Smooth muscles, also known as involuntary or non-striated muscles, are a type of muscle tissue present in the walls of various organs and structures of the body. These muscles are not under voluntary control, and they exhibit a smooth, uniform appearance under a microscope, hence the name.

Characteristics of Smooth Muscles:

Smooth muscles possess the following characteristics:


Smooth muscles are not consciously controlled by the individual, meaning they work automatically without conscious effort or thought.


Unlike skeletal muscles, which exhibit visible striations or bands under a microscope, smooth muscles lack such visible markings. This absence of striations is due to the arrangement of contractile proteins within the muscle cells.

Spindle-Shaped Cells:

Smooth muscle cells are elongated and tapered at each end, resembling a spindle. This unique cellular shape allows for flexibility and efficient contraction.


While some smooth muscle cells may be uninucleated, many are multinucleated, containing multiple nuclei within a single cell.

Slow Contraction and Relaxation:

Smooth muscle contractions are generally slower and more prolonged compared to skeletal muscles. This characteristic enables smooth muscles to maintain continuous contractions, such as the sustained contractions needed for normal digestion or regulation of blood pressure.

Found in Various Organs:

Smooth muscles are present in various organs and tissues throughout the body, including the walls of blood vessels, gastrointestinal tract, urinary system, respiratory system, reproductive system, and the iris of the eye.

Controlled by Autonomic Nervous System:

The contraction and relaxation of smooth muscles are regulated by the autonomic nervous system, a branch of the peripheral nervous system that controls involuntary bodily functions.

Overall, smooth muscles play a vital role in various physiological processes, maintaining organ function and facilitating the proper functioning of essential bodily systems.