- د. عبد الرازق 2026
- د. عبد الرازق 2026
🧠 Brainstem & Medulla Oblongata Notes
🖇 General Structure of Brainstem
- 🟠 Consists of: Midbrain – Pons – Medulla Oblongata
- 🟣 Connects: Cerebral cortex (↑) ↔ Spinal cord (↓)
- 📌 Connected to Cerebellum via:
- Midbrain → Superior Peduncles
- Pons → Middle Peduncles
- Medulla → Inferior Peduncles
- 📌 Ventricle: 4th ventricle (diamond shape) between Cerebellum (post) & Pons/Medulla (ant)
- Pons called "Abu Kirsh" (bulging belly appearance)
🖇 Functions of Brainstem
- 📌 Pathway: Ascending & descending tracts between brain & spinal cord
- 📌 Cranial nerves: Origin of CN III–XII (except I & II)
- 📌 Vital centers: Cardiovagal + Respiratory → essential for life (affected in hanging)
- 📌 Reticular Formation: Consciousness & arousal
🖇 Medulla Oblongata – External Features
🔸 Ventral (Anterior) Surface
- Anterior Median Fissure → divides medulla into halves
- Pyramids → corticospinal tract (motor)
- Decussation of Pyramids → 90% fibers cross → contralateral paralysis in lesions
- Olives → lateral to pyramids, over Inferior Olivary Nucleus
- Cranial Nerves:
- CN XII → Pre-olivary sulcus (anterolateral)
- CN IX, X, XI → Post-olivary sulcus (retro-olivary)
🔸 Dorsal (Posterior) Surface
- Divided into Closed Medulla (↓) & Open Medulla (↑, part of 4th ventricle)
- Closed Medulla:
- Posterior Median Sulcus
- Gracile tubercle (medial, Gracile nucleus)
- Cuneate tubercle (lateral, Cuneate nucleus)
- Open Medulla:
- Superior border → Striae Medullares
- Floor of 4th ventricle:
- Hypoglossal Trigone (CN XII nucleus)
- Vagal Trigone (CN X nucleus)
🖇 Key Questions (Exam Focus)
- 📌 Why CN III–XII only in Brainstem? → CN I & II are special sensory (not in brainstem)
- 📌 Which tract forms the Pyramids? → Corticospinal tract (motor to spinal cord)
- 📌 Clinical significance of Pyramidal Decussation? → Explains contralateral paralysis
- 📌 Which cranial nerve emerges dorsally? 🚨 CN IV (Trochlear) (unique exception)
- 📌 Why vital centers are important in hanging? → Their damage = death