Axial Skeleton

What is the axial skeleton?

The adult human body has 206 bones. These bones are divided into two main parts: Your appendicular skeleton and your axial skeleton. Your axial skeleton is made up of the bones along your vertical axis. Axial comes from the word “axis,” which means line. The bones line up along the central core of your body.

What’s the difference between the axial and appendicular skeleton?

Your axial skeleton is made up of the bones in your head, neck, back and chest. Your appendicular skeleton is made up of everything else — the bones that attach (append) to your axial skeleton. Your appendicular skeleton includes the bones in your shoulders, pelvis and limbs, including your arms, hands, legs and feet.

What is the major function of the axial skeleton?

Your axial skeleton provides support and cushioning for your brain, spinal cord and organs in your body. Muscles in your body that move your head, neck and trunk attach to your axial skeleton. These muscles help you breathe and steady parts of your appendicular skeleton.

How many bones are in the axial skeleton?

Your axial skeleton is made up of 80 bones.

What are the five parts of the axial skeleton?

The five parts of your axial skeleton include the bones in your skull, ossicles (small bones) of your middle ear, hyoid bone of your neck, vertebra (bones of your spine) and thoracic cage (ribcage).

Which bones belong to the axial skeleton?

The axial skeleton includes bones in your skull, ears, neck, back and ribcage:

Skull

Your skull has two sets of bones: Eight cranial bones and 14 facial bones. The cranial bones make up the top and back of your skull and support and protect your brain. The eight cranial bones include:

• Two parietal bones (left and right).
• Two temporal bones (left and right).
• One frontal bone.
• One occipital bone.
• One ethmoid bone.
• One sphenoid bone.

The facial bones make up the face of your skull and form an entrance to your body. The 14 facial bones include:

• Two maxilla bones (left and right).
• Two zygomatic bones (left and right).
• One mandible bone.
• Two nasal bones (left and right).
• Two palatine bones (left and right).
• Two nasal concha bones (left and right).
• Two lacrimal bones (left and right).
• One vomer bone.

Ears

The auditory ossicles (small bones) of your middle ear are the smallest bones in your body. These tiny bones transfer vibrations from your eardrum to your inner ear. The middle ear bones include:

• Two malleus bones (one in each ear).
• Two incus bones (one in each ear).
• Two stapes bones (one in each ear).

Neck

The hyoid bone is a horseshoe-shaped bone that sits at the front of your neck. Muscles and ligaments hold it in place between your jaw bone and thyroid. Your hyoid bone helps you breathe, speak and swallow.

Back

The vertebral column, or spine, includes 24 vertebrae plus your sacrum and your tailbone (coccyx). The vertebral column extends from the base of your skull to your pelvis. It’s grouped into five sections:

• Seven cervical vertebrae: These bones form your neck and support your head.
• 12 thoracic vertebrae: These bones form the rear anchor of your ribcage.
• Five lumbar vertebrae: These bones support most of your body’s weight and attach to your back muscles.
• Sacrum: The sacrum is a triangular bone that forms the back wall of your pelvis.
• Coccyx (tailbone): The coccyx sits at the bottom of your spine and connects to many muscles in your body.

Ribcage

The thoracic cage, or ribcage, protects your heart, lungs and other organs. It attaches to muscles involved with breathing and arm movement. The bones in your ribcage include:

• Sternum (breastbone): This is a long, flat bone that runs down the middle of your chest.
• 24 ribs: Most people have 12 pairs of ribs.

What conditions can affect the axial skeleton?

Many conditions can cause problems with your axial skeleton. Some develop due to wear and tear as you age. Others happen as a result of disease or injury. Conditions that may affect your axial skeleton include:

• Ankylosing spondylitis: Ankylosing spondylitis is a type of arthritis that causes long-term (chronic) spine inflammation and lower back pain.
• Axial spondylometaphyseal dysplasia: Axial spondylometaphyseal dysplasia is a genetic bone growth disorder that causes shortened height (stature).
• Fibrous dysplasia: Fibrous dysplasia causes bones to break easily because fibrous, bone-like tissue replaces normal, healthy bone.
• Fractures: Bones lose their density as you age, and less-dense bones can lead to broken bones.
• Melorheostosis: Melorheostosis is a rare disease that causes the outer layers of your bones to thicken or widen.
• Osteoporosis: Osteoporosis is a disease that can lead to fragile, brittle bones if you don’t get enough calcium.
• Paget’s disease of the bone: Paget’s disease of the bone is a disorder that causes your bones to grow larger and weaker than normal.

How can I keep my axial skeleton healthy?

The best way to take care of your axial skeleton is to maintain a healthy lifestyle. To keep your bones strong and healthy:

• Exercise: Cardio and strength training can both help strengthen your bones.
• Sleep: Get at least seven hours of sleep each night so your bones can recover and rebuild overnight.
• Maintain a healthy weight: Excess weight can put too much pressure on your bones.
• Get plenty of calcium and vitamin D: Consume milk, yogurt and almonds to keep your bones strong.
• Don’t smoke: Smoking decreases adequate blood flow, which your bones need to stay healthy.
• See your healthcare provider regularly: If you’re over 65, ask your healthcare provider about taking a bone density test.

A note from Cleveland Clinic

Your axial skeleton is made up of the 80 bones within the central core of your body. This includes bones in your head, neck, back and chest. Your axial skeleton protects and cushions your brain, spinal cord and organs. Many different health conditions can affect your axial skeleton, so it’s important to keep it healthy and strong. By maintaining a healthy lifestyle, you should be able to lower your overall risk for disease and injury. By taking good care of yourself, you’ll be able to protect your bones so they can keep protecting you.