2. Embryology Flashcards
What do cranial neural tube defects result in?
Anencephaly.
What do caudal neural tube defects result in?
Spina bifida.
What is seen neurologically in spina bifida?
Neurological deficits, but no cognitive delay (if untreated then can secondarily cause cognitive delay). Hydrocephalus nearly always occurs.
What are the two types of spina bifida?
Meningocele - failure of the vertebral arch to form, spinal cord still within body cavity, cyst involved the meninges and CSF.
Myelomeningocele - failure fo the vertebral arch to form, spinal cord NOT within body cavity, cyst involved meninges, CSF and spinal cord.
What is anencephaly?
Failure of the neural tube to close cranially leading to absence of cranial structures including the brain. Is incompatible with life.
What is rachischisis?
Failure of neural fold elevation to form the neural tube. Is incompatible with life.
How can neural tube defects be diagnosed?
Screening for raised maternal serum alpha-fetoprotein. USS.
How can neural tube defects be prevented?
Taking folic acid pre-conceptually for 3 months and for the first trimester.
Describe the development of the spinal cord?
Formed from most of the length of the neural tube. Is the same length as the vertebral column until the 3rd month, when the vertebral column then grows faster, so spinal roots elongate to still exit at their intervertebral foramen, and the cauda equina is formed.
What are the 3 primary brain regions formed during neural fold formation which become the 3 primary brain vesicles in the 4th week?
Forebrain - prosencephalon.
Midbrain - mesencephalon.
Hindbrain - rhombencephalon.
In the fifth week, the 3 primary brain vesicles form 5 secondary brain vesicles. What does the prosencephalon form and what mature derivatives does this give rise to?
Prosencephalon:
Telencephalon - cerebral hemispheres.
Diencephalon - thalamus.
In the fifth week, the 3 primary brain vesicles form 5 secondary brain vesicles. What does the mesencephalon form and what mature derivatives does this give rise to?
Mesencephalon:
Mesencephalon - midbrain.
In the fifth week, the 3 primary brain vesicles form 5 secondary brain vesicles. What does the rhombencephalon form and what mature derivatives does this give rise to?
Rhombencephalon:
Metencephalon - pons and cerebellum.
Myelencephalon - medulla oblongata.
What does the cervical flexure form?
Spinal cord-hindbrain junction.
What does the cephalic flexure form?
Midbrain region.
What is the role of the ventricular system within the brian which develops as a result of the tubular structure of the developing CNS?
To cushion the brain and spinal cord within their bony cases.
What part of the ventricle system of the brain develops from the telencephalon, diencephalon, mesencephalon, metencephalon and myelencephalon?
Telencephalon - body of the lateral ventricle.
Diencephalon - third ventricle.
Mesencephalon - cerebral aqueduct.
Metencephalon and myelencephalon - fourth ventricle
What can a ventricular system abnormality cause?
Hydrocephalus - is most common in newborns with spina bifida but can occur anywhere where there is blockage of the ventricular system eg tumour or infection.
What function does the dorsal alar plate in the neural tube form in the brain?
Sensory function.
What function does the ventral basal plate in the neural tube form in the brain?
Motor function.
What do neural crest cells in the lateral border of the neuroectoderm go on to form?
Enter the mesoderm, undergo epithelial to mesenchymal transition, and form structures of the nervous system eg sympathetic ganglion, structures of the head, neck and midline eg connective tissue and bones of the face and skull and a few other structures eg the adrenal medulla.
Give an example of an abnormality of neural crest cell migration affecting just one structure
Hirschsprung’s disease - forming an aganglionic megacolon.
Give an example of an abnormality of neural crest cell migration affecting multiple structures
DiGeorge syndrome - causing thyroid deficiency, immunodeficiency secondary to a thymus defect, cardiac defects and abnormal facies.
