pelvis pelvis the pelvis (plural pelves or pelvises) is the lower part of the trunk, between the abdomen and the thighs (sometimes also called pelvic region), together with its embedded skeleton (sometimes also called bony pelvis, or pelvic skeleton). pelvismale type pelvisfemale type pelvisdetailsidentifierslatinpelvismeshd010388ta98a01.1.00.017 a02.5.02.001ta2129anatomical terms of bone the same human pelvis, front imaged by x-ray (top), magnetic resonance imaging (middle), and 3-dimensional computed tomography (bottom) the pelvic region of the trunk includes the bony pelvis, the pelvic cavity (the space enclosed by the bony pelvis), the pelvic floor, below the pelvic cavity, and the perineum, below the pelvic floor. the pelvic skeleton is formed in the area of the back, by the sacrum and the coccyx and anteriorly and to the left and right sides, by a pair of hip bones. the two hip bones connect the spine with the lower limbs. they are attached to the sacrum posteriorly, connected to each other anteriorly, and joined with the two femurs at the hip joints. the gap enclosed by the bony pelvis, called the pelvic cavity, is the section of the body underneath the abdomen and mainly consists of the reproductive organs (sex organs) and the rectum, while the pelvic floor at the base of the cavity assists in supporting the organs of the abdomen. in mammals, the bony pelvis has a gap in the middle, significantly larger in females than in males. their young pass through this gap when they are born. structure the pelvic region of the trunk is the lower part of the trunk, between the abdomen and the thighs. it includes several structures: the bony pelvis, the pelvic cavity, the pelvic floor, and the perineum. the bony pelvis (pelvic skeleton) is the part of the skeleton embedded in the pelvic region of the trunk. it is subdivided into the pelvic girdle and the pelvic spine. the pelvic girdle is composed of the appendicular hip bones (ilium, ischium, and pubis) oriented in a ring, and connects the pelvic region of the spine to the lower limbs. the pelvic spine consists of the sacrum and coccyx. the pelvic cavity, typically defined as a small part of the space enclosed by the bony pelvis, delimited by the pelvic brim above and the pelvic floor below; alternatively, the pelvic cavity is sometimes also defined as the whole space enclosed by the pelvic skeleton, subdivided into: the greater (or false) pelvis, above the pelvic brim the lesser (or true) pelvis, below the pelvic brim the pelvic floor (or pelvic diaphragm), below the pelvic cavity the perineum, below the pelvic floor pelvic bone further information: hip bone the skeleton of the human pelvis: 2–4. hip bone (os coxae) 1. sacrum (os sacrum), 2. ilium (os ilium), 3. ischium (os ischii) 4. pubic bone (os pubis) (4a. corpus, 4b. ramus superior, 4c. ramus inferior, 4d. tuberculum pubicum) 5. pubic symphysis, 6. acetabulum (of the hip joint), 7. obturator foramen, 8. coccyx/tailbone (os coccygis) dotted. linea terminalis of the pelvic brim. the pelvic skeleton is formed posteriorly (in the area of the back), by the sacrum and the coccyx and laterally and anteriorly (forward and to the sides), by a pair of hip bones. each hip bone consists of three sections: ilium, ischium, and pubis. during childhood, these sections are separate bones, joined by the triradiate cartilage. during puberty, they fuse together to form a single bone. pelvic cavity main article: pelvic cavity the pelvic cavity is a body cavity that is bounded by the bones of the pelvis and which primarily contains reproductive organs and the rectum. a distinction is made between the lesser or true pelvis inferior to the terminal line, and the greater or false pelvis above it. the pelvic inlet or superior pelvic aperture, which leads into the lesser pelvis, is bordered by the promontory, the arcuate line of ilium, the iliopubic eminence, the pecten of the pubis, and the upper part of the pubic symphysis. the pelvic outlet or inferior pelvic aperture is the region between the subpubic angle or pubic arch, the ischial tuberosities and the coccyx. ligaments: obturator membrane, inguinal ligament (lacunar ligament, iliopectineal arch) alternatively, the pelvis is divided into three planes: the inlet, midplane, and outlet. pelvic floor female perineummale perineum the pelvic floor has two inherently conflicting functions: one is to close the pelvic and abdominal cavities and bear the load of the visceral organs; the other is to control the openings of the rectum and urogenital organs that pierce the pelvic floor and make it weaker. to achieve both these tasks, the pelvic floor is composed of several overlapping sheets of muscles and connective tissues. the pelvic diaphragm is composed of the levator ani and the coccygeus muscle. these arise between the symphysis and the ischial spine and converge on the coccyx and the anococcygeal ligament which spans between the tip of the coccyx and the anal hiatus. this leaves a slit for the anal and urogenital openings. because of the width of the genital aperture, which is wider in females, a second closing mechanism is required. the urogenital diaphragm consists mainly of the deep transverse perineal which arises from the inferior ischial and pubic rami and extends to the urogenital hiatus. the urogenital diaphragm is reinforced posteriorly by the superficial transverse perineal. the external anal and urethral sphincters close the anus and the urethra. the former is surrounded by the bulbospongiosus which narrows the vaginal introitus in females and surrounds the corpus spongiosum in males. ischiocavernosus squeezes blood into the corpus cavernosum penis and clitoridis. variation