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39 Cards in this Set
- Front
- Back
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Mesodermal tissues are formed in synchrony with |
endo and ectodermal tissues |
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Notochord neural tube floor plate neural tube roof plate epidermal ectoderm lateral plate mesoderm |
Shh Shh BMP, Wnt, Neutrophin 3 BMP, Wnt BMP, FGF |
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Somitogenesis |
somites formation - sclerotome, miotome, dermatome A-P |
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Tissue specification inside putative somites |
happens prior to somitogenesis each somite forms specific structures Hox genes expression, NO REVERSAL |
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Segmental plate mesoderm determined before |
somitogenesis forms thoracic somite, gives rise to vertebrae and ribs if transplanted to cervical somite area would still form thoracic vertebrae |
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Somites contribute to the formation of (5) |
1. cartilage/bones of vertebrae and ribs 2. muscles of rib cage, limbs, abdominal wall, back, tongue 3. dorsal dermis 4. tendons 5. vascular cells of aorta and intervertebral blood vessels This commitment LATE after somite is formed |
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Osteoblasts differentiate from |
mesenchymal progenitor cells - give rise to myocytes, adipocytes, and chondrocytes Runx2 essential for osteoblast differentiation |
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Myotome divides and forms |
Medial cells,primaxial, epaxial myotome --> ribs and back muscles Lateral cells, abaxial, hypaxial myotome --> body wall, limbs, tongue |
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Myotome |
primaxial - low shh, wnt abaxial - wnt, bmp4, fgf5 |
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Myogenesis |
Medial (primaxial) - Wnts, Shh, Myf5 which induces MyoD Lateral dermamyotome - (abaxial) wnts induce pax3 which induces myoD |
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MyoD and Myf5 |
myogenic bHLH proteins transcription factors MyoD activates muscle specific genes |
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Sclerotome |
Shh induces sclerotome cells to secrete pax1 cartilage/vertebral formation |
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Dermatome |
Neurotrophin and wnt from roof plate Shh antagonist |
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notochord |
degenerates through apoptosis remains as nucleus pulposus |
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Myoblasts to muscles |
Fgf - proliferation of myoblasts fibronectin - alignment for fusion Cadherins, CAMs Myogenin - differentiation Ca ions, meltrinalpha - fusion to myotube ( muscle fibre) |
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Muscle stem cells |
satellite cells remain in adult as quiscent stem cells muscle hypertrophy in response to stimuli, muscle regeneration and repair after injuries |
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Osteogenesis |
1. CNC originated from ectoderm gives rise to branchial arches, craniofacial bones, cartilage 2. Somites from paraxial mesoderm give rise to axial sceleton 3. Somatic part from laternal plate mesoderm generates into limb skeleton |
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Two modes of bone formaiton |
1. Intramembranous (perichondral) ossigication or direct ossigication (NCC) 2. Endochondral ossigication - indirect, uses hyaline cartilage model for bone construction, requires break down of cartilage prior to ossification |
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Endochondral ossification |
paraxial mesoderm - somites, sclerotome 1. mesenchymal cells commit to become cartilage (Shh induces Pax1) 2. Cells condense into compact nodules, differentiate into condrocytes (BMP induces Ncadherin, NCAM, Sox9) 3. Chondrocytes proliferate and lay down collagen matrix |
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Endochondral ossification cont... |
middle chondrocytes stop dividing, grow, becomes hypertrophic chondrocytes (Runx2) Secrete factors that differentiate osteoblasts and initiate apoptosis Death leaves cavity in cartilage Increase in secretion of VEGF causes angiogenesis |
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Endochondral ossification cont... |
Cells surrounding cartilage differentiate into osteoblasts, perichondrium replaced with periosteum Dependent on mineralization of CA+ Blood vessels invade, bring osteoprogenitor cells, develop into osteoclasts - some develop into osteoblasts |
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Endochondral ossification cont... |
Remodeling, more VEGF, increases blood vessles Osteoblasts from bone matrix, which then forms bone collar Osteoclasts reform bone marrow cavity, hollow out internal bone Continued development Balance between osteoclasts and osteoblasts |
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Endochondral ossification cont... |
Secondary ossification centers form in epiphyses - blood vessels migrate into ephiphyses carrying osteoblasts Grows in length |
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Periosteum |
Peripherlaly adds new bone material Fibrous sheath that covers bone Arises by condensation of mesechyme that forms perichondrial sheath around cartilage Connective tissue, capillaries and bone progenitor cells that form osteoblasts Cause bone growth in width |
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Osteocyte Osteoblast Osteoprogenitor cell Oseoclast |
mature bone cell that maintains the bone matrix immature bone cell that secretes matrix stem cell that produces osteoblasts secretes acids and enzymes to disolve bone matrix |
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Longitudinal bone development |
1. Fetal hyaline cartilage model develops 2. Cartialge calcifies, periosteal bone colar forms 3. Primary ossification center -diaphysis 4. Secondary ossification centres - epiphyses 5. Bone replaces cartilage 6. Epiphyseal plates ossify, form epi. lines |
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Epiphyseal plate |
Expression of runx2 is critical in development of intramembranous and endochondral bone Indian hedgehog causes prechondrocyte to produce runx2 by repressing its inhibitor twist |
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Osteoporosis |
1/4 women post meopausal 1/8 men - age related Drastic increase in morbidity major health care costs |
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Respecification of sclerotome forming vertebra |
Outgrowth of segmental spinal neurons splits sclerotome into rostral and caudal Posterior and anterior of cut sclerotome combine to form vertebral rudiment that becomes vertebra - resegmentation Enables innervation of muscles |
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Tendon formation |
arise from syndetome most dorsal part of sclerotome next to myotome express scleraxis gene |
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Iduction of sceraxis |
by FGF8 syndetome established after myotome and dermatome fgf is received from myotome |
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Urogenital system |
formation of kidney and gonads and duct systems intermediate mesoderm interacts with paraxial mesoderm Kidney - pax2,pax8,lim1, induced by paraxial mesoderm If paraxial and intermediate mesoderms were separated then no kidneys would form |
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Pronephros |
Intermediate mesoderm Nephrogenic cord MET Nephric duct Grows A-P Induces surrounding nephrogenic cords to form new tubules of initial kidney |
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Mesonephros |
anterior pronephros degenerates middle induces new tubules, will eventually degenerate capable of urine filtration |
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Metanephros |
posterior is metanephrogenic mesenchyme induces ureteric buds from nephric duct starts forming permanent kidney |
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Reciprocal inductive interactions |
ureteric bud and metanephric mesenchyme RA Hox genes in metanephric mesenchyme secrete growth factors for ureteric buds and have growth factor receptors that collect growth factors from ureteric buds that stimulate growth and differentiation into glomeruli and kidney tubules GDNF-glial derived neurotrophic factor |
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Terminal hindgut |
ends in cloaca - an endoderm lined chamber, contacts ectoderm and allantois Ventral cloaca - develops into bladder and urogenital sinus |
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Positional specification |
1. Foxc1, foxc2 regulate metanephrogenic mesenchyme specification 2. Hoxa11, hoxc11, hoxd11 required to induce the ureteric bud 3. wt1 required to respond to the ureteric bud |
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Metanephrogenic mesenchyme secretes GDNF |
Induce and direct ureteric bud vital for growth and expression |
