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Axial Skeleton

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Overview

The skeleton which is present at the axis of the body is called axial skeleton. The skull consists of the bones of the head and it is divided into cranium and facial bones. Trunk consists of bones of the vertebral column and the thorax. The vertebral column supports the head, helps in upright posture and locomotion. The first cervical vertebra is called atlas which supports the globe-like head.This note provides us the information about axial skeleton and information about types of bones or bones of the tr
Axial Skeleton

The skeleton which is present at the axis of the body is called axial skeleton. There are 80 bones in the axial skeleton of an adult and 87 in infants.

Skull

The skull consists of the bones of the head and it is divided into cranium and facial bones. Altogether, there are twenty nine bones in the skull.

Cranium: The cranium is a large bony box and is composed of eight flat bones. One bone of the cranium interlocking with the edge of another bone by saw-like edges is known as suture. The bone of cranium are as follows:

Frontal bone:

The frontal bone is one in number and forms the forehead or the front of the cranium.

Parietal bone: The parietal bones are two in number and form anterior sides and the roof of the skull.

Temporal bone: The temporal bones ate two in number and lie on each side of the head and form temples and complete the side-walls of the skull.

Occipital bone: The occipital bone is one in number and forms the back of the head and the posterior base of the skull.

Sphenoid bone: The sphenoid is one in number and it is bat shaped bone.

Ethmoid bone: The ethmoid is one in number and lies in front of the sphenoid.

Facial bones:

The facial part of the skull is formed of fourteen bones. All of them except the lower jaw are immovable. The bones of the facial parts are as follows:

Mandible or lower jaw bone: Mandible bone is only movable bone of the skull having 16 sockets for the lower set of the teeth on its upper edge.

Maxillae or upper law bones: Maxillae bone forms a portion of the roof of the mouth, lateral walls of the nasal cavity and part of the floor of the orbital cavities.

Palatine bone: Palatine bone are 'L' shaped and forms the upper part of the palate or roof of the mouth cavity.

Zygomatic bones: There are two zygomatic bones which form the prominences of the cheeks and part of the floor and lateral wall of the orbit eyes.

Vomer bone: It is a thin and flat single bone that extends upwards and forms the part of the middle partition in the nose and divides the two nostrils of the nose.

Nasal bone: Two small flat bones that form the bridge of the nose. The lower part of the nose is formed of cartilage.

Inferior nasal conchae: The two conchae are bones of the nose, one on each chamber of it.

Lacrimal bone: These are two small lacrimal bones in inner wall of the orbit of the eyes. Lacrimal bone contains the passage for tears from the eyes to the nose.

Ear ossicles:

There are three bones in the middle ear which are called ear ossicles. It consists of two malleus, two incus and two stapes in the ears. The stapes are the smallest bones of the body.

Hyoid:

Hyoid is a ‘U’ shaped single bone and it supports our tongue. It is located in the neck region below the lower jaw.

Bones of the trunk

Trunk consists of bones of the vertebral column and the thorax.

Vertebral column:

The vertebral column supports the head, helps in upright posture and locomotion. The individual bones of the vertebral column are known as vertebrae. Each vertebra is provided with the canal called neurocoel.

Cervical vertebrae: The first two cervical vertebrae are different from all other vertebrae. The first cervical vertebra is called atlas. It supports the globe-like head. The second cervical vertebra is called axis. It helps in movement of head from side to side.

Thoracic vertebrae: Thoracic vertebrae ate 12 in number and form the upper part of the back.

Lumber vertebrae: Lumber vertebrae are 5 in number and form the lower part of the back.

Sacral vertebrae or sacrum: In infants sacral vertebrae consist of 5 separate bones but in adult they are found fused to form a large wedge-shaped sacrum.

Coccygeal vertebrae or coccyx: In infant, coccygeal vertebrae consist of 4 separate bones but in adult they are fused to form a very small triangular bone.

Thoracic bones:

There are 12 pairs of semi-circular bones present in the thorax called ribs and a long and broad bone called sternum. The spaces between the ribs are called intercostal spaces which are occupied by intercostal muscles.

True ribs: The first seven pairs of ribs are directly attached to the sternum by means of cartilage called true ribs.

False ribs: The 3 pairs of ribs are attached to that of the seventh pair of ribs and not to sternum directly are called false ribs.

Floating ribs: The last true ribs which are free and do not even reach the sternum are called floating ribs.

Things to remember
  • The skeleton which is present at the axis of the body is called axial skeleton.
  • The skull consists of the bones of the head and it is divided into cranium and facial bones.
  • Maxillae bone forms a portion of the roof of the mouth, lateral walls of the nasal cavity and part of the floor of the orbital cavities.
  • Lacrimal bone contains the passage for tears from the eyes to the nose.
  • Hyoid is a ‘U’ shaped bone and it supports our tongue.
  • Trunk consists of bones of the vertebral column and the thorax.
  • The vertebral column supports the head, helps in upright posture and locomotion.
  • The first cervical vertebra is called atlas which supports the globe-like head.
  • The last true ribs which are free and do not even reach the sternum are called floating ribs.
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.
Videos for Axial Skeleton
Axial Skeleton - Basic Summary
Axial Skeleton and the Skull
Bones of the Axial Skeleton
Bones of the thoracic cage- ribs
Bones of the Thoracic Wall
Skeletal System : The Vertebrae
Questions and Answers
There are six types of cranium bones. Which are given below:
i) Frontal bone - 1
ii) Parietal bone - 2
iii) Temporal bone - 2
iv) Ethmoid bone - 1
v) Sphenoid bone - 1
vi) Occipital bone - 1
Total -8 bones
There are eight different types of facial bone. They are:
  1. Mandible - 1
  2. Maxilla - 2
  3. Zygomatic - 2
  4. Nasal - 2
  5. Lacrimal - 2
  6. Vomer - 1
  7. Palatine - 2
  8. Inferior nasal conchae - 2

Total - 14 bones
Within skull, cranium contains 8 bones and face contains 14 bones. So, in total skull contains 22 bones.
Out of eight different bones in face, mandible and vomer are not found in pair.
A function of cranium is it protects the most sensitive part i.e. brain of human body and a function of bone marrow is it replenishes insufficient calcium into the body.
The single bone in the neck which lies above larynx and below mandible is called hyoid bone.
Its function is to stick tongue.
There are three bones in ear ossicles. They are:
Malleus, Incus and Stepes.
Bone of forehead: Frontal
Bone of lower jaw: Mandible
Trunk is made by the combination of vertebral column and the thoracic bones.
In children, vertebral column consists of thirty three small irregular separate vertebras where as in adult there is only twenty six vertebras.
The name and number of vertebra bones in vertebral column are as follows:
i) Cervical vertebrae - 7
ii) Thoracic vertebrae - 12
iii) Lumber vertebrae - 5
iv) Sacral - 5
v) Coccyx - 4
Total bones - 33
Out of seven cervical vertebrae, the first one is called the atlas and the second one is called the axis.
Thoracic bone contains total of 12 pairs or 24 bones. They are:
i) True ribs - 7 pair = 14
ii) False ribs - 3 pairs = 6
iii) Floating ribs - 2 pairs = 4
The vertical bone at the centre of thoracic bone which acts as a cage around the lungs and heart is called sternum.
Quiz

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