Skeletal System

The human skeletal system is the internal framework of the body. It consists of bones, cartilages, joints and ligaments working together. A human body has around 300 bones at the time of birth, and this number decreases to 206 bones in a full-grown adult, because some of the bones fuse together as the body grows.

What makes up the skeleton

The skeleton is an amalgamation of bones, joints, cartilages, tendons and ligaments:

1. Bones are the rigid part of the skeleton. They provide support to the body, and their different shapes suit different functions - for example, the metacarpals and phalanges allow the hand to form a fist.
2. Cartilage is more flexible than bone. It gives shape and flexibility to the body so that it can make various movements - it shapes our ears and nose, and it also lets the chest expand during breathing.
3. Tendons and ligaments are strong bands of fibrous connective tissue. Tendons connect muscle to bone, whereas ligaments connect one bone to another bone.

Why bone is rigid, yet alive

A bone is not a dead, inert rod - it is a living tissue. Its rigidity comes from a matrix of the protein collagen hardened by deposits of calcium and phosphate minerals, which is why a diet poor in calcium can weaken bone over time. A thin membrane called the periosteum covers most of a bone's surface, carrying the blood vessels and nerves that keep the bone alive and allow it to repair itself after a fracture. Inside many bones is bone marrow, which, besides producing blood cells (covered under the skeleton's functions), also stores fat as an energy reserve. …