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The lumbar vertebrae are located between the thoracic vertebrae and pelvis. They form the lower part of the back in humans, and the tail end of the back in quadrupeds. In humans, there are five lumbar vertebrae. The term is used to describe the anatomy of humans and quadrupeds, such as horses, pigs, or cattle.
They are attached to the body of the first sacral vertebra and to each ala, by short thick pedicles; on the upper surface of each pedicle is a vertebral notch, which forms the lower part of the foramen between the last lumbar and first sacral vertebrae. The apex is directed downward and presents an oval facet for articulation with the coccyx.
The sacrum is curved upon itself and placed very obliquely, its base projecting forward and forming the prominent sacrovertebral angle when articulated with the last lumbar vertebra. It is also known as the "lumbosacral angle". [1]
The number of vertebrae in a region can vary but overall the number remains the same. In a human spinal column, there are normally 33 vertebrae. [3] The upper 24 pre-sacral vertebrae are articulating and separated from each other by intervertebral discs, and the lower nine are fused in adults, five in the sacrum and four in the coccyx, or tailbone.
Each vertebra (pl.: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal segment and the particular species.
In the thoracic region and lumbar region, each vertebral foramen is additionally bounded anteriorly by (the inferior portion of) the body of vertebra (particularly in the thoracic region) and adjacent intervertebral disc (particularly in the lumbar region). [2]: 425
The superior processes or prezygapophysis project upward from a lower vertebra, and their articular surfaces are directed more or less backward (oblique coronal plane). The inferior processes or postzygapophysis project downward from a higher vertebra, and their articular surfaces are directed more or less forward and outward.
Superior to the 7th cervical vertebra, the supraspinous ligament is continuous with the nuchal ligament. [2]: 45 It is thicker and broader in the lumbar region than in the thoracic region, and intimately blended with the neighboring fascia in both these regions. [3]