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.
Gastrulation of a diploblast: The formation of germ layers from a (1) blastula to a (2) gastrula. Some of the ectoderm cells (orange) move inward forming the endoderm (red).Micrograph of a teratoma, a tumour that characteristically has tissue from all three germ layers.The image shows tissue derived from the mesoderm (immature cartilage-left-upper corner of image), endoderm (gastrointestinal glands-center-bottom of image) and ectoderm (epidermis-right of image). H&E stain.he image shows tissue derived from the mesoderm (immature cartilage-left-upper corner of image), endoderm (gastrointestinal glands-center-bottom of image) and ectoderm (epidermis-right of image). H&E stain.