The medical term for the lower back is the lumbosacral region. This part of the spine is made up of the lumbar vertebrae and the sacrum, notes WebMD. Each of this lower back parts consist of five vertebrae each.
The spine is composed of 33 vertebrae. The five bones of the lumbar region are quite strong and large because they must support the weight of the upper body. The lumbar and sacral vertebrae are two of the five spine regions.
The other regions are the cervical, thoracic and coccygeal regions. There are seven cervical vertebrae, which are found in the neck area. The 12 thoracic vertebrae are located between the cervical and lumbar vertebrae. There are four coccygeal vertebrae, and this region consists only of the coccyx or tailbone, states Inner Body.