Development of the CNS Flashcards
The CNS first appears as a thickening of the ectoderm in the region of the primitive streak. At what stage in development does this occur?
Week 3
What structures does the ectoderm give rise to?
CNS, PNS, sensory epithelium of the ear, nose and eye, epidermis, hair and nails, subcutaneous, mammary and pituitary glands, enamel of the teeth
The notochord develops in the opposite direction to the primitive streak. T/F?
True
What structure is important in inducing the development of the neuroectoderm?
Notochord
The notochord is part of the mesoderm. T/F?
True
What is the initial event in the process of neurulation?
Thickening of the ectoderm overlying the notochord
At what day in development do the neural folds approach the midline and fuse to form the neural tube?
Day 22
The median hinge points form before the dorsolateral hinge points in the development of the neural tube. T/F?
True
What type of cells link the developing neural tube with the overlying ectoderm?
Neural crest cells
The up-regulation of FGF causes inhibition of which molecule to cause induction of the neural plate?
BMP-4
In addition to FGF, which molecules can inhibit BMP-4 in neural tube development?
Chordin and noggin
During development the neural plate switched from E-cadherin to N-cadherin expression. What does this allow?
This allows the two ends of the neural tube to recognise each other and fuse
It also prevents fusion of the neural tube to the overlying ectoderm
What cell and structures do the neural crest cells give rise to?
Ganglia Schwann cells Adrenal medulla Melanocytes Connective tissue in the head region
Neural crest cells can contribute to the craniotomy-facial skeleton. T/F?
True
Treacher Collins syndrome results in the underdevelopment of which structures due to a mutation in the TCOF-1 gene or retinoid acid exposure?
Zygomatic bones and ears
A 22q11.2 deletion can result in a cleft palate, cardiac abnormalities, abnormal faces and thyme aplasia. What is the name of this syndrome?
Di George syndrome
By which day of development does the anterior neuropore close?
Day 25
By which day of development does the posterior neuopore close?
day 27
Once the neural tube closes, the neuroeptihelial cells give rise to neuroblasts under the influence of which signalling molecules?
notch and delta
The mantle layer (which later forms the grey mater of the spinal cord) is formed by what type of cells?
Neuroblasts
In development, the marginal layer of the spinal cord in superficial to the mantle layer. T/F?
True
In development, the mantle layer goes on to form the white mater of the spinal cord. T/F?
False - the mantle layer forms the grey mater and the marginal layer forms the white mater
Which cells are formed from the neuroepithelial layer in the mantle and marginal layers and differentiate to form astrocytes and oligodendrocytes?
Glia blasts
What phagocytic cells of the CNS are derived from the vascular membrane?
Microglial cells
What spinal cord structure forms from the basal plate?
Ventral motor horns
What spinal cord structure forms from the alar plates?
Dorsal sensory horns
What structure separates the alar and basal plates of the developing spinal cord?
sulcus limitans
At what week in development do the alar and basal plates differentiate into the ventral and dorsal horns?
Week 7-8
What is the name of the dorsal midline portion of the developing spinal cord which serves as a pathway for nerve fibres to cross from one side of the spinal cord to the other?
Roof plate
What is the name of the ventral midline portion of the developing spinal cord which serves as a pathway for nerve fibres to cross from one side of the spinal cord to the other?
Floor plate
In development, from where do the dorsal nerve roots, which carry sensory fibres, originate?
The dorsal root ganglia, outside the spinal cord
In what week of development do the three primary brain vesicles develop?
week 3
In what week of development do the five secondary brain vesicles develop?
week 5
What are the three primary brain vesicles?
Prosencephalon (forebrain)
mesencephalon (midbrain)
rhombencephalon (hindbrain)
What are the two flexures which are present during early brain development?
Cephalic flexure and cervical flexure
From which brain vesicle does the cerebrum develop?
Telencephalon
Which primary brain vesicle does not split into two secondary vesicles?
The mesencephalon which forms the midbrain
From which brain vesicle do the thalamus, hypothalamus and epithalamus develop?
Diencephalon
From which brain vesicle do the pons and cerebellum develop?
Metencephalon
What brain structure develops from the myelencephalon?
Medulla oblongata
What condition arises from a failure of posterior neuropore closure?
Spina bifida
What other condition is associated with spina bifida?
Hydrocephalus
What condition arises as a result of failure of anterior neuropore closure?
Anencephaly
From what cells do the meninges develop?
Mesenchymal and neural crest cells
Between which days in develop do mesenchymal and neural crest cells migrate around the neural tube to start formation of the meninges?
days 20-35
Where do the choroid plexuses develop?
Where the Pia mater and ependyma come into direct contact such as on the roof of the fourth ventricle
Why does CSF build up in the head in spina bifida cystic?
Obstruction of the foramen magnum by the cerebellum
Hydrocephalus can be treated by shunting the excess fluid from the brain ventricles to the…?
Peritoneal cavity
In what day of development does the developing eye first appears as a pair of shallow grooves?
day 22
From which brain vesicle do the eyes develop?
Diencephalon
What is the name of the shallow grooves which are the first appearance of eye development in an embryo?
Optic vesicles
What is the name of the structure from which the lens of the eye develops?
Lens Placode
The placed cells become columnar and invaginated to form the optic cup. Describe the bilaminar structure of this cup?
The outer layer forms the pigmented layer of the retina and the inner layer forms the nervous layer fo the retina
The potential space between the layers of the optic cup disappear as development progresses. T/F?
True
Which layer of the optic cup proliferate to form rod cells, cone cells and cell bodies of neurons?
Inner layers
At the rim of the optic cup, both layers of the retina give rise to which structures?
Iris and ciliary body
What is produced by the ciliary body of the eye?
Aqueous humour
The lens is derived from surface ectoderm. T/F?
True
By which week in development does the optic cup become connected to the brain via the optic stalk?
week 6
What is the name of the branch of the ophthalmic artery which passes along the choroidal fissure to supply the lens and developing retina?
Hyaloid artery
What is the name of the grooves which arise on the ventral surface of the optic cup?
The choroidal fissure
By which week in development does the cavity of the optic stalk disappear and the inner layer of the optic cup provide a network of neuroglia to support the optic nerve fibres?
Week 7
By which week in development does the optic stalk become the optic nerve?
Week 9
In week 9 of development the optic stalk becomes the optic nerve. What do the hyaloid artery and vein become?
The central artery and vein of the retina
The mesenchyme around the optic cup condenses to form what structures?
The choroid and sclera
What is the name of the substance which fills the posterior chamber of the eye?
Vitreous humour
The eyelids form from folds of ectoderm with mesenchyme over them that grow over the cornea and fuse. What structure is formed from the inner layer of ectoderm?
The conjunctiva
How do the lacrimal glands from?
As ectodermal buds from the upper conjunctival sac into the surrounding mesoderm
In development, When do the eyelids separate?
Between months 5 and 7 of development
What molecule is a key regulator of eye development?
PAX6
SHH is responsible for eye field separation. How does it achieve this?
It up regulates PAX2 in the optic stalks and restricts PAX6 to the optic cup and lens
Congenital cataracts can be caused by genetics but also by which infection during weeks 4-7 of gestation?
Rubella infection
What can cause microphtalmia (small eyes)?
Genetic abnromalities
Intrauterine infections
Foetal alcohol syndrome
What is the name for the absence of the eye which can be caused due to genetic or infectious factors?
Anopthalmia
Why does cyclopean ( a single eye) develop?
Failure of the prosencephalon to divide the orbits of the eye due to mutations in SHH