Neuroanatomy Spinal Cord & Meninges

What are the five major functions of the spinal cord?

Sensory, motor, autonomic, reflexes, and pathway functions.

What sensory function does the spinal cord perform?

Receives input from peripheral receptors.

What motor function does the spinal cord perform?

Drives skeletal muscle output.

What autonomic function does the spinal cord perform?

Visceral regulation.

What reflexes function does the spinal cord perform?

rapid, stereotyped response circuits

What pathway function does the spinal cord perform?

connects body and brain via ascending/ descending fibers

What is the spinal cord a continuation of?

The medulla oblongata ( most inferior portion of brainstem)

Where does the spinal cord begin?

At the foramen magnum.

Where is the spinal cord located?

Within the vertebral canal ( protected by meninges, veterbrae, and veterbral spinal cord)

Where does the spinal cord end in adults?

Approximately L1–L2

Veterbal canal continues inferiorly beyond cord

What is the tapered end of the spinal cord called?

Conus medullaris

near L1- L2

How many spinal cord segments are there?

31 segments

How many cervical spinal cord segments are there?

8 ( 1st cervical spinal nerve exits superior to c1 vertebrae)

How many thoracic spinal cord segments are there?

12

How many lumbar spinal cord segments are there?

5

How many sacral spinal cord segments are there?

5

How many coccygeal spinal cord segments are there?

1

What forms the dorsal root?

Dorsal rootlets

What type of information do dorsal rootlets carry?

Sensory

Emerge from the posterolateral sulcus; ventral rootlets from the anterolateral sulcus

What forms the ventral root?

Ventral rootlets

What type of information do ventral rootlets carry?

Motor information

What forms a mixed spinal nerve?

dorsal and ventral roots join to form

What does the dorsal root ganglion contain?

The enlargement of the dorsal root contains primary sensory neuron cell bodies.

The dorsal root ganglion is derived from what embryologic structure?

Neural crest cells

Peripheral process

Travels to skin, muscle, joints, or viscera

central process

enters the posterior spinal cord

What common virus can remain latent in the dorsal root ganglion?

Varicella-zoster virus (chickenpox/shingles).

How do C1–C7 spinal nerves exit the vertebral column?

Above their corresponding vertebrae.

Where does the C8 spinal nerve exit?

Between C7 and T1.

How do thoracic, lumbar, sacral, and coccygeal nerves exit?

Below their corresponding vertebrae

What are the two enlargements of the spinal cord?

Cervical enlargement and lumbosacral enlargement.

Which enlargement supplies the upper extremities?

Cervical enlargement

C5 -T1

Which enlargement supplies the lower extremities?

Lumbosacral enlargement

L2 - S3

Why do spinal cord enlargements occur?

To increase motor neurons for limb control

What is the cauda equina?

Lumbar, sacral, and coccygeal nerve roots below the conus medullaris.

Why is the cauda equina called the “horse’s tail”?

Because of its appearance.

What is the filum terminale?

A thin fibrous structure that anchors the spinal cord inferiorly.

What is the lumbar cistern?

A CSF-filled subarachnoid space below the spinal cord; dural sac extends to S2

What shape is spinal cord gray matter in cross-section?

H-shaped

Where is gray matter located relative to white matter?

Gray matter is surrounded by white matter.

Which horn receives sensory input?

Posterior horn

Which horn contains motor neuron cell bodies?

Anterior horn

What is found in the central canal near center or gray matter?

Cerebrospinal fluid (CSF).

What is gray matter composed of?

Cell bodies, dendrites, and synapses

It processes and intergrates information

organized into posterior horn, anterior horn and intermediate regions

What is white matter composed of?

Axons traveling up and down the cord; transmit signals

Organized into posterior, lateral, and anterior funiculi( columns)

Why does white matter appear white?

Because many axons are covered with myelin.

What does the posterior horn process?

Somatic and visceral sensation, including pain and temperature

What is the substantia gelatinosa?

A pain and temperature processing zone at the tip of the posterior horn.

which roots do anterior horn axons leave the spinal cord?

exits via ventral roots to reach muscle

Larger at cervical and lumbosacral englargements

Intermediate gray made up of

Interneurons and autonomic neurons

Where is the lateral horn found?

Thoracic and upper lumbar spinal cord.

What is the function of the lateral horn?

Autonomic nervous system function

Central canal contains CSF

Remnant of the embryonic neural tube cavity

What is the anterior white commissure?

contains crossing fibers that goes across spinal cord midline.

Which spinal cord region contains the most white matter?

Cervical region; large anterior horns

Which spinal cord region contains small anterior horns?

Thoracic ( lateral horn present)

Which spinal cord region contains large anterior horn?

Lumbar

Lumbar and Cervical both have large anterior horn

Which spinal cord region contains more gray matter less white matter?

Sacral

What are the three meningeal layers?

Dura mater, arachnoid mater, and pia mater.

Which meningeal layer is outermost?

Dura mater.

Which meningeal layer is middle?

Arachnoid mater

Which meningeal layer is innermost?

Pia mater.

What is the function of the meninges?

Protect and stabilize the CNS.

What space contains CSF?

The subarachnoid space (between arachnoid and pia)

What kind of space is the subdural space?

A potential space

What is the dura mater made of?

Thick, tough connective tissue.

Is spinal dura single-layered or double-layered?

Single-layered

What does the spinal dura form?

The dural sac.

What separates the spinal dura from the vertebral periosteum?

The epidural space.

What type of membrane is the arachnoid mater?

A thin, avascular membrane.

Between which layers is the subarachnoid space located?

Between the arachnoid mater and pia mater.

To approximately what vertebral level do the dura and arachnoid extend?

S2

Which meningeal layer closely adheres to neural tissue?

Pia mater

What structures are formed by pia mater to stabilize the spinal cord?

Denticulate ligaments

What does pia mater contribute to inferiorly?

Filum terminale

What are denticulate ligaments?

Lateral pia extensions that anchor the spinal cord to the dura.

Where are denticulate ligaments located?

Between anterior and posterior rootlets.

What is the function of denticulate ligaments?

Stabilize the spinal cord during movement.

What is the filum terminale derived from?

Pia mater

extends inferiorly from the conus medullaris

What does the filum terminale anchor the spinal cord to?

The coccyx.

Helps stabilize the spinal cord within the vertebral canal.

Is the spinal epidural space real or potential?

Real

What does the spinal epidural space contain?

Fat and a venous plexus

Which meningeal space is accessed during a lumbar puncture?

The subarachnoid space.

Into which space are epidural injections delivered?

Epidural space

What are the functions of CSF?

Cushions the cord, provides buoyancy, and maintains a stable chemical environment.

What does the lumbar cistern contain?

CSF and cauda equina roots

At what levels is a lumbar puncture typically performed?

L3–L4 or L4–L5

Why is a lumbar puncture performed in the lumbar cistern?

It is below the end of the spinal cord.

During a lumbar puncture, the needle passes among what structures?

Cauda equina root

Artert of Adamkiewicz

Major supply to lumbosacral cord

key surgical and vascular landmark

Posterior spinal arteries

paired vessels: arise from vertebral artieries or posterior inferior cerebellar arteries

supply posterior third of spinal cord