Week 4 - The Embryological Development of the CNS Flashcards
What is Embryology?
Study of initial development of an embryo
In humans, all organ systems are developed by 8 weeks.
What is the embryonic period known for?
Period encompassing all organogenesis, highly susceptible to disruption and disorder
Development of the CNS is especially complex.
Define Neurulation.
The process where the neural plate forms the neural tube
Initiated by the notochord.
What is the significance of the notochord in CNS development?
Organizes surrounding tissues and provides structural support
Regulates left/right asymmetry and arterial/venous identity.
What are the primary vesicles formed by week 4?
- Prosencephalon
- Mesencephalon
- Rhombencephalon
What occurs during Gastrulation?
Generation of the 3 germ layers: Ectoderm, Mesoderm, Endoderm
Occurs along the Primitive Streak.
What is neurogenesis?
Process by which neurons and glia proliferate, migrate, and are specified to form the mature brain
Includes synapse formation and myelination.
What are the three types of cell division by neural stem cells?
- Asymmetric (PAX6)
- Symmetric (EMX2)
Fill in the blank: The _______ is a transient structure that organizes surrounding tissues during neurulation.
notochord
True or False: The cranial neuropore closes at day 28 of development.
False
The cranial neuropore closes at day 24.
What are the derivatives of neural crest cells?
- Neurons and glia of the PNS
- Adrenal medulla
- Melanocytes
- Facial cartilage and bone
- Corneal epithelium
What is the role of morphogens in CNS development?
Control the specification and development of multiple organ systems
Includes factors like SHH, Chordin, and Noggin.
What are Neural Tube Defects?
Developmental defects resulting from failure to close the neural tube
Includes conditions like Anencephaly and Spina Bifida.
What is Anencephaly?
Failure of the cranial neuropore to close, leading to absence of major brain aspects
Not viable; ethical debate surrounding organ donation.
What is Spina Bifida?
Most common neural tube defect caused by failure of closure of the caudal neuropore
Linked with hydrocephalus.
What is Craniorachischisis?
Most severe neural tube defect with both brain and spinal cord exposed
Multi-factorial causes include genetic and environmental disruptions.
What is Microcephaly?
Smaller than normal head circumference due to lack of brain development
Associated with teratogens, including Zika virus.
When do primary sulci initiate formation?
From week 12 to 28
Most gyri and sulci form in the second and third trimester.
Fill in the blank: The _______ is the process of shaping and folding during neurulation.
Neuralation
What is the significance of folic acid in neural tube development?
Linked to neural tube defects; mandated enrichment has reduced incidence
Possible role in epigenetic reprogramming.
What is the term for smaller than normal head circumference due to lack of brain development?
Aly
Associated with many exposures to teratogens, especially viruses like Zika, and several genetic links including all viable trisomies.
What is the primary defect associated with Holoprocencephaly (HPE)?
Failure of the procencephalon to segment at the midline
Occurs during weeks 5-6 of development and can be detected via ultrasound.
What is the prognosis for Holoprocencephaly?
Generally poor, but less severe variants can be viable
Often suffer from seizures, endocrine disorders, and autonomic dysfunction.
List the variants of Holoprocencephaly.
- Lobar
- Semi-lobar
- Alobar
The degree of severity is reflected in the facial patterning of the fetus.
What severe facial defect can result from the most severe cases of Holoprocencephaly?
Cyclopia
Less severe cases can co-occur with cleft lip and/or palate.
When does the development of the CNS and brain specifically start during embryonic development?
Midway through the 3rd week
Neural tube formation is essential for brain development and fetal viability.
What is neurogenesis?
A divergent process resulting in a variety of neural cells required for brain maturation
Essential for the proper development of the CNS.
What happens during the development of the CNS?
Vesicles develop and segmentation occurs, resulting in the adolescent brain
Disruption can result in several severe defects.
What is neurulation?
The process of forming the neural tube
The notochord plays a crucial role in this process.
Define specification in the context of neurogenesis.
The process by which neural cells become determined in their function
Critical for the development of specific neural structures.
What are the primary and secondary vesicles in brain development?
- Primary vesicles: Prosencephalon, Mesencephalon, Rhombencephalon
- Secondary vesicles: Telencephalon, Diencephalon, Metencephalon, Myelencephalon
They develop into specific structures in the adult brain.
List pathologies associated with neurulation or neural tube defects.
- Spina bifida
- Anencephaly
- Encephalocele
These defects can lead to significant neurological impairment.
