The L3 vertebra is the third lumbar vertebra in the lower back, part of the lumbar spine, which consists of five vertebrae labeled L1 to L5. It is located between the L2 and L4 vertebrae and plays a crucial role in supporting the upper body while allowing for flexibility and movement. The lumbar spine is essential for activities such as bending and lifting. The L3 vertebra is larger and stronger than the cervical and thoracic vertebrae, as it bears more weight. It also serves as an attachment point for muscles and ligaments, contributing to the stability of the lower back. Issues with the L3 vertebra can lead to pain or discomfort in the lower back and legs, often requiring medical attention.