Anatomy of the Central Nervous System: The Pons

Overview

• Focus on the Pons, a part of the brainstem.
• The Central Nervous System (CNS) consists of:
  • Encephalon
  • Spinal Cord
• Encephalon subdivisions include:
  • Brainstem (medulla, pons, midbrain/mesencephalon)
  • Cerebellum
  • Diencephalon
  • Telencephalon

External Surfaces of Pons

Anterior Surface

• Basilar Sulcus in the midline.
• Middle Cerebellar Peduncles extend to cerebellum.
• Cranial Nerves Emerging:
  • 6th Cranial Nerve (Abducens): Eye abduction.
  • 7th Cranial Nerve (Facial): Facial expressions.
  • 8th Cranial Nerve (Vestibulocochlear): Hearing and balance.
  • 5th Cranial Nerve (Trigeminal): Facial sensory/motor functions.

Posterior Surface

• Covered by the cerebellum.
• Rhomboid Fossa:
  • Upper part formed by Pons.
  • Contains nuclei for cranial nerves.
• Cerebellar Peduncles:
  • Inferior to medulla.
  • Middle to pons.
  • Superior to midbrain.

Internal Structure of Pons

• Gray Matter: Contains nuclei.
• White Matter: Contains nerve tracts.

Important Landmarks

• Trapezoid Body: Divides internal pons into:
  • Tegmentum (dorsal part)
  • Basilar Part (ventral part)

Gray Matter Structures

• Pontine Nuclei:
  • Origin of frontopontine tract.
  • Forms pontocerebellar tracts.
• Cranial Nerve Nuclei (6-8): In rhomboid fossa.
• Reticular Formation: Throughout brainstem.

White Matter Structures

• Basilar Part:

  • Descending Tracts (Motor):
    • Frontopontine Tract
    • Pontocerebellar Tract
    • Corticopontine Tract (includes occipitopontine, temporopontine, etc.)
    • Corticospinal Tract: Skeletal muscle innervation.
    • Corticonuclear Tract: Head/neck muscle control.

• Tegmentum:

  • Ascending Tracts (Sensory):
    • Medial Lemniscus: Sensory touch, proprioception.
    • Spinal Lemniscus: Pain, temperature, pressure, touch.
    • Trigeminal Lemniscus: Sensory from trigeminal nerve.
    • Anterior Spinocerebellar Tract: To cerebellum via superior peduncles.
    • Lateral Lemniscus: Auditory pathway.
  • Descending Tracts:
    • Tectospinal Tract: Coordinated eye and neck movements.
    • Rubrospinal Tract: Supports voluntary movements.
    • Reticulospinal Tract: Balance and posture.
    • Vestibulospinal Tract: Balance control.
    • Medial Longitudinal Fasciculus: Involuntary head, neck, and eye movements coordination.

Conclusion

• Pons structure includes both gray and white matter, each with specific functions and pathways.
• Upcoming video: Fourth Ventricle and Rhomboid Fossa.
• Remember to review the tracts and nuclei for complete understanding.