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 cardiomyocytes 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. By contrast, skeletal muscle consists of multinucleated 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.{{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}} 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 cells. The three types of cell junction recognised as making up an intercalated disc are desmosomes, fascia adherens junctions, and gap junctions.{{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 }}
- Fascia adherens are anchoring sites for actin, and connect to the closest sarcomere.{{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}}
- Desmosomes prevent separation during contraction by binding intermediate filaments, anchoring the cell membrane to the intermediate filament network, joining the cells together.
- Gap junctions connect the cytoplasms of neighboring cells electrically allowing cardiac action potentials to spread between cardiac cells by permitting the passage of ions between cells, producing depolarization of the heart muscle.
All of these junctions work together as a single unit called the area composita.
Clinical significance
Mutations in the intercalated disc gene are responsible for various cardiomyopathies that can lead to heart failure.
File:Histopathology of ruptured intercalated discs.jpg.]]
Ruptured intercalated discs, when seen on histopathology, have two main causes:
- Microtome sectioning, thereby being a visual artifact.[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}}
- Forceful myocardial contraction, in turn mainly caused by ventricular fibrillation[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}} or electrical injury.{{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}}
Additional signs indicating forceful myocardial contraction are:
- Alternating bundles of hypercontracted myocytes with hyperdistended ones.
- Square-shaped myocardiocyte nuclei.
- Hyperdistended myocardiocytes with detached sarcomeres, and in proximity of hypercontracted myocardiocytes.
File:Cardiac myofiberbreak-up -- very high mag.jpg|Square-shaped nuclei, indicating forceful myocardial contraction.
References
{{Reflist}}
External links
- {{BUHistology|22502loa}} — "Ultrastructure of the Cell: cardiac muscle, intercalated disk "
{{Muscle tissue}}
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