Cerebral vesicles

from Wikipedia, the free encyclopedia

Cerebral vesicles , also called cerebral vesicles , appear as the first visible structures of the developing brain during embryonic development in chordates . They arise in the system of the central nervous system as extensions of the anterior neural tube in connection with the development of a head area in which special sensory organs are formed.

The floating larval stages of tunicates (Urochordata) as sea squirts of the tail area above the forms at the front end of notochord located neural tube one called "Viszeralganglion" collection of motor nerve cells, and before that a sensory bubbles with unpaired sense organs ( statocyst , light sense organs , Pressure receptors). Next to it is a second vesicle, which in the adult sessile (stuck) animal becomes the “cerebral ganglion” because the rest of the central nervous system (larval sensory vesicles, visceral ganglion, neural tube) as well as the tail and muscles are regressed.

In the case of the acrania counting (Cephalochordata) Lanzettfischchen the front portion of is - lying in full length over the dorsal axial skeleton of the notochord (epichordalen) - neural tube to a "Zerebralvesikel" extended. In the front of this brain vesicle there is an unpaired light sense organ as a frontal eye and a secretory infundibular organ, in the middle a photoreceptive lamellar body and projection neurons, and in the back primary motor neurons.

Stages in the embryogenesis of the brain of cranial animals : First
three primary cerebral vesicles of the prosencephalon , mesencephalon and rhombencephalon arise from the anterior neural tube (left half of the picture, about 5th week in humans). Then the prosencephalon differentiates into telencephalon and diencephalon and the rhombencephalon into metencephalon and myelencephalon , so that five secondary cerebral vesicles can be distinguished.

In cranial animals (craniata) - which, together with the tunicates and the skullless animals - are considered to be chordates - like humans , the brain also develops from the anterior neural tube, which extends forward beyond the chorda dorsalis (rostral). The prechordal part is differentiated as the archencephalon (“primordial brain”) from the epichordal part of the brain of the deuterencephalon (“second brain”) and is set off by the ventral fold (plica encephali ventralis) of the parietal bend , also called the midbrain bend (flexura mesencephalica) . Because between these two parts a middle part of the brain is pushed, creating three primary cerebral vesicles :

This resulting from the anterior neural tube primary brain system goes behind the neck bending (flexure cervicalis) caudally without sharp border in the spinal cord via forming medullary Neuralrohrabschnitt.

Subsequent further differentiation of the systems of the prosencephalon into two brain areas and the subdivision of the rhombencephalon into two areas by the bend of the bridge (flexura pontina) then achieve the five-part structure of the brain typical for all vertebrates , created as five secondary cerebral vesicles :

Which is from the lumen of the neural tube liquorführende system of the brain ventricle and central canal of the spinal cord.

Individual evidence

  1. a b Josef Dudel, Randolf Menzel, Robert F. Schmidt (ed.): Neuroscience: From Molecule to Cognition. 2nd Edition. Springer-Verlag, 2013, ISBN 978-3-642-56497-0 , p. 17 f; here online
  2. J. Dudel, R. Menzel, R. Schmidt (Ed.): Neuroscience: From Molecule to Cognition. 2nd Edition. Springer-Verlag, 2013, p. 19.

Web links