Vertebra
Irregular bone forming the vertebral column of vertebrates.
A vertebra (pl.: vertebrae) is an irregular bone composed of bone and some hyaline cartilage that makes up the vertebral column, or spine, of vertebrates. The basic configuration of a vertebra varies, but it generally consists of a vertebral body (centrum) that bears the load of the column, and a posterior vertebral arch formed by pedicles, laminae, and seven processes. Vertebrae articulate with each other to give strength and flexibility to the spinal column, and their shape determines the range of movement. Vertebrates take their name from the vertebrae that compose the vertebral column.
- type
- Irregular bone
- composition
- Bone and hyaline cartilage
- parts
- Vertebral body, vertebral arch (two pedicles, two laminae, seven processes)
- function
- Supports spinal column, protects spinal cord, allows movement
- location
- Vertebral column of vertebrates
Lore & Background
Each vertebra is an irregular bone with a complex structure. The vertebral body, or centrum, is composed of cancellous bone covered by a thin coating of cortical bone, and its upper and lower surfaces give attachment to the intervertebral discs via vertebral endplates. The posterior vertebral arch consists of two pedicles that extend from the body, and two laminae that project backward and medially to complete the arch, forming the vertebral foramen that accommodates the spinal canal. Seven processes project from each vertebra: one spinous process, two transverse processes, and four articular processes, which serve for muscle and ligament attachment and to restrict movement.
Reader's Guide
The vertebra is a fundamental structural unit of the vertebrate skeleton, providing both support and protection for the spinal cord. Its design varies along the spinal column to meet different needs related to stress and mobility. In humans, there are usually thirty-three vertebrae: seven cervical, twelve thoracic, five lumbar, five fused sacral, and four coccygeal. The cervical vertebrae are small and delicate, with transverse foramina for vertebral arteries; the atlas (C1) has no body, and the axis (C2) has a dens. Thoracic vertebrae have facets for rib articulation, and lumbar vertebrae are larger. The intervertebral foramina, formed by vertebral notches, allow spinal nerves to exit. The endplates of the vertebral body function to contain discs, spread loads, and provide anchorage for collagen fibers. The study of vertebrae is essential for understanding spinal anatomy, pathology, and the evolution of vertebrates.
Did You Know?
- The vertebral arch is formed by two pedicles and two laminae.
- The spinous process of C7 is not bifurcated and is substantially longer than other cervical spinous processes.
- The atlas (C1) has no body and no spinous process, but has a ring-like form with anterior and posterior arches.
- The transverse foramen of cervical vertebrae gives passage to the vertebral artery and vein and a sympathetic nerve plexus.
Frequently Asked Questions
What is a Vertebra?
A vertebra is an irregular bone (with a small amount of hyaline cartilage) that stacks together to build the spine of every vertebrate animal. Think of it as the fundamental building block of the vertebral column.
What parts make up a single Vertebra?
Each vertebra has a load-bearing vertebral body (the centrum) at the front and a posterior arch made of two pedicles, two laminae, and seven bony processes. Together these structures create the openings and surfaces that let vertebrae lock together while still allowing movement.
What is the main job of a Vertebra in the body?
Vertebrae carry the mechanical load of the column, shield the spinal cord running through their central canal, and—because of their specific shape—determine how much that segment of the spine can bend or twist.
Why do vertebrates actually get their name from Vertebrae?
The very class name 'Vertebrata' comes from the vertebrae that form the backbone, since these stacked irregular bones are the defining structural feature that separates vertebrates from invertebrates.
How do individual Vertebrae work together to give the spine both strength and flexibility?
Each vertebra articulates with its neighbors through the processes and intervertebral spaces, so the column resists compression as a unit yet still permits the range of motion dictated by the shape of each segment.
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