20. Some urea diffuses out of the collecting duct, because the tubule is permeable to urea. This adaptation allows the interstitial fluid of the inner kidney to become more concentrated than the filtrate. In turn, more water is reabsorbed by blood. What a perfect system! The filtrate reaching the collecting duct is called urine. Is urine more or less concentrated than the initial filtrate

Urine is more concentrated than initial filtrate. Urine is, in fact, four times more concentrated than initial filtrate.

Explanation:

The urinary system is the one in charge of filtrate blood and propduce urine. The main stars in the system are kidneys and the functional unit of them are the nephrons.

There are many steps in producing urine. Fluid goes between different parts of the kidney: renal tubule, renal corpuscle, bowman's capsule, etc. We have through all these parts these following steps: filtration, reabsorption to blood, secretion from blood and excretion.

From filtrate, the boody reabsorbs sodium chloride, glucose, water and amino acids. When the fluids moves down the loop of Henle, it becomes less concentrated, so it is full of water. At the end, urine is four times more concentrated than initial filtrate.

layer 3 is younger than layer 6.