Chapter 30 Structure and Function of the Kidney

1. Chapter 30Structure and Function of the Kidney

2. Structure and Locations of the Kidneys • Structure • Paired, bean-shaped organs • Multilobular structure, composed of up to 18 lobes • Each lobule is composed of nephrons, the functional units of the kidney. • Location • Outside the peritoneal cavity in the back of the upper abdomen • One on each side of the vertebral column at the level of the 12th thoracic to 3rd lumbar vertebrae

3. Capillary Systems Supplying the Nephron • Glomerulus capillary system • A unique, high-pressure capillary filtration system located between the afferent and the efferent arterioles • Selectively dilates or constricts to regulate glomerular capillary pressure • Peritubular capillary system • A low-pressure reabsorptive system that originates from the efferent arteriole

4. Function of the Nephron • Glomerular filtration • Three layers of filtration • Reabsorbs water, electrolytes, and other substances needed to maintain the constancy of the internal environment into the bloodstream • Secretes unneeded compounds into the tubular filtrate for elimination

5. Factors Affecting the Glomerular Filtration Rate • Glomerular capillary hydrostatic pressure • Glomerular capillary osmotic pressure • Hydrostatic and osmotic pressures in Bowman’s capsule

6. Four Segments of the Nephron Tubule • Proximal convoluted tubule • A highly coiled segment; drains Bowman’s capsule • Loop of Henle • A thin, looped structure • Distal convoluted tubule • A distal coiled portion • Collecting tubule • Joins with several tubules to collect the filtrate

7. Na+ Transport as the Driving Force • Na+/K+ ATPase maintains concentration gradient • Symport • Antiport • Exchange

8. Question • Which of the following best describes the function of the nephron? • The detoxification of blood • The retention of important organic materials found in the filtrate • The resorption of water, electrolytes, and other substances from the bloodstream • The synthesis and storage of urine

9. Answer • The detoxification of blood • The retention of important organic materials found in the filtrate • The resorption of water, electrolytes, and other substances from the bloodstream • The synthesis and storage of urine

10. Tubular Filtration • Urine filtrate flows through the tubular component of the nephron • As the filtrate flows through the tubule, the concentration of water and electrolytes in the filtrate changes due to: • Reabsorption of water and solutes by tubular cells into the peritubular capillary blood • Secretion from the blood into the tubular lumen

11. Regulation of Urine Concentration • Response to changes in interstitial osmolarity • 1200 mOsm normal • Antidiuretic hormone changes the permeability of the tubules of the collecting duct.

12. Elimination Functions of the Kidney • Renal clearance • Regulation of sodium • Potassium elimination • pH-dependent elimination of organic ions • Uric acid elimination • Urea elimination • Drug elimination

13. Endocrine Functions of the Kidney • Juxtaglomerular complex • The renin-angiotensin-aldosterone mechanism • Plays an important part in regulation of blood pressure • Erythropoietin • Regulates the differentiation of red blood cells in bone marrow • Vitamin D • Increases calcium absorption from the gastrointestinal tract • Helps regulate calcium deposition in bone

14. Question • Which of the following hormones is produced in the kidney? • Antidiuretic hormone • Erythropoietin • Aldosterone • Angiotensin

15. Answer • ADH • Erythropoietin: Erythropoietin is formed in the kidney in response to decreased blood oxygenation. • Aldosterone • Angiotensin

16. Action of Diuretics • Loop diuretics • Exert their effect in the thick ascending loop of Henle • Thiazide diuretics • Prevent the reabsorption of NaCl in the distal convoluted tubule

17. Action of Diuretics (cont.) • Aldosterone antagonists (potassium-sparing diuretics) • Reduce sodium reabsorption and increase potassium secretion in the late distal tubule and cortical collecting tubule site regulated by aldosterone

18. Renal Clearance • Definition • The volume of plasma that is completely cleared each minute of any substance in the urine • Determining factors • The ability of the substance to be filtered by the glomeruli • The capacity of the renal tubules to reabsorb or secrete the substance

19. Characteristics of Normal Urine • Clear, amber-colored fluid • Approximately 95% water and 5% dissolved solids • The kidneys normally produce approximately 1.5 L of urine each day. • Contains metabolic wastes and few or no plasma proteins, blood cells, or glucose molecules

20. Tests for Renal Function • Urinalysis • Glomerular filtration rate • Blood tests • Serum creatinine • Blood urea nitrogen • Cystoscopy • Ultrasonography • Radiologic and other image studies

21. Question • Normal urine should be_______________. • Cloudy • Have a pH of 7.0 or greater • Should have a specific gravity of 1.0 • Sterile

22. Answer • Cloudy • Have a pH of 7.0 or greater • Should have a specific gravity of 1.0 • Sterile: There will be no bacteria present in a healthy urinary tract.