Question

Write about the human axial skeleton, giving suitable labelled diagram.

[Review question: Pg. No: 231]

Answer 1

The axial skeleton consists of the bones along the axis or central line of the human body. It consists of the skull, facial bones sternum, ribs and vertebral column.

Skull:

1. It is a hard structure made of 22 bones.
2. 8 bones are fixed together to form the cranium and 14 hones fuse to form the face.
3. The lower jaw is the only movable bone of the skull.

Vertebral column:

1. It is called the backbone and runs of the back of the body.
2. It is made of 33 individual bones called vertebrae as follows :
   • 7 Cervical vertebrae
   • 12 Thoracic vertebrae
   • 5 Lumbar vertebrae
   • 5 Fused sacral vertebrae
   • 4 Fused coccygeal vertebrae
3. The hollow tube of the vertebral column contains the spinal cord.
4. Vertebrae are joined by gliding points which allow the body to be bent back, front or side – wards.

Function of vertebral column:

1. It protects the spinal cord
2. It supports the head
3. It serves as an attachment for ribs
4. Helps in walking, standing erect and posture.

Sternum or Ribcage:

1. It is a cone shaped structure in the chest region and made up of 12 pairs of ribs.
2. The ribs attached to the vertebral column at the back and the breast bone in the front.
3. There are 12 pairs of ribs.
   • First 10 pairs are attached to breast bone.
   • 2 pairs are called free floating ribs and are free in the front.
4. Rib cage can contract and expand during breathing.
5. It protects the lungs, hearts and a part to the liver.