15. Medulla oblongata - the internal structure – grey matter.

MEDULLA OBLONGATA

• Brainstem: is a stalklike structure within the posterior cranial fossa. Consists of the midbrain, pons & medulla oblongata.

- Medulla oblongata:

• The most inferior /caudal part of the brainstem
• Superiorly it's connected to the pons, and inferiorly it becomes the spinal cord at the foramen magnum.
• Is the longest portion of the brainstem (~3cm)

External medulla oblongata:

1. Pyramid (pyramis medullae oblongatae) – a paired elevation of the medulla oblongata containing the corticospinal tract
2. 1.1 Decussation of pyramids / motor decussation (decussatio pyramidum) – the site where the fibres of the corticospinal tract cross to the opposite side
3. Ventral median fissure (fissura mediana anterior)
4. Inferior olive (oliva) – a paired elevation on the ventral surface of the medulla oblongata formed by the the inferior olivary complex
5. 3.1 Pre-olivary groove (sulcus preolivaris) – a groove in front of the inferior olive, the exit of the n. XII
6. 3.2 Retro-olivary groove (sulcus retroolivaris) – a groove behind the inferior olive, the exit of the n. IX, X and XI

4. Medullopontine sulcus (sulcus bulbopontinus) – a transverse groove between the medulla oblongata and pons – the exit of the n. VI
5. Inferior cerebellar peduncle (pedunculus cerebellaris inferior) – consists of the restiform and juxtarestiform body – connects the medulla oblongata to the cerebellum – contains the afferent and efferent tracts of the cerebellum
6. Rhomboid fossa (fossa rhomboidea) – together with the pons forms the rhomboid-shaped floor of the fourth ventricle
7. Gracile tubercle (tuberculum gracile) – the medial tubercle on the dorsal surface is formed by the gracile nucleus
8. Cuneate tubercle (tuberculum cuneatum) – the lateral tubercle on the dorsal surface is formed by the cuneate nucleus
9. Trigeminal tubercle (tuberculum trigeminale) – a tubercle on the lateral surface is formed by the spinal nucleus and tract of trigeminal nerve