Prenatal development

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Prenatal development

Growth and development before birth are the most dramatic

Foetal Development:
• Weeks 0-4: Early development of CNS; heart forms and begins to beat
• Weeks 4-8: Early development of organs; Facial features form; external genitalia appear
• Weeks 8-12: Fusion of eyelids; kidney begin to function (urine is excreted); circulation functions; sucking and swallowing starts
• Weeks 12-16: Development of skeleton
• Weeks 16-20: Finger nails appear
• Weeks 20-24: Foetus becomes viable; most organs functioning; has periods of sleep
• Weeks 24-28: Eyelids open; some respiration
• Weeks 28-32: Fat and iron stored in body
• Weeks 32-36: Ear cartilage soft
• Weeks 36-40: Skull firm

Normal prenatal development of the lower limb:
Week: Changes:
1 After fertilisation and implantation, zygote rapidly divides to become a morula, then becomes a blastocyst (implants in posterior aspect of uterine wall)
2 Aminiotic cavity forms; endoderm and ectoderm appear
3 Mesoderm appears; organs begin to develop; neural plate closes to form neural tube
4 Neural folds fuse; limb buds appear
5 Foot plates appear; nerves to extremities develop
6 Limb perpendicular to torso
7 Lower limbs commence medial rotation towards 90°; feet in equinus and inversion; hallux 50° adducted; digital rays begin to appear with interdigital clefts; muscles appear; ossification points of femur and tibia appear
8 Distinction between thigh, leg and foot; ossification points of fibular appear; all basic organ development is complete
9 Osseous nuclei of metatarsals and phalanges appear; digits well developed; foot completely inverted (Week 9 is considered the end of the embryonic period and the start of the foetal period)
10 Dorsiflexion of foot begins
12 Arms and legs move independently of trunk; nails begin to form
16 Eversion of feet due to valgus torsion of talus and calcaneus commences
22 Toe nails lie in the dorsal position
32-34 Anterior transverse crease on sole of foot
36-38 Occasional creased on the anterior two thirds of foot
39-40 Sole covered with creases

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