Final answer:
The ischium is part of the hip bone located in the hip region, distinguished by the ischial tuberosity which supports weight when sitting. The ilium, however, forms the superior part of the hip bone, topped by the iliac crest.
Step-by-step explanation:
The ischium is located in the hip region, specifically forming the posterolateral portion of the hip bone. It is well known for the ischial tuberosity, a large, roughened area on the lower part of the ischium, which serves as an attachment point for the posterior thigh muscles and is the part that carries the body's weight when seated. This can be felt when wiggling against the seat of a chair. Moreover, the ischial ramus extends from the ischial tuberosity, moving superiorly and anteriorly, and the ischial spine separates the greater and lesser sciatic notches on the posterior margin of the ischium.
Among the components of the hip bone, the ilium is the one that forms the superior part. The iliac crest forms the superior margin of the ilium, with several notable points such as the anterior superior and posterior superior iliac spines. The iliac fossa is formed by the medial surface of the upper ilium, and the arcuate line marks the limit of this area. Additionally, the ilium features the greater sciatic notch on its posterior margin.