FIGURE 1-25 All organs are organized arrangements of various tissues, as illustrated in this cross section of a small artery (arteriole). Blood flows through the vessel lumen, which is lined by a thin sheet of endothelial cells forming the endothelium and by the underlying basal lamina. This tissue adheres to the overlying layer of smooth muscle tissue; contraction of the muscle layer controls blood flow through the vessel. A fibrillar layer of connective tissue surrounds the vessel and connects it to other tissues.

[SPL/Science Source.]