The Structure and Function of a Nephron

1. The Structure and Function of a Nephron A physiology mini lecture presented by: Kaylee Knowles Lydia Morrison

2. The Kidney!! • 6 General Functions! • Extracellular fluid volume • and blood pressure regulation. 2. Osmolarity regulation 3. Ion balance 4. pH homeostasis 5. Excretion 6. Hormone production

3. Anatomy of the Kidney:

4. THE NEPHRON The functional unit of the kidney. 1 million nephrons in a kidney – and that never changes! 80% - cortical nephrons & 20% juxtamedullary

5. Filtration: -Takes place in the renal corpuscle -Substances flow out of the glomerular capillaries into the surrounding Bowman’s capsule

6. -Substances must cross three filtration barriers: -glomerular capillary endothelium -basal lamina -epithelium of Bowman’s capsule -What drives filtration? -Hydrostatic pressure! 10 mm Hg of it! -GFR (glomerular filtration rate) -average kidney is ~125 ml/min that’s: 180 L/day which calculates to: 60 times the kidney filters the entire blood plasma volume. so: Your little kidneys filter your entire blood plasma volume 2.5 time in an hour!!! Go kidneys go!

7. Proximal tubule transport particles out of the lumen into the interstitial fluid (70% of filtrate reabsorbed) Active or Passive Total: over 99% of filtrate is reabsorbed Reabsorption

8. Molecules move from ECF to the nephron lumen • Active • Membrane transport protein • Na+/K+ transport Secretion • Decrease secretion by competition • Penicillin

9. More solute reabsorbed than reabsorbed water • descending limb of the loop of Henle: into the renal medulla • ascending limb of the loop of Henle: returns to the renal cortex • Juxtaglomerular apparatus (JGA): BP Loop of Henle

10. 2 cells types: • principal cells: ADH and Aldosterone receptors • intercalated cells:maintain blood pH • Bowman’s capsule  proximal convoluted tubule  Loop of Henle  distal convoluted tubule  collecting duct  papillary duct  minor calyx  major calyx  renal pelvis  ureter Distal Convoluted Tubule

11. Goodpasture(Pulmonary renal syndrome;) • Autoimmune disease attacking collagen • Treatment: removing blood plasma to get rid of anti-GBM antibodies and replace it with fluid, protein, or donated plasma • Nephrogenic diabetes insipidus • Acquired • Tubules do not respond to ADH • Treatment: anti-diuretic Kidney Diseases

12. Used once 85-90% of kidney function is lost • Removes excess Na+, waste, and water from the body • Maintains K+, Na+, and bicarbonate levels • Aids in the control of blood pressure • Hemodialysis: intervenous • Peritoneal: put dialysate in the peritoneal cavity • via a catheter • via a machine Dialysis

13. Charytan, D. M. (2006, November 16). Goodpasture syndrome. Medline Plus Medical Encyclopedia. Retrieved February 24, 2009, from http://www.nlm.nih.gov/medlineplus/ency/article/000142.htm National Kidney Foundation. (2009). A to Z Health Guide: Dialysis. Retrieved February 25, 2009, from http://www.kidney.org/atoz/atozItem.cfm?id=39 Patel, P. (2008, April 14). Diabetes insipidus - nephrogenic. Medline Plus Medical Encyclopedia. Retrieved February 24, 2009, from http://www.nlm.nih.gov/medlineplus/ency/article/000511.htm Silverthorn, D. U., Ober, W. C., Garrison, C. W., Silverthorn, A. C., & Johnson, B. R. (2007). The Kidneys. In D. Espinoza, I. Nunes, & W. Earl (Eds.), Human Physiology: An Integrated Approach (pp. 614-635). San Fransisco: Pearson Education as Benjamin Cummings. Tortora, G. J. (2005). The Uninary System. In B. Roesch, & K. Trost (Eds.), Principles of Human Anatomy (pp. 810-). Hoboken, NJ: John Wiley & Sons. References