The pelvis is a central anatomical structure that forms the base of the trunk, connecting the spine to the lower limbs. This region supports movement, posture, and protects several organ systems. Understanding its location provides insight into how the body supports weight. In women, the pelvic region is specifically adapted to accommodate reproductive functions.
Defining the Pelvic Region
The pelvic region is situated in the lower trunk, positioned between the abdomen and the thighs. It serves as a transitional zone and a foundation for the upper body. The area is divided into two major parts by the pelvic brim.
The superior portion is the greater pelvis, or false pelvis, which is continuous with the abdominal cavity. This upper space supports lower abdominal organs, such as portions of the small and large intestines. Below the pelvic brim is the lesser pelvis, also called the true pelvis. This bowl-shaped area contains the deep pelvic organs and is the primary focus of core female anatomy.
The Bony Framework
The structure of the pelvis is established by the pelvic girdle, a ring-like arrangement of bones that provides a strong, protective basin. The girdle is composed of four main bones: the two hip bones, the sacrum, and the coccyx. Each large hip bone is formed by the fusion of three separate bones—the ilium, the ischium, and the pubis—which unite in adulthood.
The fan-shaped ilium is the broad, flared upper portion, commonly felt as the hip bone. The ischium forms the strong, lower-posterior part, including the ischial tuberosities, or “sit bones.” The pubis is the anterior section, where the two pubic bones meet at the midline to form the pubic symphysis. Posteriorly, the hip bones articulate with the sacrum, a triangular bone capped by the coccyx.
Key Internal Structures
The lesser, or true, pelvis contains several soft tissue organs, collectively known as the pelvic viscera. This space houses the internal female reproductive organs, nestled between the urinary and digestive systems. The uterus, a muscular, pear-shaped organ, is centrally located and anchored by ligaments.
Flanking the uterus are the two ovaries, which produce eggs and reproductive hormones. The fallopian tubes extend outward, arching toward the ovaries to transport eggs to the uterine cavity. Anterior to the uterus is the urinary bladder, a reservoir for urine. The terminal end of the large intestine, the rectum, is positioned at the back of the pelvis, curving along the sacrum.
Primary Roles
The pelvic area performs multiple functions related to bodily support and movement. Its primary role is structural, serving to transfer the weight of the upper body from the vertebral column to the lower limbs. This weight transfer is necessary for maintaining upright posture and stability during standing.
The bony ring also acts as the attachment point for numerous muscles and ligaments responsible for hip movement, gait, and core stability. This connection allows for bipedal locomotion, facilitating efficient walking and running. The female pelvis is noted for its adaptation to childbirth, being generally wider, shallower, and having a more rounded inlet compared to the male pelvis.
During labor, the hormone relaxin helps soften the ligaments connecting the pelvic bones, allowing a slight increase in the size of the pelvic outlet. This flexibility is a biological adaptation that helps the infant pass through the birth canal.