Neural Tube Development Flashcards
What is the neural tube
Embryonic tube like structure that is the PRECURSOR to the CNS (brain and spinal cord)
How is the neural tube formed?
Neurulation - during the first month of development
How do neural tube defect occur
When the neural tube fails to close during neurulation
What are the embryonic stages leading to neural tube development
Fertilization and implantation
Gastrulation
Neurulation
What is neurulation
The process of forming the neural tube from the ectoderm in the embryo
Before implantation, what happens in fertilization? (Days 0-7)
- Fertilized egg (zygote)
- First 24 hours, the zygote splits to form 2 cell structures
- Days 1-2: rapid divisions of zygote
What happens in fertilization in days 3-6
32 cells structure are made called BLASTULA (or blastocyst)
Continues to move towards the uterus as the cells are splitting
What type of cells are blastula made up of
Epithelial cells
What happens in implantation (day 7 after fertilization)
The blastocyst is implanted in uterine lining
Over the next week, the blastocyst matures and transforms into a GASTRULA
What is gastrulation
Process of transforming the blastocyst into gastrula
What is gastrula
Blastocyst is reorganized from a simple round ball of cells into a “multi-layered and multidimensional organism”
What happens in day 15-16 of gastrulation
Gastrulation is complete and comprises a tri-layered organism
What are the 3 primary germ layers in gastrulation
- Endoderm
- Mesoderm
- Ectoderm
What is mesoderm in gastrulation
Middle germ layer
Skeletal system (muscle, connective tissue, cartilage )
Circulatory system (heart, blood vessels)
Serous membranes lining the body cavities
What is endoderm in gastrulation
Internal germ layer
Forms the lining of the gut and other internal organs
GI tract, respiratory tract, bladder
What is the ectoderm in gastrulation
External germ layer
Forms the skin, the brain, THE NERVOUS SYSTEM, and other external tissues
When does neural tube development begin
During the 3rd week
When does the neural tube closes (fuses)
End of the 4th week
What happens in week 3 of neurulation (approximately days 17-18 after fertilization)
Neural plate forms
Neural groove is first seen along the midline of the neural plate
What happens in week 3 of neurulation (approximately day 20 after fertilization)
The neural groove begins to thicken, elevate and fold, eventually becomes the NEURAL CREST
What happens in week 4 of neurulation
- Neural folds fuse to form the neural tube
- Fused folds starting progress to both rostral and caudal
- “Zips up” neural groove
- Leaves 2 openings at each end called NEUROPORES
What are the 2 neuropores
Rostral (anterior) neuropore
Caudal (posterior) neuropore
What happens at the END of week 4 of neurulation
Neural tube completely fused by day 27
After neurulation is complete, what happens to the neural tube
Goes on to develop into the CNS
Central portion of the tube called the central canal
