Nervous-Musculoskeletal Development and Limb Formation Flashcards
Describe somatic reflex (Hand touches flame)
Hand makes contact with flame, sensory afferents tract (pseudounipolar) conducted through dorsal root ganglion and then synapses at interneuron at dorsal horn. Another synapse into ventral horn, which flows through efferent tracts on ventral side and out to the same muscle
Where trilaminar embryonic disk came from. Describe dorsal and ventral side
Bilaminar embryo (the EPIBLAST layer, which underwent gastrultion at the primitive streak and ultimately becme ecotderm, mesoderm, endoderm). Dorsal side: amnionic cavity Ventral side: yolk sac
Describe destinies of Ectoderm, mesoderm, and ectoderm
Ectoderm: Communication with external environment (Nervous System, Epidermis, sensory receptors, some glands)
Mesoderm: Bones and muscles (support), skeletal, urogenital, muscular, cardio systems
Endoderm: Digestion, breathing, secreting ….glands fro dayz. Epithelia for urinary bladder, GI-respiratory, more glands
Describe organ formation
Comes from multiple germ layers and are made of multiple tissue types
What kind of matter makes up the cortex/horns layer? Where do you find the cortex?
Cortex is only found in the brain. After which, the grey matter transforms into the dorsal and ventral horns of the spinal cord
In PNS, where do you find schwann and where do you find satellite cells?
Schann cells: axons
Satellite cells: soma
When does neurolation start? What comes about from it?
Starts after gastrulation (so, after the 3rd week). Makes dorsal running neural tube, which makes brain and spinal cord. The cell bodies are in CNS but their axons extend through pns
Describe neural tube formation (neuralation)
- Ecoderm inducted by notochord factors (found in black dot aka midline rod of medoderm)
- Developing neuroectoderm cells organize in midline as thickening neural plate
- Proliferating neural plate “buckle” to form depression called neural groove with bilateral neural folds.
- Further buckling and folding or neural folds approximate and fuse in DORSAL midline to form neural tube.
- Neural tube detatches from epidermis-forming surface ectoderm
- Neural pore closes (anterior and posterior porse both close)
Neural tube defect
Defect associated with 4th week of development, where neural tube fails to close properly
Craniorachischisis
“Cleft skull and spine”
Defective closure of ENTIRE neural tube. Not compatible with life
Anencephaly
Screw up with the formation of cranial vault, exposing BRAIN to AMNIOTIC FLUID, leading to degeneration. Specifically involves defective closure of cranial neural pore. “Polyhydramnios” = too much amniotic fluid….the defect is of the brain, so the end result is a destruction of the swallowing reflex. Note that the embryo needs to swallow amniotic fluid…not compatible with life
Spina bifida…and describe difference between occulta and cystica
Screw up with lower lumbar-sacral region. Focused in the caudal region.
Occulta: mild defect involving defect in fusion of vertebral arches WITHOUT herniation of the underlying neural tissue.
Cystica: legitimate screw-up with fusion of vertebral arches WITH herniation of underlying neural tissue. 3 types, 2 of which focus on herniation of vertebral column and the other involves the subarachenoid space poring out of brain (head) area
Preventing neural tube defects
Increase intake of Folic Acid (type of vitamin B). Greens, plants, and such
What are neural crest cells? What do they do?
Arises from the DORSAL edges of neural tube (which makes cns). They detach from dorsal edges of the tube and form GANGLIA. Cells that remain closer to the tube = dorsal root ganglia. Cells that migrate further away = Sympathetic ganglia, enteric ganglia
Embryo development from week 2 to week 3
Week 2: EPIBLAST (bilaminar embryonic disk)
Week 3: ECTODERM (trilaminar emryonic disk, gastrulattion), neuroectoderm (neuroepithelium and neural crest). Focused on caudal region, which is the spinal cord and the central neural canal consisting of the 31 pairs of spinal nerves
Where is the central canal located?
Dead center point of the spinal card. GO back to the cross section of the ventral and dorsal roots. The point in the very center of the butterfly
Sulcan limitans
Line that marks polarity of neural tube (separates dorsal and ventral halves)
What lines neural tube lumen/neural canal? Describe these cells
Neuroepithelium…literally proliferates from the neual tube to the lateral side of the tube. These neuroepithelium cells proliferate and DIFFERENTIATE into CNS neuroblast cells (primitive neurons). Note that neuroblast cells CANNOT divide (amitotic). There for life.
Describe difference between mantle layer and marginal layer of spinal cord
Mantle layer: grey matter
Marginal (like the margin of word doc) layer: white matter
Importance of alar plate and basal plate
Alar plate = DORSAL thickening of neuroblast cells at the edge of the mantle.
Basal plate is the result fo neuroblast cells thickening a the VENTRAL side of the mantle layer
What do alar plate and basal plate become?
Alar plate: becomes dorsal horn
Basal plate: becomes ventral horn. Note that there are cell bodies in these horns.
What do neuroepithelial cells proliferate into?
CNS neuroblasts (primitive neurons) and glioblasts (primative neuroglia –> astrocytes, ependymal cells, oligodendrocytes, all of which develop here. Microglia are also present, but later…migrating during development)
