The bones and cartilages of the skeletal system that lie along the axis of the body and support and protect the brain and soft organs of the body cavity are called axial skeleton. It consists of 80 bones. Axial skeleton consists of Skull, Vertebral and Thoracic case.
Skull
Carotid and facial bones together are called cranium. It consists of 22 bones in total. The bones of the skull are – carotid, facial bone, cochlear and vocal cord or hyoid.
1. Cranium: The bones of the skull that cover the brain are called calvarium. Bones are connected by suture joint. The stitches are called stitched stitches. There are 6 spaces or Fontanels in the skull. Due to the presence of fontanel, the shape of the baby’s head changes during delivery and it comes out easily through the birth canal. By the age of two, the baby’s carotid bones are completely fused by the suchar joints. Carotid artery is made up of 8 hard and flat bones. The bones are:
(i) Frontal Bone: The frontal is a cranial bone shaped like an oyster. It has two eye sockets and a nose. It has two pairs of mounds. One pair on the forehead and the other pair on the eyebrows.
(ii) Parietal bones: There are 2 parietal bones like quadrangular plates. It has a raised section on the outer floor.
(iii) Occipital bone: The occipital bone surrounds the navel. It has a hole called Foramen magnum. The occipital bone consists of a shell part, 2 lateral parts and an occipital part. It connects the carotid with the atlas. (iv) Temporal bones: Two temporal bones exist on either side of the carotid. Each bone consists of four segments. squama, petromastoid, tympanic and styloid processes. In this bone the hearing organ, auditory canal, carotid canal and facial nerve canal are located.
(v) Ethmoid bone: Ethmoid is a spongy bone. It forms the eye socket and nasal septum. It consists of 6 plates. 1 transverse plate, 1 vertical plate, 2 orbital plates and 2 labyrinth plates. Each labyrinth plate contains tiny air chambers.
(vi) Sphenoid bone: Sphenoid is the bone forming the carotid floor. It looks like a bat or a butterfly. It consists of a body stem and 3 pairs of appendages. Its parts are the greater wing, the lesser wing and the pterygoid process.
2. Facial skeleton
The front and lower part of the carotid body is called the face. It consists of 14 bones in total. The facial bones are:
(i) Nasal bone: It is a rectangular bone. It forms the bridge of the nose.
(ii) Nasal Concha: A pair of thin and curved bones located on either side of the nasal cavity are the nasal concha.
(iii) Vomare: It is a quadrangular plate like bone. It forms the NASA interface.
(iv) Palatine bone: It forms the roof of the nose and the wall of the nasal cavity.
(v) Lacrimal bone: It consists of a lacrimal shaft, lacrimal sac and nasolacrimal duct.
(vi) Zygomatic bone: It is a quadrangular bone. It consists of an elevated part called the zygomatic arch.
(vii) Maxilla: The upper jaw consists of two equal maxillae. Right and left maxilla. It has four amplifiers. These are – zygomatic, palatine, frontal and alveolar.
(viii) Mandible: Mandible is the lower jaw. It looks U shaped. It consists of a trunk and 2 branches. It has two amplifiers. Coronoid and condyloid.
3 | Ear Ossicles
There are 3 small bones in the middle ear. These are-
(i) Malleus: It looks like a hammer. One end is attached to the tympanic membrane and the other end to the incus.
(ii) Incus : It looks like anvil. One end is attached to the malleus and the other end to the stapes.
(iii) Stepis: Stepis looks triangular or like a horse’s stirrup. It is the smallest bone in the human body. One end is attached to the incus and the other end to the fenestra ovalis.
4. Hyoid Bone
The U-shaped bone between the lower jaw and the larynx is called the hyoid. It consists of a body stem and 4 cornua. Its middle part is called body or hyoid body. There are two small cornua on either side of the body and two large cornua on the back.