Welcome to Hicksville Physical Therapy’s patient resource about Lumbar Spine problems.
If you are experiencing lower back problems, it may be beneficial to learn about the anatomy of your back so you can properly convey your back pain to your doctor, and have the knowledge for future care.
There are two terms that stand out when talking about the lower back. The “anterior” refers to the spine’s front, while the “posterior” refers to the spine’s back. Another important term is the “lumbar spine”, referring to the section that makes up the lower back, and with it the “anterior lumbar area” that is the front of the lower back, while the “posterior lumbar area”, or the back of the lower part of the spine.
This article is meant to help you gain a general sense of the anatomy of the low back. It is meant to make you understand:
Notable parts of the lumbar spine are the:
The following section will focus on summarizing the importance of these structures.
Bones and Joints
The human spine consists of 24 spinal bones, called vertebrae, that stack on top of each other and form the spinal column. The spinal column serves to support the body and allows you to keep yourself upright.
The spine forms three curves from the side. The curves are called the cervical spine, which curves inwards on the neck, the thoracic spine that curves outwards on the middle back, and the lower back or lumbar spine curves inwards. Exaggerated curving of the thoracic spine is called kyphosis, while exaggerated curving of the spine is called lordosis.
The lumbar spine consists of the lower five vertebrae, and are often labeled with the tags L1 to L5. The lowest vertebra of the lumbar spine, L5, connects to a triangular bone at the base of the spine between your two pelvic bones, a bone called the sacrum. Some people may have a sixth vertebra beyond the common lumbar five, but having an extra doesn’t seem to affect your spine or cause additional problems.
Vertebra come into fruition through vertebral bodies, or round blocks of bone. The lumbar vertebral bodies are taller and bulkier when compared to other parts of the spine, as the lower back has to withstand pressure due to body weight and when the body conducts motions like lifting, carrying and twisting. The large muscles that attach in the proximity of the lumbar spine may also place extra force on the lumbar vertebral bodies.
A bony ring latches onto the back of each vertebral body, and has two parts: two pedicle bones that directly attach to the back of the vertebral body, while two lamina bones fuse with the pedicles and complete the ring. The lamina bones also make up the outer rim of the bony ring. When the vertebrae stack on top of each other, the bony rings form a hollow tube that surrounds the spinal cord and nerves, and the laminae protect the nerve tissues.
The area where the two lamina bones join together, at the back of the spine, will have a bony knob. The bony knob projects at this point, and the projections, called spinous processes, are the points that you feel if you touch the back of the spine. Each of your vertebrae also have two bony knobs that point to the side, named transverse processes, and are located on your left and right. These projections are broader than other areas of the spine, as your large back muscles tend to place powerful forces onto them.
Located between the vertebrae of each section of your spine are two facet joints. They are located on the back of the spinal column, and are between each pair of vertebrae, on each side of the spine. They are made of small bony knobs lining up along your back, and when meeting, fuse together to form a joint connecting your two vertebrae. The facet joints of the lumbar spine are the ones that allow for mobility if you bend forward and backwards.
The facet joints are covered by articular cartilage, which is a smooth and rubbery material that lines the ends of bones when they form joints. They are the tissues that provide cushion and allow bones to move together in a friction-free environment.
Each side of the vertebra includes a small tunnel named a neural foramen (plural foramina). The two nerves that leave the spine at each vertebra go through the foramina through the left side and the right side. The intervertebral disc (which will be elaborated on later in this document) is located directly in front of the opening; if the disc starts protruding or bulging, it becomes herniated, and can narrow the opening, putting pressure on the nerves. A facet joint is also positioned in the back of the foramen. If a bone spur occurs on the facet joint, it can protrude into the tunnel, leading for the hole to become narrower and thus pinching the nerve.
The spinal cord consists of millions of nerve fibers, making it an integral and very sensitive part of your back. It is surrounded by a hollow tube of bony rings that protect it, mimicking your brain’s skull.
The spinal cord is a long wire that goes down all the way to the L2 vertebra. Below this level, the spinal canal is filled with fluid that bathes the nerves, and then goes down to the lower limbs and pelvic organs. The nerves the spinal cord contains are called cauda equina, Latin for horse’s tail.
Two large nerves branch off the spinal cord on both the left and right side, between the vertebrae, and through the neural foramina The spinal nerve groups together, forming the main nerves going to the organs and limbs. The cauda equina nerves that were previously mentioned go to the pelvic organs and the lower limbs.
Connective tissues are made of systems of fibers that help the body with cohesion and internal support, while ligaments are connective tissues that band your bones together. Several long ligaments attach to each other on the front and back sections of your vertebrae. The anterior longitudinal ligament is a ligament that runs along the length of the front of the vertebral bodies, while two other ligaments run at their fullest within the spinal canal. Meanwhile, the posterior longitudinal ligament runs on the back of the vertebral bodies, and the ligamentum flavum is a yellow band of elastic that gets its color from elastin (a springy type of collagen, an abundant protein found in your connective tissues) and connects itself to the frontal surface of the lamina bones behind the spinal cord. Thick ligaments secure the bones of the lumbar spine to the sacrum, a bone below L5, and your pelvis.
Between each vertebral body is a cushion called an intervertebral disc. Each disc absorbs the stress and shock the body incurs during movement and prevents the vertebrae from grinding against one another. The intervertebral discs are the largest structures in the body without a vascular supply. By means of osmosis, each disc absorbs needed nutrients.
A special structure in the spine located between each vertebral body is a cushion made of connective tissue called an intervertebral disc. Each disc serves as a shock-absorption device and protects the vertebrae, made of collagen cells, or abundant and naturally-occurring proteins made in the body.
These discs are made of two parts: the center, called the nucleus, that provides most of the spine’s shock absorption, and the annulus ligaments that surround the nucleus and hold it in place.
The lower back’s muscles are arranged in several layers. The superficial layer that lines the skin’s surface are a thick tissue called the fascia. In the middle is the erector spinae, which actually consists of several muscles, and runs through the lower ribs, chest, and lower back. The middle layer, together with the lumbar spine, form a thick tendon to bind the lower back, pelvis and sacrum. Then, the last and deepest layer of muscles attaches to the back of the spine bones, allowing for the lower back, pelvis and sacrum to join together. These muscles, along with the muscles of the abdomen, keep the spine poised whenever you’re doing any kind of activity.
Learning about the spinal segment can also help you understand the rest of the back. The spinal segments contain two vertebrae that are divided by an intervertebral disc, nerves leaving the spinal column at each vertebra, and the facet joints linking the spinal column levels together.
The intervertebral disc splits the vertebral bodies of the spinal segment up, and serves in shock absorption, protecting the spine from any hard-hitting activities like jumping, running and lifting, and from the forces of gravity.
The spinal segment is binded by two facet joints; when these joints move together, the lumbar spine bends and also allows for your lower back to move and turn.
The back consists of many different bones and muscles that protect the spine and allow for flexible movement. Having insight to the basic anatomy and parts of the lumbar spine can assist in proper back care and allow for you to convey any issues you may have with your back to your doctor at Hicksville Physical Therapy.