The Body's Extremes
Every anatomy student eventually learns the same short list of superlatives, and they tend to stick because each one is a little surprising the first time you hear it. The skin, not the liver or the lungs, is the largest organ in the human body — spread flat, an adult's skin covers roughly two square meters and accounts for about 15 percent of total body weight, once its deeper fat-storing layer is included. Among internal organs, the liver takes the title of largest, weighing in around 1.5 kilograms and handling several hundred distinct metabolic functions. At the opposite extreme, the stapes — one of three tiny bones in the middle ear — is the smallest bone in the body, measuring only about 3 millimeters, small enough that it was the last of the ear's three ossicles to be formally described by anatomists, in the 16th century.
Length has its own champion: the femur, the single bone of the thigh, is both the longest and the strongest bone in the body, engineered to bear the full weight of an upright, walking human. Muscles have their own records too — the gluteus maximus, in the buttocks, is the largest muscle by mass, while the masseter, a jaw muscle used in chewing, is often cited as the strongest muscle relative to its size, and the tiny stapedius muscle of the middle ear, attached to that same tiny stapes bone, is the smallest skeletal muscle in the entire body.
Why These Records Matter
These aren't just trivia footnotes — each record reflects something functional about how the body is built. Tooth enamel is the hardest substance the body produces, composed of about 96 percent mineral by weight, because it has to withstand a lifetime of mechanical grinding every time a person chews; unlike bone, it contains no living cells and cannot repair itself once damaged, which is part of why it's built so durable in the first place. The femur's combination of length and strength exists because bipedal walking concentrates enormous compressive force through a single thigh bone with every stride, and a shorter or weaker bone simply couldn't do the job.
Perhaps the most functionally significant record belongs to the liver, which stands out as the only major organ in the body capable of regenerating substantial lost tissue — it can regrow to nearly its original size even after losing as much as 75 percent of its mass, through the rapid multiplication of its existing cells rather than growth from stem cells. No other solid organ in the human body shares this ability, which is part of why the liver's regenerative power inspired the ancient Greek myth of Prometheus, whose liver was said to regrow every night after being eaten by an eagle during the day. Learning these records is a fast, memorable way into anatomy — each superlative is really a small lesson in why the body is built the way it is.
Source: Encyclopaedia Britannica and Gray's Anatomy.