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embryo - 14d limbs move at shoulder 15d elbow and wrist...

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NEUROEMBRYOLOGY OF THE CHICK, RAT and HUMAN CHICK 23h neural plate 28h neural groove 31h neural tube cervical proliferation begins 60h 1st axons leave cord 72h 1st neuromuscular junctions spinal ganglia differentiate 84h onset of motility 4d cell death begins inhibitory receptors present 5d limbs move ventral proliferation ends sensory axons reach skin and spinal cord 6d 1st synapses seen in cord peak of dorsal proliferation S-waves of motility (intersegmental connections) 7d closure of reflex arcs coordinated leg activity 8d reflex arcs throughout cord 9d all proliferation ends 10d 1st evidence of inhibitory synapses brain influences spinal activity 13d motility peaks 15d cerebellar function begins respiration begins 17d onset of prehatching behavior 1st evidence of forebrain function responds to light, sound, vibration 18d activity declines greatly 19d hatching sequence begins 20d hatching RAT 7d neural plate 8d neural groove 9d neural tube 11d cervical proliferation begins 12d lumbar proliferation begins 14d limbs move at shoulder
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Unformatted text preview: 14d limbs move at shoulder 15d elbow and wrist move lateral bending of neck 16d closure of reflex arcs swallowing observed 18d motility peaks oral capture of artificial nipple 19d more vigorous, less frequent activity facial wiping to quinine (chemosensation) 20d activity declines greatly stretch response to milk infusion 21d birth The Appearance of Fetal Movements in Early Pregnancy Movement Gestation of First Appearance (wks) Heartbeat 6 Any movement 7 Startle 8 Generalized movements 8 Hiccups 8 First cutaneous sensitivity (cheek) 8 Isolated arm movements 9 Head retroflexion 9 Hand—face contact 10 Breathing 10 Jaw opening 10 Stretching 10 Head anteflexion 10 Swallow 10 Cutaneous sensitivity (palms) 11 Yawn 11 Suck 12 Cutaneous sensitivity (soles) 12 First detection of movement by mother 16 Circadian rhythmicity 20-22 Gross activity increases from 8 to 14-19 weeks, and then from 16-32 weeks, declines...
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