Sphincter Muscle -

Composed of smooth muscle, these are managed by the autonomic nervous system. You don’t have to think about them; they work automatically to keep stomach acid down or manage internal waste flow.

Sphincter muscles are the unsung heroes of human biology, acting as the body's primary "gatekeepers." These circular or ring-like muscles remain tonically contracted to close off natural body passages and orifices, relaxing only when necessary to allow the passage of substances like food, liquids, and waste. Without these over , essential processes like digestion, vision, and excretion would be chaotic and uncontrollable. The Mechanics of Control Sphincters are categorized by how they are controlled: sphincter muscle

Anatomy, Abdomen and Pelvis, Sphincter Urethrae - StatPearls - NCBI Composed of smooth muscle, these are managed by