Tegmentum

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Latin = Tegmentum
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Caption = Transverse section of mid-brain at level of superior colliculi. ("Tegmentum" visible center right.)


Caption2 = Section through superior colliculus showing path of oculomotor nerve. (Tegmentum not labeled, but surrounding structures more clearly defined.)
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The tegmentum (from Latin for "covering" [http://www.bible-history.com/latin/latin_t.html] ) is a general area within the brainstem. It is located between the ventricular system and distinctive basal or ventral structures at each level. It forms the floor of the midbrain. [old.lf3.cuni.cz/physio/Physiology/education/materialy/cns/neuro2.ppt] It is a multisynaptic network of neurons that is involved in many unconscious homeostatic and reflexive pathways.

Development

In embryos the tegmentum is the anterior half of the neural tube. However, for fetuses to adults, tegmentum only refers to the parts of the brain that remains relatively unchanged after development is complete, i.e. at the brain stem and midbrain. Other parts, on the other hand, develop further, through folding and thickening, and have different names. Still, it is considered a continuous central region through all levels of the brainstem.

Structures that develop 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 are not part of the primitive neural tube but grow 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.

Divisions

The tegmentum forms distinguished divisions in the midbrain, pons and medulla

Midbrain tegmentum

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.

Pontine tegmentum

Lateral tegmental field

The lateral tegmental field (LTF) [ [http://jn.physiology.org/cgi/reprint/61/5/1011.pdf Lateral Tegmental Field Neurons of Cat Medulla: A Source of Basal ...] ] is the source of several neurons of the noradrenaline system of the brain

Other

Other pertinent areas of the tegmentum are:
* Ventral Tegmental Аrea (VTA)
* Periaqueductal Gray Matter
* Reticular Formation
* Red Nucleus
* Substantia nigra

References