Q 1.25. Spinal Cord: Anatomy, Physiology, and Blood Supply

Anatomy and Structure of the Spinal Cord

• The spinal cord is a vital part of the central nervous system (CNS). It resides within the vertebral canal of the vertebral column.
• During development, there’s a discrepancy between spinal cord growth and vertebral column growth. The spinal cord completes its growth by age 4, while the vertebral column continues growing until around ages 14-18.
• The spinal cord extends from the foramen magnum at the base of the skull down to the L1/L2 vertebra, where it terminates as the conus medullaris (medullary cone).
• A delicate thread called the filum terminale extends from the tip of the conus medullaris to the first coccygeal vertebra (Co1), anchoring the spinal cord in place.
• Remember this extent with the mnemonic “SCULL”: Spinal Cord Until L2 (LL).

Spinal Cord Segments

• Along its length, the spinal cord consists of several segments:
  • Cervical: Located in the neck region. Contains eight cervical segments.
  • Thoracic: Found in the upper back. Consists of 12 segments.
  • Lumbar: Situated in the lower back. Contains five lumbar segments.
  • Sacral: Occupying the pelvic region. Contains five sacral segments.
  • Coccygeal: The final segment near the tailbone. Contains one coccygeal segment.

Blood Supply of the Spinal Cord

• The vertebral arteries are the primary source of blood supply to the spinal cord.
• Additionally, specific arteries branch directly from the vertebral arteries to supply the spinal cord:
  • One anterior spinal artery
  • Two posterior spinal arteries
  • Anterior and posterior radicular arteries

Function of the Spinal Cord

• The spinal cord serves as a conduit for information between the brain and the periphery.
• It conducts impulses from the brain to the body and plays a crucial role in generating reflexes that facilitate our daily functioning.

Let’s summarize the main motor, sensory, and other pathways within the spinal cord cross section:

1. Motor Pathways:

• • Corticospinal Tract (Pyramidal Tract):
    • Location: Located in the lateral white matter.
    • Function: Carries voluntary motor commands from the cortex to skeletal muscles.
    • Decussation: Most fibers decussate (cross) in the medulla oblongata.
    • Lesion Effects: Damage leads to contralateral weakness.

2. Sensory Pathways:

• • Dorsal Column-Medial Lemniscus Pathway:

    • Location: Found in the posterior white matter.
    • Function: Transmits fine touch, vibration, and proprioception information.
    • Decussation: Fibers decussate in the medulla.
    • Lesion Effects: Damage results in ipsilateral loss of fine touch and proprioception.

  • Spinothalamic Tract (Anterolateral Pathway):

    • Location: Located in the anterolateral white matter.
    • Function: Carries pain and temperature information.
    • Decussation: Fibers decussate at the spinal cord level.
    • Lesion Effects: Damage leads to contralateral loss of pain and temperature sensation.

3. Other Pathways:

• • Spinocerebellar Tracts: Transmit proprioceptive information to the cerebellum for coordination.
  • Reticulospinal and Vestibulospinal Tracts: Influence muscle tone and posture.
  • Autonomic Pathways: Control involuntary functions (e.g., heart rate, digestion).

References:

1 kenhub.com

2 geekymedics.com

3 med.libretexts.org

4 open.oregonstate.education

5 openstax.org