Definition of mesencephalon
A part of the brain located rostral to the pons and caudal to the thalamus and the basal ganglia, composed of the tectum (dorsal portion) and the tegmentum (ventral portion).
Examples of mesencephalon in the following topics:
- Late in the fourth week of gestation, the superior part of the neural tube flexes at the level of the future midbrain—the mesencephalon.
- Superior to the mesencephalon is the prosencephalon (future forebrain) and inferior to it is the rhombencephalon (future hindbrain).
- The fourth week of gestation is characterized by the flexion of the superior portion of the neural tube to create the mesencephalon.
- Caudally the mesencephalon adjoins the pons (metencephalon) and rostrally it adjoins the diencephalon (Thalamus, hypothalamus, etc.).
- During embryonic development, the midbrain arises from the second vesicle, also known as the mesencephalon, of the neural tube.
- Unlike the other two vesicles, the prosencephalon and rhombencephalon, the mesencephalon remains undivided for the remainder of neural development.
- The mesencephalon is considered part of the brainstem.
- The human mesencephalon is archipallian in origin, meaning its general architecture is shared with the most ancient of vertebrates.
- This tube initially differentiates into three vesicles (pockets): the prosencephalon at the front, the mesencephalon, and between the mesencephalon and the spinal cord, the rhombencephalon.
- The tectum, pretectum, cerebral peduncle, and other structures develop out of the mesencephalon, and its cavity grows into the mesencephalic duct (cerebral aqueduct).
- The nucleus of the trochlear nerve is located in the caudal mesencephalon beneath the cerebral aqueduct.
- It is immediately below the nucleus of the oculomotor nerve (III) in the rostral mesencephalon.
- Late in the fourth week, the superior part of the neural tube flexes at the level of the future midbrain—the mesencephalon .
- Above the mesencephalon is the prosencephalon (future forebrain) and beneath it is the rhombencephalon (future hindbrain).
- The diencephalon, mesencephalon, and rhombencephalon constitute the brain stem of the embryo.
- It continues to flex at the mesencephalon.
- It includes the medulla oblongata (myelencephalon), pons (part of metencephalon), and midbrain (mesencephalon).
- There are four subdivisions of the neural tube that will each eventually develop into distinct regions of the central nervous system (see ) by the division of neuroepithelial cells: The prosencephalon, the mesencephalon, the rhombencephalon and the spinal cord.
- The mesencephalon develops into the midbrain.
- The medial reticular formation and lateral reticular formation are two columns of neuronal nuclei with ill-defined boundaries that send projections through the medulla and into the mesencephalon (midbrain).