Best Answer: Using single quotation marks around a word or phrase instead of double quotation marks is the standard way of indicating a quotation in British English. In normal, modern British English one uses single quotation marks, with double quotation marks reserved for a quotation within a quotation.
tubular secretion. the passage of substances from the blood in the peritubular capillaries to the tubular filtrate. Functions of tubular secretion. elimation of waste products not filtered by the glomerulus and regulation of the acid-base balance in the body through the secretion of hydrogen ions. what happens to the protein bound substances entering the peritubilar capillaries.
In that case... Secretion is an active process. In the kidney tubules, somethings, like K+ is secreted from the peritubular capillaries, into tubular cells, and then out into the lumen to mix with the fluid. Excretion is passive. What is excreted by the kidneys is everything that is not reabsorbed and what is secreted.