PREPARATION: RENAL SYSTEM AHL Topic 11.3 IB Biology Miss Werba

EXCRETION Excretion: removal of waste products from the body 11.3.1 EXCRETION Excretion: removal of waste products from the body Prevents toxic accumulation of wastes Mainly through the lungs, skin and renal system Animals waste products: Carbon dioxide Nitrogenous compounds (eg. urea) from the breakdown of proteins J WERBA – IB BIOLOGY 2

11.3.2 KIDNEY STRUCTURE J WERBA – IB BIOLOGY 3

11.3.3 NEPHRON STRUCTURE J WERBA – IB BIOLOGY 4

ULTRAFILTRATION & REABSORPTION J WERBA – IB BIOLOGY 5

ULTRAFILTRATION & REABSORPTION 11.3.4 ULTRAFILTRATION & REABSORPTION Filtrate collects within the Bowman's capsule and then flows into the proximal tubule. (PCT) Here all of the glucose and amino acids, >90% of the uric acid, and ~60% of inorganic salts are reabsorbed by active transport. As these salts are removed from the filtrate, a large volume of the water follows them by osmosis (80– 85%). J WERBA – IB BIOLOGY 6

ULTRAFILTRATION & REABSORPTION 11.3.4 ULTRAFILTRATION & REABSORPTION Filtrate then flows into the descending limb of the loop of Henle. Here, water continues to leave by osmosis because the interstitial fluid is very hypertonic. This is caused by the active transport of salt out of the filtrate as it moves up the ascending segment of the loop of Henle. In the distal tubules, more salt is reclaimed by active transport, and still more water follows by osmosis. Final adjustment of the sodium and water content of the body occurs in the collecting ducts, under the control of the hormone, ADH. J WERBA – IB BIOLOGY 7

ADH ADH opens aquaporins in the collecting duct (“water-pores”) 11.3.7 ADH ADH opens aquaporins in the collecting duct (“water-pores”) This makes the collecting duct permeable to water. Enables diffusion of water out of collecting duct. Ref: IB Biology OSC J WERBA – IB BIOLOGY 8

11.3.5 OSMOREGULATION J WERBA – IB BIOLOGY 9

11.3.5 OSMOREGULATION J WERBA – IB BIOLOGY 10

CONCENTRATION COMPARISONS 11.3.8 CONCENTRATION COMPARISONS Component Plasma Nephric Filtrate Urine Urea 0.03 1.8 Uric acid 0.004 0.05 Glucose 0.10 None Amino acids Total inorganic salts 0.9 <0.9–3.6 Proteins and other macromolecules 8.0 J WERBA – IB BIOLOGY 11

11.3.9 DIABETES Without insulin (or reduced insulin sensitivity), glucose is not absorbed into cells. Results in high levels of glucose in blood Most of the glucose will be released in the urine. May cause damage renal blood vessels or renal failure. J WERBA – IB BIOLOGY 12