Lecture Notes: Medulla Oblongata Anatomy

Overview

• The medulla oblongata is one of three sections of the brainstem.
• It is the most inferior section, located below the pons and continuous with the spinal cord.
• Functions as a conduit for ascending and descending nerve tracts.
• Controls vital body functions: heart rate, breathing, and blood pressure.
• Contains nuclei of cranial nerves 9, 10, 11, and 12.

External Anatomy

Anterior Surface

• Anterior Median Fissure: Midline feature, continuous with the spinal cord.
• Sulci:
  • Ventral lateral sulcus
  • Posterolateral sulcus
• Pyramids: Bundles of motor fibers forming the corticospinal tract.
• Olives:
  • Lateral swellings next to pyramids.
  • Contain olivary nuclei for movement coordination and learning.
• Inferior Cerebellar Peduncles: Connect medulla to the cerebellum.

Posterior Surface

• Posterior Median Sulcus: Midline feature, aligned with the spinal cord’s posterior median sulcus.
• Conveys sensory input from below the neck.
• Gracilis and Cuneate Tubercle:
  • Carry sensory information to the brain, mainly touch.

Internal Anatomy

Levels of the Medulla

• Decussation of the Pyramids:
  • Point of major decussation for descending motor fibers.
  • Contains sensory tracts like spinocerebellar and lateral spinothalamic tracts.
• Decussation of the Medial Lemniscus:
  • Major decussation for medial lemniscus fibers (sensory).
  • Nucleus gracilis and nucleus cuneatus present.
• Olives and Inferior Cerebellar Peduncles:
  • Central canal expands to fourth ventricle.
  • Connects brainstem to cerebellum.
  • Contains various sensory tracts and important nuclei.

Functions and Centers

• Nuclei for Cranial Nerves 9, 10, 11, 12.
• Respiratory Center: Located in pons and medulla, controls breathing.
• Vasomotor Center: Regulates blood pressure and heart rate.

Blood Supply

• Complex vasculature depending on medulla level.
• Includes vertebral arteries, posterior and anterior spinal arteries, and posterior inferior cerebellar artery.

Summary

• Medulla is crucial for both sensory and motor pathway decussation.
• Controls vital autonomic functions and serves as a critical relay station in the central nervous system.
• Understanding its structure is key to diagnosing medullary lesion syndromes.