Smooth muscle is characterized by which features?

Smooth muscle is characterized by which features?

• A. Not striated, spindle-shaped, involuntary
• B. Striated and under voluntary control
• C. Cylindrical and multinucleated
• D. Rapid, forceful contractions

Answer: (A)

Distinguishing muscle tissue types by how they look and are controlled. Smooth muscle is not striated under light microscopy, has spindle-shaped cells, and usually a single nucleus. This combination lets it form the walls of hollow organs and blood vessels, where it can contract slowly and involuntarily to move substances along or regulate flow. In contrast, skeletal muscle is striated, composed of long cylindrical fibers with multiple nuclei, and is under voluntary control, capable of rapid, forceful contractions. Cardiac muscle is also striated but has branching cells with intercalated discs and is involuntary. So the description “not striated, spindle-shaped, involuntary” best matches smooth muscle.

Distinguishing muscle tissue types by how they look and are controlled. Smooth muscle is not striated under light microscopy, has spindle-shaped cells, and usually a single nucleus. This combination lets it form the walls of hollow organs and blood vessels, where it can contract slowly and involuntarily to move substances along or regulate flow. In contrast, skeletal muscle is striated, composed of long cylindrical fibers with multiple nuclei, and is under voluntary control, capable of rapid, forceful contractions. Cardiac muscle is also striated but has branching cells with intercalated discs and is involuntary. So the description “not striated, spindle-shaped, involuntary” best matches smooth muscle.