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.
ectoderm. the outermost of the three primitive germ layers of the embryo; from it are derived the epidermis and epidermal derivatives, such as the claws, hair and glands of the skin, the nervous system, external sense organs (eye, ear, etc.) and mucous membrane of the mouth and anus.1  Facebook. 2  Twitter. the outermost of the three primary cell layers of an embryo. The ectoderm gives rise to the nervous system, the organs of special sense, the epidermis, and epidermal tissues such as fingernails, hair, and skin glands.