Definition

1. Noun:
   • Involuntary muscle tissue: A type of muscle tissue that is not under conscious control. Its cells are spindle-shaped and lack the striped (striated) appearance seen in skeletal muscle when viewed under a microscope.
   • An organ composed of such tissue: A specific muscle, made of this tissue, found in the walls of internal organs and blood vessels.

Examples of Usage

• Noun:
  • The walls of the stomach and intestines are lined with smooth muscle.
  • Contraction of smooth muscle in blood vessels helps regulate blood pressure.
  • Unlike skeletal muscle, you cannot voluntarily contract your smooth muscle.

Advanced Usage

• "Visceral muscle": Another term for smooth muscle, emphasizing its location in the internal organs (viscera).
  • Peristalsis, the wave-like motion that moves food through the gut, is driven by visceral muscle.
• "Non-striated muscle": A descriptive term highlighting its microscopic appearance in contrast to striated (skeletal and cardiac) muscle.
  • Under the microscope, the non-striated muscle from the bladder wall was clearly visible.

Variants and Related Words

• Involuntary muscle (n): A general synonym for smooth muscle, describing its key characteristic of automatic function.
• Myocyte (n): A general term for a muscle cell. A smooth muscle cell is a type of myocyte.
• Peristalsis (n): The rhythmic, wave-like contractions of smooth muscle in tubular organs, like the esophagus or intestines.

Synonyms

• Involuntary muscle
• Visceral muscle
• Non-striated muscle

Related Phrases and Concepts

• Autonomic nervous system: The part of the nervous system that controls smooth muscle, cardiac muscle, and glands automatically.
  • The autonomic nervous system regulates the contraction of smooth muscle in the airways.
• Tone (muscle tone): The continuous and passive partial contraction of smooth muscle, important for maintaining pressure in organs like blood vessels.
  • Vascular smooth muscle tone is crucial for controlling blood flow.

Noun

1. muscle tissue that does not appear striated under the microscope; has the form of thin layers or sheets
2. a muscle that contracts without conscious control and found in walls of internal organs such as stomach and intestine and bladder and blood vessels (excluding the heart)