External anal sphincter may be injured in 25 - 35 % of women during the first and subsequent vaginal child births and is likely the most common cause of anal incontinence. Since its first description, almost 300 years ago, EAS is believed to be a circular or a "donut-shaped" structure. We performed 3D-transperineal ultrasound imaging, magnetic resonance imaging, diffusion tensor imaging and muscle fiber tracking to delineate various components of EAS and their muscle fiber directions. These novel imaging techniques suggest "purse-string" morphology, with "external anal sphincter" muscles crossing contra-laterally in the perineal body to contra-lateral transverse pernei & bulbospongiosus muscle thus attaching "external anal sphincter" to the pubic rami. Spin-tag magnetic resonance imaging demonstrated "purse-string" action of the external anal sphincter muscle. Electromyography of transverse perinei/bulbospongiosus and external anal sphincter muscle revealed their simultaneous contraction and relaxation. Lidocaine injection into transverse perinei/bulbospongiosus muscle caused significant reduction in the anal canal pressure. These studies support "purse-string" morphology of external anal sphincter to constrict/close the anal canal opening. Our findings have implications for the effect of episiotomy on anal closure function and currently used surgical technique (overlapping sphincteroplasty) for the external anal sphincter reconstructive surgery to treat anal incontinence.