Covers the medulla oblongata as the caudal brainstem segment, then its external surface: the pyramids and motor decussation, the inferior olive with its neighbouring grooves and the cranial nerves emerging there, the medullopontine sulcus, the inferior cerebellar peduncle, and the tubercles forming the fourth ventricle floor. It then describes internal cross-sections at the decussation and olive levels, listing cranial nerve nuclei, specific brainstem nuclei and the ascending and descending tracts.
Topic 140 of 264 in the MU Sofia syllabus for Anatomy (Dental Medicine, Year 2). The free AceMed note covers it in 4 sections, about 689 words (5 min of reading), with 10 flashcards.
In this note
MEDULLA OBLONGATA
External medulla oblongata:
Internal Surface
Cross Sections :
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
1.1 Decussation of pyramids / motor decussation (decussatio pyramidum) – the site where the fibres of the corticospinal tract cross to the opposite side
2 Ventral median fissure (fissura mediana anterior)
3 Inferior olive (oliva) – a paired elevation on the ventral surface of the medulla oblongata formed by the the inferior olivary complex
3.1 Pre-olivary groove (sulcus preolivaris) – a groove in front of the inferior olive, the exit of the n. XII
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
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