Spinal Cord Structure and Development
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Questions and Answers

The spinal cord is often referred to as the spinal medulla.

True (A)

The anterior median fissure is a shallow groove located on the dorsal side of the spinal cord.

False (B)

The posterior median septum of neuroglia within the spinal cord connects to the complete posterior median septum of arachnoid.

False (B)

In a fetus, the spinal cord extends to the lower limit of the spinal dura mater at the level of the S2 vertebra.

<p>True (A)</p> Signup and view all the answers

At birth, the conus medullaris is located opposite the L1 or L2 vertebrae.

<p>False (B)</p> Signup and view all the answers

The cervical enlargement of the spinal cord corresponds to segments C5 to T1, influencing the lumbar and sacral plexuses.

<p>False (B)</p> Signup and view all the answers

The lumbosacral enlargement extends from T9 to L1, reflecting the increased mass of motor cells present.

<p>True (A)</p> Signup and view all the answers

Spinal nerves are located inside the spinal theca.

<p>False (B)</p> Signup and view all the answers

The anterior and posterior roots of the spinal nerves unite within the intravertebral foramina.

<p>False (B)</p> Signup and view all the answers

Each anterior root is formed by approximately twenty rootlets which emerge irregularly along the anterolateral surface of the spinal cord.

<p>False (B)</p> Signup and view all the answers

Each posterior root is formed by several rootlets attached horizontally to the posterolateral surface of the cord.

<p>False (B)</p> Signup and view all the answers

The anterior and posterior roots evaginate the dura mater separately before uniting to form the mixed spinal nerve.

<p>True (A)</p> Signup and view all the answers

The ganglion on the posterior nerve root lies in the intervertebral foramen, within the tubular evagination of the dura and arachnoid at the point of union of anterior and posterior nerve roots.

<p>True (A)</p> Signup and view all the answers

The posterior root ganglia of cervical nerves lie just medial to the intervertebral foramina, close to the vertebral artery.

<p>False (B)</p> Signup and view all the answers

For all levels from C2 to L2 vertebrae, the anterior and posterior nerve roots pass in front of and behind the denticulate ligament respectively.

<p>False (B)</p> Signup and view all the answers

The more inferior a nerve root, the less steeply it slopes down to the intervertebral foramen

<p>False (B)</p> Signup and view all the answers

Below L1 vertebra, the roots pass almost horizontally through the subarachnoid space, forming the cauda equina.

<p>False (B)</p> Signup and view all the answers

The cauda equina consists of spinal nerves

<p>False (B)</p> Signup and view all the answers

The filum terminale is classified as part of the cauda equina.

<p>False (B)</p> Signup and view all the answers

The roots of the spinal part of the accessory nerve emerge from the lateral surface of the upper five or six segments of the cord, in front of the denticulate ligament.

<p>False (B)</p> Signup and view all the answers

Flashcards

Spinal Cord

A cylindrical structure that transmits signals between the brain and body.

Anterior Median Fissure

A deep groove on the front of the spinal cord that separates the two hemispheres.

Posterior Median Sulcus

A shallow groove on the back of the spinal cord that aids in identifying its anatomy.

Conus Medullaris

The tapering end of the spinal cord, lying between vertebrae L1 and L2 in adults.

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Cervical Enlargement

Thickened region of the spinal cord that supplies nerves to the upper limbs.

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Lumbosacral Enlargement

Thickened region of the spinal cord for nerves to the legs and pelvic region.

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Spinal Nerve Roots

The roots that emerge from the spinal cord and combine to form spinal nerves.

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Anterior Root

The front section of a spinal nerve that carries motor signals from the spinal cord.

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Posterior Root

The back section of a spinal nerve that carries sensory signals to the spinal cord.

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Segmental Levels of Plexuses

Specific regions of the spinal cord associated with limb movement nerves.

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Rootlets

Small nerve fibers that come together to form a nerve root.

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Intervertebral Foramina

Spaces between vertebrae where spinal nerves exit.

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Dura Mater

The tough outer covering of the spinal cord and brain.

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Spinal Nerve

The mixed nerve formed by the union of anterior and posterior roots.

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Root Ganglion

A cluster of nerve cell bodies located along the posterior root.

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Cauda Equina

A bundle of spinal nerve roots located below the L1 vertebra.

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Filum Terminale

A delicate thread of pia mater extending from the conus medullaris.

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Cervical Nerve Roots

The nerves that emerge from the cervical spinal segments.

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Accessory Nerve

A cranial nerve with roots originating from the upper spinal cord segments.

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Study Notes

Spinal Cord Structure and Function

  • The spinal cord, also known as the spinal medulla, is a cylinder-shaped structure flattened front to back. Its lower end tapers into a cone.
  • Ventrally, a deep groove (anterior median fissure) is present, and dorsally, a shallow groove (posterior median sulcus) is visible.
  • A connecting neuroglia structure, the posterior median septum, is part of the spinal cord and is connected to the arachnoid membrane outside the spinal cord.

Spinal Cord Growth and Development

  • In a fetus, the spinal cord extends to the S2 vertebra's level.
  • The spinal dura mater remains at this level, while the spinal cord reduces in length.
  • The bony spinal column and dura mater grow faster than the spinal cord, resulting in the conus medullaris (lowest part of the spinal cord) being at the location of L3 (lower third lumbar vertebra).
  • The spinal cord doesn't reach its lower most levels (L1 or L2) until about age 20.
  • This developmental difference leads to nerve roots sloping downwards more noticeably, especially at the lumbar and sacral regions.

Spinal Cord Enlargements

  • The spinal cord has two symmetrical enlargements:
    • Cervical enlargement (brachial plexus), located at segments C5 to T1
    • Lumbosacral enlargement (lumbar and sacral plexus), located at segments L2 to S3
  • The enlargement locations are in relation to the segments involved in the particular plexus. The vertebrae locations are significantly different.
  • Examples are given to illustrate the differences between the segmental location and vertebral location for each enlargement.
  • The enlargements are associated with increased motor neuron masses in the anterior horns of gray matter.

Spinal Nerve Roots

  • Spinal nerves are not located within the vertebral canal.

  • Anterior and posterior roots unite within the intervertebral foramina.

  • Nerve rootlets extend from the spinal cord into the subarachnoid space.

  • Anterior roots consist of 3-4 rootlets emerging on the cord's anterolateral surface.

  • Posterior roots consist of multiple rootlets attached to the cord's posterolateral surface which come together to form a single root.

  • The roots exit the cord and go through the intervertebral foramina. Here, the roots' dura is separated before the nerve joins completely as a mixed spinal nerve.

  • The ganglion, associated with the posterior nerve root, is located in the intervertebral foramen and is within the tubular evagination of the dura and arachnoid before the nerve roots join.

  • The ganglion's location varies from CI to LI vertebral level- upper levels are lateral to the foramen (closer to the vertebral artery); lower levels are within the foramen itself.

  • The lower spinal roots descend vertically, forming the cauda equina, and are made up of nerve roots not spinal nerves. The filum terminale, (a part of the pia mater) descends along the nerve roots and attaches to the tip of the conus medullaris.

  • Spinal accessory nerve roots emerge from the lateral sides of the upper 5-6 segments of the spinal cord below the denticulate ligament.

  • They join as a single trunk, pass upward through the foramen magnum and attach to the cranial root.

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Description

Explore the fascinating structure and growth of the spinal cord. This quiz covers anatomical features, the development process in fetuses, and how the spinal cord changes in relation to the vertebrae over time. Test your knowledge on spinal cord anatomy and its significance!

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