Medulla Oblongata Lecture Notes

Introduction

• Focus on medulla oblongata internal structures.
• Three cross-sections:
  • Pons-medulla junction (rostral)
  • Sensory decussation (middle)
  • Pyramidal decussation (caudal)

Anatomical Structure of the Medulla

Rostral Portion (Pons-Medulla Junction)

• Hypoglossal Nucleus (Cranial Nerve 12)
• Dorsal Nucleus of Vagus (Cranial Nerve 10)
• Nucleus of Tractus Solitarius
• Vestibular Nuclear Complex
  • Medial and inferior vestibular nuclei.
• Cochlear Nuclei
  • Dorsal and ventral.
• Inferior Cerebellar Peduncles
• Ponto Bulbar Body
• Ventral Spinocerebellar Tract
• Inferior Olivary Nuclear Complex
• Arcuate Nucleus
• Corticospinal Tracts
• Medial Lemniscus
• Spinal Lemniscus
• Spinal Nucleus and Tract of Trigeminal Nerve
• Tectospinal Tract
• Rubrospinal Tract
• Medial Longitudinal Fasciculus
• Nucleus Ambiguous (Special Visceral Efferent)
• Inferior Salivatory Nucleus
• Descending Sympathetic Tract

Middle Portion (Sensory Decussation)

• Fasciculus Gracilis and Nucleus Gracilis
• Fasciculus Cuneatus and Nucleus Cuneatus
• Sympathetic Tract
• Spinal Nucleus and Tract of Trigeminal Nerve
• Dorsal and Ventral Spinocerebellar Tracts
• Olivo-Spinal and Spino-Olivery Tracts
• Inferior Olivary Nucleus
• Corticospinal Tracts
• Medial Lemniscus Formation
• Vestibulospinal Tract
• Sensory Decussation

Caudal Portion (Pyramidal Decussation)

• Fasciculus Gracilis and Nucleus Gracilis
• Fasciculus Cuneatus and Nucleus Cuneatus
• Spinal Nucleus and Tract of Trigeminal Nerve
• Sympathetic Tract
• Dorsal and Ventral Spinocerebellar Tracts
• Olivo-Spinal and Spino-Olivery Tracts
• Corticospinal Tracts and Pyramidal Decussation
• Vestibulospinal Tract
• Lateral, Ventral Spinothalamic, and Spinotectal Tracts

Functions of the Medulla Structures

Corticospinal Tracts

• Descending motor pathways.
• Upper motor neurons from the cortex.
• Lateral and ventral corticospinal tracts.
• Pyramidal Decussation.

Sensory Pathways

• Medial Lemniscus: Proprioception, fine touch, vibration.
• Spinal Lemniscus: Pain, temperature, crude touch.
• Trigeminal Lemniscus: Sensory pathways from the face.

Inferior Olives

• Spino-Olivery Tract: Proprioception to olives, then contralateral cerebellum.
• Olivo-Spinal Tract: Descending pathways, mainly speculative.

Vestibular System

• Receives input from the inner ear.
• Connects to cerebellum and spinal cord.
• Vestibulospinal Tract: Motor control for extensor muscles.

Tectospinal and Rubrospinal Tracts

• Tectospinal Tract: Reflexive movements of head/eyes.
• Rubrospinal Tract: Flexor control from red nucleus.

Sympathetic Tract

• Descends from hypothalamus, controls thoracolumbar outflow.

Spinocerebellar Tracts

• Dorsal, Ventral Spinocerebellar Tracts: Unconscious proprioception.

Cranial Nerves and Functions

Hypoglossal Nerve (CN 12)

• Controls tongue muscles: Styloglossus, Hyoglossus, Genioglossus.

Glossopharyngeal Nerve (CN 9)

• Nucleus of Tractus Solitarius: Taste from posterior 1/3 of tongue.
• Nucleus Ambiguous: Stylopharyngeus for swallowing.
• Inferior Salivatory Nucleus: Parotid gland salivation.
• Sensations from the ear.

Vagus Nerve (CN 10)

• Dorsal Nucleus of Vagus: Visceral sensation and motor control.
• Nucleus of Tractus Solitarius: Taste.
• Nucleus Ambiguous: Pharyngeal and laryngeal muscles.

Accessory Nerve (CN 11)

• Supplies sternocleidomastoid and trapezius muscles.
• Part of the pharyngeal plexus.

External Anatomy Highlights

• Pyramids: Anterior bulges of the medulla.
• Olives: Lateral to pyramids.
• Cerebellar Peduncles: Connect brainstem to cerebellum.

Conclusion

• Understanding the medulla's anatomy and its associated structures is crucial for comprehending its functions and clinical implications.