Bones

Each hand has 27 bones and each foot has 26.

It sits in the neck and supports the tongue.

The skeleton is largely replaced over about a decade.

Red cells, white cells and platelets are made inside bones.

It runs from the hip to the knee.

Babies are born with around 300 that later fuse.

Gram for gram, compact bone is stronger than steel. Its hierarchical structure of collagen fibers and hydroxyapatite crystals gives it both flexibility and hardness. Unlike steel, bone is living tissue: it is constantly remodelled by osteoblasts (cells that build bone) and osteoclasts (cells that break it down). The entire skeleton is replaced roughly every 10 years. The femur (thigh bone) can withstand compressive forces of up to 1,700 kg.

The stapes, or stirrup bone, located in the middle ear, measures only about 2.5 by 3 millimeters. It's crucial for transmitting sound vibrations from the eardrum to the inner ear, allowing us to hear.

A newborn baby has around 300 bones, while an adult has 206. Many of a baby's bones are made of cartilage and eventually fuse together as they grow, like those in the skull and spine, forming stronger, larger structures.