Final answer:
Glucose, amino acids, sodium, and calcium are typically completely reabsorbed in the nephron, resulting in no presence of these chemicals in a healthy patient's urine, while other substances like urea and potassium are secreted as waste.
Step-by-step explanation:
In a healthy patient, substances like glucose, amino acids, sodium (Na+), and calcium (Ca++) are normally completely reabsorbed by the nephron in the kidneys, resulting in none of these chemicals being present in the urine. Homeostatic plasma concentrations of these substances are maintained through processes occurring in the renal system, particularly the nephron's proximal convoluted tubule (PCT). In contrast, other substances, such as urea, potassium (K+), and some drugs, are secreted into the urine as waste products. The kidneys, along with the lungs, play a key role in maintaining acid-base balance by regulating the secretion and reabsorption of hydrogen ions (H+) and bicarbonate (HCO₃⁻).