If the skin isn't as flexible (it will be in due time) then exercise could cause it to stretch quickly from increased blood flow. This quick stretch could explain the pins and needles feeling because the skin is quickly being pulled on the micro-level.
Definition. During development, most animals form a gastrula. A gastrula is an embryo that has undergone gastrulation, or the process that produces different germ layers. Germ layers are the initial tissue layers of an embryo, and animals can have up to three. 1  Ectoderm is the outermost layer of cells.
1 Formation of the neural tube consists of 3 successive stages of development. 2  THE NEURAL PLATE results from thickening and differentiation of ectoderm overlying the notochord.3  The ectoderm of the plate is called neuroectoderm and will give rise to the central nervous system, consisting of the brain and spinal cord. The neural crests: when the neural folds fuse and, before the neural groove closes completely, some neuroectodermal cells detach themselves from the region where the neural tube borders on the ectoderm (lateral edges of the neural plate).