page_title: Artery
section_title: Structure
hierarchical_section_title: Artery / Structure
caption_attribution_description: English: Cross of a human artery
context_page_description: An artery is a blood vessel that takes blood away from the human heart to all parts of the body. Most arteries carry oxygenated blood; the two exceptions are the pulmonary and the umbilical arteries, which carry deoxygenated blood to the organs that oxygenate it. The effective arterial blood volume is that extracellular fluid which fills the arterial system.
  The arteries are part of the circulatory system, which is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, the maintenance of optimum blood pH, and the circulation of proteins and cells of the human immune system
context_section_description: The anatomy of arteries can be separated into gross anatomy, at the macroscopic level, and microanatomy, which must be studied with a microscope. The arterial system of the human body is divided into systemic arteries, carrying blood from the heart to the whole body, and pulmonary arteries, carrying deoxygenated blood from the heart to the lungs.
  The outermost layer of an artery (or vein) is known as the tunica externa, also known as tunica adventitia, and is composed of collagen fibers and elastic tissue - with the largest arteries containing vasa vasorum (small blood vessels that supply large blood vessels). Most of the layers have a clear boundary between them, however the tunica externa has a boundary that is ill-defined. Normally its boundary is considered when it meets or touches the connective tissue.  Inside this layer is the tunica media, or media, which is made up of smooth muscle cells, elastic tissue (also called connective tissue proper) and collagen fibres. The innermost layer, which is in direct contact with the flow of blood, is the tunica intima, commonly called the intima. The elastic tissue allows the artery to bend and fit through places in the body. This layer is mainly made up of endothelial cells (and a supporting layer of elastin rich collagen in elastic arteries). The hollow internal cavity in which the blood flows is called the lumen.
caption: Cross-section of a human artery
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