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Anatomy of the Spine: How It Works & What Makes It Hurt

Published April 30, 2021
| Written By SpineNation Editorial Staff   | Medically Reviewed by Allen Conrad, BS,DC,CSCS
The spine, or spinal column, is comprised of vertebrae stacked vertically and separated by the cushioning of intervertebral discs. Most people are born with 33 vertebrae. During the body’s normal development, the vertebrae at the bottom of the spine fuse, leaving the post-adolescent spine with 24 vertebrae.  

The primary purpose of the spine is to keep the body upright, to allow safe bending and twisting movements, and to protect the spinal cord. 

The spinal cord is directly connected to the brain stem and is an extension of the central nervous system—the body’s hub for all voluntary and involuntary movement.

The spine consists of bones, joints, ligaments, discs, and nerves. There are five sections of the spine, and each one alternates between a lordotic and kyphotic curve.


The 5 sections of the spine

C1-C7

The cervical spine, aka your neck, consists of seven bones that begin at the cranium and end at the first thoracic vertebra. This is the most flexible part of the spine, and yet it is strong enough to hold 10-13 pounds of weight from the head.

These seven vertebrae support the skull while allowing for a wide range of neck movement. This spinal region is also responsible for sensations in the neck, shoulders, portions of the upper arms, face, and scalp. The cervical spine stimulates saliva, gallbladder, and intestinal activity, controls pupil and airway constriction, slows the heartbeat and inhibits the release of glucose. 

Common Injuries 
Common disorders that affect this portion of the spine are cervical spondylosis, degenerative disc disease, and herniated discs.

Curvature 
The cervical spine has a lordotic curve.

T1-T12

The thoracic spine embodies 12 vertebrae and is commonly known as the upper back.

This portion of the spinal column is directly attached to the rib cage, limiting its range of motion but in turn creating the section of the spine that is the most stabilizing and the least prone to injury.

The thoracic region nerves inhibit stomach, gallbladder, and intestinal activity, aid in breathing and coughing, increases heartbeat, stimulates glucose release, and secretes epinephrine. 

Common Injuries 
Scoliosis, disc herniation, and abnormal kyphosis are disorders that can affect the thoracic spine. 

Curvature 
The thoracic spine curves kyphotically.

L1-L5

The lumbar spine is part of the lower back and it ends at the sacrum. Most people have five lumbar levels (L1-L5), although it is possible to have 6 (L6). 

The lumbar spine bears more weight than any other section of the spine, making it the most likely to become injured or cause pain.?The nerves in this region supply the legs, pelvis, bowel and bladder, and control sexual function. They are also responsible for sensations in the feet, legs, pelvis, and lower abdomen.  

The spinal cord ends between L1 and L2. 

Common Injuries 
Common lower back dysfunctions include herniated discs, sciatica, and muscle strain. 

Curvature 
The lumbar spine has a lordotic curvature.

S1

The sacrum is a triangular-shaped bone at the bottom of the spine that is connected to the pelvis. It contains a bundle of small nerves that transmit messages between the brain and the lower body, including organs such as the large intestines and bladder. 

The sacrum aids in bladder contraction and sexual function. 

Curvature 
The sacrotic portion of the spine has a kyphotic curvature. 

C

The coccyx, or tailbone, is considered vestigial, or no longer functional because of evolution. 

It does, however, offer some assistance within the pelvis, including pelvic floor aid and balance while sitting.

Curvature 
Like the sacrum, the coccyx has a kyphotic curve.  


Anatomy-of-the-Spine-vertebrae.jpeg


Parts of the spine

Vertebrae

The bones that join to form the spinal column. The main functions of the spine are to protect the spinal cord, nerve roots, and several internal organs; provide support to maintain an upright posture; and enable flexible movement. Damage to the vertebrae, depending on the severity, can result in pain, difficulty with motion, even paralysis.  

Facet joints

Connects individual vertebra and allows flexion and extension (forward and backward movement) of the spine. Each vertebra contains two facet joints, which act as a doorway through which nerve signals travel to other parts of the body. Symptoms of facet joint disorders include localized, referred, and/or radiating pain, tenderness, stiffness, and feelings of grinding or grating in the joints upon movement. 

Discs

The rubbery cushions between each vertebra that absorbs shock and allows movement. Common ailments include herniated disc, bulging disc, and degenerative disc disease. Some symptoms of disc damage are pain ranging from mild to debilitating, weakness, numbness, tingling, sciatica, and difficulty walking. 

Ligaments

A natural brace that provides joint stability and helps prevent injury by restricting some instances of hyper-extension and hyper-flexion, and by prohibiting movement in certain directions altogether. Torn ligaments can cause pain, swelling, bruising, and muscle spasms. Movement will also be impaired.  

Muscles

Make bending, stretching, lifting, and arching movements possible. There are four types of spinal muscles—forward flexors; lateral flexors; rotators; and extensors. The muscles of the spine work together with the ligaments to stabilize the spine and keep it in an upright posture, as well as controlling movements during rest and activity. If a muscle becomes strained, it can cause inflammation, pain, and spasms.

Spinal cord

A tubular structure made up of nerves that begin at the brain stem and end within the lumbar spine. The spinal cord works in unison along with the brain to make up the central nervous system. It is the message pathway from the brain to the body for movement, sensation, and control of bodily functions. When any part of the spinal cord is injured, the ability to control limbs and bodily functions is at risk. To what extent depends on the location and severity of the injury. 

A complete spinal cord injury is when all feeling and movement ability is lost below the spinal cord. If the areas below the spinal cord retain at least some feeling and function, then the injury is called incomplete.  


Forms of Paralysis

Quadriplegia

When the injury affects the arms, hands, trunk, legs, and pelvic organs. 

Paraplegia

When the injury affects the trunk, legs, and pelvic organs.  



A healthy spine

From the front view, the healthy spine is straight. Viewed from the side, the spine has four alternating curves — kyphotic or lordotic—that form an “S” shape. A kyphotic curve is the outward curve seen in the thoracic level and the sacrum. A lordotic curve, when viewed laterally, is an inward curve of the spine, as is found in the cervical and lumbar portions of the spine. 


Abnormal curvatures

Lordosis

While some lordosis is normal, too much (aka swayback) puts pressure on the lumbar and cervical spine and can cause discomfort.

Kyphosis

Excessive rounding of the thoracic spine causes “round back” or “hunchback.”

Scoliosis

A lateral (sideward) curvature of the spine when viewed from the front or back. There are eight types of scoliosis, which fit into three categories: idiopathic, congenital, and neuromuscular. Most types of scoliosis are from an unknown cause and fit into the idiopathic category. Congenital forms result from a defect that is present at birth. Neuromuscular forms develop because of neurological or muscular disease.  
Updated: May 5, 2021
Disclaimer

Information provided within this article is for educational purposes and is not a substitute for medical advice. Those seeking specific medical advice should consult his or her doctor or surgeon. If you need to consult with a specialist, you may be able find a health care provider in our Specialist Finder. SpineNation does not endorse treatments, procedures, products or physicians.


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Contributors and Experts

Dr. Allen Conrad, BS,DC,CSCS is a Doctor of Chiropractic and a Certified Strength and Conditioning Specialist through the National Strength and Conditioning Association (NSCA).
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