Neural Tube

From IKE
Jump to: navigation, search

Development

A chronology of neural tube formation

Basics

  • neural tube is destined to form the brain, three brain vesicles cranially, and the spinal cord caudally
  • towards the end of the third week, the notocord induces overlying ectoderm (neuroectoderm) to thicken and fold
  • forms neural folds separated by neural groove
  • bilateral neural folds unite in the midline to form neural tube
  • The tube incorporates part of the amniotic cavity (neural groove) as a canal within
  • The midline fusion of the neural folds begins in the cervical region and proceeds cranially and caudally
  • neural tube remains open at rostral and caudal ends (aka neuropores) until end of fourth week
  • These anterior and posterior neuropores will eventually seal off
  • brain vesicles proliferate at a fast rate and are clearly identifiable early in development as three enlargements

Brain vesicles and ventricles

Prosencephalon

  • develops into:
    1. Telencephalon, which further develops into the definitive cerebral hemispheres and basal ganglia
    2. Diencephalon, which gives rise to thalamus, hypothalamus, mamillary bodies, subthalamus, optic disc, etc.

Mesencephalon

  • gives rise to the midbrain enclosing the narrow cerebral aqueduct (of Sylvius)

Rhombencephalon

  • develops into
    1. Metencephalon, which later gives rise to the pons and cerebellum
    2. Myelencephalon, which becomes the medulla oblongata
    • The fourth ventricle is enclosed within the metencephalon and myelencephalon

Ventricles

  • Forebrain:
    • Within the cerebral hemispheres is the bilateral pair of lateral ventricles
    • Within the diencephalon is the mid-sagitally placed third ventricle
    • The lateral ventricles are connected to the third ventricle by the interventricular foramina (of Monro)
  • Midbrain: aqueduct (of Sylvius)
  • Hindbrain: 4th ventricle

Table 1. A table summarizing the development of the ventricles and vesicles

Primary Secondary Definitive Adult Brain
Prosencephalon Telencephalon definitive cerebral hemispheres and basal ganglia
Diencephalon thalamus, hypothalamus, mamillary bodies, subthalamus, optic disc, etc.
Mesencephalon midbrain
Rhombenchephalon Metencephalon pons and cerebellum
Myelencephalon medulla oblongata


Defects

  • errors in the process can occur if the neural folds don't meet everywhere.
  • This is a neural tube defect, which is bad.
  • failure of neural tube closure results in anencephaly (if the anterior neuropore doesn't seal cranially) and a severe form of spina bifida (if the posterior neuropore fails to close caudally)

Resources