The Axial Skeleton: Bones and Related Pain

The axial skeleton consists of all the bones in the central part of your body. This includes everything from your skull and ears to your neck, breastbone (sternum), spine, and ribcage.

There are 80 bones in the axial skeleton. They protect important organs and structures in your body such as your brain, heart, lungs, and spinal cord.

This article discusses the bones that make up the axial skeleton and some of the conditions that might affect them.

The Bones of the Axial Skeleton

There are 80 bones in the axial skeleton, which are divided into five groups:

• Bones of the skull and face
• Bones in the middle ear (the ossicles)
• Bone in the front of your neck (the hyoid bone)
• Rib cage
• Bones of the spine

The axial skeleton is distinguished from the appendicular skeleton, which includes the bones in your shoulders, arms, hands, pelvis, legs, and feet.

Bones of the Skull

The bones of the skull can be divided into two groups: the cranial bones and the facial bones.

There are eight cranial bones:

• Left and right parietal bones
• Left and right temporal bones
• Frontal bone
• Occipital bone
• Ethmoid bone
• Sphenoid bone

There are 14 facial bones:

• Left and right maxilla bones
• Left and right zygomatic bones
• Left and right nasal bones
  
• Left and right nasal concha bones
• Left and right palatine bones
• Left and right lacrimal bones
• Vomer bone
• Mandible
  

Ear Bones

The bones of the ear are called the auditory ossicles. They help transfer vibrations from your eardrum to your inner ear and are the smallest bones in your body. There are three ossicles bones in each ear:

• Malleus bones
• Incus bones
• Stapes bones

The Hyoid Bone

The hyoid bone is a horseshoe-shaped bone located at the front of your neck between your jaw bone and thyroid gland. It helps you breathe, move your tongue, and swallow. This bone is mobile, meaning it "floats" in place.

Rib Cage

There are typically 25 bones in the rib cage, including:

• The sternum (breastbone), which runs down the middle of your chest and provides a connection point for most of your ribs
• 12 pairs of ribs, though some people have an extra rib or an extra pair of ribs just above the collarbone. An extra rib is called a cervical rib.

Spine

Your spine includes 26 bones:

• 7 bones in your neck, called the cervical vertebrae
• 12 bones that attach to your ribcage from behind, called the thoracic vertebrae
• 5 bones that support your back, called the lumbar vertebrae
• The sacrum, which is the triangular bone at the back of your pelvis
• The coccyx or tailbone
  

Axial Skeleton Function

The bones of the axial skeleton help protect and support the organs and structures in the central part of your body, including your:

• Brain
• Heart
• Lungs
• Spinal cord

The muscles that you use to breathe and to move your head, neck, and torso are attached to the bones of your axial skeleton.

Conditions of the Axial Skeleton

Problems with the bones in the axial skeleton can cause pain that remains confined to the axial skeleton or radiates to an extremity. Some of these conditions can develop over time as the bones in your axial skeleton wear down. Others are caused by trauma or infection.

Trauma and Fractures

Fractures of the axial skeleton can happen due to traumatic injury. Older people are more susceptible to fracture because of loss of bone density and increased susceptibility to falls.

Radiculopathy

This condition is caused by irritation of a spinal nerve root. It tends to cause pain that originates in the axial skeleton and extends to an extremity.

Lumbar radiculopathy is also called sciatica. In the United States, up to 25% of all lower back pain is caused by lumbar radiculopathy. Sciatica is also used to describe the type of pain associated with radiculopathy: pain and electrical sensations that go down one leg or arm. 

This type of pain can have a number of causes, which include, but are not limited to, a pressured or irritated spinal nerve root.

Spinal Arthritis

Spinal arthritis can occur because of wear and tear in the bones of the back. It can also be caused by an autoimmune condition, injury, or infection. It is more common in the lower back, though it can occur anywhere on the spine.

People with spinal arthritis have pain and stiffness in the back. The condition is usually treated conservatively with non-steroidal anti-inflammatory medications (NSAIDs), physical therapy, or steroid injections. In rare cases, surgery may be needed.

Osteoporosis

People with osteoporosis have bone loss that causes their bones to become brittle and easily broken. The condition is associated with poor calcium and vitamin D intake, a sedentary lifestyle, and frequent consumption of alcohol.

Osteoporosis can cause back pain if the vertebra fractures or collapses. People with this condition also walk with a stooped posture and may lose height over time.

Paget's Disease of the Bone

Paget's disease of the bone is a condition that causes bones to become fragile and misshapen over time. It is caused by excessive breakdown of old bone and regrowth of new bone. In the axial skeleton, it is most common in the skull and spine.

Paget's disease is uncommon in younger people and the risk of developing it increases as you age. The condition is usually treated with bisphosphonates, medications that help strengthen your bones.

Vertebral Tumors

Tumors in the spine are often metastases from cancers that occur in other parts of the body. Less commonly, a tumor can begin in the spine. 

Vertebral tumors often cause neurological symptoms such as loss of sensation or weakness in the arms and legs, difficulty walking, and pain that radiates to other parts of the body.

Vertebra tumors may be treated with surgery, radiation, chemotherapy, or other medications. 

Bone and Joint Infections

It is possible to get an infection in the bones or joints of the axial skeleton. Some of the causes include:

• Septic arthritis, inflammation of the joints caused by a microbial infection
• Osteomyelitis, an infection that causes inflammation in the bone
• Infection of the spine by a bacteria or fungus that has spread from another part of the body
  

Preventing Axial Skeleton Conditions

You can keep your axial skeleton strong by adopting a healthy lifestyle. This includes:

• Exercising regularly
• Maintaining a healthy weight
• Getting plenty of sleep
• Quitting smoking
• Eating foods that contain calcium and vitamin D

Summary

Your axial skeleton includes the bones of your skull, ears, neck, spine, and ribs. There are a total of 80 bones in the axial skeleton.

The axial skeleton helps support and protect the organs and structures in the central part of your body, including the brain, heart, and lungs. 

Conditions of the axial skeleton include trauma and fractures, radiculopathy, spinal arthritis, and conditions that cause bone loss. It is also possible to develop tumors and infections in the bones of the axial skeleton.