Table 2

Summary of limb development before birth in the tammar fetus

STAGE

FORELIMB

HINDLIMB


Day 18

Bud has formed with no defined shape as yet

Thickening of the hindlimb has occurred with a small protrusion as the beginnings of a bud

Day 19-21

Paddle like structure with the regions of the future digital rays beginning to form.

Elongation of the bud has occurred with no distinct structure

Day 22-23

Digital rays more pronounced and the interdigital tissue has begun to regress

The bud has formed into a flattened arrow-head like structure with the beginnings of the digital condensations. The pointed edge of the paddle appears to be the presumptive 4th digit

Day 23-24

Interdigital webbing has regressed. Epitrichial claws are present and fingers are open but not clenched. The distinct protrusion of the future elbow joint is beginning to form

The digital rays have begun to form and a distinct separation of the hindlimb digits begins. The interdigital webbing is reduced and an asymmetrical shape has started to form

Day 25

A well-defined forelimb with claws present with digits in a clenched position. The future elbow joint has become more pronounced

The interdigital webbing has regressed and all four digits are distinct. The 4th digit has become more pronounced and has an asymmetrical shape.


Chew et al. BMC Developmental Biology 2012 12:2   doi:10.1186/1471-213X-12-2

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