Q.Differentiate between bone & cartilage.

You have probably never seen your own bones, yet you know they are there. When you jump, your legs do not crumple. When you pick up a book, your arm does not flop like a rope. Something rigid holds you together and gives you shape. That something is the skeleton.

Think of a building. Without a steel frame, the walls would collapse and the floors would sag. Your skeleton is that steel frame — but alive, growing, and self-repairing. It is not just a pile of dry sticks; it is a dynamic system of 206 bones (in an adult) connected by cartilage (the smooth, rubbery material at joints) and held together by ligaments.

The skeleton does four big jobs:

• Support — it holds your body upright and gives your soft organs a place to hang.
• Protection — the skull shields your brain; the rib cage guards your heart and lungs.
• Movement — bones are levers that muscles pull on.
• Storage & production — bones store calcium and make blood cells inside their marrow.

Now, how do you organise 206 bones so they make sense? Anatomists split them into two clear groups.

Axial skeleton — 80 bones. This is the core: the skull (22 bones), the vertebral column (26 bones: 24 vertebrae + sacrum + coccyx), and the rib cage (12 pairs of ribs + sternum). It forms the upright pillar of your body and protects the brain, spinal cord, and thoracic organs.

Appendicular skeleton — 126 bones. This is everything that sticks out from the axis: the shoulder girdle (clavicle and scapula), the arms (humerus, radius, ulna, carpals, metacarpals, phalanges), the pelvic girdle (two hip bones), and the legs (femur, tibia, fibula, patella, tarsals, metatarsals, phalanges). It handles movement and manipulation.