SYSTEMIC EMBRYOLOGY

SYSTEMIC EMBRYOLOGY: DEVELOPMENT OF BRAIN

Formation and Fate of Neural Tube

• The neural tube is formed by folding and fusion of the neural plate.
• It undergoes secondary and tertiary folding to form the neural canal.
• The neural canal eventually closes to form the neural tube.
• The neural tube differentiates into three primary brain vesicles: forebrain, midbrain, and hindbrain.
• The forebrain further differentiates into telencephalon and diencephalon.
• The midbrain remains as a single entity, and the hindbrain differentiates into metencephalon and myelencephalon.
• The metencephalon gives rise to the pons and cerebellum, while the myelencephalon forms the medulla oblongata.

Derivatives of Neural Crest

• The neural crest cells migrate from the neural tube and differentiate into various cell types.
• The derivatives of neural crest cells include:
  • Adrenal medulla
  • Sympathetic and parasympathetic ganglia
  • Neuroblasts of the peripheral nervous system
  • Melanocytes
  • Cartilage of the pharyngeal arches
  • Connective tissue of the face and neck

Formation of Eye Ball

• The eye develops from two swellings: the optic cup and the optic vesicle.
• The optic cup forms the retina, ciliary body, and iris.
• The optic vesicle forms the lens and the vitreous body.
• The anterior portion of the optic cup differentiates into the cornea, iris, and ciliary body.
• The posterior portion of the optic cup gives rise to the retina.
• The lens develops from the ectoderm and differentiates into the lens fibers.

Formation of Pituitary Gland

• The pituitary gland develops from two distinct tissues: the ectoderm and the endoderm.
• The ectoderm forms the anterior pituitary gland.
• The endoderm gives rise to the posterior pituitary gland.
• The anterior pituitary gland differentiates into various cell types, including somatotrophs, lactotrophs, and thyrotrophs.
• The posterior pituitary gland develops from the infundibulum and contains the axons of the hypothalamic neurons.