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.
The outermost of the three primary germinal layers of an embryo (the other layers being mesoderm and endoderm) from which the eye is derived. It differentiates into outer surface ectoderm and inner neuroectoderm, which gives rise to neural crest cells.he ectoderm gives rise to the nervous system; the organs of special sense, such as the eyes and ears; the epidermis and epidermal tissue, such as fingernails, hair, and skin glands; and the mucous membranes of the mouth and anus. See also embryo, endoderm, mesoderm. ectodermal, ectodermic, adj.