Anatomy of the pelvis and perineum

Abstract The roof of the abdominopelvic cavity is the diaphragm and the floor is the pelvic diaphragm. It is conventional to divide the abdominopelvic cavity into two regions: the abdominal cavity and the pelvic cavity. The two are continuous with each other through the pelvic brim. Below the pelvic floor lies the perineum. Surgical conditions involving pelvic viscera and structures in the perineum account for a very considerable part of surgical and gynaecological practice. A clear understanding of pelvic and perineal anatomy is fundamental to the proper clinical management of these conditions. The perineum refers to the lowest part of the trunk. It lies immediately below the pelvic floor (levator ani) and is flanked by the inner aspects of the proximal ends of the thighs and also by the inferior aspects of the buttocks. The perineum may be pictured as lying within a diamond-shaped outline. The perineum is divisible anatomically into two regions: the urogenital triangle anteriorly and a posterior region termed the anal triangle.