The Urinary System Chapter 26. The organs of the urinary system include:
Chapter 23— The Urinary System
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Transcript of Chapter 23— The Urinary System
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Chapter 23— The Urinary System
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Ch. 23 Study Guide
1. Critically read 23.1 to right before the 23.7 (Urine Storage and Elimination) section (pp. 905-931)
2. Comprehend Terminology (those in bold)3. Study-- Figure questions, Think About It
questions, and Before You Go On (section-ending) questions
4. Do end-of-chapter questions:– Testing Your Recall— 2-10, 12-17, 19-20– True or False– 1-9– Testing Your Comprehension-- #1-2
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I. Functions of the Urinary System
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§ Major Nitrogenous WastesAmmonia: very toxic; from
amino group in the a.a.Urea: less toxic; converted
from ammonia in the __________
Uric acid:nucleic acid catabolism
Creatininecreatine phosphate
catabolism
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§ Major Nitrogenous WastesBUN (Blood Urea Nitrogen)1.Measure the amount of ________ in your blood2.Why is it done?
3.Disorders: – Azotemia: an abnormally elevated BUN is
called; may indicate renal insufficiency– Uremia: toxic effects as wastes (urea)
accumulate in the blood; patients with renal failure
• Symptoms– vomiting, diarrhea, cardiac arrhythmia etc.
• Treatment--Hemodialysis 23-5
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§ Major kidney functions (1)
1. Eliminate wastes & foreign compounds– Major nitrogenous wastes?– Major foreign cpds?
2. Maintain blood volume and electrolyte (ion) concentration – For example, water balance during exercise– Another example, [K+] and ectopic focus
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§ Major kidney functions (2)
3.Produce hormones— two major ones?
4.Detoxifies free radicals and drugs
5.In times of starvation-- gluconeogenesis (makes glucose from amino acids or fats)
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II. Anatomy of the Kidney
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§ The urinary system1. Kidneys (a pair)
• Functions--
2. The ureter (a pair)
3. The single urinary bladder• A muscular sac for _________________
4. The urethra• Draining urine to the outside• In females vs. in males (length and
external orifice) + proper toilet habits
Figure 23.123-9
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Figure 23.1b
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§ Gross Anatomy of Kidney1. Renal cortex: outer 1 cm; extensions of
the cortex called renal columns
2. Renal medulla: inner zone; renal columns divide the medulla into 6-10 renal pyramids (each blunt point called renal papilla)
3. The renal papilla is nestled in a cup called a minor calyx major calyx
4. Lobe of kidney: pyramid and it’s overlying cortex
Fig. 23.4 + a practice figure23-11
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Figure 23.5a§ Renal circulation--
A
B
C
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Path of Blood Through Kidney
• Renal artery: into segmental artery and then A--interlobar arteries (up renal columns, between lobes)
B--arcuate arteries (over pyramids)
C--interlobular arteries (up into cortex)
afferent arterioles
glomerulus (cluster of capillaries)
efferent arterioles (near medulla vasa recta)
peritubular capillaries
interlobular veins arcuate veins interlobar veins
• Renal vein 23-14
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A. B.
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Two kinds of Nephrons, depending upon locations1. Cortical nephrons (85%)
– short nephron loops of Henle– efferent arterioles branch off into peritubular
capillaries
2. Juxtamedullary nephrons (15%)– Where?– very long nephron loops-- – Vasa Recta– Efferent arterioles descend into
the medulla and give rise to Vasa Recta instead of peritubular capillaries.
– The capillaries of the vasa recta lead into venules that empty into the interlobular and arcuate veins 23-17
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§ The Nephron (1)
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§ The Nephron (2)
1. How many nephrons in each kidney? Answer: ___________
2. The nephron are blood-processing units and each one of them is a functional unit of the kidneys
3. Vascular and tubular parts of the nephron
• Vascular parts first--Figure 23.6, 23.7
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3. Glomerulus
To renal pelvis 5. Peritubular capillaries
6. Interlobular vein
1. Interlobular Artery
2. Afferent arteriole
4. Efferent arteriole
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Glomerular capsule & glomerulus together: Renal Corpuscle
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§ Vascular part of the Nephron (3)1. The renal artery (. . . interlobular
artery)–
2. Afferent arteriole – • supplies each nephron and delivers blood to
the glomerulus
3. The glomerulus– cluster of capillaries (1st set of capillary in each nephron);
function?
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§ Vascular part of the Nephron (4)4.The efferent arteriole—
• Where the glomerular capillaries rejoin
5.The peritubular (2nd set of) capillaries--• Impt in exchanges between blood and
______________
6.The renal veins--• The major blood vessels leave the kidney
---------------------------------------------------------------
• Tubular parts of the nephron– @Fig. 23.8
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2. Proximal tubule
4. Distal tubule
5. Collectingduct
1. Bowman’s capsule
Glomerulus
CortexMedulla
3. Loop of Henle (nephron loop)
To renal pelvis
Vein
Artery
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§ Tubular part of the Nephron (5)
• A hollow tube formed by a single layer of epithelial cells; They are, in order:
1.Bowman’s (Glomerular) capsule– • Cup-shaped; double-wall invagination• Surround each __________
2.Proximal tubule– closest to Bowman’s capsule• Lies entirely within the cortex
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§ Tubular part of the Nephron (6)3.The loop of Henle (nephron
loop)– • Forms a U-shaped loop
4.The distal tubule– • most distant from the capsule; lies entirely within
the ____________
5.Collecting tubule/duct— • drains fluid from up to 8 nephrons
Figure 23.8 23-26
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Figure 23.8b1.
2.
3.
4.
5.ID parts (1-5) of the nephron.
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Questions?Muddiest points?
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III. Urine Formation
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§ Three urine forming processes
1.-- Glomerular filtration• From the glomerulus into Bowman’s
(glomerular) capsule
2A.--Tubular reabsorption• From the tubular lumen into ___________
2B.--Tubular secretion• From the peritubular capillaries into the
__________________
3.-- Water conservation
Figure 23.9 23-30
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1. Glomerular filtrate (in the capsular space)
2. Tubular fluid (proximal tubule to distal tubule)
3. Urine (collecting duct and beyond)
Different names (fluid in renal tubules) in different areas:
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III. Urine Formation; 1. GLOMERULAR FILTRATION
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§ 1. Glomerular filtrationA. Def.– filtering blood by forcing small
molecules into the Bowman’s capsule
B. What in the filtrate?• Small molecules can pass—
• Large molecules cannot—
C. Mechanism? ATP?• What is the major force? Glomerular blood
hydrostatic pressure (BHP)23-33
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§ 1. Glomerular filtration (cont.)D. Layers of the glomerular filtration mem.
i. 1-Fenestrated endothelium of capillaries• Large pores (100x more permeable)• Molecules can pass–
ii. 2-(Acellular) basement mem.• Collagen & glycoproteins• Function--
iii. 3a-Filtration slits; present in inner layer of the Bowman’s capsule-- podocytes (3b) bear many foot processes (pedicles)
Figure 23.10 (a-d)23-34
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Afferent arteriole Efferent arteriole
Glomerulus
Bowman’scapsule
Lumen ofBowman’scapsule
Outer layer ofBowman’s capsule
Inner layerof Bowman’s capsule(podocytes)
Proximal convoluted tubule
Lumen ofglomerularcapillaryEndothelialcell
Basementmembrane
Podocytefoot process
(seenextslide)
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2. Basementmembrane
1. Capillarypore
3a.Filtrationslits
3b. Podocyte& foot process
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3b. Podocytefoot process
3a.Filtrationslit
2. Basementmembrane
1a. Capillarypore
1b. Endothelialcell
Lumen of glomerularcapillary
Lumen ofBowman’s capsule (capsular space)
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C.Filtrationslit
B.
A. Endothelialcell
Lumen of glomerularcapillary
Lumen ofBowman’s capsule
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§ 1. Glomerular filtration (cont.)
Disorders:
1.Albuminuria– also called proteinuria; presence of ________ in the urine• Criteria: >250 mg/day: pathological
2.Hematuria– presence of ______ in the urine
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III. Urine Formation; 2A. TUBULAR REABSORPTION
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§ 2. Tubular reabsorption
1. Def. reclamation process to move molecules back into the blood
2. Goal: to move molecules from tubular lumen to the peritubular capillaries (or vasa recta)
Table x & Figure y
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§ 2. Tubular reabsorption (cont.)
Substances in filtrate
% of filtered substances
reabsorbed
% of filtered substances excreted
Water 99 1
Sodium 99.5 0.5
Glucose 100 0
Urea 50 50
Phenol 0 100
Table x
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§ 2.Tubular reabsorption (cont.)
1. What are reabsorbed?• All the glucose, vitamins, and . . .
2. How efficient?• Glucose— no glucose escapes• Water— 180 L filtrate to 1-2 L of urine/day• Analogy— Clean out a cluttered drawer
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III. Urine Formation; 2A. TUBULAR REABSORPTION–
in the proximal convoluted T.
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§ 2. Tubular reabsorption (cont.) Two examples—Na+, water in proximal
convoluted tubules and beyond3.--1st example– sodium reabsorption• Where are sodium ions been
reabsorbed? Most of the tubuleException is the descending limb of the loop of Henle
• Routes taken: both transcellular and paracellular routes
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§ 2. Tubular reabsorption (cont.)• Mechanisms of sodium reabsorption—
– A--symport proteins (channels)—
– B--Na+-H+ antiport—
– C--Na+-K+ pumps– basal and lateral membrane
– D– Paracellular route--
Figures 23.1623-46
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§ 2 Tubular reabsorption (cont.)4. --2nd example– water reabsorption
Locations? All the renal tubule; however, 2/3 occurs in PCT
• Mechanisms— Via water channels (aquaporins) Between cells Water moves into blood plasma
Figures 23.1623-4823-48
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§ Reabsorption Limit1. Def.-- A limit to the amount of solute the
renal tubule can reabsorb2. Why? Limited no. of transport proteins
3. Tm = Transport maximum; example--– Glucose’s Tm is 320 mg/min – Glucose normally enters the renal tubule
at 125 mg/min; will all of it be reabsorbed?– Threshold of glucose in the plasma– 220
mg/dL (= 220mg/100mL); begin to see glucose in the urine called glycosuria
– Untreated diabetes mellitus patients– 400 mg/dL (plasma glucose)
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III. Urine Formation; 2A. TUBULAR REABSORPTION–
in the nephron loop
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§ The nephron loop (loop of Henle)
• Primary function— to generate a salinity gradient that enables the collecting duct to concentrate the urine and conserve water
• Mechanism—– Thick segment (ascending limb) of
the loop: Impermeable to water– Tubular fluid becomes very dilute by the
time it reaches the DCT
Fig. 23.1923-5223-52
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Increasing Osmolarity
Low
High
Nep
hro
n lo
op
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Cortex
Medulla
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III. Urine Formation; 2A. TUBULAR REABSORPTION–
in the distal convoluted tubule and collecting duct
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§ DCT and collecting duct (CD)• Reabsorption regulation– by several
hormones including aldosterone etc. (see following slides)
• Cells here in DCT and CD—A. PRINCIPAL CELLS– – more abundant; they have receptors for
these hormones– Functions– involved in salt and water
balanceB. INTERCALATED CELLS– – fewer; functions– in acid-base balance
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§ Aldosterone (1)• Chemistry – peptide, steroid, or
monoamine? (which one)• Secreted by – the adrenal cortex • Function-- to promote sodium
retention and increase blood pressure• Triggered by –
– low blood sodium concentration – a drop in blood pressure (via renin)
Fig. 23.1523-5623-56
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Renin-Angiotensin-Aldosterone mechanism
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§ Aldosterone (2)• Acts on– three areas in the kidneys
– the thick segment of the ascending limb of the nephron loop
– The DCT– The cortical portion of the collecting duct
• Physiology Effects—– Retain NaCl and water– Maintain blood volume
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§ Atrial Natriuretic Peptide (1)• Chemistry – • Secreted by – atrial myocardium of the
heart
• Triggered by – high blood pressure
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§ Atrial Natriuretic Peptide (2)• Physiology Effects–
– Promoting sodium and water loss– Reducing blood volume and pressure
• Actions— on Kidney– Dilates the afferent arteriole and
constricts the efferent arteriole– Inhibits renin and aldosterone secretion– Inhibits ADH secretion and the action of
ADH on the kidney– Inhibits NaCl reabsorption by the
collecting duct23-60
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III. Urine Formation; 2B. TUBULAR SECRETION
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§ Tubular secretion1. Process— transfer of selective molecules
from the capillary blood and secrete them into the ___________
2. Locations– PCT, nephron loop, DCT3. Purposes—
– Waste removal—• For example—
– Acid-base balance– hydrogen and bicarbonate ions
Fig. x23-6223-62
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Glomerularcapillaries
Efferentarteriole
Peritubularcapillaries
Venousblood
Urine
Tubule (from proximal tubule to collecting duct)
Bowman’scapsule
Filtratepathway
Bloodpathway
Glomerularfiltration
Tubularreabsorption
Tubularsecretion
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Fig.-- the nephron & molecule movements (demo)
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III. Urine Formation; 3. WATER CONSERVATION
The principal function left to the collecting duct is to conserve water.
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§ The Collecting Duct (CD)1. Location –
– Begins in the cortex and passes through the medulla
2. Mission – it reabsorbs water and concentrates the urine
3. Mechanisms—– Osmolarity of the ECF is ______ times as
high in the lower medulla as it is in the cortex
– Medullary portion of the CD is more permeable to _______ than to NaCl
Fig. 23.19 23-65
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Figure 23.17
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Which portion of the renal tubule?
Cortex
Medulla
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§ Control of water lossHow concentrated the urine becomes depends on the state of hydration1. Dehydration– your urine becomes little & more concentrated:
– High blood osmolarity release ADH (more/less; circle one)
renal tubule synthesize aquaporins install them in the plasma mem. CD reabsorbs more water
2. Well hydrated– opposite to the above
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§ Countercurrent Multiplier (1)1. The ability of the collecting duct to
concentrate urine depends on the salinity gradient of the renal medulla.
– Mechanism behind this: The nephron loop acts as a countercurrent multiplier
– Result: the nephron continues to return salts to the deep medullary tissue
– Hence it is called multiplier b/c it multiplies the salinity deep in the __________
– Countercurrent? Fluid flows in opposite directions. Where? Descending limb and ascending limb of the nephron loop
Fig. 23.2023-6823-68
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Cortex
Medulla
1
2
3 4
5
Nephron loop23-69
PCT DCT
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§ Countercurrent Multiplier (2)2. How countercurrent multiplier works?
A. Medulla-- An environment of increasing salinity toward deeper part of medulla
B. Descending limb (nephron loop)– very permeable to _______ but not to NaCl
C. Ascending limb– impermeable to _____, but has pumps to transport ions
– Keeps the osmolarity high in medulla– Tubular fluid: more and more diluted
toward the distal tubule23-70
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§ Countercurrent Multiplier (3)3. In the lower end of collecting duct
(CD)– urea helps to maintain (40%) the osmotic gradient in medulla
How?– Lower end of CD is permeable to urea; urea
diffuses into the ECF– Urea enters the descending thin segment; but
the thick segment of the loop and DCT is NOT permeable to urea
– Therefore, continual recycling of urea from the CD to the medulla and back
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Next slide
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§ Countercurrent Exchange System
1. Vasa recta that supply the medulla recycle the salt and urea; How?
– Blood flows in opposite directions in adjacent parallel capillaries called countercurrent exchange system
– It flows downward– exchanges water for salt– It flows back toward the cortex– exchange salt
for water– Thus, vasa recta gives the salt back and DO
NOT subtract from the osmolarity of the medulla
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IV. Urine and Renal Function Tests
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§ Urine Volume (1)
1. Normally, 1-2 liters of urine per day
2. Polyuria (or diuresis)– output in excess of 2 L/day (detail next slide)
– Causes– fluid intake, some drugs, diabetes
3. Oliguria– output of less than 500 mL/day
4. Anuria– output of 0-100 mL/day– Causes– kidney disease, dehydration, etc.– Result-- Azotemia
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§ Urine Volume (2)
5. Polyuria (details)—A. Results from all four forms of diabetes—
• Diabetes mellitus type I, type II, gestational diabetes (all three above are due to hyperglycemia), and diabetes insipidus (due to ADH hyposecretion)
B. Diabetes mellitus and gestational diabetes are glycosuria but NOT in diabetes insipidus patients
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§ Urine Volume (3)
6. Diuretics— def. chemicals that increase urine volume
– Mechanisms– A. increasing glomerular filtration rate (GFR) or
B. reducing tubular reabsorption
– Example 1: Caffeine, dilates the afferent arteriole and increases GFR (due to A or B above; circle one)
– Example 2: Alcohol inhibits ADH secretion (due to A or B above; circle one)
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§ Renal Clearance
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1. Def.– the volume of blood plasma from which a particular waste is completely removed in 1 minute; Example: A. Urea concentration in urine = 6.0 mg/mL
B. Rate of urine output = 2 mL/min
C. Urea concentration in plasma = 0.2 mg/mL– Renal clearance = AB/C = (6.0 mg/mL x 2
mL/min)/0.2 mg/mL = 60 mL/min– This means the equivalent of 60 mL of blood
plasma is completely cleared of urea per minute
• Renal clearance of glucose? (healthy adults)
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§ Glomerular filtration rate (GFR)-(1)
1. Def.– the rate at which glomerular filtrate is formed; volume of filtrate formed each minute by all glomeruli; Example: Inulin (no tubular reabsorption, nor tubular secretion)
A. Urine concentration of inulin = 30 mg/mL
B. Urine output is = 2 mL/min
C. Plasma concentration of inulin = 0.5 mg/mL
D. GFR = AB/C = (30 x 2)/0.5 = 120 mL/min = Renal clearance of inulin (why?) (next slide)
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§ Glomerular filtration rate (GFR)-(2)
For inulin, GFR (120 mL/min) is equal to the renal clearance. Why?
1. All inulin filtered by the glomerulus remains in the renal tubule and appears in the urine.
2. A solute that is reabsorbed by the renal tubules will have renal clearance less than the GFR; renal clearance of urea @ 60 mL/min
3. A solute that is secreted by the renal tubules will have a renal clearance greater than the GFR; renal clearance of creatinine @ 140 mL/min