In the upper three vertebrae they arise from the junctions of the pedicles and laminae, but in the lower two they are set farther forward and spring from the pedicles and posterior parts of the vertebral bodies. They are situated in front of the articular processes instead of behind them as in the thoracic vertebrae, and are homologous with the ribs.Three portions or tubercles can be noticed in a transverse process of a lower lumbar vertebrae: the lateral or costiform process, the mammillary process, and the accessory process. The costiform is lateral, the mammillary is superior (cranial), and the accessory is inferior (caudal). The mammillary is connected in the lumbar region with the back part of the superior articular process. The accessory process is situated at the back part of the base of the transverse process. The tallest and thickest costiform process is usually that of L5. First and fifth lumbar vertebrae
The first lumbar vertebra is level with the anterior end of the ninth rib. This level is also called the important transpyloric plane, since the pylorus of the stomach is at this level. Other important structures are also located at this level, they include; fundus of the gall bladder, celiac trunk, superior mesenteric artery, termination of spinal cord, beginning of filum terminale, renal vessels, middle suprarenal arteries, and hila of kidneys.
The fifth lumbar vertebra is characterized by its body being much deeper in front than behind, which accords with the prominence of the sacrovertebral articulation; by the smaller size of its spinous process; by the wide interval between the inferior articular processes, and by the thickness of its transverse processes, which spring from the body as well as from the pedicles. The fifth lumbar vertebra is by far the most common site of spondylolysis and spondylolisthesis.Most individuals have five lumbar vertebrae, while some have four or six. Lumbar disorders that normally affect L5 will affect L4 or L6 in these latter individuals. Segmental movements
The range of segmental movements in a single segment is difficult to measure clinically, not only because of variations between individuals, but also because it is age and sex dependent. Furthermore, flexion and extension in the lumbal spine is the product of a combination of rotation and translation in the sagittal plane between each vertebra.Ranges of segmental movements in the lumbar spine (White and Punjabi, 1990) are (in degrees):

Congenital anomalies
Congenital vertebral anomalies can cause compression of the spinal cord by deforming the vertebral canal or causing instability. Other animals
African apes have three and four lumbar vertebrae, (bonobos have longer spines with an additional vertebra) and humans normally five.