Embryo: Development of the Nervous System Flashcards
Formation of 3 germ layers (endoderm, mesoderm, and ectoderm)
Gastrulation
What week does Gastrulation begin?
Week 3
Components of gastrulation
- formation of 3 germ layers
- Primitive streak
- Notochordal process
What germ layer is the primitive streak made up of?
Embryonic ectoderm
3 parts to the primitive streak?
- Primitive node
- Primitive groove
- Primitive pit
What region of the embryo does the primitive streak occur at?
Caudal region of the embryo
What region of the embryo does the primitive node occur at?
Rostral region of the embryo
What germ layer is the notochordal process made of?
Mesoderm
What does the notochordal process become?
It is the template for formation of the vertebral column and induces the formation of the neural plate
When does neurulation begin?
Day 22-23
Notochord induces neural plate formation: ?
- Neural plate
- Neural groove
- Neural folds
- Neural tube
What does the notochord release to form the neural plate?
Sonic Hedge Hog (Shh)
What is the neural plate (germ layer)?
Thickening of ectoderm
What is the space called when the neural folds have not yet met each other?
Neural groove
Neurulation
- In the end, the surface ectoderm becomes?
Developing epidermis
Neurulation
- In the end, the neural crest becomes?
Developing spinal ganglion
Neurulation
- When the neural folds met up, it is now called?
Neural tube
What are the germ layers involved with the neural plate?
Neuroectoderm, surface ectoderm, and neural crest
What germ layer is the neural tube made of?
Neuroectoderm
Neurulation
- What day does the rostral neuropore close?
Day 25
Neurulation
- What day does the caudal neuropore close?
Day 27/28
What does primary neurulation give rise to?
Brain and down to the lumbar region of the spinal cord
What day does primary neurulation begin?
Day 22-23
What day does secondary neurulation begin?
Day 20-42
What is the group of cells from neuroectoderm that forms the sacral and coccyx region of the spinal cord ?
Caudal eminence
What are the cells of the nervous system that come from neuroectoderm?
- Dendrite
- Protoplasmic astrocyte
- Fibrous astrocyte
- Oligodendrocyte
- Ependyma and Epithelium of choroid plexus
What are the cells of the nervous system that come from mesoderm?
**Microglial cell
from blood monocytes
Neural tube forms portion of the brain cranial to the ? somites
Fourth
What are the three primary brain vesicles?
- Prosencephalon
- Mesencephalon
- Rhombencephalon
Prosencephalon is what part of the brain?
Forebrain
Mesencephalon is what part of the brain?
Midbrain
Rhombencephalon is what part of the brain?
Hindbrain
What week do the forebrain and hindbrain divide?
5th week
Prosencephalon gives rise to?
Telencephalon and
diencephalon
Rhombencephalon gives rise to?
Metencephalon and
myelencephalon
What area do we find in the region of the telencephalon?
Lateral ventricle
What area do we find in the region of the diencephalon?
Third ventricle
What area do we find in the region of the Mesencephalon?
Cerebral aqueduct
What is bonded between metencephalon and
myelencephalon?
Fourth ventricle
Spinal cord has opening to the ?
Central canal
Have ? that give rise the adult formation of the brain
Flexures
Telencephalon consists of?
Cerebral hemisphere
Diencephalon consists of?
Thalamus and hypothalamus
Mesencephalon consists of?
Midbrain
Metencephalon consists of?
Pons and cerebellum
Myelencephalon consists of?
Medulla
Cervical flexure develops in what week?
Week 5
Demarcates the hindbrain from the spinal cord
Cervical flexure
Divides hindbrain into caudal myelencephalon and rostral metencephalon
Pontine flexure
What flexure develops later?
Pontine flexure
Bend between midbrain and forebrain
Cephalic flexure
persists and gives our brain the adult structure
What week are basal ganglion and cortical structure developing?
Between weeks 6 to 32
What is a collection of different cell bodies or nuclei?
Basal Ganglion
Basal ganglion includes?
Caudate nucleus, putamen, globus pallidus, subthalamic nucleus, and substantia nigra
Telencephalon consists of?
– Cerebral cortex – ** Subcortical white matter (including internal capsule) (made of ectoderm) – Olfactory bulb and tract – Basal ganglia – Amygdala – Hippocampus
Diencephalon consists of?
– ** Thalamus (made of ectoderm)
– Hypothalamus
– Epithalamus
– Eye (optic nerve)
Midbrain consists of?
– Cerebral peduncles
– Superior and inferior colliculi
– 2 cranial nerves
Medulla oblongata consists of?
- Olive
- Pyramid
What are the adult structures of the brain?
- Telencephalon
- Diencephalon
- Midbrain
- Cerebellum
- Pons
- Medulla oblongata
What results from incomplete separation of cerebral hemispheres?
Holoprosencephaly (HPE)
Holoprosencephaly
– Most associated with ?
– Reduction of ?
–Eyes close together aka ?
- facial abnormalities
- frontonasal prominence
- Hypotelorism
Causes of Holoprosencephaly
- Genetic and environmental factors
- Maternal diabetes
- Teratogens (alcohol) (can cause the cyclopia)
- Retinoic acid
Clinical features of Holoprosencephaly
- Microcephaly (small head), microphthalmia (small eyes), ocular hypotelorism, midfacial hypoplasia, and cleft lip with or without cleft palate
- ** Intellectual disability (mental retardation) or developmental delay
- Epilepsy, hydrocephalus, dystonia, movement disorder, autonomic
dysfunction, and
hypothalamic/pituitary dysfunction
Holoprosencephaly spectrum
- Median cleft lip and palate
- Mild - Cebocephaly
- One nose - Ethmocephaly
- Nose from frontal nasal prominence does not migrate correctly = Probiscus - Cyclopia
- Most severe
- Usually die
Pituitary Gland
- First arch ectoderm gives rise to:
– Roof of mouth
**– Contributes to anterior lobe of pituitary gland
– Hypophysial
diverticulum (Rathke’s
pouch)
Pituitary Gland
- Posterior lobe of pituitary gland is from?
** Neuroectoderm
Posterior lobe of pituitary gland is from neuroectoderm and comes from?
– Diencephalic floor
– Neurohypophysial
diverticulum
So the anterior lobe of pituitary is ? and posterior lobe is ?
- Surface ectoderm
- Neuroectoderm
Formation of Spinal Cord and Brain Regions:
Neural tube is caudal or inferior to the ?
Fourth pair of somites