Development of the Central Nervous System

• Ectoderm, Mesoderm, Endoderm - The embryo differentiates into the following germ layers.
• Central Nervous System & Epidermis of the skin - The ectoderm will form the following.
• Neuroectoderm - Dorsal midline thickening of the ectoderm overlying the notochord.
• Neural Folds - They are the elevated lateral margins of the neural plate.
• Neural Groove - They are on each side of the longitudinal midline.
• Neural Tube - It is formed from the apposition and fusion of the neural folds.
• Adult CNS - Formed from completed Neural Tube.
• Brain - Formed from the maximal growth in the Rostral Part.
• Spinal Cord - Formed from the Caudal Portion.
• Neuroaxis - Axis of the Neural Tube.
• Ventricles (Brain) and Central Canal (Spinal Cord) - Formed from the central cavity within the neural tube.
• Autonomic Ganglia, Sensory Ganglia, Melanocytes, Cells of Supra renal medulla - Neural Crest give rise to the following.
• Differentiation of the Spinal Cord - Grey Matter & White Matter
• Sulcus Limitans - Longitudinal groove along the inner surface of the lateral walls of the developing spinal cord.
• Alar & Basal - Sulcus Limitans differentiates into the following.
• Alar Plate - Sensory in function.
• Basal Plate - Motor in function.
• Three primary brain vesicles - Prosencephalon, Mesencephalon, Rombencephalon.
• Fore Brain - Prosencephalon
• Mid Brain - Mesencephalon
• Hind Brain - Rombencephalon
• 2 Flexures of Neuraxis - Cephalic Flexure & Cervical Flexure
• Cephalic Flexure - Mid Brain.
• Cervical Flexure - Between the brain and spinal cord.
• Division of Prosencephalon - Telencephalon & Diencephalon
• Telencephalon - Largest brain vesicle. Forms the two Cerebral Hemispheres
• Diencephalon - Formed mainly of the Thalamus.
• Division of Rombencephalon - Metencephalon & Myelencephalon
• Pontine Flexure - Third flexure that appears between the Metencephalon and the Myelencephalon.
• Metencephalon differentiates into: Pons & Cerebellum
• Myelencephalon will form Medulla Oblongata.
• Four Colliculi - Represents brain centers. Superior and inferior.
• Prosencephalisation - Rostral part of the brain becomes the highest kevel of perception and correlation of all sensory modalities.
• Anencephaly - Brain and skull are minute.
• Spina Bifida - Underdevelopment of the lower part of the spinal cord and the nerve roots.
• Complications of Spina Bifida - Paralysed anesthetic lower limbs, Incontinence of urine and stool.
• Meningiomyelocele - It is Spina Bifida with the appearance of the meninges of the spinal cord on the back of the body.