**3.1. CNS anomalies**

**2.3. Development of upper and lower extremities**

26 Congenital Anomalies - From the Embryo to the Neonate

buds start to develop.

from the crurotarsal region.

• Carnegie stage 12: The upper limb buds begin to develop.

innervation begins in the lower limb buds as well.

notch on the rim of the foot plate is still incomplete.

are present between the toe rays in the foot plate.

feet are approaching each other at this stage.

closer.

The embryonic development of the limbs [1] is illustrated here using computer graphics [2].

• Carnegie stage 13: The upper limb buds gain more definite shape, while the lower limb

• Carnegie stage 14: The upper limb buds grow and taper toward the tip, which forms the hand plate later on. In the upper limbs, innervation and blood supply begin at this stage. The development of the lower limb buds is delayed with respect to the upper limb buds. • Carnegie stage 15: The hand plates in the upper limb buds have become distinct. In the lower limbs, the rostral half is rounded, whereas the caudal half is tapered. At this stage,

• Carnegie stage 16: The hand plates form a central part, a carpal part, and a digital flange,

• Carnegie stage 17: Finger rays can be recognized in the hand plate while the rim of the hand plate becomes crenated due to the appearance of individual fingers in some advanced specimens. The lower limb buds have increased in size and a rounded digital plate is set off

• Carnegie stage 18: The upper limbs have lengthened and are slightly bent at the elbow. Finger rays are distinct. As for the lower limb bud, toe rays begin to appear, although the

• Carnegie stage 19: The upper limbs rotate medially, as if to hold the chest. Apoptoses occur in the mesenchymal tissues of interdigital areas to create deeper interdigital notches in the

• Carnegie stage 20: The upper limbs are bent at the elbow and hand joints, resulting in a pronated position. Meanwhile, the lower limbs are also bent at the knee joints, and notches

• Carnegie stage 21: Elbows and knees become distinct in the upper and lower limbs, respectively. Hands are crossed over the chest. Meanwhile, fingers grow longer and distal phalangeal portions become slightly swollen, indicating the beginning of palmar pads. The

• Carnegie stage 22: Hands get larger in front of the body and fingers elongate, which may clasp over with those of the other hand. Although toe digits are still webbed, feet approach

• Carnegie stage 23: The upper and lower limbs have lengthened, well formed, and bent at joints. Fingers grow longer and toes cease to be webbed; all the digits are separate and distinct.

foot plate. Toe rays become prominent, and knees and ankles become noticeable.

whereas the lower limb buds form a femoral part, a crural part, and a foot plate.
