5203 Dr. Moira Jenkins SPINAL CORD ◼ GENERAL FUNCTIONS – Integrates and modulates input for motor responses – Transmits information to/from brain Spinal Nerve ◼ Afferent neuron cell bodies (pseudounipolar) are in the DRG ◼ Ventral root (M)and dorsal root (S)combine in the IVF and form the spinal nerve (mixed) ◼ Spinal nerve branches into dorsal and ventral rami (mixed) Spinal Nerves • 31 pairs (C8, T12, L5, S5, C1) • axons of sensory nerves from receptors to CNS • axons of motor nerves from CNS to effector tissue (muscles, glands) Dermatomes & Myotomes A dermatome is an area of skin that is mainly supplied by a single spinal nerve. Each of these nerves relays sensation (including pain) from a particular region of skin to the brain A myotome is a group of muscles that a single spinal nerve root innervates ◼ Spinal cord is continuous with the medulla of the brain stem at the level of the foramen magnum External Morphology ◼ SULCI/FISSURE – Dorsal median, dorsolateral, dorsal intermediate, dorsolateral ventrolateral sulci; ventral median fissure ◼ SEGMENTATION – 31 cord segments – Defined by attachment of paired dorsal and ventral rootlets • Cord tapers to a cone (conus medullaris) and ends at L1 vertebral body • L1 - C0 segments are housed by T9 - L1 vertebrae • Lumbosacral roots are long and oblique as they descend to their IVFs (cauda equina) • Spinal cord ends L1/L2 • Dural sac ends S2 SPINAL NERVES:  8 cervical  12 thoracic  5 lumbar  5 sacral  1 (?) coccygeal 31 pairs First 7 nerves exit above corresponding vertebrae The 8th nerve does not enter the thoracic cavity, called C8 C8 spinal nerve exits below the C7 vertebra, and above the T1 vertebra Nerves then exit below corresponding vertebra Enlargements in the Spinal Cord The cord is enlarged at C5-T1 and L4-S4 levels. The parts of the cord that control the upper and lower limbs. Brachial Plexus and Lumbosacral Plexus Enlargements in the Spinal Cord Spinal Meninges and Epidural Venous Plexus spinal cord pia mater arachnoid mater dura mater epidural venous plexus epidural space (filled with fat) bony vertebral canal lined with periosteum ◼ Dura Mater – Outer layer, thick – Innervated primarily by the recurrent meningeal nerve (posteromedian area is devoid of fibers) ◼ Arachnoid mater – Delicate, loose membrane ◼ Collectively extend to form the dural/thecal sac; ends at mid S2 vertebral body ◼ Both extend laterally to invest nerve roots (sleeve) Basic and Clinical Anatomy of the Spine, Spinal Cord, and ANS by Cramer and Darby ◼ Under arachnoid is the subarachnoid space – CSF – Enlarged to form lumbar cistern ◼ Pia mater – 2 cell layers thick – Invests cord and roots – Derivatives • Denticulate ligaments • Filum terminale Basic and Clinical Anatomy of the Spine, Spinal Cord, and ANS by Cramer and Darby • spinal cord terminates at conus medullaris • nerve roots come off the spinal cord and form cauda equina • stretched spinal cord remnant (pia) forms filum terminale internum • Ends at S2, end of dural sac and inferiormost point of lumbar cistern • Filum terminal externum – continuation outside of dural sac, dense connective tissue, anchored at C0. • Also known as coccygeal ligament LUMBAR PUNCH (SPINAL TAP) – subarachnoid space Usually between 3rd, 4th, or 5th lumbar verts EPIDURAL ANESTHESIA – epidural space Blood Supply There is usually at least one large contribution every 4-6 segments and there is often a large vessel in the lower thoracic region critical to the supply of the lumbar enlargement (artery of Adamkiewicz).