mesencephalon

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mesencephalon

 [mes″en-sef´ah-lon]
1. the short part of the brainstem just above the pons; it contains the nerve pathways between the cerebral hemispheres and the medulla oblongata, as well as nuclei (relay stations or centers) of the third and fourth cranial nerves. The center for visual reflexes, such as moving the head and eyes, is located here.
The mesencephalon (midbrain). From Applegate, 2000.
2. the middle of the three primary brain vesicles of the embryo; called also midbrain. adj., adj mesencephal´ic.

mes·en·ceph·a·lon

(mes-en-sef'ă-lon), [TA]
That part of the brainstem developing from the middle of the three primary cerebral vesicles of the embryo (the caudal of these being the rhombencephalon or hindbrain, the rostral the prosencephalon or forebrain). In the adult, the mesencephalon is characterized by the unique conformation of its roof plate, the lamina tecti (tectal plate [TA] or quadrigeminal plate [TAalt]). composed of the bilaterally paired superior and inferior colliculus, and by the massive paired prominence of the crus cerebri at its anterolateral (ventrolateral) surface. On transverse section, its patent central canal, the cerebral aqueduct, is surrounded by a prominent ring of gray matter poor in myelinated fibers; the periaqueductal gray is adjoined by the myelin-rich mesencephalic tegmentum, and covered posteriorly (dorsally) by the mesencephalic tectal plate. Prominent cell groups of the mesencephalon include the motor nuclei of the trochlear and oculomotor nerves, the red nucleus, and the substantia nigra.
Synonym(s): midbrain vesicle ☆ , midbrain
[mes- + G. enkephalos, brain]

mesencephalon

(mĕz′ĕn-sĕf′ə-lŏn′, mĕs′-)
n.
The midbrain.

mes′en·ce·phal′ic (-sə-făl′ĭk) adj.

mesencephalon

The midbrain, which contains the cerebral peduncles and tectum (tectal lamina) and the corpora quadrigemina (the two superior and two inferior colliculi).

mes·en·ceph·a·lon

(mes'en-sef'ă-lon) [TA]
That part of the brainstem developing from the middle of the three primary cerebral vesicles of the embryo. In an adult, the mesencephalon is characterized by the unique conformation of its roof plate, the lamina of the mesencephalic tectum, composed of the bilaterally paired superior and inferior colliculi, and by the massive paired prominence of the crus cerebri at its ventral surface. Prominent cell groups of the mesencephalon include the motor nuclei of the trochlear and oculomotor nerves, the red nucleus, and the substantia nigra.
Synonym(s): midbrain.
[G. mes- middle + G. enkephalos, brain]

mesencephalon

The middle section of the embryonic brain.

mesencephalon

see MIDBRAIN.

mes·en·ceph·a·lon

(mes'en-sef'ă-lon) [TA]
That part of the brainstem developing from the middle of the three primary cerebral vesicles of the embryo. In an adult, the mesencephalon is characterized by the unique conformation of its roof plate, the lamina of the mesencephalic tectum, composed of the bilaterally paired superior and inferior colliculi, and by the massive paired prominence of the crus cerebri at its ventral surface.
Synonym(s): midbrain.
[G. mes- middle + G. enkephalos, brain]