Anatomical structures of the lumbar spine

• 5 moveable vertebrae (L1-L5)
• Joints
• Ligaments
• Paraspinal muscles
• Nerves

Spinal Curves

The normal spine has an S-shaped curve when viewed from the side. This shape allows for an even distribution of weight and flexibility of movement. The Spine curves in the following ways:

• The cervical spine curves slightly inward, sometimes described as a backward C-shape or lordotic curve (lordosis)
• The thoracic spine curves outward, forming a regular C-shape with the opening at the front—or a kyphotic curve (kyphosis)
• The lumbar spine curves inward and, like the cervical spine, has a lordotic or backward C-shape (lordosis)

The curves, along with the intervertebral disks, help to absorb and distribute stresses that occur from everyday activities such as walking or from more intense activities such as running and jumping.

Muscles

The spine has muscles that help to move your trunk and they provide strength and stability to your lower back. These muscles also significantly reduce the excessive load on the bones and discs. Therefore, the spine would be exposed and inadequate to support the body without the muscles.

Vertebrae

The spinal (or vertebral) canal is formed between the vertebrae. A single vertebra is made up of two parts, the front portion is called “the body” and the back portion is referred to as the vertebral or neural arch that has protrusions that act as levers for the muscle action.

Each vertebra has an anterior arch and a posterior arch, which forms a hole, called a foramen. The spinal cord passes through the foramen of each vertebra.

The anterior arch is called the vertebral body. Discs separate one vertebral body from another, allowing the movement of the spine and cushioning it against heavy loads.

Facet Joints

These spinal joints (connections) between the vertebrae are called facet joints and are located both in the front and back side of the spine. On the front side, the connection becomes through the intervertebral discs. There are two facet joints between each pair of vertebrae, one on each side. These joints provide flexibility (allow the spine to turn or bend with movement) and stability (prevent excessive motion).

Intervertebral discs

The intervertebral disc is a fibrocartilaginous cylinder that lies between the vertebrae, joining them together. This disc is made of two components: the annulus fibrosis and the nucleus pulpous. The annulus fibrosis is the outer portion of the disc. It is composed of layers of collagen and proteins, called lamellae. The nucleus pulpous is the inner gel material surrounded by the annulus fibrosis and is composed primarily of loose collagen fibers, water, and proteins.

The intervertebral disks allow the vertebral column to be flexible and act as shock absorbers during everyday activities such as walking, running and jumping.

The vertebral “tripod”

The spine consists of a column of movable bones called vertebrae, which are connected to each other. Each vertebra functions as part of a three-joint complex, with a large disc in the front and two facet (zygapophyseal) joints in the back. This tripod design is strong — keeping the bones linked together while allowing our spine to bend and twist. The more someone bends, the more the load on the discs increases. As one stretches backwards, the load on the facet joints increases. Degenerative changes in the spine may cause body weight to shift unevenly to the facet joints. This extra burden causes wear and tear on the joint and changes it over time. This may develop facet arthropathy.

Spinal canal

Your spine is made up of small bones (vertebrae) that are stacked on top of each other to create the spinal column. Each vertebra has a hole in the centre. The holes line up to make a tunnel called the spinal canal that runs the length of your spine. The spinal canal holds and protects the entire spinal cord and its nerve roots.

Spinal cord

The spinal cord itself is a large collection of nerve tissue that carries messages from your brain to the rest of your body and it is located inside the spinal (vertebral) canal in the cervical and thoracic spine. The spinal cord is a bundle of nerves like an electrical cable that carries messages back and forth between your brain and the rest of your body. It is very delicate and that’s why it is protected inside the spinal canal.

Meninges

The spinal cord is protected by a sheath that is called meninx. Between it and the spinal cord, there is a space which is filled with cerebrospinal fluid (CSF) that is produced in the brain.

Spinal nerve roots

There are 30 pairs of nerve roots where, depending on their location, they form the nerves in the upper limbs, lower limbs, pelvis, intestine and bladder.