Final answer:
Collagen and elastin fibers in the skin weaken due to decreased production by fibroblasts, increased activity of matrix metalloproteinases (MMPs), and exposure to factors like UV radiation and smoking.
Step-by-step explanation:
As we age, collagen and elastin fibers in the skin weaken due to several factors. One factor is the reduced activity of cells responsible for synthesizing collagen and elastin, known as fibroblasts. As we age, fibroblasts produce less collagen and elastin, leading to a decrease in their levels in the skin.
Additionally, there is an increase in the activity of enzymes called matrix metalloproteinases (MMPs) that break down collagen and elastin in the skin. The increased activity of MMPs contributes to the degradation of collagen and elastin fibers, further weakening them.
Furthermore, exposure to factors like UV radiation from the sun and smoking can accelerate the breakdown of collagen and elastin fibers in the skin. These factors increase the production of reactive oxygen species and lead to oxidative stress, which damages collagen and elastin fibers, causing them to weaken and sag.