How does nephron function change with age?

Nephron function generally declines with age due to a decrease in the number of functioning nephrons.

Nephrons are the functional units of the kidneys, responsible for filtering waste products, excess ions, and water from the bloodstream to form urine. As we age, the number of functioning nephrons decreases, which can lead to a decline in kidney function. This is a natural part of the ageing process and is not necessarily indicative of a disease state.

The decline in nephron function with age is due to several factors. Firstly, there is a decrease in the number of glomeruli, the tiny filtering units within each nephron. This is due to glomerulosclerosis, a process where the glomeruli become scarred and hardened, reducing their ability to filter blood. Secondly, there is a decrease in renal blood flow with age, which can reduce the amount of blood reaching the nephrons for filtration.

Additionally, the tubules of the nephrons, which reabsorb useful substances back into the blood and secrete waste products into the urine, also undergo age-related changes. These changes can reduce the nephrons' ability to concentrate urine, leading to increased urine production and potentially, increased frequency of urination.

Furthermore, ageing can lead to a decrease in the kidneys' ability to regulate acid-base balance, which is another important function of the nephrons. This can result in a condition known as metabolic acidosis, where there is too much acid in the body fluids.

In summary, the function of nephrons declines with age due to a combination of factors including a decrease in the number of functioning nephrons, reduced renal blood flow, changes in the tubules, and a decreased ability to regulate acid-base balance. This can lead to changes in urine production and composition, and potentially, a decrease in overall kidney function.