Human skeletal bones are categorised into two groups. The bones comprising the upper and lower limbs, shoulders and pelvic girdles are constituents of the appendicular skeleton. The axial skeletal system involves the bones along the body’s long axis.
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Axial Skeleton Definition
The entire human skeleton is made up of axial and appendicular skeletons. A vertebrate’s head and trunk bones constitute the axial skeleton, one of the parts of the skeletal system. Eighty bones comprise this skeleton system and are divided into six parts: the skull, the middle ear’s ossicles, the hyoid bone, the sternum, the rib cage and the vertebral column.
The axial skeleton constitutes the skull, vertebral column, laryngeal skeleton, and thoracic cage. The girdles and limbs of the appendicular skeleton “append” to the axial skeleton.
80 Bones of the Axial Skeleton
The bones in our skull, neck, ears, back, and ribcage are part of the axial skeleton:
Skull Bones
The skull comprises two groups of bones: 14 facial bones and 8 cranial bones. The cranial bones support and protect the brain, which forms the top and back of the skull. The following are among the eight cranial bones:
- Two parietal bones (right and left)
- Two temporal bones (right and left)
- One occipital bone
- One frontal bone
- One sphenoid bone
- One ethmoid bone
The face of the skull is formed of the facial bones, which also serve as the body’s entryway. The 14 facial bones consist of:
- Two maxilla bones (right and left)
- Two nasal bones (right and left)
- Two nasal concha bones (right and left)
- Two zygomatic bones (right and left)
- Two palatine bones (right and left)
- Two lacrimal bones (right and left)
- One mandible bone
- One vomer bone
Ears (Middle Ear’s Ossicles)
The smallest bones in the human body are the auditory ossicles, located in the middle ear. These small bones send vibrations from the eardrum to the inner ear. The bones in the middle ear include:
- Two malleus bones (single in each ear)
- Two stapes bones (single in each ear)
- Two incus bones (single in each ear)
Hyoid Bone (Neck)
The horseshoe-shaped hyoid bone is located in the front of the neck. It is anchored between the jaw bone and thyroid by ligaments and muscles. The hyoid bone helps in breathing, speaking, and swallowing.
Ribcage Bones
Our heart, lungs, and other internal organs are protected by the ribcage or thoracic cage. It is attached to the respiratory and arm movement muscles. The ribcage contains the following bones:
- Breastbone or sternum: This is a flat, long bone running down the centre of our chest.
- Twenty-four ribs: 12 pairs of ribs.
Vertebral Column (Back Bone)
There are 24 vertebrae in the spinal column, including the sacrum and tailbone (coccyx). The vertebral column spans from the pelvis to the base of the skull. It is divided into five parts:
- Seven cervical vertebrae: They form the neck and support the head.
- Twelve thoracic vertebrae: They form the posterior anchor of the ribcage.
- Five lumbar vertebrae: Affixed to the back muscles, they bear most of the body weight.
- One sacrum: The sacrum, a triangle bone, constitutes the pelvic back wall.
- One coccyx (tailbone): The coccyx, located at the base of the spine, connects to various body muscles.
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