Editing Intercalated disc

{{Short description|Microscopic feature of cardiac muscle}}
{{Infobox microanatomy
| Name        = Intercalated disc
| Latin       = discus intercalaris, discus intercalatus
| Image       = Glanzstreifen.jpg
| Caption   = [[Cardiac muscle]], an intercalated disc can be seen joining [[cardiomyocyte]]s in magnified section
| Image2      = 1020 Cardiac Muscle.jpg
| Caption2    = Intercalated discs, desmosomes and gap junctions in cardiac muscle fiber.
| Precursor   =
| System      =
| PartOf = [[Cardiac muscle]]
}}
'''Intercalated discs''' or '''lines of Eberth''' are microscopic identifying features of [[cardiac muscle]]. Cardiac muscle consists of individual heart muscle cells ([[cardiomyocytes]]) connected by intercalated discs to work as a single functional [[Syncytium#Cardiac muscle|syncytium]]. By contrast, skeletal muscle consists of [[multinucleate]]d muscle fibers and exhibits no intercalated discs. Intercalated discs support synchronized contraction of cardiac tissue in a wave-like pattern so that the heart can work like a pump.<ref name="Openstax Anatomy & Physiology attribution">{{CC-notice|cc=by4|url=https://openstax.org/books/anatomy-and-physiology/pages/10-7-cardiac-muscle-tissue}} {{cite book|last1=Betts|first1=J Gordon|last2=Desaix|first2=Peter|last3=Johnson|first3=Eddie|last4=Johnson|first4=Jody E|last5=Korol|first5=Oksana|last6=Kruse|first6=Dean|last7=Poe|first7=Brandon|last8=Wise|first8=James|last9=Womble|first9=Mark D|last10=Young|first10=Kelly A|title=Anatomy & Physiology|location=Houston|publisher=OpenStax CNX|isbn=978-1-947172-04-3|date=June 8, 2023|at=10.7 Cardiac muscle tissue}}</ref> They occur at the Z line of the [[sarcomere]] and can be visualized easily when observing a longitudinal section of the tissue.

==Structure==
Intercalated discs are complex structures that connect adjacent [[cardiac muscle cell]]s. The three types of [[cell junction]] recognised as making up an intercalated disc are [[desmosome]]s, [[Fascia adherens|fascia adherens junctions]], and [[gap junction]]s.<ref name="Zhao">{{cite journal |last1=Zhao |first1=G |last2=Qiu |first2=Y |last3=Zhang |first3=HM |last4=Yang |first4=D |title=Intercalated discs: cellular adhesion and signaling in heart health and diseases. |journal=Heart Failure Reviews |date=January 2019 |volume=24 |issue=1 |pages=115–132 |doi=10.1007/s10741-018-9743-7 |pmid=30288656|s2cid=52919432 }}</ref>

* [[Fascia adherens]] are anchoring sites for [[actin]], and connect to the closest sarcomere.<ref name=":0">{{Citation|last=Feher|first=Joseph|title=5.7 - The Cellular Basis of Cardiac Contractility|date=2012-01-01|url=http://www.sciencedirect.com/science/article/pii/B9780128008836000513|work=Quantitative Human Physiology (Second Edition)|pages=547–555|editor-last=Feher|editor-first=Joseph|place=Boston|publisher=Academic Press|language=en|doi=10.1016/b978-0-12-800883-6.00051-3|isbn=978-0-12-800883-6|access-date=2020-12-28|url-access=subscription}}</ref>
* [[Desmosome]]s prevent separation during contraction by binding [[intermediate filament]]s, anchoring the cell membrane to the intermediate filament network, joining the cells together. <ref name="Zhao"/><ref name=":0" />
* [[Gap junctions]] connect the cytoplasms of neighboring cells electrically allowing [[cardiac action potential]]s to spread between cardiac cells by permitting the passage of ions between cells, producing [[depolarization]] of the heart muscle.<ref name=":0" /><ref name="Zhao"/>

All of these junctions work together as a single unit called the '''area composita'''.<ref name="Zhao"/>

==Clinical significance==
Mutations in the intercalated disc gene are responsible for various [[cardiomyopathies]] that can lead to [[heart failure]].<ref name="Zhao"/>
[[File:Histopathology of ruptured intercalated discs.jpg|thumb|Ruptured intercalated discs, in this case regarded as a [[visual artifact]].]]
Ruptured intercalated discs, when seen on [[histopathology]], have two main causes:
*[[Microtome]] sectioning, thereby being a [[visual artifact]].<ref>[https://books.google.com/books?id=7SxiDwAAQBAJ&pg=PA38 Page 38] in: {{cite book|title=The Etiopathogenesis of Coronary Heart Disease: A Heretical Theory Based on Morphology, Second Edition|author=Giorgio Baroldi|publisher=CRC Press|year=2004|isbn=9781498712811}}</ref>
*Forceful myocardial contraction, in turn mainly caused by [[ventricular fibrillation]]<ref name=Fineschi2016>[https://books.google.com/books?id=PcsqBgAAQBAJ&pg=PA55 Page 55] in: {{cite book|title=Pathology of the Heart and Sudden Death in Forensic Medicine|author=Vittorio Fineschi, Giorgio Baroldi, Malcolm D. Silver|publisher=CRC Press|year=2016|isbn=9781420006438}}</ref> or [[electrical injury]].<ref name="FineschiKarch2005">{{cite journal|last1=Fineschi|first1=Vittorio|last2=Karch|first2=Steven B.|last3=D'Errico|first3=Stefano|last4=Pomara|first4=Cristoforo|last5=Riezzo|first5=Irene|last6=Turillazzi|first6=Emanuela|title=Cardiac pathology in death from electrocution|journal=International Journal of Legal Medicine|volume=120|issue=2|year=2005|pages=79–82|issn=0937-9827|doi=10.1007/s00414-005-0011-8|pmid=16078070|s2cid=24759863}}</ref>
Additional signs indicating forceful myocardial contraction are:<ref name=Fineschi2016/><ref name="FineschiKarch2005"/>
*Alternating bundles of hypercontracted myocytes with hyperdistended ones.
*Square-shaped myocardiocyte nuclei.
*Hyperdistended myocardiocytes with detached sarcomeres, and in proximity of hypercontracted myocardiocytes.
<gallery>
File:Cardiac myofiberbreak-up -- very high mag.jpg|Square-shaped nuclei, indicating forceful myocardial contraction.
</gallery>

==References==
{{Reflist}}

==External links==
* {{BUHistology|22502loa}} — "Ultrastructure of the Cell: cardiac muscle, intercalated disk "

{{Muscle tissue}}
{{Authority control}}

[[Category:Cardiac anatomy]]