mesencephalon

Examples of mesencephalon in the following topics:

• Fourth Week of Development

  • The fourth week of gestation is characterized by the flexion of the superior portion of the neural tube to create the mesencephalon.
  • 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).
  • At four weeks the embryo's brain can be differentiated into the proscephalon, mesencephalon, and rhombencephalon.

• Midbrain

  • The midbrain or mesencephalon (from the Greek mesos - middle, and enkephalos - brain) is a portion of the central nervous system (CNS) associated with vision, hearing, motor control, sleep and wake cycles, arousal (alertness), and temperature regulation.
  • Caudally (posteriorly) the mesencephalon adjoins the pons (metencephalon), and rostrally it adjoins the diencephalon (eg., thalamus, hypothalamus).
  • The human mesencephalon is archipallian in origin, sharing its general architecture with the most ancient of vertebrates.
  • 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.

• Development of the Central Nervous System

  • 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).

• Trochlear (IV) Nerve

  • 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.

• Embryonic Development of the Brain

  • 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.

• Embryonic Development

  • 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.

• Functions of the Brain Stem

  • The midbrain (mesencephalon) is associated with vision, hearing, motor control, sleep and wake cycles, alertness, and temperature regulation.

• Reticular Formation

  • 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).