Neural Crest Cell Differentiation

Neural crest cells

  • The neural crest cells develop into numerous and varied cell types and migrate to regions far anterior (ventral) from their site of origin

NEURAL CREST CELL DERIVATIVES

Basic derivatives

  • Peripheral nervous system (PNS) cells: glial cells & Schwann cells.
  • Meninges: Specifically, the inner layers: the pia and arachnoid
  • Melanocytes
  • The Enteric Nervous System

Cranial neural crest cell derivatives

  • Pharyngeal Arch Components
    • Musculoskeletal structures
    • Pharyngeal arch cranial nerves

Trunk and lumbosacral neural crest cell derivatives include:

  • Dorsal root ganglia
  • Sympathetic chain ganglia
  • Adrenal medullary cells
  • Prevertebral ganglia

NEURAL TUBE: PRIMARY BRAIN VESICLES

Primary brain vesicles

From anterior to posterior:

  • Prosencephalon
  • Mesencephalon
  • Rhombencephalon
  • Caudal neural tube

Neural crest cell organization

  • Neural crest cells originate along the midline of the dorsal aspect of the neural tube.
  • Somites lie lateral to them.

Placodes

  • The placodes are areas of thickened surface ectoderm that play an integral role in development of key cranial nerves (CNs 1, 2, and 8 – the solely sensory set) and also contribute to the development of merge the pharyngeal arch cranial nerves along with the neural crest cells.
  • Examples of placodes:
    • The olfactory placode forms the olfactory nerves and epithelium.
    • The lens placode forms the optic nerve.
    • The geniculate placode contributes to the development of cranial nerve 7 (along with the neural crest cells of the 2nd pharyngeal arch).
    • The otic placode forms the vestibulocochlear nerve.

NEURAL CREST CELL DEVELOPMENT

Superior view

  • Folding of the neural plate into the neural tube is key to the development of the neural crest cells.

Day 18

  • The neural folds form the neural crests.
  • The neural groove forms the base of the neural tube.

Trilaminar germ disc

  • From top to bottom, the trilaminar germ disc comprises ectoderm, intraembryonic mesoderm, and endoderm.
  • Mesoderm comprises somites and notochord (which induces the overlying ectoderm to form the neural plate).
    Then, draw the underlying endoderm.
  • Along the floor of the ectoderm lies the neural folds (again the neural crests are the neural fold tips).
  • The neural groove is the floor of the neural tube.

Day 21

  • The neural folds abut centrally, first, and remain open at their ends anteriorly and posteriorly.
  • The neural crest lies along the dorsal neural tube.
    • Elsewhere we see that this is the roof plate of the neural tube and is biologically influenced by the neural crest cells.

Day 23

  • The neural tube is folded a long distance along its center but remains open at the anterior (cranial) and posterior (caudal) neuropores.
  • The somites are visible, centrally, where the neural folds abut.
  • The somites generate bumps that appear on the surface of the overlying neural tube.
  • The neural crest cells make their migrations ventrally.

NEURAL CREST CELL MIGRATION

  • Migrate to form the peripheral nervous system derivatives

Relevant structures:

  • Ectoderm
  • Mesoderm
  • Neural tube
  • Notochord
  • Dorsal aorta
  • A portion of the Gut Tube
  • Somites (the paraxial mesoderm), which forms axial musculoskeletal elements, from lateral to medial:
    • Dermatome (dermis)
    • Myotome (muscle)
    • Sclerotome (skeleton): it migrates to form around the neural tube as the spine and posterior basal occipital bone.

Peripheral nervous system derivatives

  • Portions of Cranial Nerves: 5, 7, 9, and 10 (the Pharyngeal Arch cranial nerves) and portions of CNs 3 and 8, as well.
  • Dorsal root ganglia
  • Sympathetic chain ganglia
  • Adrenal medulla (the chromaffin cells)
  • Prevertebral ganglia
  • Enteric nervous system

Additional neural crest cell derivativs

  • Don’t forget, however, that the neural crest cells are responsible for much more than the aforementioned peripheral nervous system derivatives.

Other elements include:

  • Additional peripheral nervous system cellular structures:, for instance – glial cells and Schwann cells.
  • Melanocytes
  • [Inner meningeal layers (pia and arachnoid – the leptomeninges)
  • Musculoskeletal elements of the head and neck, such as the key cartilages and ear bones (learned elsewhere).

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