Anus external muscle sphincter
Anal Sphincter Medical Definition | Merriam-Webster Medical Dictionary
Internal anal sphincter
Description: Retrieved from " https: In a considerable proportion of cases the fibers decussate in front of the anus, and are continuous with the superficial transverse perineal muscle. This permits muscles to contract quickly when stimulated without having to overcome the inertia of total relaxation. Muscles accelerator, accessorius, adductor, agonist, antagonist, arytenoid, biceps, buccinator, compressor, constrictor, contractor, corrugator, deltoid, depressor, digrastic, dilator, elevator, erector, evertor, extensor, flexor, gastrocnemius, gluteus or glutaeus, levator, lumbricalis, masseter, opponent, pectoral, peroneal muscle, pronator, psoas, quadriceps, rectus, retractor, rhomboideus, rotator, sartorius, scalenus, soleus, sphincter, supinator, suspensory or suspensor, tensor, trapezius, triceps. The dimensional relationships between these light and dark bands are altered during contraction of the muscle fiber.