Final answer:
The ischium is part of the hip bone, featuring the ischial tuberosity that supports body weight when seated and the ischial ramus, as well as the lesser sciatic notch and ischial spine that separate the sciatic notches.
Step-by-step explanation:
The body of the ischium refers to the posteroinferior region of each hip bone, which is a crucial part of the pelvic structure.
The ischial tuberosity is a prominent feature of the ischium; it is a large, roughened protuberance where the posterior thigh muscles attach and which supports the body's weight while seated.
From the ischial tuberosity, the ischial ramus extends anteriorly and superiorly.
The lesser sciatic notch is a curvature along the posterior margin of the ischium and above this notch is the ischial spine, a pointed bony projection that separates the greater sciatic notch from the lesser sciatic notch.