9. Parts of the skeleton: Axial Skeleton

The skeletal system comprises the bones and related structures aid in the body's movement. The skeletal system of humans is divided into two major parts:
The axial skeleton and the appendicular skeleton.

 

The skeleton that consists of the bones present along the axis or central line of the human
body is known as the axial skeleton. The axial skeleton consists of the skull, facial bones, sternum, ribs, and vertebral column.

 

  

The skull is a hard structure made up of many bones known as the cranial bones and facial bones. It is also known as the cranium or brain box. It  is formed by \(22\) bones, out of which \(8\) bones are fixed together to form the cranium (cranial bones), and the other \(14\) bones fuse to form the face (facial bones).

 

  

It is also known as the spine or the backbone.  It extends from the base of the skull to the hip bone forming a tube, and consists of many small bones called vertebrae that are \(33\ \)in number (during birth and later fuses into \(27\)) and are serially arranged.

  

  

 

 

 

It is a cone-shaped structure that occupies the chest region. It is made up of \(12\ \)pairs of ribs that are attached to vertebrae at the back, curve around to form a cage.

 

Out of these \(12\) pairs, \(10\) pairs of the ribs are attached to the breast bone at the front (true ribs), \(2\ \)pairs of lower ribs are free at the front. These are known as free-floating ribs. The ribcage is set up in such a way so that it can contract and expand during the process of breathing. The ribcage protects the underlying lungs, heart and some part of the liver.