Anatomy of the Spine
Your spine is a complex structure that supports your entire body, allowing you to bend, twist, stretch, walk and stand. The bones in your spine also protect the delicate spinal cord, which allows nerves throughout your body to communicate with your brain. Knowing your spine’s anatomy and the functions of all its various parts can help you better understand back and neck pain or a spinal condition or injury when talking about your treatment plan or communicating with your provider.
Spine Anatomy Basics
Your spine has 33 individual bones called vertebrae. These bones are connected to muscles, ligaments, cartilage and other tissues that help your body move. The spinal cord runs through holes in the center of these vertebrae, forming the spinal canal. Combined, your vertebrae, tissues and spinal cord form your spinal column, also called the vertebral column. Look at the spine diagram to help visualize the anatomical features of your spine.
Regions of the Spine
Your spine has five distinct regions, and your vertebrae are all given spine numbers depending on the region.
- Cervical spine, or neck: Your neck vertebrae hold the weight of your head and form the beginning of your spine. Cervical vertebrae are numbered C1 through C7. The top two vertebrae are also known as the atlas (C1) and the axis (C2) because they allow your head to move in various directions. Neck pain may also be referred to as cervical pain.
- Thoracic spine, or mid-back: Your thoracic vertebrae are the next 12 bones below the neck. They are numbered T1 through T12 and form joints with the ribs. Upper/middle back pain may be called thoracic back pain.
- Lumbar spine, or lower back: Your lumbar vertebrae are the next five bones below your mid-back and are numbered L1 through L5. These vertebrae are larger, as they bear the weight of your upper body. The lumbar spine, commonly affected by chronic low-back pain, is the region most likely to cause pain.
- Sacrum: The sacrum is a set of five vertebrae that fuse into one larger bone. The sacrum sits at the base of your spine and provides support for your body weight and pelvis.
- Coccyx: Often referred to as the tailbone, the bones of the coccyx are also fused. Your coccyx functions as an attachment point for several muscles and ligaments.
Parts of the Spine
In addition to your vertebrae, your back anatomy consists of nerves, joints, muscles, tendons and ligaments. These help you move but can also cause pain and other issues if they become injured.
- Cauda equina: A Latin phrase that means “horse’s tail,” this is the bundle of nerves at the end of the spinal cord.
- Facet joints: The bony articulations between vertebrae, facet joints allow the spine to bend and twist. Each vertebra has four facets, two above (superior) and two below (inferior).
- Intervertebral discs: Situated between adjacent vertebral bodies, intervertebra discs act as shock absorbers in the spine. They consist of an outer ring and an inner, gel-filled area. As you age, this tissue tends to break down, causing multiple types of disc problems.
- Ligaments: Ligaments are fibrous bands that connect your bones. Your spine has multiple ligaments that provide stability between vertebrae.
- Muscles: Your spine muscles allow you to move but also provide stability.
- Sacroiliac joint: Also called the SI joint, this joint connects the sacrum and the ilium in your pelvis. Many people experience sacroiliac joint pain.
- Spinal cord: The spinal cord is the major neurological pathway of the body. About 18 inches long, it connects your brain to the nerves elsewhere in your body. Spinal cord anatomy includes nerves and layers of protective tissue.
- Spinal nerves: You have 31 pairs of spinal nerves. Each pair of spinal nerves exits the spine through a small hole between the vertebrae known as the foramen.
