Aspartame is the most controversial food additive in history, and its approval for use in food was the most contested in FDA history. In the end, the artificial sweetener was approved, not on scientific grounds, but rather because of strong political and financial pressure.
The arterioles then divide further into capillaries. Capillaries are the smallest blood vessels and their walls are only one cell thick which allows diffusion between the blood and cells to occur. Nutrients and oxygen from the blood diffuses through the capillary walls into the tissues that need it. This is aided by the relatively high blood pressure that also squeezes the oxygen and nutrients through the capillary wall and into the cells of the tissue.
The arteries are the blood vessels that deliver oxygen-rich blood from the heart to the tissues of the body. Each artery is a muscular tube lined by smooth tissue and has three layers:1  The intima, the inner layer lined by a smooth tissue called endothelium. 2014 WebMD, LLC. All rights reserved. The arteries are the blood vessels that deliver oxygen-rich blood from the heart to the tissues of the body. Each artery is a muscular tube lined by smooth tissue and has three layers: 1  The intima, the inner layer lined by a smooth tissue called endothelium.