Spinal Cord

What is the spinal cord in relation to the brainstem?

Direct continuation of the neural tissue of the brainstem

What structures protect the spinal cord?

Vertebrae ligaments muscles meninges and cerebrospinal fluid

From where to where does the adult spinal cord extend?

From the foramen magnum to approximately the L2 vertebra

How many pairs of spinal nerves are there?

31 pairs of spinal nerves

What is the conus medullaris?

The tapered end of the spinal cord

What is the cauda equina?

A bundle of spinal nerve roots that extend inferior to the spinal cord

What is the filum terminale?

An extension of pia mater that anchors the conus medullaris to the posterior surface of the coccyx

What type of axons are found in the ventral (anterior) root?

Motor axons

What type of axons are found in the dorsal (posterior) root?

Sensory axons

What is the dorsal root ganglion (DRG)?

A collection of sensory neuron cell bodies

Where do dorsal rootlets enter the spinal cord?

At the posterolateral sulcus

Where do ventral rootlets leave the spinal cord?

From the anterolateral sulcus

What structure is formed when dorsal and ventral roots unite?

A spinal nerve

What term describes fibers that carry information away from the CNS?

Efferent

What term describes fibers that carry information toward the CNS?

Afferent

What are the four functional components of the spinal cord?

Visceral efferent somatic efferent somatic afferent visceral afferent

What functional component carries conscious sensation from the body?

Somatic afferent

What functional component innervates voluntary skeletal muscle?

Somatic efferent

What system mainly innervates smooth muscle cardiac muscle and glands?

Visceral nervous system

What is another name for the visceral efferent system?

Autonomic nervous system

Into what two divisions is the autonomic nervous system subdivided?

Sympathetic and parasympathetic

What functional component monitors changes in the viscera?

Visceral afferent

Which functional component provides innervation to skeletal muscle?

Somatic efferent

What are the five regional groups of spinal nerves?

Cervical thoracic lumbar sacral coccygeal

How many cervical spinal nerves are there?

Eight cervical spinal nerves C1–C8

How many thoracic spinal nerves are there?

Twelve thoracic spinal nerves T1–T12

How many lumbar spinal nerves are there?

Five lumbar spinal nerves L1–L5

How many sacral spinal nerves are there?

Five sacral spinal nerves S1–S5

How many coccygeal spinal nerves are there?

One coccygeal spinal nerve Co1

What are the two spinal cord enlargements?

Cervical enlargement and lumbosacral enlargement

What spinal cord levels form the cervical enlargement?

C5–T1

What spinal cord levels form the lumbosacral enlargement?

L1–S3

What is a dermatome?

An area of skin innervated by a single spinal nerve

What is the embryological origin of dermatomes?

Somites

Why are dermatomes clinically useful?

They help determine the level of a spinal cord lesion based on sensory deficits

What is the order of spinal meninges from superficial to deep?

Bone epidural space dura mater subdural space arachnoid mater subarachnoid space pia mater

What is the epidural space in the spinal cord?

An actual space between bone and dura mater containing blood vessels and fat

What type of space is the subdural space?

A potential space between dura mater and arachnoid mater

What type of space is the subarachnoid space?

An actual space

What fills the subarachnoid space?

Cerebrospinal fluid

What meningeal layer is tightly adhered to the spinal cord?

Pia mater

What structures extend laterally from the pia mater to anchor the spinal cord?

Denticulate ligaments

What structure anchors the conus medullaris inferiorly?

Filum terminale

What is the lumbar cistern?

An expanded subarachnoid space in the lumbar region

What is the purpose of epidural anesthesia?

To anesthetize spinal nerve roots of the cauda equina

Where is anesthetic injected during an epidural?

Into the epidural space

What are common uses of epidural anesthesia?

Labor abdominal surgery and lower-extremity surgery

What is the purpose of a lumbar puncture?

To draw off cerebrospinal fluid

At which vertebral levels is a lumbar puncture typically performed?

Between L3/L4 or L4/L5

Why is lumbar puncture performed below L2?

To avoid injury to the spinal cord below the conus medullaris

What artery supplies the anterior aspect of the spinal cord?

Anterior spinal artery

From what vessels does the anterior spinal artery arise?

Vertebral arteries

How many longitudinal arteries supply the spinal cord?

Three longitudinal arteries

What arteries supply the posterior spinal cord?

Posterior spinal arteries

From what artery do the posterior spinal arteries arise?

Posterior inferior cerebellar artery

What provides collateral arterial circulation to the spinal cord?

Branches from the aorta

How is venous blood drained from the spinal cord?

Via anterior and posterior spinal veins

Where do spinal veins drain?

Into the internal vertebral plexus in the epidural space

What is the anterior median fissure?

A deep groove on the anterior surface of the spinal cord extending toward the center

What structure lies within the anterior median fissure?

Anterior spinal artery

What is the anterior white commissure?

A region where the two sides of the spinal cord communicate

What is the posterior median sulcus?

An indistinct groove containing a glial septum

Where is the posterior intermediate sulcus found?

At cervical and thoracic levels

What does the posterior intermediate sulcus partially divide?

The posterior funiculi

What is a funiculus?

A large collection of spinal cord tracts

What are the three white matter funiculi?

Anterior lateral and posterior funiculi

What is the main function of the anterior funiculus?

Motor

What functions are associated with the lateral funiculus?

Motor and sensory pain and temperature

What function is associated with the posterior funiculus?

Sensory fine touch

What is another name for the posterior funiculus?

Dorsal or posterior columns

What is a fasciculus?

A nerve tract or “little bundle”

What fasciculi are found in the posterior funiculus?

Fasciculus gracilis and fasciculus cuneatus

What is the general shape of spinal cord gray matter?

H-shaped or butterfly-shaped

What are the three horns of spinal cord gray matter?

Anterior posterior and intermediate horns

What neurons are found in the anterior horn?

Lower motor neurons

What muscles are innervated by anterior horn neurons?

Skeletal muscle

What is the result of anterior horn injury?

Flaccid paralysis with limp weak atrophied muscles

What functional component is associated with anterior horn neurons?

Somatic efferent

How are motor neuron pools organized in the anterior horn?

Medial clusters for axial muscles lateral clusters for limb muscles

What type of neurons are found in the posterior horn?

Projection neurons

What is the function of the substantia gelatinosa?

Pain and temperature processing

What fibers are found in Lissauer’s tract?

Finely myelinated and unmyelinated fibers

What functional components are processed in the posterior horn?

Somatic and visceral afferent

Where are preganglionic sympathetic neuron cell bodies located?

T1–L3 intermediolateral cell column

Where do sympathetic preganglionic axons exit the spinal cord?

Via ventral roots

Where are parasympathetic neuron cell bodies located?

S2–S4

Do parasympathetic neurons form a distinct horn?

No

What functional component is associated with the intermediate horn?

Visceral efferent

What are key features of the cervical spinal cord?

Large oval shape large anterior horn FG and FC present

What motor function is emphasized at cervical levels?

Upper limb innervation

What are key features of the thoracic spinal cord?

Small anterior horn intermediolateral cell column FG present FC rostral to T6

What muscles are innervated at thoracic levels?

Intercostal muscles

What are key features of the lumbar spinal cord?

Large anterior horn more white matter FG present

What motor function is emphasized at lumbar levels?

Lower limb innervation

What are key features of the sacral spinal cord?

Small size less white matter large anterior horn cauda equina may be seen

At what levels is the intermediolateral cell column found without a distinct horn?

S2–S4