Chapter 16: The Spinal Cord and Spinal Nerves

Vocabulary practice flashcards covering the gross anatomy, meninges, internal sectional architecture, roots, rami, and major plexuses of the spinal cord and spinal nerves.

Spinal Cord

A cylindrical structure measuring approximately $\frac{3}{4}\text{ of an inch}$ in diameter and $16\text{–}18\text{ inches}$ ($41\text{–}45\,cm$) long, extending from the foramen magnum to the L1 vertebra; serves as an integration center for reflexes and a vital conduction pathway between the brain and body.

Spinal Meninges

A system of three protective connective tissue membranes (dura mater, arachnoid mater, and pia mater) that enclose the spinal cord and extend along spinal nerve roots through the intervertebral foramina.

Denticulate Ligaments

Paired, triangular-shaped lateral extensions of the spinal pia mater that anchor and stabilize the spinal cord to the surrounding dura mater.

Dura Mater

The outermost, most superficial meninx composed of tough, dense irregular connective tissue that provides a protective outer sheath around the spinal cord.

Epidural Space

The anatomical space situated between the dura mater and the bony inner wall of the vertebral canal.

Arachnoid Mater

The middle avascular meninx composed of cells and a delicate web of collagen and elastic fibers.

Subdural Space

The potential space located between the dura mater and the arachnoid mater.

Subarachnoid Space

The space located deep to the arachnoid mater and superficial to the pia mater that contains shock-absorbing cerebrospinal fluid (CSF).

Pia Mater

The innermost, highly vascular, transparent connective tissue layer consisting of thin squamous to cuboidal cells and interlaced collagen and elastic fibers that adheres directly to the surface of the spinal cord.

Foramen Magnum

The large opening at the base of the skull through which the medulla oblongata continues inferiorly as the spinal cord.

Conus Medullaris

The tapered, cone-shaped inferior terminal end of the spinal cord, located around the L1 vertebra.

Cauda Equina

A bundle of nerve roots resembling a "horse's tail" that extends inferiorly through the lower vertebral canal below the conus medullaris.

Filum Terminale

A thin strand of pia mater located within the cauda equina that anchors the conus medullaris to the coccyx.

Lumbar Cistern

The enlarged subarachnoid space inferior to the conus medullaris that contains cerebrospinal fluid and the cauda equina.

Lumbar Puncture (Spinal Tap)

A clinical procedure typically performed between the L3–L4 or L4–L5 vertebrae to safely extract cerebrospinal fluid from the lumbar cistern without injuring the spinal cord.

Cervical Enlargement

The widened region of the inferior cervical spinal cord (spinal nerve levels C5–T1) containing the motor and sensory neurons supplying the upper limbs.

Lumbosacral Enlargement

The widened portion of the spinal cord spanning the lumbar and sacral regions (spinal nerve levels L1–S2) innervating the lower limbs.

Gray Matter (Spinal Cord)

The centrally located, butterfly-shaped tissue of the spinal cord composed of neuron cell bodies, dendrites, unmyelinated axons, and neuroglia that processes neural information.

White Matter (Spinal Cord)

The outer region of the spinal cord composed primarily of myelinated axons grouped into tracts that carry sensory and motor impulses to and from the brain.

Anterior Horn

The anterior projection of spinal gray matter that houses cell bodies of somatic motor neurons innervating skeletal muscles.

Lateral Horn

The lateral projection of spinal gray matter found exclusively in segments T1–L2 that houses autonomic (visceral) motor neuron cell bodies innervating cardiac muscle, smooth muscle, and glands.

Posterior Horn

The posterior projection of spinal gray matter containing interneuron cell bodies and the incoming axons of somatic and visceral sensory neurons.

Gray Commissure

A central horizontal bar of gray matter connecting the right and left spinal gray horns, enclosing the central canal.

Central Canal

A narrow longitudinal channel situated in the center of the gray commissure that carries cerebrospinal fluid.

Funiculus

One of three white matter regions (posterior, lateral, and anterior funiculi) containing bundles of myelinated axons called tracts.

Rootlet

A small bundle of nerve fibers entering or exiting directly at the surface of the spinal cord; multiple join to form a spinal nerve root.

Posterior (Dorsal) Root

A nerve bundle formed by posterior rootlets that transmits sensory impulses inward toward the spinal cord.

Posterior Root Ganglion

An enlargement along the posterior root housing the cell bodies of sensory neurons.

Anterior (Ventral) Root

A nerve bundle formed by anterior rootlets arising from anterior and lateral gray horns that carries motor impulses away from the spinal cord.

Tract

A bundle of axons located within the white matter of the central nervous system that conducts sensory information up toward the brain or motor instructions down from the brain.

Spinal Nerve

One of 31 pairs of mixed peripheral nerves formed by the lateral union of an anterior root and a posterior root.

Posterior Ramus

A mixed branch of a spinal nerve that supplies sensory and motor innervation to the deep muscles and skin of the back.

Anterior Ramus

A mixed branch of a spinal nerve that innervates the anterior and lateral trunk and the limbs; frequently joins other anterior rami to form nerve plexuses.

Nerve Plexus

An interwoven network of nerves formed by fibers branching and reconnecting from the anterior rami of spinal nerves.

Cervical Plexus

A network formed by the anterior rami of spinal nerves C1–C5 that supplies the neck and diaphragm.

Brachial Plexus

A network formed by the anterior rami of spinal nerves C5–T1 that innervates the shoulder girdle and upper limbs.

Lumbar Plexus

A network formed by the anterior rami of spinal nerves L1–L4 that innervates the lower abdominal wall and parts of the lower limbs.

Sacral Plexus

A network formed by the anterior rami of spinal nerves L4–S4 that innervates the pelvis, buttocks, and much of the lower limbs.