Week 3: Neurulation Flashcards
Explain the ventralization and dorsalization processes, as well as any feedback, of the neural tube as it relates to signaling factors.
Wnts and BMPs secreted from the overlying ectoderm “rain down” on neural tube tissue, helping it differentiate into dorsal tissue. This process ends when BMP concentration becomes significantly high enough to activate noggin, which feeds back negatively on BMP signaling. This allows neural crest and dorsal tissue to begin differentiating into afferent nerve cells.
On the ventral side, SHH secreted from the notochord “rises up” and binds to the ventral side of the neural tube, and helps it differentiate into ventral/efferent nerve tissue.
What does the neural tube form from?
Invagination of the overlying definitive ectoderm cells into the neural groove, and then closure and migration down into the sclero/myotome to form the neural tube
What is the original cell type of neural tube cells?
They are undefined pseudostratified columnar epithelium, collectively called neuroectoderm.
What are the layers of the neuroectoderm from the inside out?
I’ve Never Thought More: Internal membrane, Neuroepithelial cells, Thin external membrane, Mesenchyme
What are the terms for the differentiated dorsal and ventral regions of the neural tube, respectively? What are they divided by?
The alar and basal plates, which are divided by the sulcus limitans
After the ventral and dorsal regions of the neural tube have formed and differentiated, what are the four layers of distinct neural tissue that form, and what is the way you remember them? What will these cells become, and which have special qualities? Describe them
Very Irate Mr. Spock:
Ventricular zone - neurons and glia
Intermediate zone - neurons and glioblasts
Marginal Zone - white matter of the spinal cord (myelinated)
Spinal meninges - forms from the condensation of the mesenchyme into the primordial meninx, then the pia mater, arachnoid space, and dura mater form. The first two are formed by neural crest cells.
What kinds of cells do neural crest cells differentiate into? How do you remember this?
Does My Mother Offer Good People Charity
Dorsal root ganglia
Melanocytes
Meninges
Odontoblasts
Glial cells
Pharangeal arches
Cardiac development cells
(In the cranium, also craniofacial cartilage and bone…and more)
What are common neural tube defects, and how do they arise?
Spina bifida occulta–failure of the vertebral arch to close, with a dimple on the back with a tuft of hair. No treatment required.
Meningocele–saclike protrusion along vertebral column filled with CSF and meninges. Surgery is required.
Myelominingocele–saclike protrusion along the vertebral column filled with CSF, meninges, nerve roots and spinal cord. Can cause paralysis if not fixed, and surgical repair is required.
What is a common biochemical reason that neural tube issues can arise in development?
Folic acid is required for certain types of AA synthesis, along with vitamins B2, B12, and B6. Without it, issues like spina bifida occulta can arise. Can also cause anencephaly.
What are some common neural crest cell defects?
Craniofacial, cardiac, and peripheral nerve defects. Usually involved in issues with Super Oxide Dismutase (SOD) as well as other enzymes that scavenge free radicals. Without SOD, neural crest cells are vulnerable to compounds like alcohol and retinoic acid.
What are some common brain development differences that arise in individuals with ASD?
Individuals with Autism Spectrum Disorder develop polymicrogyria in the temporal, parietal and occipital lobes, and in part of the cingulate cortex. This causes persistent defects in social communication and interaction, repetitive patterns of behavior/interests/activities, and symptoms usually present in the first 2 years of development
How do outflow tract defects arise?
These major heart issues arise due to failure of neural crest-derived conotruncal cushion formation. They include:
Persistent truncus arteriosus
Transposition of the great vessels
Aortic/pulmonary stenosis
and Tetrology of Fallot
What is PTA? How can it be corrected?
Neural crest cell defect–Persistent Truncus Arteriosus. Causes irreversible pulmonary hypertension, and involves the incorrect formation of the aorta at the center point of the two ventricles, coupled with ventricular septal defect. Can be fixed by surgery.
What occurs in the heart with transposition of the great arteries?
Aorta and pulmonary artery are switched, aorta departs RV with deoxy blood, PA departs LV with mixed-oxygenated blood. Can be fixed with surgery.
Describe the pathology of hypoplastic left heart syndrome
The left ventricle is underdeveloped, and the mitral and aortic valves are either not formed are too small. The ascending aorta is also underdeveloped, and these babies also often have an atrial septal defect. Can be fixed with the Norwood procedure (valves replaced and artificial enlargement of atria/ventricles)
