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Excretory System

11.3 The Kidney Learning Targets: Define excretion and osmoregulation. Label structures and explain functions of the kidney and the nephron in ultrafiltration and reabsorption. Excretory System. Renal arteries – carries blood to kidneys from heart Renal veins

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Excretory System

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  1. 11.3 The KidneyLearning Targets: Define excretion and osmoregulation. Label structures and explain functions of the kidney and the nephron in ultrafiltration and reabsorption.

  2. Excretory System • Renal arteries – carries blood to kidneys from heart • Renal veins – carries blood from kidneys to heart • Ureter – collects urine (water and metabolic wastes) • Bladder – stores urine delivered by ureters

  3. Excretory System Excretion – the removal from the body of the waste products of metabolic pathways.

  4. Kidney • Renal cortex • Renal medulla • Collecting ducts • Renal pelvis • Ureter

  5. Osmoregulation Osmoregulation - the body’s response mechanisms which attempt to maintain homeostatic levels of water.

  6. Nephron • Nephrons are kidney structures that help mammals conserve water – almost 99% of water and solutes are reabsorbed (wastes are excreted)

  7. Basement membrane • Glomerulus • Blood pressure forces fluid out of blood in this ball of capillaries 2. Bowman’s capsule • Receives water and small solutes (salts, glucose, vitamins, urea) through “ultrafiltration” from glomerulus

  8. NaCl Glucose H2O 3. Proximal tubule • Regulates pH by secreting H+ and absorbing HCO3- • Pumps NaCl and nutrients out of filtrate, H2O follows by osmosis 4. Descending Loop of Henle • Permeable to water but not solutes • Medulla has high urea concentration so water leaves Active Passive Increasing Solute Gradient H2O

  9. NaCl Glucose H2O H2O NaCl 5. Ascending Loop of Henle • Permeable to salt, not water • NaCl leaves (passive and active) 6. Distal tubule • Regulates pH by secreting H+ and absorbing HCO3- • Pumps out salt, water follows Active Passive Increasing Solute Gradient NaCl H2O

  10. NaCl Glucose H2O H2O NaCl 7. Collecting duct • Pumps out salt, water follows • Urea diffuses out to raise solute concentration in medulla Active Passive H2O Increasing Solute Gradient NaCl H2O Urea

  11. NaCl Glucose H2O H2O NaCl 7. Collecting duct • Regulated by ADH (antidiuretic hormone) secreted by pituitary (region of brain) • Salt or dehydration triggers release of ADH • Body responds with thirst, collecting duct becomes more permeable to water (body reabsorbs more water) Active NaCl Passive H2O Increasing Solute Gradient NaCl H2O Urea Urea Urea

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