what does the nephrons have to do with chronic renal failure?

Thats a hard question but I will take a stab at it. The nephrons are usually dispelled in your urine but in chronic renal failure they are floating around in the blood stream. The kidneys are like sponges and it is the sponge part that takes the brunt of the damage so they no longer filter the toxins out of the blood.

The nephron is the functional unit of the kidney that removes waste and excess substances from the blood to be excreted in the urine or reabsorbed into the blood depending on the needs of the body. About one million nephrons are in the cortex (surface or outer layer) of each kidney, and each one consists of a renal corpuscle and a renal tubule which carry out the functions of the nephron. Nephrons also regulate blood volume and pressure, control levels of electrolytes and metabolites, and regulate blood pH. Its functions are vital to life.
The millions of nephrons in the kidneys allow them to sustain a certain amount of damage. The kidneys cannot however, replace damaged nephrons, so once damage occurs, it is irreversible. Because of their large reserve capacity the first signs and symptoms of kidney disease are not typically seen until at least half of the total nephrons are damaged.
The Kidney in Congestive Heart Failure: Sodium Homeostasis, Renal Hemodynamics and Nephron Function
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Norman K. and Paul J. Cannon Hollenberg With the destruction of the nephrons your kidneys can't function properly, they lose their filtering ability causing dangerous levels of fluid and waste to accumulate. This condition is called renal failure and can lead to complications listed in the website below:

Renal failure can be divided into two groups:
*Acute (a rapid onset) renal failure is often the result of major damage to the kidneys, such as infection, decreased blood flow to the kidneys, drugs that can be harmful to the kidneys, toxins, or blockage of urine outflow from the kidneys, such as stones lodged in the ureters or urethra.
*Chronic kidney failure progresses slowly over time with few signs or symptoms in the early stages.
Many people with chronic kidney failure don't realize they have a problem until their kidney function has decreased to less than 25 percent of normal. High blood pressure and diabetes are the most common causes of chronic kidney failure.
For other causes of chronic renal failure check out this website:

what part of the kidney is damaged in chronic renal failure?

Calcinosis of Chronic Renal Failure

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