While most people associate growth with childhood and adolescence, certain body parts subtly defy this common understanding. This prompts questions about which parts of our anatomy continue to evolve beyond our formative years.
The Continuously Changing Parts
The two body parts that undergo continuous, noticeable changes throughout life are the nose and the ears. Unlike bones, which achieve a fixed size, these structures are primarily composed of cartilage and soft tissues. The external ear is made of elastic cartilage, allowing it to bend and return to its original shape. Similarly, the nose’s framework includes several cartilages, providing its shape and support. These tissues do not “grow” in the traditional sense, but rather experience gradual alterations in shape and size.
The Science Behind Their Apparent Growth
The perceived growth of the nose and ears is a result of several biological mechanisms at play over a lifetime. Gravity exerts a constant, downward pull on the soft tissues and cartilage, causing them to elongate and sag. This persistent force contributes to the gradual drooping and stretching observed in these features as individuals age.
Another significant factor is the natural breakdown of collagen and elastin, proteins vital for maintaining the skin’s and cartilage’s structure, elasticity, and firmness. As the body ages, the production of these proteins decreases, and existing fibers become fragmented and more loosely distributed. This loss of structural support leads to a reduction in tissue integrity, making the nose and ears more susceptible to stretching and changes in shape.
Cartilage itself also undergoes a process of remodeling and accumulation of tissue. While cartilage cells can continue to divide and form new tissue, this is more about changes in density and shape rather than a growth plate activity. These combined effects lead to the visible alterations, contributing to the appearance of “growth” in these cartilaginous structures.
Why Other Body Parts Stop Growing
Most other body parts, particularly bones, cease growing at a specific point in life. Long bones, responsible for an individual’s height, grow in length at specialized areas called growth plates, or epiphyseal plates. These plates are composed of cartilage cells that continuously divide and mature, creating new tissue that eventually hardens into bone.
Around puberty, hormonal changes, particularly an increase in estrogen levels in both sexes, signal the eventual closure of these growth plates. The cartilage in these plates gradually transforms into bone tissue, a process known as epiphyseal fusion or ossification. Once the growth plates have completely fused, typically by late adolescence (around 14-19 years for most individuals), further longitudinal bone growth is no longer possible, and a person reaches their final adult height. While hair and nails continuously grow, and skin regenerates, these processes differ fundamentally from the structural changes observed in the nose and ears.