Axial skeleton Systems / Skull bones/ Auditory ossicles / Vertebral column/ Thoracic cage

Axial skeleton anatomy

The adult axial skeleton consists of 80 bones. It’s made up of the bones that form the vertical axis of the body, such as the bones of the head, neck, chest, and spine.

Skull bones

The adult skull comprises 22 bones. These bones can be further classified by location:

• Cranial bones: The eight cranial bones form the bulk of your skull. They help to protect your brain.

• Facial bones: There are 14 facial bones. They’re found on the front of the skull and make up the face.

Auditory ossicles

The auditory ossicles are six small bones found within the inner ear canal in the skull. There are three auditory ossicles on each side of the head, known as the:

• malleus (hammer)

• incus (anvil)

• stapes (stirrup)

They work together to transmit sound waves from the surrounding environment to the structures of the inner ear.

Hyoid

The hyoid is a U-shaped bone found at the base of the jaw. It serves as a point of attachment for muscles and ligaments in the neck.

Vertebral column

The vertebral column is made up 26 bones. The first 24 are all vertebrae, followed by the sacrum and coccyx (tailbone).

The 24 vertebrae can be further divided into the:

• Cervical vertebrae: These seven bones are found in the head and neck.

• Thoracic vertebrae:  These 12 bones are found in the upper back.

• Lumbar vertebrae: These five bones are found in the lower back.

The sacrum and coccyx are both made up of several fused vertebrae. They help support the weight of the body while sitting. They also serve as attachment points for various ligaments.

Thoracic cage

The thoracic cage is made up of the sternum (breastbone) and 12 pairs of ribs. These bones form a protective cage around the organs of the upper torso, including the heart and lungs.

Some of the ribs attach directly to the sternum, while others are linked to the sternum via cartilage. Some have no attachment point and are referred to as “floating ribs.”