Pelvis

Pelvis. This term, derived from a Latin word signifying "a basin,1' is applied to that portion of the human skeleton which intervenes between the lumbar vertebrae and the thigh-bones. The pelvis is made up by the sacrum and coccyx posteriorly, while on each side are what are termed the innominate bones. Each innominate bone consists of three parts - the ilium above, the ischium below and behind, and the pitbes anteriorly. The two pubic portions of the innominate bones are united in front, forming what is known as the symphysis pubis. The two iliac portions of the innominate bones articulate with the lateral aspects of the sacrum, forming the sacro-iliac joints. The three portions of the os innominatum are fused in the adult, but are distinct bony masses in early life; they meet together at the acetabulum, the cup-like cavity with which the head of the femur articulates. Just below and in front of this cavity there is a large opening in the os innominatum, which is called the obturator foramen. The pelvis is divided into two parts - the true and the false pelvis; these are separated from one another by a plane which is called the brim of the true pelvis. This brim is mapped out by the promontory of the sacrum behind, and by two ridges which extend on each side from the sacral promontory to the anterior portion of the pubes, and are known as the ilio-pectineal lines. [Kidney.]