Midbrain tegmentum
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| Brain: Midbrain tegmentum | ||
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| Transverse section of mid-brain at level of superior colliculi. ("Tegmentum" visible center right.) | ||
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| Section through superior colliculus showing path of oculomotor nerve. (Tegmentum not labeled, but surrounding structures more clearly defined.) | ||
| Latin | Tegmentum Mesencephali | |
| Gray's | subject #188 802 | |
| Part of | Midbrain | |
| NeuroNames | hier-482 | |
| MeSH | Tegmentum+Mesencephali | |
The tegmentum (from Latin for "covering") was originally used by anatomists to describe the anterior half (if a horizontal line was drawn from medial to lateral through the neural canal) of a primitive neural tube. However, the word has only remained true to the parts of the brain that have remained relatively unchanged after development is complete ie. at the brain stem and midbrain, as other parts that developed further, through folding and thickening, were given different names by anatomists.
As the part of the primitive neural tube that would become the brain stem developed, the neural canal expanded dorsally and laterally creating the fourth ventricle whereas the neural canal that did not expand and remained the same at the level of the midbrain superior to the fourth ventricle formed the cerebral aqueduct. Likewise, the neural canal in the spinal cord that did not change formed the central canal.
Hence, the midbrain tegmentum is the part of the midbrain extending from the substantia nigra to the cerebral aqueduct in a horizontal section of the midbrain and forms the floor of the midbrain which surrounds the cerebral aqueduct.
Structures that have developed to grow ventral or lateral outside this primitive tube as add-ons(e.g. the crus cerebri in the anterior of the midbrain) are not considered part of the 'tegmentum' as they were not part of the primitive neural tube but grew as projections from the cerebral cortex. Whereas, parts that were inside the primitive neural tube and remained an integral part of it after complete development (e.g. the red nucleus) are considered part of the tegmentum.
Pertinent areas of Tegmentum
[edit] See also
medulla tegmentum
[edit] External links
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