Spine Anatomy: Structure, Regions and Functions of the Spine

Spine anatomy refers to the central skeletal structure formed by bones called vertebrae that extend between the head and the pelvis in the human body. This structure creates a protective canal for the spinal cord, enables the body to remain upright, and contributes to the balanced execution of movement ability and load-bearing functions.

The cervical, thoracic, and lumbar spine regions form the three main functional segments of the spine anatomically. While the cervical region supports neck movements, the thoracic vertebrae are connected to the rib cage; the lumbar vertebrae, on the other hand, consist of strong and broad structures that carry most of the body weight.

The intervertebral disc structure is one of the main components of spine anatomy that provides movement and flexibility. These discs consist of a gel-like nucleus pulposus and the surrounding annulus fibrosus layers; they absorb shock, reduce friction between vertebrae, and help the spine move flexibly.

Spinal ligaments and the muscle system are supportive anatomical structures that ensure the stability of the spine. While ligaments maintain the connection and alignment of the vertebrae, paravertebral muscles control spinal movements and play an important role in maintaining posture, balancing the distribution of mechanical load.

What Is Spine Anatomy?

Our spine may appear from the outside as a simple, load-bearing column made up of stacked bones. However, when examined more closely within the body, it becomes immediately apparent that this structure is an incredibly complex and dynamic system. It is a magnificent bridge that carries the load of our body, allows us to bend and straighten, and more importantly, protects the vital nerve networks that originate from our brain and extend to all our organs. Every millimeter of this bridge works in perfect biomechanical harmony. Thanks to advancing technology and modern medicine’s advanced imaging devices, we can now map this massive structure not just as a static skeleton, but as a living, breathing, nourished, and constantly interacting network. Today, many neck and lower back conditions can be treated by directly targeting the source of the problem without the need for large incisions in the body. For such delicate and minimal interventions to be successful, it is essential to have a thorough understanding of the hidden topography of the spine. The subtle curves of the bones, the narrow pathways of the vessels, and the dark corridors where nerves branch are the keys to achieving healing without harming the patient. The better this structure is understood, the safer and more effective the procedures become.

Why Is the Anatomy of the Second Cervical Vertebra (C2) in Our Neck Region So Sensitive?

Our neck region is the most mobile, most flexible, and at the same time the most delicate part of the spine anatomically. In particular, the second cervical vertebra (C2), known in medical terminology as the “axis,” is located at the very center of the mechanism that allows our head to rotate right and left. The sense of freedom we feel when turning our head to check the blind spot while driving is largely due to the unique design of this vertebra. However, this region stands out not only for its mobility but also for the vital structures it contains. One of the main arteries that carries blood to the brain, the vertebral artery, passes extremely close to this vertebra, almost brushing against it. Therefore, severe accidents, falls, or advanced joint degeneration in the neck region require a very careful approach. When it becomes necessary to stabilize the neck bones in such cases, the procedures must be performed with millimetric precision. Screw fixation procedures performed using the thin bridges located at the back of the bones are the safest way to protect this critical artery leading to the brain. However, just as not everyone’s bone structure, height, or weight is the same, the thickness of these bones also varies. Millimetric measurements made with computed tomography scans taken before the procedure ensure that the treatment is planned entirely specific to the individual.

The anatomical parameters considered in cervical vertebra measurements are as follows:

• Width
• Length
• Thickness
• Angle

How Does the Anatomy of the Artery of Adamkiewicz That Nourishes Our Spine Work?

For our spine and the spinal cord within it to function properly, they must be well nourished, meaning adequately supplied with blood. One of the most complex and perfectly functioning vascular networks in our body is located here. Small branches originating from our main artery, the aorta, extend toward the spine, continuously carrying oxygen and nutrients to these delicate tissues. The most vital part of this system is the vessel known in medicine as the “artery of Adamkiewicz.” This vessel is like the main electrical grid of a large metropolis. It is responsible for supplying a vast portion of the spinal cord, extending from the lower chest region to the lumbar area, almost single-handedly. On imaging devices, it is seen to progress with a characteristic hairpin-like curve. During needle-based local treatments or when intervening in malignant tumors around the spine, identifying the location of this artery is an absolute necessity. If this artery is accidentally damaged or blocked during the procedure, the blood flow to that part of the spinal cord is suddenly cut off. The consequences are quite severe; serious neurological losses can occur, ranging from sudden loss of strength in the legs and inability to control urination to permanent paralysis. For this reason, the exact route of the artery is mapped with contrast imaging before the procedure.

The body levels where the artery of Adamkiewicz may originate are as follows:

• Back
• Chest
• Lower back

What Does the Spinal Anatomy Network Known as the Batson Venous Plexus Tell Us?

Not only the arteries that deliver clean blood to tissues but also the venous system that collects and returns deoxygenated blood has a very unique structure around the spine. This complex network is called the “Batson venous plexus.” In many veins in our body, such as those in our legs, there are small one-way valves that prevent blood from flowing backward due to gravity. However, this special vascular network around the spine lacks such valves. This means that blood can move freely in both directions within these vessels depending on pressure changes inside the body. During intense coughing, straining, or lifting heavy objects, when intra-abdominal pressure increases, blood can flow backward in these vessels. While this is a natural way for the body to balance pressure, it has important medical consequences. These valve-free pathways allow malignant tumor cells from another part of the body, such as the prostate or breast tissue, to spread more easily to the spine via the bloodstream and settle there. At the same time, the possibility that filling materials used in bone fractures may be carried to the lungs through these vessels is always taken into account due to this structure.

The risk factors that may arise related to the spinal venous network are as follows:

• Leakage
• Metastasis
• Embolism

How Does the Kambin Triangle Within Spine Anatomy Provide a Safe Zone in Procedures?

If we imagine our spinal cord as a massive multi-lane highway, the toll booths through which vehicles exit this highway are the small bony windows we call the “neural foramen.” The sensory and motor nerves that spread to every part of our body exit the spine through these openings. The condition commonly known as a herniated disc in the neck or lower back occurs when the cushioning structures between the vertebrae protrude outward and enter this narrow opening, compressing the nerve trying to pass through. The compressed nerve cannot function properly, gradually swells, becomes inflamed, and this turns into unbearable stabbing pain radiating to the leg or arm. In such a situation, when we want to reach this area with a needle and relieve the nerve, we must absolutely avoid touching this already highly sensitive nerve with the needle tip. At this point, the “Kambin Triangle” offered by nature comes into play. This triangle is a virtual space formed by the anatomical structures in the target region. It is like a clean corridor where one can safely walk in a dangerous terrain. Using live X-ray devices, the tip of the needle is directed precisely to the center of this triangle, into the safe zone.

The structures forming the boundaries of the Kambin triangle are as follows:

• Nerve
• Vertebra
• Joint

How Is Cement Treatment Anatomy Applied in Spine Fractures Caused by Osteoporosis?

As age progresses, the gradual decrease in bone quality, commonly known as osteoporosis, can cause the vertebral bones to weaken and silently collapse inward. Sometimes, other diseases that spread to the spine similarly destroy the structural strength of the bone. These collapsing bones cause severe pain in the back with every breath or when getting out of bed, leading over time to height loss and a hunched posture. While such patients previously required major and difficult open surgeries, today there are much more refined methods using “bone cement.” To address this mechanical weakness in the spine, a needle is inserted through a tiny point in the back under live imaging guidance directly into the center of the fractured bone. A medical filling material in liquid form is slowly injected into that area. This special substance hardens within minutes, preventing the fractured pieces inside the bone from rubbing against each other and immediately relieving the pain. In necessary cases, before injecting the filling material, a small medical balloon is placed inside the bone. This balloon is slowly inflated to lift the collapsed bone back toward its original height.

The clinical conditions where cement treatment is frequently applied are as follows:

• Osteoporosis
• Tumor
• Fracture
• Collapse

How Are Transforaminal Injections Performed Under the Guidance of Spine Anatomy?

In cases of cervical and lumbar disc herniation that do not require urgent surgical intervention, one of the most commonly used and effective methods is transforaminal epidural injections, also known as “targeted injections.” The main purpose of this procedure is to reach the narrow area where the herniation compresses and inflames the nerve with an extremely thin needle and deliver medications directly onto the target to suppress the edema and cellular inflammation around the nerve. Since the medication is delivered only to the problematic area rather than entering systemic circulation, it provides a much stronger and faster recovery compared to oral medications or intramuscular injections. The secret behind this success lies in perfectly reading the patient’s anatomical map. While the patient lies face down, the spinal region is visualized with a live X-ray (fluoroscopy) device. When the device is tilted at a certain angle to achieve the correct view, the vertebrae on the screen form a silhouette resembling a small dog (“Scotty Dog”). The targeted entry point corresponds to the neck area of this silhouette. Before administering the medication, a special contrast dye is injected to confirm the exact position of the needle.

The guidance angles used in targeted procedures are as follows:

• Anterior
• Posterior
• Lateral
• Oblique

How Are Facet Joint Anatomy-Related Pain Treated with the Radiofrequency Method?

Many people with chronic lower back pain believe that the problem is only caused by herniated discs in the spinal canal. However, a large portion of chronic neck and lower back pain that lasts for years originates from the small joints located at the back that connect the vertebrae. These small support points are called “facet joints.” Just like the joints in our knees, shoulders, or fingers, these joints also wear out, dry out, and develop degeneration over time and with heavy load. Degenerated joints begin to produce pain by rubbing against each other as the patient moves. The stiffness felt especially when getting out of bed in the morning is a typical sign of this condition. This pain is perceived by very fine nerves surrounding the joint like a network and transmitted to the brain. To confirm that the problem originates from these joints, a diagnostic test is first performed; these fine nerves are temporarily numbed with medication. If the patient’s pain disappears immediately, the target is confirmed. Then, to provide more lasting relief, an advanced technology called radiofrequency ablation (RFA) is used. By reaching these nerves with the tip of a needle, controlled heat is generated with radio waves, preventing the nerve from sending pain signals for a long time.

The different application types of radiofrequency technology are as follows:

• Thermal
• Pulsed
• Cooled

Which Nerves Are Affected by Cervical and Lumbar Disc Herniations Within Spine Anatomy?

The human body functions in an extraordinary order, like a magnificent electrical system. Each nerve emerging from our spine is responsible for the muscle strength, sense of touch, and even sweating of a specific region of the body. Therefore, carefully listening to where a patient feels numbness or weakness is the first and most important step in determining exactly where the problem lies in the spine. When a disc in the neck region protrudes outward, it compresses the “electrical cables,” that is, the nerves that extend to our shoulders, arms, and fingers. For example, a herniation at a specific vertebral level may cause numbness only in the thumb and lead to dropping objects, while a herniation at a lower level may affect the middle finger or the muscles at the back of the arm. This mapping works with excellent harmony in the lumbar region as well. Whether the herniation protrudes from the center of the spinal canal or from a narrow lateral passage directly changes the number of the compressed nerve. The valuable clues obtained during physical examination are combined with MRI images to fully clarify the anatomical problem.

The main regions where numbness and pain are experienced in cervical disc herniations are as follows:

• Shoulder
• Arm
• Elbow
• Hand
• Finger

What Is the Anatomy of Spinal Canal Narrowing (Spinal Stenosis) and What Are the Non-Surgical Solutions?

Over the years, the relentless effects of gravity, our lifestyle, and the natural aging process change the shape of our spine. Degenerative changes in the bones, thickening of the posterior joints, and the loss of elasticity of the ligaments that have supported the spine for years gradually narrow the tunnel through which the spinal cord and nerves safely pass. This condition is called spinal canal narrowing (spinal stenosis). When this normally spacious canal becomes narrowed, the nerve tissues passing through it begin to be compressed. The most typical complaint of individuals with this condition is a heavy sensation radiating to the legs after walking or standing for a while, along with tingling, weakness, and unbearable cramps. The patient feels the need to sit down and rest or bend forward. It is not possible to mechanically widen this narrowing caused by bones and hardened ligaments with an external needle. However, the severe inflammation and edema around the nerves constantly rubbing in this narrow area can be significantly reduced with targeted injection treatments. When the edema decreases, the nerves can “breathe” more easily, and the patient’s walking capacity improves.

The complaints experienced by patients with spinal canal narrowing while walking are as follows:

• Pain
• Numbness
• Cramp
• Tingling
• Weakness

How Is Safety Ensured in Interventional Procedures Under the Guidance of Spine Anatomy?

Reaching the target directly through needle punctures without making large surgical incisions in the patient’s back or neck provides great comfort and safety for the patient. There are no difficult recovery processes after the procedure, and patients can return home walking on the same day. However, since we cannot directly see the vital structures deep within the body with the naked eye, these procedures require extremely meticulous and uncompromising safety protocols. Even the slightest deviation of the needle tip can damage nerves or vessels. Therefore, the golden rule is clear: no interventional procedure can be performed blindly, based on estimation, or solely by feel. Advanced imaging devices that provide real-time visualization of the inside of the body must be used. Thanks to these systems, the progression of the needle is monitored millimeter by millimeter. To prevent accidental injection into a vessel in the neck or lower back region, special contrast agents are used during the procedure. To minimize the risk of bleeding, the patient’s daily blood-thinning medications are carefully managed well before the procedure, and hygiene standards are maintained at the highest level.

The devices used for live imaging during the procedure are as follows:

• Fluoroscopy
• Ultrasonography
• Tomography

Frequently Asked Questions

Prof. Dr. Özgür KILIÇKESMEZ

Prof. Dr. Özgür Kılıçkesmez is one of Türkiye’s leading interventional radiology and neuroradiology specialists, focusing on minimally invasive endovascular treatments. His primary areas of expertise include aneurysm and stroke treatments, embolization procedures, non-surgical treatments of thyroid and parathyroid diseases, interventional oncology, and peripheral vascular interventions. He currently serves as the Head of the Interventional Radiology and Neuroradiology Department at Istanbul Memorial Göztepe Hospital.
Graduating from Istanbul University Cerrahpaşa Faculty of Medicine in 1997, Prof. Dr. Kılıçkesmez received advanced training in interventional radiology and oncology as a Clinical Fellow at London Guy’s & St Thomas’ and King’s College Hospital between 2012 and 2013. He earned the title of Professor in 2020 and, in the same year, became the Founding Interventional Radiologist at SBÜ Çam and Sakura City Hospital. He also holds the EBIR (European Board of Interventional Radiology) certification.
Prof. Dr. Kılıçkesmez has 94 international and 40 national publications and over 2500 citations. He serves as a reviewer for prestigious journals such as the American Journal of Roentgenology (AJR) and Diagnostic & Interventional Radiology. With his clinical and academic expertise, he is a nationally and internationally recognized authority in stroke treatment, brain aneurysm, embolization, tumor ablation, and minimally invasive treatments of thyroid/parathyroid diseases.