Editing Artery (section)

==Structure==
[[File:Blausen 0055 ArteryWallStructure.png|thumb|Microscopic anatomy of an artery]]
[[File:Artery.png|thumbnail|Cross-section of a human artery]]
{{See also|Arterial tree}}

The anatomy of arteries can be separated into [[gross anatomy]], at the [[macroscopic scale|macroscopic level]], and [[histology|microanatomy]], which must be studied with a [[microscope]]. The arterial system of the [[human body]] is divided into [[systemic circulation|systemic arteries]], carrying blood from the heart to the whole body, and [[pulmonary artery|pulmonary arteries]], carrying deoxygenated blood from the [[heart]] to the [[lung]]s.

Large arteries (such as the aorta) are composed of many different types of cells, namely endothelial, smooth muscle, fibroblast, and immune cells.<ref>{{Cite journal |last1=Scipione |first1=Corey A. |last2=Hyduk |first2=Sharon J. |last3=Polenz |first3=Chanele K. |last4=Cybulsky |first4=Myron I. |date=December 2023 |title=Unveiling the Hidden Landscape of Arterial Diseases at Single-Cell Resolution |url=https://linkinghub.elsevier.com/retrieve/pii/S0828282X2301663X |journal=Canadian Journal of Cardiology |language=en |volume=39 |issue=12 |pages=1781–1794 |doi=10.1016/j.cjca.2023.09.009|pmid=37716639 |url-access=subscription }}</ref> As with veins, the arterial wall consists of three layers called tunics, namely the ''[[tunica intima]]'', ''[[tunica media]]'', and ''[[tunica externa]]'', from innermost to outermost. The ''externa'', alternatively known as the ''tunica adventitia'', is composed of [[collagen]] fibers and [[elastic tissue]]—with the largest arteries containing [[vasa vasorum]], small blood vessels that supply the walls of large blood vessels.<ref name=":1">{{Cite web |last1=Steve|first1=Paxton|last2=Michelle|first2=Peckham|last3=Adele|first3=Knibbs|date=2003|title=The Leeds Histology Guide|url=https://www.histology.leeds.ac.uk/circulatory/arteries.php|language=en}}</ref> 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.<ref>{{Cite book|title=Rutherford's Vascular Surgery and Endovascular Therapy|last=Sidawy|first=Anton|publisher=Elsevier, Inc.|year=2019|isbn=9780323427913|location=Amsterdam, Netherlands|pages=34–48}}</ref>  Inside this layer is the ''tunica media'', which is made up of [[smooth muscle]] cells, [[elastic tissue]] (also called ''connective tissue proper'') and [[collagen]] fibres.<ref name=":1" /> The innermost layer, which is in direct contact with the flow of blood, is the ''tunica intima''. The elastic tissue allows the artery to bend and fit through places in the body. This layer is mainly made up of [[endothelium|endothelial cell]]s (and a supporting layer of [[elastin]] rich [[collagen]] in elastic arteries). The hollow internal cavity in which the blood flows is called the [[lumen (anatomy)|lumen]].

===Development===
{{Further|Angiogenesis|Vasculogenesis}}
Arterial formation begins and ends when [[endothelial cell]]s begin to express arterial specific genes, such as [[EPH receptor B2|ephrin B2]].<ref>{{cite journal|last=Swift|first=MR|author2=Weinstein, BM|title=Arterial-venous specification during development.|journal=Circulation Research|date=Mar 13, 2009|volume=104|issue=5|pages=576–88|pmid=19286613|doi=10.1161/CIRCRESAHA.108.188805|doi-access=free}}</ref>