Anatomy of Smooth Muscle

What is a Smooth Muscle?

The human body contains three main types of muscular tissue: skeletal, cardiac, and smooth. Smooth muscle is a type of non-striated muscle that is common in the walls of hollow organs and blood vessels. However, smooth muscle can be found throughout the body but is most common around the digestive tract, in the walls of blood vessels, arteries, and around other organs such as the eyes.

As stated above, smooth muscle cells are not striated. This means they have no visible bands of contractile proteins like those found in skeletal muscles. These muscles are also involuntary, which means the contraction of these muscles is not dependent on conscious thought. They can contract in response to chemical or electrical signals, which they receive from autonomic nerves and hormones like epinephrine and vasopressin. Smooth muscle tissues are usually arranged as circular layers and tubes around the gut or as sheets between layers of connective tissue. Furthermore, this type of muscle has no more than one nucleus per cell.

The Role of Smooth Muscle

The vasculature system that transports blood throughout the body is controlled by smooth muscle. Smooth muscles contract to regulate blood pressure and other cardiovascular processes. They also aid in food digestion through peristalsis, which is the rhythmic wave-like contraction of muscles around the digestive tract.

Types of Smooth Muscle

There are two types of smooth muscle:

• Single-unit smooth muscle – Single-unit smooth muscle is another type of smooth muscle found in many organs, such as the stomach and intestines. It can be found both inside and outside these organ tissues.
• Multiunit smooth muscle – Multiunit smooth muscle is a type of muscle found in the walls of blood vessels. It is composed of two or more individual units (cells) that work together to contract, which causes the vessel to constrict.

Related Diseases

Certain disorders can also affect the functioning of smooth muscles. For instance, a genetic condition called Multisystemic Smooth Muscle Dysfunction Syndrome (MSMDS) results in not developing enough smooth muscles for the digestive system in an embryo. Some autoimmune disorders such as hepatitis, lupus or cirrhosis can also cause Anti-smooth muscle antibodies (ASMA).

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