Neural Tube Formation 

Neural Tube Formation 

  • Neural Plate: The neural plate forms the neural groove and neural folds.  

  • Notochord: Initiate folds/groove  

  • Neural Tube: Formed by the neural plate  

  • Myelospinal Boundary: The top of the neural tube becomes the brain, and the bottom becomes the spinal cord. 

  • Brain Openings: Three openings form in the neural plate which will become the forebrain, midbrain, and hindbrain. 

  • End of Primitive Streak: Marks the tail end of the spinal cord. 

  • Primary Neurulation: Involves the formation of the neural tube through the neural plate, with the cranial and caudal neuropores closing. (through neural plate)  

  • Neural Crest Cells: These cells are left behind by the neural tube and form peripheral neurons and glia. 

  • Anencephaly: Results from the failure of the cranial neuropore to close. 

  • Secondary Neurulation: This process grows the rest of the spinal cord through the primitive streak. (Through primitive streak) 

  • Differential Growth: The spinal cord and vertebral column grow at different rates. 

  • Spinal Nerves: Spinal nerves exit through the vertebral column. 

  • Filum Terminale: Forms as the spinal cord shortens and stretches the pia mater. 

  • Nerve Ragged Out: As the growth of vertebrae happen at different rates the spinal nerves will get ragged out 

  • Spinal cord never Grows to the bottom: The spinal cord never grows to the bottom of the vertebral column. 

Brain Vesicles and Flexures 

  • Primary Vesicles: 

  • Prosencephalon: Forebrain 

  • Telencephalon 

  • Diencephalon 

  • Mesencephalon: Midbrain 

  • Rhombencephalon: Hindbrain 

  • Metencephalon 

  • Myelencephalon 

  • Brain Flexures (Folding): 

  • Cephalic (Midbrain) (Hindbrain) 

  • Cervical (Brain and spinal cord) 

  • Pons Region: Myelencephalon and metencephalon 

  • Ventricles: 

  • Telencephalon: Lateral ventricle 

  • Diencephalon: Third ventricle 

  • Mesencephalon: Cerebral aqueduct 

  • Metencephalon: Fourth ventricle 

  • Myelencephalon: Central canal 

  • Brain Wrinkles: More surface area allows for more "stuff" to be added (i.e., increased neural complexity and function). 

  • Telencephalon Growth: It engulfs the diencephalon to increase surface area. 

  • Olfactory Bulb: Part of the telencephalon; axons elongate and connect to it. 

  • Pituitary Gland Formation: 

  • Rathke's Pouch: Pushes up from the mouth. 

  • Infundibulum: Extends down from the brain to form the pituitary gland. 

  • Neuroepithelial Cells: Found in the wall of the neural tube. 

Neural Tube Organization and Development 

  • Mantle Layer  

Alar Plate: Responsible for incoming sensory information; forms gray mat 

Basal Plate: Responsible for Outgoing motor information. 

  • Marginal Layer: Formed by sprouting axons from the mantle layer; becomes white matter. 

  • Mesencephalon: Contains both alar and basal plates for incoming and outgoing information. 

  • Rhombencephalon: 

  • Alar plate is located on top. 

  • Basal plate is located below. 

  • Stretched at the foot, containing motor nuclei. 

  • Motor Nuclei Arrangement (Medial to Lateral): 

Motor (medial) = Brachial motor, parasymphatic, somatic motor 

Sensory (lateral)= Special somatic, general somatic, visceral 

Dorsal Root Ganglia Formation: 

  • Target structures appear. 

  • Axons grow from these targets to the spinal cord. 

  • Neural crest cells produce neuroblasts, forming sensory ganglia. 

  • Processes extend: 

  • Centrally towards the spinal cord 

  • Peripherally away to target to get info. 

  • Somatic Motor Neuron: Extends out to the target.