PATHOLOGY

Detailed explanation-1: -It consists of water, urea (from amino acid metabolism), inorganic salts, creatinine, ammonia, and pigmented products of blood breakdown, one of which (urochrome) gives urine its typically yellowish colour.

Detailed explanation-2: -About 91–96% of urine consists of water. The remainder can be broadly characterized into inorganic salts, urea, organic compounds, and organic ammonium salts. Urine also contains proteins, hormones, and a wide range of metabolites, varying by what is introduced into the body.

Detailed explanation-3: -Urea, together with water and other waste substances, forms the urine as it passes through the nephrons and down the renal tubules of the kidney.

Detailed explanation-4: -The urea concentration of collecting duct fluid is increased by active absorption of NaCl from the thick ascending limb and the subsequent absorption of water from the cortical and outer medullary collecting ducts.