Final answer:
The Coccygeus muscle originates from the ischial spine and inserts into the sacrum and coccyx, which is structured by the fusion of four small coccygeal vertebrae. The ischium, part of the hip bone, includes the ischial tuberosity that supports body weight in a seated position.
Step-by-step explanation:
The Coccygeus, also known as the Ischiococcygeus muscle, is part of the pelvic floor muscles. It originates from the ischial spine of the ischium and inserts into the inferior end of the sacrum and the coccyx (tailbone). Specifically, it arises from the pelvic surface of the spine and from the dorsal surface of the sacrospinous ligament, and inserts into the lateral margins of the sacrum and coccyx, and into the sacrotuberous ligament. The coccyx itself is a small bone located at the inferior end of the vertebral column and is formed by the fusion of four small coccygeal vertebrae. It articulates with the sacrum. The ischium forms the posterolateral portion of the hip bone and includes the ischial tuberosity, which bears the body's weight when sitting.