How many lumbar vertebrae are there, and what makes them unique?

There are five lumbar vertebrae (L1–L5). They are unique for being large and robust to support body weight, featuring massive reniform bodies, no costal facets or transverse foramina, and having accessory and mammillary processes.

What are the key features of a typical lumbar vertebra?

A typical lumbar vertebra (L1–L4) has a massive, kidney-shaped body wider transversely, a triangular vertebral foramen, short, strong pedicles and thick laminae, a quadrilateral spinous process and long, slender transverse processes, and superior articular facets that are concave and face medially/backward.

How is the fifth lumbar vertebra (L5) different from the others?

L5 is atypical, with the largest vertebral body and a greater anterior height, forming a lumbosacral angle. It has short, thick transverse processes, a small rounded spinous process, and its articular facets face more backward (superior) and forward (inferior).

What are some important muscles and ligaments attached to the lumbar vertebrae?

Key attachments include psoas major on bodies and arches, thoracolumbar fascia on spinous and transverse processes, anterior/posterior longitudinal ligaments on bodies, and iliolumbar ligaments on L5 transverse process.

What are common clinical conditions associated with the lumbar vertebrae?

Common conditions include sacralization (fusion of L5 with the sacrum), spondylolisthesis (forward slip of L5 over the sacrum), and cauda equina syndrome (compression of nerve roots causing symptoms like incontinence).

How do lumbar vertebrae ossify during development?

Ossification involves 3 primary centers (body and two arch halves) fusing early in childhood, and 5 secondary centers (e.g., for epiphyses and process tips) that fuse by around age 25.

Lumbar Vertebrae (L1–L5) – Anatomy & Key Features