The Anatomy of the Skeletal System

The skeletal system comprises 206 bones and has two main parts—the axial skeleton and the appendicular skeleton. The skeletal system includes your bones, ligaments that attach bone to bone, and cartilage that provides padding between your bones.

This article discusses the anatomy of the skeletal system—what it's made of, how it's organized, conditions that affect it, and tests that assess it.

Woman teaching a class about the anatomy of the skeletal system as students take notes

SDI Productions / Getty Imgaes

Skeletal System: Labeled Diagram of Major Organs

In addition to the bones, organs of the skeletal system include ligaments that attach bones to other bones and cartilage that provides padding between bones that form joints throughout your body.

The bones are divided into two main categories—the axial skeleton, which contains the bones that support the middle of your body, and the appendicular skeleton, which includes bones that make up your appendages—arms and legs—and bones that attach your limbs to your axial skeleton.

The Skeletal System Tour

Axial Skeleton

The axial skeleton forms the "axis" that runs down the center of the body. There are 80 bones that make up the axial skeleton.

Skull (Cranium)

Your skull (cranium) is made up of cranial and facial bones. Cranial bones protect your brain, while facial bones make up your facial structure. Skull bones include the following:

Cranial bones include:

  • Frontal
  • Parietal
  • Occipital
  • Temporal
  • Sphenoid
  • Ethmoid

Facial bones include:

  • Maxillae (upper jaw)
  • Vomer
  • Mandible (lower jaw)
  • Lacrimal
  • Zygomatic (cheekbones)
  • Nasal
  • Palatine
  • Inferior nasal conchae

Auditory Ossicles

The auditory ossicles consist of a total of six tiny bones, with three in each ear. They are located in the inner ear and are structures that help create sound in your body. The auditory ossicles include the following:

  • Malleus
  • Incus
  • Stapes

Hyoid Bone

The hyoid bone is a horseshoe-shaped bone located in the throat. It is part of bodily functions like speaking, swallowing, and airway maintenance.

Vertebral column

The vertebral column (spine) protects your spinal cord, supports your head, and allows bodily movement. It contains the sacrum (made up of four bones) and coccyx (the tailbone, which is made up of five bones), and 24 vertebrae, including:

  • Cervical vertebrae: Seven bones in the neck region
  • Thoracic vertebrae: Twelve bones attached to the ribs
  • Lumbar vertebrae: Five bones in the low back region


The thorax contains the sternum (breastbone) and the thoracic (rib) cage. The thoracic cage comprises 12 pairs of ribs connecting to the thoracic vertebrae and the sternum. Your rib cage protects your heart.

Appendicular Skeleton

The appendicular skeleton includes 126 bones that comprise your appendages—your arms and legs—and the bones that attach your limbs to your axial skeleton.

Upper Extremities

Your upper extremities refer to your shoulders and arms. Bones in the upper extremities include:

  • Scapula (shoulder blade)
  • Clavicle (collarbone)
  • Humerus (upper arm)
  • Radius and ulna (forearm bones)
  • Carpals (eight tiny bones in the wrist)
  • Metacarpals (in the palm)
  • Phalanges (bones of the fingers)

Lower Extremities

Bones in the lower extremities make up your hips and legs and include:

  • Pelvis
  • Femur (thigh bone)
  • Patella (kneecap)
  • Tibia and fibula (lower leg bones)
  • Tarsals (eight tiny bones in the ankle)
  • Metatarsals (in the middle of the foot)
  • Phalanges (bones of the toes)

Which Bones Are Most Commonly Broken?

The most commonly fractured bones include the distal radius (on the thumb side of your wrist), the ankle, the femur (thigh bone), the humerus (upper arm bone), and the metacarpals (bones of the palms).

With osteoporosis, the most commonly fractured bones are the vertebrae (in the spine).

What Is the Purpose of the Skeletal System?

The primary purpose of the skeletal system is to give the body its shape and to provide attachment points for the muscles that move the body.

Other purposes of the skeletal system include:

  • Storing minerals (such as calcium) and fats
  • Producing red blood cells
  • Protecting internal organs

Calcium in Your Bones

Most of the body's calcium is stored in your bones.

Skeletal System Associated Conditions

Various conditions and injuries can affect the skeletal system. Examples include:

Skeletal System Tests

Many different tests can help diagnose conditions that affect the skeletal system.

Imaging Tests

Healthcare providers use various imaging tools to get detailed pictures of your bones. Depending on the reason for imaging, a healthcare provider will conduct one or more of the following tests:

Other Skeletal System Tests

Healthcare providers may perform additional tests if they need further information about your bones or skeletal system. These tests may include:

  • Joint aspiration: This test involves removing a sample of fluid from a joint to help diagnose infection.
  • Biopsy: For the skeletal system, this procedure can involve removing a small sample of bone or bone marrow so that it can be tested for conditions such as cancer.
  • Blood tests: These tests help diagnose infections that can affect the skeletal system.


The skeletal system is made up of your bones, ligaments, and cartilage. Though its main function is to provide structural support for the body, it also stores important minerals—such as calcium—forms red blood cells, and protects your internal organs. The skeletal system can break down into two main categories—the axial skeleton, which forms the "long axis" of the body, and the appendicular skeleton, which forms your arms and legs.

Many different injuries and diseases can affect the skeletal system. Imaging procedures, such as X-rays, MRI, and bone density tests, and other tests, such as blood work or tissue biopsy, can help to diagnose these conditions.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Cancer Institute. Cranium.

  2. National Cancer Institute SEER Training Modules. Axial skeleton (80 bones).

  3. Fisher E, Austin D, Werner HM, et al. Hyoid bone fusion and bone density across the lifespan: prediction of age and sexForensic Sci Med Pathol. 2016;12(2):146-157. doi:10.1007/s12024-016-9769-x

  4. Osmosis from Elsevier. Bones of the vertebral column.

  5. National Cancer Institute SEER Training Modules. Appendicular skeleton (126 bones).

  6. American Academy of Orthopaedic Surgeons. Osteoporosis and spinal fractures.

  7. National Cancer Institute SEER Training Modules. Introduction to the skeletal system.

  8. MedlinePlus. Calcium and bones.

  9. National Institute of Arthritis and Musculoskeletal and Skin Diseases. Muscle and bone diseases.

  10. MedlinePlus. Diagnostic imaging.

  11. Understanding tests used to detect bone problems.

  12. Johns Hopkins Medicine. Joint aspiration.

By Aubrey Bailey, PT, DPT, CHT
Aubrey Bailey is a physical therapist and professor of anatomy and physiology with over a decade of experience providing in-person and online education for medical personnel and the general public, specializing in the areas of orthopedic injury, neurologic diseases, developmental disorders, and healthy living.