The back is the posterior part of the human body, extending from the base of the skull (neck) to the pelvis. It includes the spinal column, which is made up of vertebrae that protect the spinal cord—a vital part of the nervous system. The spine is divided into cervical, thoracic, lumbar, sacral, and coccygeal regions, each contributing to flexibility, strength, and support. Surrounding the spine are layers of muscles, such as the trapezius, latissimus dorsi, and erector spinae, which help with posture, movement, and lifting.

The back plays a critical role in many bodily functions, including standing upright, bending, twisting, and maintaining balance. It also connects to the shoulders and hips, enabling upper and lower body coordination. The skin, fat, and connective tissues overlying the back provide protection and flexibility. A healthy back is essential for mobility and quality of life, while injuries or poor posture can lead to chronic pain and reduced function.