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 three germ consiting of Ectoderm, mesoderm and endoderm give rise to all the organs and structures in the body. The list of structures developed from 3 primitive germ layers in given below.Developing embryo.he three germ consiting of Ectoderm, mesoderm and endoderm give rise to all the organs and structures in the body. The list of structures developed from 3 primitive germ layers in given below. Developing embryo.