Sacrum lumbar vertebra, and its lower part with the coccyx (tailbone) via the sacral and coccygeal cornua. The sacrum has three different surfaces which are shaped to accommodate surrounding pelvic structures. Overall it is concave (curved upon itself). The base of the sacrum, the broadest and uppermost part, is tilted forward as the sacral promontory internally. The central part is curved outward toward the posterior, allowing greater room for the pelvic cavity. In all other quadrupedal vertebrates, the pelvic vertebrae undergo a similar developmental process to form a sacrum in the adult, even while the bony tail (caudal) vertebrae remain unfused.
History of beliefs about the human body History of beliefs about the human body The human body has been subject of much debate. How people are defined, and what defined them – be it their anatomy or their energy or both – depends on culture and time. Culture not only defines how sex is perceived but also how gender is defined. Today gender, sex, and identity continue to be of much debate and change based on what place and people are being examined. The early modern idea of the body was a cultural ideal, an understanding and approach to how the body works and what place that