The L4 vertebra is one of the five lumbar vertebrae located in the lower back, specifically the fourth one in the lumbar region. It plays a crucial role in supporting the weight of the upper body and allows for flexibility and movement in the lower spine. The lumbar vertebrae are larger than those in the cervical and thoracic regions, as they bear more weight. In addition to providing structural support, the L4 vertebra is important for protecting the spinal cord and nerves that exit the spine. It is connected to the L3 vertebra above and the L5 vertebra below, forming part of the lumbar spine that helps facilitate various movements, such as bending and twisting.