MaleMusFIG 45: Ultrastructure of the sphincter muscle.

A. Low-power TEM featuring the sphincter muscle. (PAG) Pre-anal ganglion; (v/dsrL/R) ventral and dorsal spicule retractors, (v/dspL) ventral and dorsal spicule protractors; (d/vBWM) dorsal and ventral body wall muscle. (Image source: N2Y [MRC] 596-24.)
B. TEM of boxed area in 45A showing close up of the myosin and actin filaments within the sphincter muscle. (N) Nucleus. (Image source: N2Y [MRC] 942-L.)