Editing Angiogenesis (section)

===Intussusceptive angiogenesis===
{{main|Intussusceptive angiogenesis}}
[[Intussusceptive angiogenesis]], also known as ''splitting angiogenesis'', is the formation of a new blood vessel by splitting an existing blood vessel into two.

Intussusception was first observed in [[neonatal]] rats. In this type of vessel formation, the capillary wall extends into the [[lumen (anatomy)|lumen]] to split a single vessel in two. There are four phases of intussusceptive angiogenesis. First, the two opposing capillary walls establish a zone of contact. Second, the [[endothelial]] [[cell junction]]s are reorganized and the vessel [[bilayer]] is [[perforated]] to allow [[growth factors]] and cells to penetrate into the lumen. Third, a core is formed between the 2 new vessels at the zone of contact that is filled with [[pericyte]]s and [[myofibroblast]]s. These cells begin laying [[collagen]] fibers into the core to provide an [[extracellular matrix]] for growth of the vessel lumen. Finally, the core is fleshed out with no alterations to the basic structure. Intussusception is important because it is a reorganization of existing cells. It allows a vast increase in the number of [[capillaries]] without a corresponding increase in the number of [[endothelial cell]]s. This is especially important in embryonic development as there are not enough resources to create a rich [[Microcirculation|microvasculature]] with new cells every time a new vessel develops.<ref name="Burri2004">{{cite journal | vauthors = Burri PH, Hlushchuk R, Djonov V | title = Intussusceptive angiogenesis: its emergence, its characteristics, and its significance | journal = Developmental Dynamics | volume = 231 | issue = 3 | pages = 474–488 | date = November 2004 | pmid = 15376313 | doi = 10.1002/dvdy.20184 | s2cid = 35018922 | doi-access = free }}</ref>