Structure and Function of the Renal and Urologic Systems Chapter 35 Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc.

2 Structures of the Kidney  Kidneys  Retroperitoneal  Renal capsule  Renal fascia  Hilum

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 3 Structures of the Kidney

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 4 Structures of the Kidney  Renal cortex  Renal medulla  Renal pyramids  Renal columns  Minor calyx  Major calyx  Renal pelvis

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 5 Structures of the Kidney

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 6 Nephron  1.2 million nephrons per kidney  Functional unit of the kidney  Superficial cortical nephrons  Midcortical nephrons  Juxtamedullary nephrons

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 7 Nephron  Renal corpuscle  Glomerulus  Bowman capsule  Mesangial cells  Bowman space

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 8 Glomerulus  Filtration  Formation of primary urine

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 9 Glomerulus  Glomerular filtration membrane  Glomerular endothelium  Basement membrane  Capillary epithelium Also referred to as podocytes or visceral epithelium Also referred to as podocytes or visceral epithelium Filtration slits Filtration slits

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 10 Nephron  Juxtaglomerular apparatus  Juxtaglomerular cells  Macula densa

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 11 Juxtaglomerular Apparatus

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 12 Nephron  Renal tubules  Proximal tubule  Loop of Henle  Distal tubule  Collecting duct  Principal cells  Intercalated cells

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 13 Structures of the Kidney

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 14 Structures of the Kidney

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 15 Blood Vessels  Renal arteries  Interlobar arteries  Arcuate arteries  Interlobular arteries  Afferent arterioles  Glomerular capillaries  Efferent arterioles  Peritubular capillaries and vasa recta

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 16 Structures of the Kidney

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 17 Structures of the Kidney  Ureters  30 cm long  Long, intertwining muscle bundles  Pass obliquely though posterior aspect of bladder  Peristaltic activity  Micturition compresses the lower end of the ureter to avoid urine reflux

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 18 Structures of the Urologic System  Bladder  Detrusor muscle  Transitional epithelium  Trigone  Micturition reflex  Urethra  Internal and external sphincters  3 to 4 cm in females  18 to 20 cm in males

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 19 Bladder and Urethra

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 20 Renal Blood Flow (RBF)  Receive 1000 to 1200 ml of blood per minute  ml as plasma (renal plasma flow [RPF])  Glomerular filtration rate (GFR)  Filtration of plasma into the Bowman space  20% of the RPF ( ml/min)  Directly related to the perfusion pressure in the glomerular capillaries (RBF) Strict maintenance of mmHg provides constant GFR Strict maintenance of mmHg provides constant GFR

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 21 Regulation of RBF/GFR  Autoregulation  Myogenic mechanism (stretch)  Tubuloglomerular feedback (NaCl content)  Neural regulation  Sympathetic nervous system Vasoconstriction (diminishes GFR) Vasoconstriction (diminishes GFR)

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 22 Renal Functions  Regulation of blood volume and serum osmolarity (water/sodium balance)  ADH  Renin-angiotensin-aldosterone system

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 23 Renal Functions  Excrete metabolic wastes  Creatinine, urea (end product of protein metabolism), certain drugs  Regulate acid-base balance  Balance of H + and HCO 3  Secrete hormones  Renin-angiotensin-aldosterone system  Erythropoietin  Conversion of vitamin D to usable form

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 24 Renal Processes  Filtration  Movement of protein free plasma across the glomerular membrane (hydrostatic pressure)  Tubular reabsorption  Movement of fluid/solutes from tubular lumen to the peritubular capillaries  Tubular secretion  Transfer of substances from the peritubular capillaries to the tubular lumen  Excretion  Elimination of fluids/substances in the final urine

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 25 Nephron Function  Glomerular filtration  Net filtration pressure Glomerular hydrostatic pressure Glomerular hydrostatic pressure Capsular hydrostatic pressure Capsular hydrostatic pressure Blood oncotic pressure Blood oncotic pressure  Filtration rate

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 26 Tubular Transport  Active transport of fluids and substances  Reabsorption: normally 99% of the glomerular filtrate is reabsorbed!  Urea: major constituent of urine, along with water  50% of urea is reabsorbed, 50% excreted in the urine  Provides osmotic gradient

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 27 Renal “Clearance”  The ability of the kidneys to filter a substance and excrete it in the urine is a reflection of the GFR, tubular secretion, and tubular reabsorption (thus also RBF and functioning of nephrons)

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 28 Glomerular Filtration

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 29 Nephron Function

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 30 Nephron Function

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 31 Concentration and Dilution of Urine  Countercurrent exchange system  Contributes to production of concentrated urine  Fluid flows in opposite direction through parallel tubes  Fluid moves up and down the parallel limbs of the loop of Henle  The longer the loop, the greater the concentration gradient

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 32 Countercurrent Exchange System

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 33 Concentration and Dilution of Urine  Urea  Catecholamines  Antidiuretic hormone (ADH)  Urodilantin  Natriuretic peptide  Diuretics

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 34 Renal Hormones  Vitamin D  Erythropoietin

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 35 Tests of Renal Function  Clearance and glomerular filtration rate  Inulin  Creatinine  Clearance and renal blood flow  Blood tests  Plasma creatinine concentration  Plasma cystatin C concentration  Blood urea nitrogen (BUN)

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 36 Tests of Renal Function  Urinalysis  Urine color  Urine pH  Specific gravity  Urine sediment RBCs RBCs Casts Casts Crystals Crystals WBCs WBCs

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 37 Tests of Renal Function  Urinalysis  Reagent strips (dipsticks) Glucose Glucose Bilirubin Bilirubin Urobilinogen Urobilinogen Leukocyte esterase Leukocyte esterase Nitrates Nitrates Ketones Ketones Proteins Proteins RBCs, hemoglobin, and myoglobin RBCs, hemoglobin, and myoglobin

Mosby items and derived items © 2010, 2006 by Mosby, Inc., an affiliate of Elsevier Inc. 38 Aging and Renal Function  Decrease in kidney size  Decrease in renal blood flow and GFR  Number of nephrons decrease due to renal vascular and perfusion changes  Glomerular capillaries atrophy  Tubular transport response decreases  Increased bladder symptoms  Urgency, frequency, and nocturia