First, “epithelial tissue is tissue that covers surfaces exposed to external environment” (Krogh, 2011, p. 484). This tissue serves as a barrier for the skin, they also transport tissue that materials are moving across. The epithelial tissue may be a number of cells thick or thin that serves a different function. For example, “the food that enters the bloodstream does so by being transported across the epithelial tissue that lines your small intestines” (Krogh, 2011, p.484). Second, is connective tissue, it is “tissue that stabilizes and support other tissue” (Krogh, 2011, p.484). These tissues are used to connect bodily structures and their support and stabilization. Additionally, connective tissue is never exposed to the environment. The function of this tissue is to produce extracellular material that separate cells. Third, is muscle tissue, which “is tissue that is specialized in its ability to contract or shorten” (Krogh, 2011, p. 484). This type of tissue comes in three forms skeletal, cardiac, and smooth muscle. Each muscle tissue is different in their structure and in the way in which they contract. Skeletal muscle is attached to bone, such as our biceps, cardiac muscle exist only in the heart, and smooth muscle makes up the digestive tract and blood vessels. Last, is the nervous tissue, “tissue that is specialized for the rapid conduction of messages” (Krogh, …show more content…
Gastrulation “is a process in early development in which an embryo’s cells migrate to form three layers of tissue: the endoderm, the mesoderm, and the ectoderm” (Krogh, 2011, p. 620). The movement of cells during this phase will help to develop the embryo. After all movement has been completed, the cells will configure themselves into the three different layers. Each of these layers will have an assign role in the inside, outside, and the middle of the process. The three layers will help to develop tissues and organs. Starting on the blastula’s vegetal pole, cells at pole will detach from the ring of blastula cells and move to the blastocoel. The movement of the cells will cause the vegetal pole to pinch inward, moving the vegetal pole halfway towards the animal pole. The development of an archenteron begins to form, the cells growing around the archenteron will send out small extensions of themselves. The contractions from the extensions will pull the archenteron towards the animal pole. After the archenteron reaches the rim of the blastocoel, the development of a feature will occur from the fusion of the two structures. The development of a tube will begin to develop, running down the vegetal pole. There are cells that will carry the archenteron to the blastocoel, upon arrival they will break away and move back into the cavity of the blastocoel. The