About Cardiac Muscle

There are three main varieties of muscle tissue in the human body: skeletal, smooth and cardiac. Each is specialized for a different type of work, and cardiac muscle powers one of the most vital organs: the heart.

Skeletal and Smooth Muscle Tissue

• Skeletal muscles are under our conscious control and constitute our major muscle groups such as the biceps and quadriceps. They are constructed to handle large amounts of stress and have the ability to grow stronger through training. Similar to cardiac muscles, skeletal muscles have alternating sections of darker and lighter muscles known as striations, and these travel the length of the muscle. Skeletal muscles are composed of bundles of long, thin fibers called myofibrils.

  Your stomach, gastrointestinal tract, respiratory tract, veins and arteries are lined with smooth muscle. Instead of being striated, smooth muscle has the distinction of having a uniform appearance. Like cardiac muscle, this type of muscle is under the control of the autonomic nervous system, controlling involuntary bodily processes such as digestion and dilation of blood vessels. Cardiac muscle tissue falls in between these two other types, as it is the only striated, fully contracting muscle that is completely governed by the autonomic nervous system.

Identifying Cardiac Muscle Tissue

• One of the first signs that you are looking at cardiac muscle tissue is the appearance of striations. Unlike the parallel light and dark bands that cover skeletal muscle, under a microscope, cardiac muscle striations resemble branching and converging trails. In addition, most cardiac muscle tissue is bright red because of the oxygenated blood pumping through it; tissue from the left side of the heart is more of a deep purple color, because this side handles deoxygenated blood coming back into the heart from other areas of the body.

Cardiac Muscle

• Cardiac muscle tissue is only found in the heart. Like skeletal muscle, cardiac muscle is striated with dark and light bands of color, but in cardiac tissue, these bands tend to branch off instead of staying perfectly lateral. According to recent research, cardiac muscle tissue has the ability to regenerate cells, formerly thought impossible. As cardiac muscles contract, they force blood from the atria into arteries and blood vessels, fueling muscles and organs all over the body.

Special Features

• Cardiac muscles contain specialized cells known as pacemaker cells. These serve as a sort of metronome for the heart, keeping all cardiac tissues working in rhythm with each other. In order to keep these cells working in rhythm, the heart's muscle tissues are under complete control of the autonomic nervous system. Another unique feature of cardiac muscle is that it never tires; assuming no degradation of muscle tissue, a heart could conceivably keep beating for considerably longer than the average life span of about 80 years.

How the Heart Pumps Blood

• The heart is divided into an upper area called the atria and a lower portion called the ventricle. In addition, these are divided into left and right sides, creating four major chambers. Deoxygenated blood is pooled into the right atrium, and from there, the right ventricle pumps blood into the lungs to collect oxygen. The left atrium then recollects the newly oxygenated blood, which is pumped to the rest of the body by the left ventricle. Cardiac muscle is uniquely suited for these tasks because of its ability to maintain a steady rhythm with pacemaker cells and because cardiac muscle tissue can contract continuously for decades without ever tiring.