Embryology Flashcards
When does neurulation begin
Week 3
What is neurulation
Formation of the neural tube
Describe formation of the neural tube
Notochord releases signalling molecules causing the overlying ectoderm to convert to neurectoderm
Lateral edges of neural plate elevate to form neural folds
Neural folds fuse in midline to form the neural tube
Direction of neural tube formation
Fusion of folds begins in cervical region and progresses in both directions
What are neuropores
Anterior and posterior
Where the neural folds haven’t fused yet
What are the neural tube defects
Spina bifida
Anencephaly
Rachischisis
Pathophysiology of spina bifida
Posterior neural tube fails to close so there is no vertebral arch formation in a region of the spine
Consequences of spina bifida
Neurological deficit
Hydrocephalus - causes cognitive delay
Types of spina bifida and how they differ
Meningocoele - spinal cord stays within vertebrae therefore cyst in back only contains CSF
Myelomeningocoele - spinal cord doesn’t stay within vertebrae therefore cyst in back contains CSF and part of the spinal cord
Pathophysiology of anencephaly
Failure of the anterior neuropore to close leading to absence of a brain
Pathophysiology of rachischisis
Failure of neural plate elevation so there is no neural tube formation
How can neural tube defects be detected in utero
Ultrasound scan
Maternal serum alpha fetoprotein
How to prevent neural tube defects
Folic acid supplements
How does the spinal cord develop in relation to the vertebral column
Spinal cord stops growing at 3rd month but vertebral column continues to grow
This leads to formation of the cauda equina as the spinal roots must elongate to exit at their respective intervertebral foramina
What is the conus medullaris and where is it
End of the spinal cord
L3
What are the primary brain vesicles
Forebrain
Midbrain
Hindbrain
What secondary brain vesicles develop from the forebrain
Telencephalon
Diencephalon
What secondary brain vesicles develop from the midbrain
Mesencephalon
What secondary brain vesicles develop from the hindbrain
Metencephalon
Myelencephalon
What is derived from each of the secondary brain vesicles
Telencephalon - cerebral hemispheres Diencephalon - thalamus Mesencephalon - midbrain Metencephalon - pons and cerebellum Myelencephalon - medulla oblongata
What are the neural flexures
Cervical flexure - at junction between spinal cord and hindbrain
Cephalic flexure - in the region of the midbrain
What are the ventricular system derivatives of the secondary brain vesicles
Telencephalon - lateral ventricles Diencephalon - third ventricle Mesencephalon - cerebral aqueduct Metencephalon - fourth ventricle Myelencephalon - fourth ventricle
Most common cause of hydrocephalus
Spina bifida
Treatment for hydrocephalus
Shunt into peritoneum or IJV
Layers of the neural tube from outer to inner
Marginal
Intermediate or mantle
Neuroepithelial
What are the types of neural plates and what do they control (include their location and function)
Roof plate: is dorsal and controls differentiation to the alar plate which has sensory function
Floor plate: is ventral and controls differentiation to the basal plate which has motor function
Describe migration of neural crest cells
Arise from lateral neurectoderm
Enter mesoderm and undergo epithelial to mesenchymal transformation
What is derived from neural crest cells
Dorsal root ganglia Autonomic ganglia Glia Leptomeninges Adrenal medulla Melanocytes Dermis of face C cells of thyroid
Examples of neural crest defects
Hirshpring’s disease
Di George syndrome
