The Urinary System Chapter 15 1 Outline Functions

The Urinary System Chapter 15 1

• • Outline Functions of the Urinary System Overview of the Urinary System Kidney Structure Urine Formation – – – • • • Glomerular Filtration Tubular Reabsorption Tubular Secretion Maintaining Water-Salt Balance Maintaining Blood p. H Homeostasis 2

• Functions of the Urinary System Carry out excretion of metabolic wastes. – – • Excretion is the removal of metabolic waste products- Elimination is the removal of un-used or un-usable material from the body Urea is the primary nitrogenous end product, but ammonium, creatinine, and uric acid are also excreted. Maintains salt-water balance of blood and thus regulates blood volume and blood pressure. + – Ions regulated include sodium (Na ), potassium (K+), and calcium (Ca 2+). 3

Functions of the Urinary System (Con’t) • • Maintains acid-base balance of the blood. – Regulates bicarbonate ions (HCO 3 ) and hydrogen ions (H+). Performs these functions by producing urine and conducting it outside the body. Has a hormonal function. – Produces erythropoietin. – Produces renin for the renin-angiotensinaldosterone system. Activates inactive form of Vitamin D 4

Overview of the Urinary System • • • Kidneys are primary organs of the urinary system. – The concave side of a kidney has depression called the hilum where the renal artery enters and the renal vein and ureters exit the kidney. Urinary bladder gradually expands as urine enters. Urethra extends from the urinary bladder to an exterior opening. 5

Figure 15. 1 a Organs of the urinary system. Overview of the Urinary System Hepatic veins (cut) Inferior vena cava Adrenal gland Aorta Iliac crest Renal artery Renal hilum Renal vein Kidney Ureter Rectum (cut) Uterus (part of female reproductive system) (a) © 2015 Pearson Education, Inc. Urinary bladder Urethra

Figure 15. 1 b Organs of the urinary system. 12 th rib (b) © 2015 Pearson Education, Inc.

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Kidney Structure • The kidney contains three major regions: – – – • Additional structures of importance – – • Renal cortex. Renal medulla. Renal pelvis. Renal columns Renal papilla Renal pyramids Minor & major calyces Microscopically, the kidney is composed of over one-million nephrons that produce urine. 9

PATH OF URINE DRAINAGE: Nephron Collecting duct Renal hilum Minor calyx Renal cortex Renal artery Renal medulla Renal vein Major calyx Renal pelvis Renal column Renal pyramid in renal medulla Renal papilla Ureter Renal capsule be Renal lo (a) Anterior view of dissection of right kidney Urinary bladder

Blood Supply to the Kidney Glomerulus Frontal plane Afferent arteriole Peritubular capillary Efferent arteriole Interlobular vein Vasa recta Blood supply of nephron Interlobular artery Renal capsule Arcuate artery Interlobar artery Segmental artery Renal cortex Renal artery Renal vein Interlobar vein Renal pyramid in renal medulla Arcuate vein Interlobular vein (a) Frontal section of right kidney

Kidney Structure: The Nephron • Nephron is functional unit of the kidney. – • Two types of nephrons v Coritcal: 80 -85%, normal renal function v Juxtamedullary: 15 -20%, involved with generation of very dilute or very concentrated urine Each nephron has its own blood supply. – – From the renal artery, afferent arteriole leads to the glomerulus, then to the efferent arteriole and then to the peritubular capillary network (or vasa recta of juxtamedullary nephrons) which surrounds the nephron. From there blood goes into a venule that joins the renal vein. 12

Figure 15. 3 a Structure of the nephron. Cortical nephron Collecting duct Renal cortex Renal medulla Renal pelvis Fibrous capsule Proximal convoluted tubule Glomerulus Renal cortex Distal convoluted tubule Ureter Nephron loop Renal medulla (a) © 2015 Pearson Education, Inc. Juxtamedullary nephron

Kidney Structure: The Nephron (Con’t) 14

Kidney Structure: The Nephron (Con’t) • Each nephron is composed of several parts. – Glomerular capsule (Bowman’s capsule). v – Proximal convoluted tubule. v – Tubular reabsorption and secretion Distal convoluted tubule. v – Tubular reabsorption Loop of the nephron (loop of Henle). v – Filtration Tubular reabsorption and secretion Collecting duct. v Tubular reabsorption 15

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Glomerular capsule Glomerular space Glomerulus Blood flow Movement of glomerular filtrate Afferent arteriole Efferent arteriole a) The outer surface of several glomerular capillaries. Podocyte Filtrate Proximal tubule Capillary wall b) A highly magnified view of the inner surface of a single glomerular capillary, revealing its porous sievelike structure. © 2012 Pearson Education, Inc. Figure 15. 7

Renal corpuscle Afferent arteriole Glomerular filtration (filtration of blood plasma by glomerulus) Glomerular capsule Renal tubule and collecting duct Glomerulus Glomerular filtrate in renal tubule 1 2 Tubular reabsorption from glomerular filtrate into blood Efferent arteriole Peritubular capillaries 3 Tubular secretion Urine (contains excreted substances) from blood into glomerular filtrate Blood (contains reabsorbed substances)

• Urine Formation Urine formation is divided into three steps. 1. Glomerular filtration. v Filterable blood components Ø water Ø nitrogenous wastes Ø nutrients Ø salts (ions) v Nonfilterable blood components Ø white and red blood cell, platelets Ø plasma proteins 19

2. Urine Formation (Con’t) Tubular reabsorption. v Reabsorbed filtrate components Ø most water Ø nutrients Ø required salts (ions) v Nonreabsorbed filtrate components Ø some water Ø much nitrogenous waste Ø excess salts (ions) 20

Urine Formation (Con’t) 3. Tubular secretion. v Active removal from the blood of some compounds, such as drugs, with secretion into the distal convoluted tubule 21

Filtration and Reabsorption 22

Maintaining Salt-Water Balance • Reabsorption of Water- Water Balance – – – Very dilute or very concentrated urine v Dependent upon reabsorption of water from the descending limb of loops of Henle and collecting ducts Ø Mostly juxtamedullary nephrons Osmotic gradient exists within the tissues of the renal medulla. Antidiuretic hormone (ADH) released by the posterior lobe of the pituitary (due to osmolarity of plasma) causes more water to be reabsorbed in collecting ducts and less urine to form Ø Diuretics increase urine flow § § Alcohol- inhibits ADH release from posterior pituitary Caffeine- inhibits reabsorption of Na+ 23

Maintaining Salt-Water Balance • Reabsorption of Water- Water Balance – Osmotic gradient exists within the tissues of the renal medulla v Creation of osmotic gradient Ø Countercurrent multiplication- nephron tubules v Maintenance of osmotic gradient Ø Countercurrent exchange- vasa recta blood vessels 24

Creation of Osmotic Gradient Vasa recta Maintenance of Osmotic Gradient Loop of Henle Juxtamedullary nephron and its blood supply together Glomerular (Bowman’s) capsule Afferent arteriole Distal convoluted tubule Efferent arteriole 300 400 600 Osmotic gradient 800 1000 Proximal convoluted tubule Interstitial fluid in renal medulla 200 HO H 2 O 2 300 H 2 O Interstitial fluid in renal cortex 320 300 Collecting duct 300 H 2 O 100 Na+Cl– 380 H 2 O 200 1 580 Symporters in thick ascending limb cause buildup of Na+ and Cl– in 780 renal medulla H 2 O 2 Countercurrent flow 1200 through loop of Henle establishes osmotic gradient H 2 O Na+Cl– Blood flow Presence of Na+–K+– 2 Cl– symporters Flow of tubular fluid Glomerulus 400 320 H 2 O 400 H 2 O 3 Principal cells in collecting duct reabsorb more water when ADH is present 400 500 Na+Cl– 600 H 2 O 600 800 980 Urea 800 1000 H 2 O 1200 Loop of Henle 1200 (a) Reabsorption of Na +, Cl–, and water in long -loop juxtamedullary nephron 4 Urea recycling 700 800 causes buildup of urea in renal medulla H 2 O 900 H 2 O Na+Cl– 1000 Na+Cl– 1100 Papillary duct 1200 Concentrated urine (b) Recycling of salts and urea in vasa recta

Maintaining Salt-Water Balance • Reabsorption of Water- Water Balance – – Very dilute or very concentrated urine v Dependent upon reabsorption of water from the descending limb of loops of Henle and collecting ducts Ø Mostly juxtamedullary nephrons Antidiuretic hormone (ADH) released by the posterior lobe of the pituitary (due to osmolarity of plasma) causes more water to be reabsorbed in collecting ducts and less urine to form Ø Diuretics increase urine flow § Alcohol- inhibits ADH release from posterior pituitary + § Caffeine- inhibits reabsorption of Na 26

ADH & Making Dilute Urine Afferent arteriole Glomerular (Bowman's) capsule Glomerulus Distal convoluted tubule Efferent arteriole 100 300 Proximal convoluted tubule 90 300 350 150 Interstitial fluid in renal cortex 350 Collecting duct 550 750 350 550 80 Interstitial fluid in renal medulla 750 70 900 Loop of Henle 65 65 Papillary duct Dilute urine

ADH & Making Concentrated Urine Vasa recta Loop of Henle Juxtamedullary nephron and its blood supply together Glomerular (Bowman’s) capsule Afferent arteriole Distal convoluted tubule Efferent arteriole 300 400 600 Osmotic gradient 800 1000 Proximal convoluted tubule Interstitial fluid in renal medulla 200 HO H 2 O 2 300 H 2 O Interstitial fluid in renal cortex 320 300 Collecting duct 300 H 2 O 100 Na+Cl– 380 H 2 O 200 1 580 Symporters in thick ascending limb cause buildup of Na+ and Cl– in 780 renal medulla H 2 O 2 Countercurrent flow 1200 through loop of Henle establishes osmotic gradient H 2 O Na+Cl– Blood flow Presence of Na+–K+– 2 Cl– symporters Flow of tubular fluid Glomerulus 400 320 H 2 O 400 H 2 O 3 Principal cells in collecting duct reabsorb more water when ADH is present 400 500 Na+Cl– 600 H 2 O 600 800 980 Urea 800 1000 H 2 O 1200 Loop of Henle 1200 (a) Reabsorption of Na +, Cl–, and water in long -loop juxtamedullary nephron 4 Urea recycling 700 800 causes buildup of urea in renal medulla H 2 O 900 H 2 O Na+Cl– 1000 Na+Cl– 1100 Papillary duct 1200 Concentrated urine (b) Recycling of salts and urea in vasa recta

• Maintaining Salt-Water Balance Fluid Compartments & Fluid Balance – – Intracellular fluid (ICF)- inside cells Extracellular fluid (ECF)- outside cells Interstitial fluid- microscopic space outside every cell of the body v Plasma v – Renal processes of filtration, reabsorption, diffusion, and osmosis promote continuous exchange between the fluid compartments v Thus fluid balance is directly related to electrolyte (ions) balance Ø “Wherever salt goes water follows” 29

Total body mass (female) Total body mass (male) 45% Solids 40% Solids Renal effects on salt distribution will affect fluid distribution Total body fluid 2/3 Intracellular fluid (ICF) 55% Fluids 60% Fluids Tissue cells Extracellular fluid 1/3 Extracellular fluid (ECF) 80% Interstitial fluid 20% Plasma (a) Distribution of body solids and fluids in average lean, adult female and male Blood capillary (b) Exchange of water among body fluid compartments

• Maintaining Salt-Water Balance Reabsorption of Salt. – Kidneys regulate blood’s salt balance by controlling excretion and reabsorption of various ions, most important one being Na+ v – Usually more than 99% of sodium filtered at the glomerulus is returned to the blood Hormonal control of salt reabsorption Starts at juxtaglomerular apparatus (JGA) v Decrease in blood volume/pressure-renin from the JGA is released into blood-enzymatically cleaves angiotensinogen to angiotensin-I, angiotensin-I converted to angiotensin-II in lungs, angiotensin-II stimulates release of aldosterone from adrenal cortex, aldosterone stimulates Na+ reabsorption v 31

Juxtaglomerular Apparatus 32

Figure 15. 3 b Structure of the nephron. Peritubular capillaries Proximal convoluted tubule (PCT) Glomerular capillaries Distal convoluted tubule (DCT) Glomerular (Bowman’s) capsule Efferent arteriole Afferent arteriole Cells of the juxtaglomerular apparatus Cortical radiate artery Arcuate Cortical radiate vein Collecting duct (b) © 2015 Pearson Education, Inc. Nephron loop

• Maintaining Salt-Water Balance Reabsorption of Salt. – Hormonal control of salt reabsorption (Cont. ) Wherever salt goes water follows, thus increase reabsorption of water v Causes of decrease blood volume- blood loss (hemorrhage), profuse sweating (includes loss of blood water/salt), profuse vomiting, profuse diarrhea v Reabsorption of water increases blood volume v Decreased blood volume means decreased blood pressure- hence increase in blood volume- increase in blood pressure v Thus direct link between salt regulation and blood pressure regulation v ADH increases to increase water reabsorption v 34

ADH Blood volume Increase Set point Save water Kidneys Decrease Save salt Angiotensinconverting enzyme Ren Adrenal cortex in Kidneys Lungs Angiotensinogen Vasoconstriction, blood pressure Liver © 2012 Pearson Education, Inc. Figure 15. 15

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• Maintaining Salt-Water Balance Reabsorption of Salt. – Hormonal control of salt reabsorption (Cont. ) Starts at atria of heart + v Increase in Na concentration in plasma- huge salt filled meal + v 99% of Na reabsorbed- wherever salt goes water follow v Water enters blood from fluid compartmentsintracellular space, then interstitial space, then into plasma v Increase in blood volume v Increase stretch of atria of heart- release atrial natriuretic peptide + v Causes increased salt excretion (decrease Na reabsorption) v 37

• Maintaining Salt-Water Balance Reabsorption of Salt. – Hormonal control of salt reabsorption (Cont. ) Wherever salt goes water follows v Increase removal of water from blood- decrease in blood volume- decrease in blood pressure Ø Hypertension- may be a defect in atrial natriuretic peptide system v What is happening to ADH during this situation? v Increased osmolarity of blood should stimulate ADH release but that can’t happen because that would increase blood volume when you want to decrease it v Thus ADH is mostly involved when you have changes in water affecting osmolarity not salt affecting osmolarity v 38

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• • • Fate of Some Compounds, Normal Amount of Urine Nutrients- amino acids, glucose / all filtered from blood into urine in glomerulus / all reabsorbed in proximal / none in urine Water and salts / most filtered from blood into urine in glomerulus / most reabsorbed in proximal and collecting duct / concentration in urine dependent on need and hormones Metabolic wastes- urea, uric acid/ all filtered from blood into urine in glomerulus / none reabsorbed / concentration in urine higher than blood 41

Fate of Some Compounds, Low Amount of Urine- After Sleeping • • • Nutrients- amino acids, glucose / all filtered from blood into urine in glomerulus / all reabsorbed in proximal / none in urine Water / most filtered from blood into urine in glomerulus / even more reabsorbed in proximal and collecting duct due to prevention of loss during sleep / ADH increases reabsorption in collecting duct Metabolic wastes- urea, uric acid/ all filtered from blood into urine in glomerulus / none reabsorbed / concentration in urine much higher than under normal condition due to less water 42

© 2012 Pearson Education, Inc. Table 15. 1

Fate of Some Compounds, High Amount of Urine- After Mc. Donalds Meal • • • Nutrients- amino acids, glucose / all filtered from blood into urine in glomerulus / all reabsorbed in proximal / none in urine Salt and water / most filtered from blood into urine in glomerulus / most reabsorbed in proximal and collecting duct / high salt in food, goes into blood, water follows, increase volume, increase pressure, ANH released, salt reabsorption decreased, ADH turned off, water follows salt into urine Metabolic wastes- urea, uric acid/ all filtered from blood into urine in glomerulus / none reabsorbed / concentration in urine lower than normal due to large amount of water in urine 44

Maintaining Blood p. H • • Reabsorption of bicarbonate ions and secretion of hydrogen ions Exhalation of Carbon Dioxide 45

Maintaining Blood p. H 46

• • • Homeostasis In conjunction with the lungs, maintenance of acid-base balance. Maintenance of water-salt balance of blood and the overall osmolarity. Helps regulate blood volume and pressure. – Releases-erythropoietin; increases number of red blood cells Regulates the concentration of important ions such as calcium (Ca 2+) and potassium (K+). In conjunction with the liver, excretion of metabolic wastes. 47

Need to Know 1. 2. Functions of the urinary system A. Metabolic waste excretion B. Salt-Water balance C. Blood pressure regulation D. Acid-base balance E. Red blood cell quantity regulation F. Activation of inactive Vitamin D Kidney Structure: The Nephron A. Afferent and efferent arterioles B. Glomerulus C. Peritubular capillary network 48

Need to Know (Cont. ) 2. 3. Kidney Structure: The Nephron (Cont. ) D. Glomerular capsule E. Proximal convoluted tubule F. Loop of the nephron G. Distal convoluted tubule H. Collecting duct Urine formation A. Glomerular filtration concept B. Tubular reabsorption concept C. Tubular secretion concept D. Must know what’s filtered and not filtered, what’s reabsorbed and not reabsorbed and what’s secreted 49

Need to Know (Cont. ) 4. 5. Reabsorption of salt A. Juxtaglomerular apparatus B. Renin-angiotensin-aldosterone system C. Atria natriuretic hormone D. Blood pressure regulation Acid-Base balance A. Reabsorption of bicarbonate ion B. Excretion of hydrogen ion 50

Need to Know (Cont. ) 6. 7. Kidney Structure: Gross anatomy A. Renal cortex B. Renal medulla C. Renal pelvis Urinary system: General A. Kidney B. Ureters C. Urinary bladder D. Urethra 51