Spinal Cord Anatomy Quiz

The Spinal Cord

• The spinal cord begins at the foramen magnum, continuing from the medulla oblongata.
• In adults, the spinal cord ends opposite L1-L2 vertebrae.
• In newborns, the spinal cord ends at the level of L3 vertebra.
• The lower end tapers to form the conus medullaris.

Spinal Segments

• A spinal segment is the portion of the spinal cord that gives rise to a pair of spinal nerves.
• The spinal cord consists of 31 segments:
  • 8 cervical
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccygeal
• Segment size depends on the amount of tissue each segment supplies.

External Features

• The spinal cord exhibits cervical and lumbar enlargements.
• These enlargements correspond to the brachial and lumbosacral plexuses, respectively.

Fissures and Sulci

• Anterior median fissure: A deep groove along the anterior aspect of the spinal cord.
• Posterior median sulcus: A shallow groove along the posterior aspect.
• Two anterolateral sulci: Located at the attachment of the spinal nerve roots.
• Two posterolateral sulci: Also found at the attachment of the spinal nerve roots.
• Posterior median septum: Extends from the posterior median sulcus into the cord's substance.

Spinal Enlargements

• Cervical enlargement: Located in the C5-T1 spinal cord region; gives rise to the brachial plexus.
• Lumbar enlargement: Located in the L2-S3 spinal cord region; gives rise to the lumbar and sacral plexuses.

Internal Structure (Grey Matter)

• The H-shaped grey matter is symmetrical.
• Masses are connected by the grey commissure.
• The central canal passes through the grey commissure.
• Each lateral mass is divided into horns:
  • Posterior horn (sensory)
  • Anterior horn (motor)
  • Lateral horn (autonomic); only present in thoracic (T1-L2) and upper lumbar segments.

Internal Structure (White Matter)

• White matter is divided into three columns in each spinal cord half:
  • Posterior column (between posterior median septum and posterior horn)
  • Lateral column (between anterior and posterior horns)
  • Anterior column (between anterior median fissure and anterior horn)
• Anterior white columns connect by the white commissure.

The Spinal Nerves

• 31 pairs of spinal nerves emerge from corresponding segments:
  • 8 cervical
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccygeal
• Spinal nerves emerge from two roots:
  • Anterior root (motor): along the anterolateral sulcus
  • Posterior root (sensory): attached to the posterolateral sulcus
• These roots unite within the intervertebral foramina to form the nerve trunk.

Direction and Exit of Spinal Nerve Roots

• The spinal cord is shorter than the vertebral canal.
• Nerves may not precisely align with the corresponding vertebrae. • Cervical nerves generally pass horizontally. • Thoracic nerves pass obliquely. • Lumbar, sacral, and coccygeal nerves form the cauda equina. • Cauda equina nerves exit below the levels of their corresponding vertebrae.

The Spinal Meninges

• Dura mater: Tough outer layer, extending to S2 vertebra, attached to magnum foramen.

• Subdural space: Contains serous fluid, between dura and arachnoid.

• Epidural space: Lies between the dura and vertebra, containing internal vertebral venous plexus.

• Arachnoid mater: Thin vascular layer extending to S2 vertebra.

• Subarachnoid space: Filled with cerebrospinal fluid (CSF)

• Lumbar cistern: Widened subarachnoid space below conus medullaris, containing cauda equina and filum terminale.

Lumbar Puncture

• A technique used to withdraw CSF or inject medication.
• Performed between L3 and L4 or L4 and L5 vertebrae

The Spinal Pia Mater

• Filum terminale: Thread-like extension of pia beyond the conus medullaris; pierces dura, attaches to the coccyx.

• Denticulate ligament: 21-tooth-like projections attaching to the inner surface of dura, connecting the spinal cord to the surrounding tissues,

Blood Supply (Arterial)

• Anterior spinal artery: Originates from vertebral arteries, runs in the anterior median fissure, supplies 2/3 of the anterior spinal cord
• Posterior spinal arteries: Originates from vertebral or posterior inferior cerebellar artery, runs in the posterolateral sulcus, supplies 1/3 of the posterior spinal cord
• Segmental arteries: Spinal branches from deep cervical, ascending cervical, posterior intercostal, lumbar or lateral sacral arteries, nourishing the nerve roots, connecting & extending nourishment to the spinal arteries

Blood Supply (Venous)

• Several longitudinal venous channels drain the spinal cord.
• Channels are in (1) anterior median fissure, (2) anterolateral sulcus and (3) posterolateral sulcus
• Veins communicate with cranial dural venous sinuses and internal vertebral venous plexus.
• Drainage is via radicular veins into segmental veins.

Test your knowledge on the anatomy of the spinal cord, including its structure, segments, and external features. This quiz covers essential details such as the location of the spinal cord in adults and newborns, as well as the specific spinal segments and their characteristics.