Question 2: the correct answer is Skin. Got it right? Score 1 point.
Question 3 of 10
Where is the smallest bone in the human body?
Why, in question 2: What is the largest organ of the human body?
The answer is skin. In an adult, it covers 1.5 to 2 square metres and accounts for a large share of body weight. The liver is the largest internal organ, but it comes well behind the skin.
A barrier that renews itself
Skin protects the body against microbes, water loss and sunlight, helps control temperature through sweat, and houses millions of receptors for touch, heat, cold and pain.
The outer layer, the epidermis, renews itself all the time. Cells are born in the deepest part, rise to the surface and shed, in a cycle that takes about a month.
Thickness varies greatly from place to place. The skin of the eyelids is among the thinnest in the body, while that of the soles of the feet is among the thickest, because it withstands the weight and friction of every step.
Skin colour comes mainly from melanin, a pigment produced by cells called melanocytes. People with light and dark skin have similar numbers of these cells; what differs is the amount and type of melanin they produce.
