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17 Cards in this Set
- Front
- Back
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what is the primary time period in which limbs develop |
3-8 weeks upper limb bud primordium at day 24 lower limb bud primordium at day 26 |
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progression of arm and hand elongates to hand paddle move to midline, touch at 52 days, clasp at 56 bud at first to elongated digits |
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describe the apical ectodermal ridge |
AER limb inducer mesoderm surrounded by thin ectoderm, end tip is AER |
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describe the proximodistal axis development |
signaling center: AER molecular signal: FGF |
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what is the significance of the age of the mesoderm in the bud |
take ectodermal cap and put on old mesoderm, only get distal elements develop from shoulder to fingertips so if at fingertip age, will only grow fingertips |
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induction of new limbs put FGF soaked bead near bud and get a mirror image limb |
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what are some limb defects |
amelia: absence of 1 or more limbs meromelia: absence of part of a limb phocomelia: short, ill formed limb hemimelia: short distal limb AER or FGF issues |
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describe teratogens |
thalidomide (antinausea drug, now cancer)-- phocomelia valproic acid (epilepsy, bipolar, migrains)-- digit hypoplasia varicella virus-- limb hypoplasia |
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what specifies arms vs. legs? |
little is known cells are similar tbx 5 in arms, 4 in legs? |
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describe the craniocaudal axis (anterioposterior) development |
signaling center: zone of polarizing activity (ZPA) molecular signal: retinoic acid, sonic hedgehog ZPA controls it, sonic hedgehog induced by retinoic acd |
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describe some digit defects |
brachydactyly: short digits syndactyly: fused digits polydactyly: many digits adactyly: absence of all digits ectrodactyly: absence of one or more digits |
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describe the dorsoventral axis development |
signaling center: dorsal ectoderm, ventral ectoderm molecular signal: WNT7A (dorsal), EN1 (ventral) |
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describe limb rotations |
development of 2 joints rotations |
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describe digit differentiation |
tissue fan programmed apoptosis, frees digits |
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describe amniotic sac issues |
amniotic bands limb constriction digit/limb amputation not enough fluid, too constricting= club foot arthrogryposis: congenital joint contractions |
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describe tissue development |
neural tube, somite breaks down into sclerotome and dermomyotome hypomere forms limbs bone morphogenic proteins and sonic hedgehog nerves extend as limbs develop vasculature off aorta, back to cardinal vein |
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describe joint formation |
3 classes fibrous (skull structures)- little or no movement cartilagenous (pelvic)- cells differentiate into fibrocartilage synovial (shoulder, elbow, knee)- mesenchyme between bones into 3 layers= capsules and ligaments start as one long bone, joint forms in middle |
