Detailed Notes on Spinal Cord Anatomy

Meninges Layers

• Three Layers of Meninges:
  • Dura Mater: Outermost tough layer.
  • Arachnoid Mater: Middle layer, web-like appearance.
  • Pia Mater: Innermost layer, directly covers the spinal cord.

Spinal Cord Structure

• Cross-Section Appearance:
  • Anterior Median Fissure: The deep groove on the front (anterior) side of the spinal cord.
  • Posterior Median Sulcus: Shallow groove on the back (posterior) side.
• Gray Matter and White Matter:
  • Structure: Spinal cord has white matter on the outside and gray matter on the inside (contrary to cerebrum's structure).
  • Gray Matter Shape: Appears like a butterfly, divided into two halves connected by the Gray Commissure at the center.
  • Central Canal: Located in the center of the gray commissure, it contains cerebrospinal fluid (CSF).

Horns of Gray Matter

• Types of Horns:
  • Anterior (Ventral) Horn: Front projection of the gray matter.
  • Lateral Horn: Side projection, present only in certain sections of the spinal cord.
  • Posterior (Dorsal) Horn: Back projection of gray matter.
• Distribution: All spinal cord segments contain the anterior and posterior horns; lateral horns are not present in all segments.

White Matter Organization

• Columns of White Matter:
  • Anterior Funiculus: The front section of white matter.
  • Lateral Funiculus: The side section of white matter.
  • Posterior Funiculus: The back section of white matter.

Nerve Root Anatomy

• Ventral Root:
  • Located on the front side of the spinal cord.
  • Function: Carries motor information out of the spinal cord (efferent pathways).
• Dorsal Root:
  • Located on the back side of the spinal cord.
  • Function: Carries sensory information into the spinal cord (afferent pathways).
• Dorsal Root Ganglion: Bulge on the dorsal root containing the cell bodies of sensory neurons.
• Spinal Nerve Formation:
  • Formed by the union of ventral and dorsal roots.
  • Spinal Nerve Function: Mixed information; carries both sensory and motor signals, acting as a two-way street within its short segment.

Key Concepts

• One-Way vs. Two-Way Streets:
  • Dorsal root (one-way, sensory info into spinal cord) vs. Ventral root (one-way, motor info out of spinal cord), while the spinal nerve allows for mixed signals, serving as a two-way street.