Embryo 36 Day Old Showing Limb Bud
Computer Generated Image from Micro-MRI, actual size of embryo = 6.0 mm. This image provides a left-sided perspective of the developing embryo at six weeks. The age is calculated from the day of fertilization. The spinal cord can be seen here as well as the ridges beside it, which are the nerve endings. Distinct regions of the hand, forearm and arm can be discerned in the upper and lower limb region. The lower limb bud has begun to round off and will eventually form the foot. The distal portions of the limb buds become flattened to form the hand plates and footplates. Fingers and toes will develop when a process called cell death separates the these structures into five distinct parts.