Labster Logo

Cardiac Muscle

Cardiac muscle tissue is only found in the heart and is responsible for the involuntary, highly coordinated, contractions that pump blood into the vessels of the circulatory system. Cardiac muscle tissue is composed of cardiac muscle cells, also known as cardiomyocytes. These cells use aerobic metabolism almost exclusively which makes the heart highly resistant to fatigue.

Cardiac muscle cells are uninucliated, branching and striated in appearance. These cells are connected by regions called intercalated discs which contain gap junctions and desmosomes. Desmosomes prevent adjacent cells from separating during contraction, and so aid tissue stability. Gap junctions ensure that cardiac muscle contracts as a single unit by allowing ions to pass from cell to cell, transmitting current across the entire heart.

Diagram has three parts labeled a, b and c. Image A shows a schematic diagram of several cardiac muscle cells, with some in cross-section so the internal structure can also be seen. The cells are cylindrical, branching, and uninucleated. The cardiac muscle cells are joined by intercalated discs which contain gap junctions and desmosomes. Image B is a photomicrograph of the cardiac muscle cells. The cardiac muscle tissue appears striated due to the cardiac muscle cells being long and all aligned in the same direction. Cross-cutting the cardiac muscle cells are intercalated discs. These can be seen as vertical lines that cross perpendicular to the elongated cardiac cells. Image C is a schematic diagram showing a close-up of a cardiac cell with horizontal rows of sarcomeres, separated by mitochondria. At the junction between two cardiac cells, there is a winding white stripe called the intercalated disc. This intercalated disc contains desmosomes and gap junctions.

Figure 1. (a) Diagram of uninucleated cardiac muscle cells with numerous mitochondria for energy, and intercalated discs at cell junctions. (b) A photomicrograph of cardiac muscle cells shows the nuclei and intercalated discs. (c) Diagram of intercalated discs which connect cardiac muscle cells and consist of desmosomes and gap junctions.

Read more:

References: OpenStax College, Biology. (OpenStax CNX. Mar 13, 2015)