Editing Endocardium (section)

==Function== 
[[File:Endocardium and subendocardium histology.png|thumb|Histology of the endocardium and subendocardium.]]The endocardium, which is primarily made up of endothelial cells, controls myocardial function. This modulating role is separate from the [[Autoregulation|homeometric and heterometric regulatory mechanisms]] that control [[myocardial contractility]].<ref>{{cite journal |last1=Milgrom-Hoffman |first1=Michal |last2=Harrelson |first2=Zachary |last3=Ferrara |first3=Napoleone |last4=Zelzer |first4=Elazar |last5=Evans |first5=Sylvia M. |last6=Tzahor |first6=Eldad |title=The heart endocardium is derived from vascular endothelial progenitors |journal=Development |date=November 2011 |volume=138 |issue=21 |pages=4777–4787 |doi=10.1242/dev.061192 |pmid=21989917 |pmc=3190386 }}</ref> Moreover, the endothelium of the myocardial (heart muscle) capillaries, which is also closely appositioned to the cardiomyocytes (heart muscle cells), is involved in this modulatory role.<ref>{{Cite web |title=Endothelial Dysfunction |url=https://stanfordhealthcare.org/medical-conditions/blood-heart-circulation/endothelial-dysfunction.html |access-date=2023-02-23 |website=[[Stanford University|stanfordhealthcare.org]]}}</ref> Thus, the cardiac endothelium (both the endocardial endothelium and the endothelium of the myocardial capillaries) controls the development of the heart in the embryo as well as in the adult, for example during hypertrophy. Additionally, the contractility and electrophysiological environment of the cardiomyocyte are regulated by the cardiac endothelium.<ref>{{cite journal |last1=Brutsaert |first1=Dirk L. |last2=De Keulenaer |first2=Gilles W. |last3=Fransen |first3=Paul |last4=Mohan |first4=Puneet |last5=Kaluza |first5=Grzegorz L. |last6=Andries |first6=Luc J. |last7=Rouleau |first7=Jean-Lucien |last8=Sys |first8=Stanislas U. |title=The cardiac endothelium: Functional morphology, development, and physiology |journal=Progress in Cardiovascular Diseases |date=November 1996 |volume=39 |issue=3 |pages=239–262 |doi=10.1016/s0033-0620(96)80004-1 |pmid=8970576 }}</ref>

The endocardial endothelium may also act as a kind of blood–heart barrier (analogous to the [[blood–brain barrier]]), thus controlling the ionic composition of the extracellular fluid in which the [[cardiomyocytes]] bathe.<ref>{{cite book |last1=Dotiwala |first1=Ary K. |last2=McCausland |first2=Cassidy |last3=Samra |first3=Navdeep S. |title=StatPearls |date=2025 |publisher=StatPearls Publishing |chapter-url=http://www.ncbi.nlm.nih.gov/books/NBK519556/ |chapter=Anatomy, Head and Neck: Blood Brain Barrier |pmid=30137840 }}</ref>