The axial skeleton is a part of the human skeletal system. There are 206 bones in the human body, and the axial skeletal system consists of 80 bones, out of the 206 bones. The axial skeleton basically encompasses all the bones in your upper body and forms the central axis of the human skeletal system. The main functions of these bones are to provide support, protection, movement, storage, and aid in blood cell formation. Our axial skeleton protects our vital organs like the brain, heart, lungs, and liver. It helps in maintaining an upright back posture, forming blood cells and storing minerals and fats.
A bone is composed of three layers:
- Periosteum: The periosteum is a double-layered tissue that covers the hard bones, which are called the compact bones.
- Compact Bone: These are hollow-structured bones filled with blood vessels. They are rich with nerves.
- Spongy Bone: This form of bone is known to be spongy because it becomes more hollow towards the center of the bone. Here, the red bone marrow and the yellow bone marrow are located in the head of the femur and humerus.
We will make a list of bones of the axial skeletal system by segregating the axial skeleton in the following parts:
- Skull: A human skull consists of 28 different bones, and is divided into two main parts called the cranium and facial bones.
- Sternum/Breastbone: This is one flat bone that anchors the ribs, and together the sternum and ribs comprise the rib cage.
- Ribs: It contains 24 bones forming 12 pairs of ribs, which are further divided into true and false ribs.
- Vertebral Column: The vertebral column or spine, is made up of 33 irregularly shaped bones, which are divided into five categories: the cervical vertebrae, the thoracic vertebrae, the lumbar vertebrae, the sacrum, and finally the coccyx or tail-bone.
List of Bones of the Axial Skeleton
|List of Bones in the Skull||No. of Bones||Description|
|Frontal Bone||1||This bone forms the forehead, the top of the nasal cavity, and top of the bony structure of eyes.|
|Parietal Bone||2||These are the two largest bones in the skull. It forms the side and the top of the head.|
|Temporal||2||These bones form the sides and the base of the skull. It is lateral to the temporal lobes of the cerebrum.|
|Occipital||1||This bone is located at the lower part of the cranium, and has a saucer-like shape.|
|Ethmoid||1||It is located at the top of the nose, between the two orbits, and it separates the nasal cavity from the brain.|
|Sphenoid||1||This bone is situated at the base of the skull. It is one of the seven bones that forms the orbit.|
|Maxillae||2||It forms the roof of the mouth, wall of orbit and floor, and lateral wall of the nasal antrum.|
|Zygomatic||2||It is located at the base upper and the lateral part of the face, and forms the cheek, the side, and the base of the orbit.|
|Mandible||1||This is the largest and the strongest bone of the face, and forms the structure for the lower teeth.|
|Nasal Bones||2||These are two small bones which form the bridge of the nose, and its shape and size varies from person to person.|
|Palatine||2||This bone is located at the rear part of the nasal cavity between the maxilla and the pterygoid process of sphenoid.|
|Inferior Nasal Concha||2||This bone lies horizontally along the wall of the nasal cavity, and articulates with the ethmoid, maxilla, lacrimal, and palatine.|
|Lacrimal||2||These are thin and small bones located in the middle wall of each eye socket between the ethmoid bone and the maxilla.|
|Vomer||1||It is one of the unpaired bones which forms the inferior and posterior part of the nasal septum.|
|Hyoid Bone||1||This is the only bone in the throat. It forms a structure for the tongue and is situated at the root of the tongue, in front of the neck, between the lower jaw and voice box. It looks like a horse-shoe.|
|Malleus||2||These bones are located in the middle of the ear and connects with the incus. It transmits sound form the eardrums to the incus.|
|Incus||2||These bones are located in the middle ear, and connect the malleus to the stapes.|
|Stapes||2||They are small bones connected to incus and fenestra ovalis laterally.|
|List of Bones in the Vertebral Column||No. of Bones||Description|
|Cervical Vertebrae||7||This is the smallest vertebrae amongst all, and the vertebral artery passes through this.|
|Thoracic Vertebrae||12||There are 12 of these, and are located between the cervical and lumbar vertebrae. It forms the middle segment of the vertebral column.|
|Lumbar Vertebrae||5||These are the largest and the strongest segments of the vertebral column. The transverse processes are very long, so as to attach the powerful back muscle, that maintains the posture and flex.|
|Sacrum||1||This is a huge triangular bone located at the base of the spine, back of the pelvic cavity between the hip bones.|
|Coccyx||1||This is a curved bone, which is semi-flexible and is situated at the lower end of the backbone (vertebral column) in humans, representing a vestigial tail. It is referred to as a tailbone.|
|List of Bones in the Thoracic Cage/Ribs||No. of Bones||Description|
|True Ribs||7||These are the first seven pairs of ribs that are attached with the sternum.|
|False Ribs||5||The last five pairs of ribs are called the false ribs, as they are not attached to the sternum.|
|Sternum||1||This is a long, flat, dagger-shaped bone, and is located at the center of the chest region. The 12 pairs of ribs and the sternum form the thorax, that protects the delicate and vital organs of the thorax, which include the heart and lungs.|
The other part of the human skeletal system is called the appendicular skeleton, and together with the axial skeleton, it completes the human skeletal system.