Brain Stem: Medulla Oblongata Flashcards
Brain stem
Formed of: below upwards
1. Medulla oblongata
2. Pons
3. Midbrain
Above is directly continuous with diencephalon
Below is directly continuous with spinal cord
Medulla oblongata
Lower most part of brain stem
Medulla oblongata size and extent
3 cm long
Continuous above above with pons lower border and below with spinal cord
Parts
- Lower 1/2 (closed medulla): transversed by central canal
- Upper 1/2 (open medulla): forms lower 1/2 of floor 4th ventricle
External features (surfaces)
- Ventro-lateral surface
- Dorsal surface
Ventrolateral surface contents from medial to lateral
- Anterior median fissure
- Pyramid
- Olive
- Inferior cerebellar peduncle (ICP)
Anterior median fissure
Continuous with that of spinal cord
Pyramid
Elongated elevation produced by corticospinal fibers of pyramidal tract
Olive
Oval elevation produced by inferior olivary nucleus. It is separated from pyramid by anterolateral sulcus for exit of hypoglossal (12th cranial) nerve
ICP
Bundle of nerve fibers connecting medulla with cerebellum. It is separated from olive by posterolateral sulcus for exit of:
1. Glossopharyngeal: 9th cranial
2. Vagus: 10th cranial
3. Cranial root of accessory nerve: 11th cranial
Dorsal surface
- Closed medulla
- Open medulla
Closed medulla contents from median to lateral
- Posterior median sulcus
- Gracile tract and tubercle
- Cuneate tract and tubercle
- Tuberculum cinereum
- Inferior cerebellar peduncle
Posterior median sulcus
Continuous with that of spinal cord
Posterior median sulcus
Continuous with that of spinal cord
Gracile tract and tubercle
- Overlies gracile nucleus
- On each side of sulcus
Cuneate tract and tubercle
Overlies Cuneate nucleus
Tuberculum cinereum
Overlies spinal nucleus of Trigeminal
ICP dorsal surface
On either side as 2 bundles extending upwards and lateral along 4th ventricle sides till they reach lower border of pons back where they bend sharply entering cerebellum
Open medulla site
Forms lower 1/2 of 4th ventricle foor. Separated from pons back by bundle of fibers (medullary stria) and bounded lateral by ICP
Open medulla relations
Transversed by vertical median sulcus, lateral to it inverted v shaped depression called inferior fovea.
Open medulla contents
On each side, inferior fovea divides the medullary part into 3 triangular area from medial to lateral:
1. Hypoglossal trigone
2. Vagal trigone
3. Lower vestibular area
Hypoglossal trigone
Overlies hypoglossal nerve nucleus
Vagal trigone
Overlies vagus nerve dorsal nucleus
Lower vestibular area
Overlies inferior and medial vestibular nuclei
Area posterma
Vomiting center
Protuberance at 4th ventricle inferoposterior limit
Atrial supply
Branches of vertebral artery:
Anterolateral surface
1. Anterior spinal artery
2. 4th part of vertebral artery
Posterolateral surface
3. Posterior inferior cerebellar artery
Gracile and Cuneate tracts
Posterior spinal artery
