The Super-Specialized Heart Cell

The heart cell or the cardiac cell has a specialized structure in view of the super-specialized function it performs to help the heart to work in its unique fashion. Some heart cells form the connective tissue of the heart, some form the heart valves while some form the cardiac muscle or myocardium.

Heart Cell | Cardiac Cell

The cardiac muscle cells of the myocardium are called myocardiocyteal muscle cells or cardiomyocytes or just myocytes, which are formed from a basic layer of cells called the mesoderm from which other tissues are also formed such as bone and cartilage. A Myocyte is mononuclear (having one or two nuclei) like the cell of the smooth muscles.

Types of Heart Cells

For the purpose of understanding, heart cells or cardiac cells can be broadly classified into two types according to their properties and function.

1) Electrical Heart Cell

The electrical cardiac cells make up the electrical conduction system of the heart and are distributed in an orderly manner through the heart. They possess the following properties:

  • Automaticity – which means they spontaneously generate and conduct electrical impulses.
  • Excitability –  which means they are able to respond to an electrical impulse.
  • Conductivity – which means they are able to transmit the electrical impulse from one cell to another.

2) Cardiac Muscle Cell or Myocardial Cell

The cardiac muscle cells or the myocardial cells make up the muscular wall of the atria and the ventricles of the heart. They possess the following properties which enables the contraction and relaxation of the atria and ventricles.

  • Contractility is the ability of these cells to shorten and lengthen their fibers.
  • Ability to Stretch. These cells are capable of stretching.

Structure of Heart Cell

The heart cell is smaller than the skeletal muscle cell. It is irregular in shape and butted together with numerous blood vessels in between them. This creates an anastomosing network of fibers. Being small, the nucleus takes up a greater portion of its length.

The myocyte is the most energetic cell in the body contracting without a pause throughout life (about 3 billion times in an average life span. Read fascinating heart facts). Its appearance under a microscope reveals a structure full of striated myofibrils and mitochondria which then helps you understand its super specialization of energy dependent contractions.

Each myocardial cell contains long chains of sarcomeres which are contractile units of the muscle cell. They are called myofibrils. All the cardiomyocytes contract in unison and bring about the atrial and ventricle contractions.

T Tubules

T-tubules or transverse tubules are invaginations or furrows in the cell membrane which allow flow of calcium into the muscle cell and facilitate muscular contraction. In comparison to T-tubules in the skeletal muscle, those in the cardiac muscle are fewer but broader and larger.

Intercalated Discs (IDs)

An intercalated disc is a typical identifying feature of a cardiac muscle cell and absent in other muscles. Intercalated discs connect the cardiac muscle cells to each other to work as one functioning unit. They support the synchronized contraction of the heart muscles.

Under the microscope, intercalated discs appear as dark lines between adjacent cardiac muscle cells and run perpendicular to the muscle striations.

Picture of Heart cells

Heart cells.

Regeneration of Heart Cells

A study from Stockholm reported in 2009 that heart cells do regenerate. The researchers reported that heart muscle cells in a 20-year-old are renewed every year at a rate of 1% and just 0.45% in the 70 year group. By the age of 50 years, 45% of the heart muscle cells would have been regenerated. However this natural renewal process is slow and not enough to repair damage caused by a heart attack.

Making Heart Cells

Research is great which makes the researchers even greater. Heart cells (and other cells) are being made from skin cells which can make repair of any damaged tissue  a distinct possibility. Nearly ten years ago, beating cardiac cells were created from human embryonic stem cells in the laboratory.

“Israeli scientists have developed a way to create beating heart cells with skin cells reprogrammed to become stem cells, making it possible to one day clinically repair a damaged heart.” – http://www.israel21c.org/health/scientists-create-heart-cells-from-skin-cells.

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