External anal sphincter muscle

The **external anal sphincter muscle** is a voluntary, striated (skeletal) muscle that encircles the distal anal canal. It plays a critical role in maintaining fecal continence by tonically contracting to keep the anal canal closed. During defecation, it relaxes to allow passage of stool. Its fibers are organized into superficial, deep, and subcutaneous parts, contributing both to the maintenance of resting anal tone and to rapid, forceful closure when needed. The muscle is innervated by the inferior anal branch of the pudendal nerve (arising from spinal levels S2–S4), enabling voluntary control. It is not a molecular or cellular drug target such as a receptor, enzyme, or transporter, but instead a structural and functional anatomical muscle important in pelvic floor physiology[1][2][3][4][5][6][7]. **Additional notes:** - **External anal sphincter muscle tissue** is an anatomical and histological entity, not a molecular target; thus, it is not considered a classical therapeutic target (such as a receptor, enzyme, ion channel, etc.). - No known drugs interact directly with this muscle tissue at the molecular level (drugs affecting continence or the sphincter act via neural mechanisms or global muscle relaxants). - Pathological or inadvertent injury to the muscle is a recognized cause of fecal incontinence, particularly following obstetric trauma[2]. - Classification as a molecular target would be incorrect, so "is_incorrect" should be true.

Other names

Sphincter ani externusAnal external sphincterExternal anal sphincter