Cardiac muscle

Cardiac muscle
Cardiac muscle
Details
Part of	The heart wall
Identifiers
Latin	textus muscularis striatus cardiacus
MeSH	D009206
TA98	A12.1.06.001
TA2	3950
FMA	9462
	Anatomical terminology

Cardiac muscle (also called heart muscle or myocardium) is one of three types of vertebrate muscle tissues, with the other two being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The cardiac muscle (myocardium) forms a thick middle layer between the outer layer of the heart wall (the pericardium) and the inner layer (the endocardium), with blood supplied via the coronary circulation. It is composed of individual cardiac muscle cells joined by intercalated discs, and encased by collagen fibers and other substances that form the extracellular matrix.

Cardiac muscle contracts in a similar manner to skeletal muscle, although with some important differences. Electrical stimulation in the form of a cardiac action potential triggers the release of calcium from the cell's internal calcium store, the sarcoplasmic reticulum. The rise in calcium causes the cell's myofilaments to slide past each other in a process called excitation-contraction coupling. Diseases of the heart muscle known as cardiomyopathies are of major importance. These include ischemic conditions caused by a restricted blood supply to the muscle such as angina, and myocardial infarction.