The pubis, or pubic bone, is one of the three bones that form the hip bone (os coxae). It is part of the pelvic girdle, which connects the torso to the lower limbs. The pubis provides support, protection, and attachment points for various muscles and ligaments in the lower abdominal region.
Precise Anatomical Location
The pubis is situated at the front and lowest part of the hip bone, giving it the most anterior and inferior position in the pelvic girdle. Relative to its partners, the pubis is positioned inferiorly to the ilium and anteriorly to the ischium.
The two separate pubic bones, one from the left and one from the right, come together at the midline. This convergence forms a joint that completes the anterior ring of the pelvis. This placement means the pubis sits just below the abdomen, protecting the urinary and internal sexual organs and supporting the lower abdominal contents.
Key Components of the Pubic Bone
A single pubic bone is divided into three main parts: the body and two projections called rami. The body is the medial mass that meets its counterpart from the opposite side. This central part features a raised ridge called the pubic crest, which extends laterally into the pubic tubercle.
The pubic tubercle serves as an anchoring point for the inguinal ligament. Extending outward from the body are the two rami. The superior ramus projects upward toward the ilium, while the inferior ramus extends downward toward the ischium. The inferior ramus eventually fuses with the ischium, and the two rami frame the large opening in the pelvis called the obturator foramen.
The Role of the Pubic Symphysis
The pubic symphysis is the joint where the bodies of the left and right pubic bones meet in the center of the pelvis. This connection is classified as a secondary cartilaginous joint, united by a thick disc of fibrocartilage. This disc is sandwiched between thin layers of hyaline cartilage covering the ends of each pubic bone.
The function of the pubic symphysis is to provide stability to the pelvic girdle. It connects the two halves of the pelvis, allowing the transfer of weight from the upper body down to the legs. While it is a strong joint, it permits a small amount of movement, which helps absorb shock during walking or running. This flexibility is important during pregnancy, as hormones soften the ligaments, allowing the pelvis to widen for childbirth.