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Related Concept Videos

Structure of Cardiac Muscles01:13

Structure of Cardiac Muscles

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Cardiac muscle, or myocardium, is a specialized type of muscle found exclusively in the heart. Its unique structural and functional characteristics enable the heart to perform its vital role of pumping blood throughout the body continuously and rhythmically. The cardiac muscle cells, or cardiomyocytes, possess an endomysium and perimysium but do not have an epimysium.
Compared to skeletal muscles, cardiac muscle cells are small and mostly have a single nucleus. Additionally, they are usually...
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Specialized Characteristics of Cardiac Muscles01:27

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The primary role of cardiac muscles is to propel blood throughout the cardiovascular system. The cardiac muscle cells, or cardiomyocytes, exhibit specialized characteristics that allow them to perform this function.
Cardiac muscle cells are smaller than skeletal muscles, averaging 10–20 mm in diameter and 50–100 mm in length. However, they have large energy demands for continuous contraction and relaxation. This energy is almost exclusively derived from aerobic metabolism of energy...
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Electrophysiology of Normal Cardiac Rhythm01:19

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The normal cardiac rhythm is a synchronized electrical activity that facilitates the regular and coordinated contraction of the heart muscle. This process is essential for efficient blood circulation throughout the body. The fundamental elements involved in establishing and maintaining this rhythm include the unique electrical properties of cardiac muscle cells, the sinoatrial (SA) node's pacemaker function, the specialized conducting system, and the ionic mechanisms underlying each phase...
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Layers of the Heart Wall01:15

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The heart wall comprises three distinct layers: the epicardium, myocardium, and endocardium. The outermost layer, the epicardium, is the visceral layer of the serous pericardium, featuring a thin, transparent mesothelial surface and an inner layer of areolar connective tissue with fat deposits that increase with age.
The myocardium, the thickest layer, consists of cardiac muscle cells interconnected by intercalated discs and crisscrossing connective tissue fibers. These muscle fibers contract...
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Cardiac Action Potential01:30

Cardiac Action Potential

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Cardiac action potentials are essential for proper heart function, enabling the rhythmic contractions needed for adequate blood circulation. Nodal cells and Purkinje fibers, specialized for electrical conduction, generate these action potentials.
The cardiac action potential process involves a series of phases characterized by the movement of ions across the cardiac cell membranes, leading to the depolarization and repolarization of the cardiac myocytes.
Ionic Basis of Cardiac Action Potentials
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Anatomy of the Heart01:27

Anatomy of the Heart

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The human heart is made up of three layers of tissue that are surrounded by the pericardium, a membrane that protects and confines the heart. The outermost layer, closest to the pericardium, is the epicardium. The pericardial cavity separates the pericardium from the epicardium. Beneath the epicardium is the myocardium, the middle layer, and the endocardium, the innermost layer. There are four chambers of the heart: the right atrium, the right ventricle, the left atrium, and the left ventricle.
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Updated: Mar 29, 2026

Construction of Defined Human Engineered Cardiac Tissues to Study Mechanisms of Cardiac Cell Therapy
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Construction of Defined Human Engineered Cardiac Tissues to Study Mechanisms of Cardiac Cell Therapy

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Revisiting Cardiac Cellular Composition.

Alexander R Pinto1, Alexei Ilinykh2, Malina J Ivey2

  • 1From the Australian Regenerative Medicine Institute, Monash University, Melbourne, Victoria, Australia (A.R.P., A.I., R.D., A.C., L.W., N.R.); Department of Medicine, Center for Cardiovascular Research (M.J.I., J.T.K., M.L.D'A., K.A., M.D.T.) and Department of Cellular and Molecular Biology (M.J.I., J.T.K.), University of Hawaii, Honolulu, HI; National Heart and Lung Institute, Imperial College London, London, United Kingdom (N.A.R.); and The Jackson Laboratory, Bar Harbor, ME (N.A.R.). michelle.tallquist@hawaii.edu alex.pinto@monash.edu.

Circulation Research
|December 5, 2015
PubMed
Summary
This summary is machine-generated.

Cardiac endothelial cells are the most abundant heart cells, not fibroblasts. This finding reframes understanding of heart cell composition and function, crucial for tissue engineering and regeneration research.

Keywords:
endothelial cellsfibroblastsflow cytometryheartleukocytes

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Area of Science:

  • Cardiovascular Biology
  • Cellular and Molecular Medicine
  • Regenerative Medicine

Background:

  • Understanding heart cellular composition is vital for pathogenesis research.
  • Accurate cell frequency data is essential for cardiac tissue engineering and regeneration strategies.

Purpose of the Study:

  • To quantify the relative frequencies of cardiac endothelial cells, hematopoietic-derived cells, and fibroblasts in mouse and human hearts.
  • To refine existing estimates of nonmyocyte cell populations within the heart.

Main Methods:

  • Utilized genetic tools and cellular markers for cell identification.
  • Employed immunohistochemistry to determine cell proportions.
  • Applied refined cell isolation and flow cytometry for independent abundance assessment.
  • Performed high-dimensional analysis and unsupervised clustering for population confirmation.

Main Results:

  • Endothelial cells represent over 60% of nonmyocytes in the adult mouse heart.
  • Hematopoietic-derived cells comprise 5-10%, and fibroblasts less than 20%.
  • Fibroblast numbers are lower than previously estimated; Sca-1 and CD90 markers under-represent their population.
  • An alternative fibroblast surface marker was identified for more accurate identification.

Conclusions:

  • Fibroblasts constitute a minor population within the heart's noncardiomyocytes.
  • Endothelial cells are the predominant noncardiomyocyte type, suggesting a more significant role in cardiac physiology and injury response.
  • This study provides a revised perspective on cardiac cellular composition, impacting future research in heart disease and regeneration.