Embryology PDF

Neural Induction First cells to located internalize and in the giverise to dorsal lip anterior of...

Neural Induction First cells to located internalize and in the giverise to dorsal lip anterior of blastopore I endoderm of neurula stage Fig 4.26, p. 166 deep to cells next internalize Neuralizing signal First cells in form axial mesendoderm (notochord) Meso- and endoderm migrate up blastocoel roof Induce overlying ectoderm to form neural Neurula, Neural Plate, Neural Crest Neural plate forms along the dorsal midline Neural Ridges meet at the midline Neural tube sinks, ectoderm covers the top Neural Plate Neural Ridge Fig 4.28, p. 167 Neural Tube formation Neural plate rolls up to form a tube Tube sinks below ectoderm which sutures over topo Neural crest caught between the 6. two layers neural crest "4 " germinal layer neural crest Neural Crest Cells On Neural Ridge > prospective - neural “4th Germinal layer” Crest cells Can excise a piece, but when ectoderm and neurectoderm heal, neural crest forms again formation neural of folds at border - enoughto plate specification neural carries to dorsal cells crests High potency: forms bone, cartilage, muscle, of neural tube melanocytes, endocrine, neural cells (more on this later) Highly migratory require - lots of to programming know where to go > - delaminate and migrate away Fig 5.34, p 222  notochord noggin chordin - , noggin e sun Sun - form ventual floor plate Axial Mesoderm (Notochord) , Noggin, Sonic Hedgehog 3 potent signaler thicken and form neural Floor plate Axial Mesoderm (notochord) & noggin induces secretes noggin, chordin chordin Noggin induces secretion of sonic hedgehog (shh) Shh induces neural tube to form - - ventral floor plate - Ventral floor plate then secretes shh, which diffuses laterally - At a critical threshold removed from shh, motor neurons differentiate Influence of BMP induces roof plate and neural crest Modified from: https://basicmedicalkey.com/nervous-system-3/ Notochord, noggin, · shh induction Transplanted notochord locally organizes floor plate and to dorsal region suppressed motor neurons Transplanted source of noggin locally induces floor plate Transplanted source of shh induces floor plate Anti-shh antibody inhibits its action preventing floor plate – induced a cartilage spinal cord develops without dorso-ventral polarity Somites also depend upon Fig. 5.34, p. 222 regular notochord and shh affects shape its of neural dorso-ventual tube and location to form normally pattern Somites revisited Fig 5.33, p. 222 Somites form into balls (epithelialize) Separate into three components Dermomyotome- dermis, skeletal muscle - Myotome- back muscle, ribs, limbs 1 Sclerotome- vertebrae (after re-segmentation), rib cartilage  Neural Crest Migration Neural Crest Cells ① Pathway Over Somites Neural Crest Migrates by several routes ② Receive routing information Pathway Through Somites from tissues it passed through Neural Tube Addressing specific to ③ Pathway Behind Somites function Notochord Different programming > - dep on path  Neural Crest Migration Fluid pressure > - anterior ↓ (ballooning) mand T brana fluid g neural tube doesn't fuse properly clef - Super ↓ midline jaw https://embryology.med.unsw.edu. au/embryology/index.php?curid=9 23 Branchial Arches =Pharyngeal Pouch Senders et al., 2003 Archives of Facial Plastic Surgery Vol. 5, No. 1 =Gill arches Neural Crest Migration Neural Crest Derivatives Fig 5.39, p. 225