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The Urinary System. Chapter 17. Chapter 17 Objectives. To understand: Renal hormones that control blood volume Renal control of acid-base balance Mechanism of action of diuretics Kidney disease Role of the kidneys in heart failure. Kidney Function.

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chapter 17 objectives
Chapter 17 Objectives

To understand:

  • Renal hormones that control blood volume
  • Renal control of acid-base balance
  • Mechanism of action of diuretics
  • Kidney disease
  • Role of the kidneys in heart failure
kidney function
Kidney Function
  • Regulates plasma and interstitial fluid by formation of urine
  • In process of urine formation, kidneys regulate:
    • Volume of blood plasma, which contributes to BP
    • Waste products in plasma
    • Concentration of electrolytes
      • Including Na+, K+, HCO3-, and others
    • Plasma pH
structure of urinary system
Structure of Urinary System
  • Kidneys – by vertebral column below diaphragm
    • About size of fist
    • Filtration and urine production
  • Urine flows into ureters
    • empty into bladder
  • Bladder – temporary storage for urine
  • Urethra – drains urine to the external environment
structure of kidney
Structure of Kidney
  • Cortex – outer region
    • contains many capillaries
  • Medulla – consists of renal pyramids
    • separated by renal columns
    • Pyramids contain minor calyces, unite to form a major calyx
structure of kidney6
Structure of Kidney
  • Major calyces join to form the renal pelvis
    • Collects urine
    • Conducts urine to ureters which empty into bladder
micturition reflex urination
Micturition Reflex (Urination)
  • Bladder – temporary storage for urine
    • Detrussor musclesmooth muscular wall
    • Stretching can cause spontaneous action potentials and contraction
    • Also innervated and controlled by parasympathetic ANS
      • Drugs for overactive bladders target muscarinic ACh receptors
micturition reflex urination8
Micturition Reflex (Urination)
  • Internal and external urethral sphincters – regulated by reflex center in sacral part of spinal cord
  • Filling of bladder – activates stretch receptors that send impulses to the micturition reflex center
    • Activates parasympathetic neurons with contraction of the detrusor muscle
    • Relaxes internal urethral sphincter creating sense of urgency
    • There is voluntary control over external urethral sphincter
  • Urination consciously initiated – descending motor tracts stimulus to micturition center
    • Inhibit somatic motor fibers of external urethral sphincter and urine is expelled
  • Functional unit of kidney
    • responsible for forming urine
    • >1 million nephrons/kidney
  • Consists of small tubes or tubules
    • and associated capillaries
  • Filtrate – fluid formed by capillary filtration
    • Enters tubules, is modified, and leaves as urine
renal blood vessels
Renal Blood Vessels
  • Blood enters kidney through renal artery
    • divides into interlobar arteries  into arcuate arteries  into interlobular arteries
renal blood vessels11
Renal Blood Vessels
  • Interlobular arteries give rise to afferent arterioles which supply glomeruli
  • Glomeruli – mass of capillaries inside glomerular capsule
    • Gives rise to filtrate that enters nephron tubule
  • Efferent arteriole drains glomerulus
    • Delivers that blood to peritubular capillariesand vasa recta
  • Blood from peritubular capillaries enters interlobular veins
the tubules
The Tubules
  • Fluid formed by capillary filtration enters the tubules to be modified by transport processes
    • Resulting in fluid that leaves as urine
  • Reabsorption – transport of molecules out of the tubular filtrate (from the tubules) back to the blood
  • Secretion – transport of secreted molecules and ions
    • Move out of the peritubular capillaries into interstitial fluid, then
    • Transported across basolateral membrane of tubular epithelial cells, and into the
    • Lumen of the nephron tubule
  • Excretion – transport of urine out of the body
nephron tubules
Nephron Tubules
  • Begins with glomerular capsule:
    • Transitions into proximal convoluted tubule (PCT) then to
    • Descending and ascendinglimbsof Loop of Henle (LH) and finally to
    • Distal convoluted tubule (DCT)
  • Tubule ends where it empties into collecting duct (CD)
renal corpuscle
Renal Corpuscle
  • Glomerular (Bowman’s) capsule and glomerulus
    • Where glomerular filtration occurs
    • Filtrate passes into proximal convoluted tubule
proximal convoluted tubule
Proximal Convoluted Tubule
  • Walls – single layer of epithelial cuboidal cells with millions of microvilli
    • Increase surface area for reabsorption
  • Reabsorption – salt, water, and other molecules needed by the body
    • transported from the lumen through the tubular cells and into surrounding peritubular capillaries
type of nephrons
Type of Nephrons
  • Corticalnephrons originate in outer 2/3 of cortex
  • Juxtamedullarynephrons originate in inner 1/3 cortex
    • Long LHs
    • Important in producing concentrated urine
glomerular filtration
Glomerular Filtration
  • Glomerular capillaries and Bowman's capsule form a filter for blood
    • Fenestrated capillaries contain large pores between its endothelial cells
      • Big enough to allow any plasma molecule to pass
      • 100-400 times more permeable than other capillaries
glomerular filtration19
Glomerular Filtration
  • To enter the tubule filtrate must pass through narrow slit diaphragms
    • formed between pedicels of podocytes
  • Filtered molecules pass out of the fenestrae and through filtration slits
    • Enter the capsular cavity
    • Plasma proteins are excluded from the filtrate by the glomerular basement membrane and slit diaphragm
sem of glomerular capillaries and capsule
SEM of Glomerular Capillaries and Capsule
  • Pedicels interdigitate around the glomerular capillaries
    • Spaces between adjacent pedicels form ‘filtration slits’
glomerular filtration21
Glomerular Filtration
  • Plasma proteins – mostly excluded from the filtrate because of large size and negative charge
    • Slit diaphragms lined with negative charges repel negatively-charged proteins
    • Some protein (especially albumin) normally enters the filtrate but most is reabsorbed, or transported across the PCT
    • Filtered albumin reabsorptionis performed by receptor-mediated endocytosis
  • Previously basement membrane was considered as the primary filter but recent research found
    • Genetic defects in proteins that compose the slit diaphragm results in massive leakage of protein in the filtrate (proteinuria)
filtration barrier
Filtration Barrier
  • Separates the capillary lumen
    • from cavity of the glomerular capsule

EM of filtration barrier between the capillary lumen and glomerular capsule

formation of glomerular ultrafiltrate
Formation of Glomerular Ultrafiltrate
  • Only a fraction of plasma proteins (green) are filtered
  • Smaller plasma solutes (purple) easily enter glomerularultrafiltrate
    • But most are reabsorbed
glomerular filtration rate gfr
Glomerular Filtration Rate (GFR)
  • Volume of filtrate produced by both kidneys/minute
    • ~115 ml/minute in women
    • ~125 ml/minute in men
    • Totals about 180L/day (45 gallons)
  • Total blood volume average ~5.5 L
    • Most filtered water must be reabsorbed or death would ensue from water lost through urination
regulation of gfr
Regulation of GFR
  • Diameter of afferent arterioles – vasoconstriction or dilation affects rate of blood flow to glomeruli and thus GFR
    • Controlled by extrinsic and intrinsic mechanisms
  • Extrinsic regulatory mechanisms – produced by sympathetic innervation
  • Intrinsic mechanisms – renal autoregulation within the kidney
sympathetic effects
Sympathetic Effects
  • Sympathetic activity constricts afferent arteriole
    • Helps maintain BP
    • Shunts blood to heart and muscles
renal autoregulation
Renal Autoregulation
  • Defined as ability of kidneys to maintain relatively constant GFR in the face of fluctuating blood pressure
  • 2 mechanisms responsible:
    • Myogenic constrictionof afferent arteriole
      • due to smooth muscle responding to an increase in arterial pressure
    • Tubuloglomerular feedback
      • via effects of locally produced chemicals on afferent arterioles
renal autoregulation29
Renal Autoregulation
  • Tubuloglomerular feedback – negative feedback between afferent arteriole and volume of filtrate
    • Increased flow of filtrate sensed by macula densa(juxtaglomerular apparatus) in thick ascending LH signals afferent arteriole to constrict
reabsorption of salt and h 2 o
Reabsorption of Salt and H2O
  • PCT – returns most molecules and H2O from filtrate back to peritubular capillaries
    • About 180 L/day of ultrafiltrate produced but only 1–2 L of urine excreted/24 hours
      • Urine volume varies according to needs of body
      • Obligatory water loss– minimum of 400 ml/day urine needed to excrete metabolic waste produced by the body
reabsorption of salt and h 2 o33
Reabsorption of Salt and H2O
  • Reabsorption – transport of molecules out of the tubular filtrated back into the blood
  • Water is never transported – other molecules transported and water follows by osmosis
reabsorption in pct
Reabsorption in PCT
  • Coupled transport of glucose and Na+ into the cytoplasm
  • Primary active transport of Na+ across basolateral membrane by Na+/K+ pump
  • Glucose is then transported out of the cell by facilitated diffusion
    • And reabsorbed into the blood
pct salt and water reabsorption
PCT – Salt and Water Reabsorption
  • Na+ actively transported out of filtrate and Cl- follows passively by electrical attraction


significance of pct reabsorption
Significance of PCT Reabsorption
  • PCT – about 65% Na+, Cl-, and H2O reabsorbed and returned into bloodstream
  • Additional 20% reabsorbed in descending loop of Henle
  • Thus 85% of filtered H2O and salt are reabsorbed early in tubule
    • Constant and independent of hydration levels
    • Energy cost 6% of calories consumed at rest
    • Remaining 15% reabsorbed variably depending on level of hydration
concentration gradient in kidney
Concentration Gradient in Kidney
  • In order for H2O to be reabsorbed, interstitial fluid must be hypertonic
  • Osmolality of medulla interstitial fluid (1200-1400 mOsm) is 4X that of cortex and plasma (300 mOsm)
    • Concentration gradient results largely from loop of Henle
      • Allows interaction between descending and ascending limbs
the countercurrent multiplier system
The Countercurrent Multiplier System
  • Extrusion of NaCl from ascending limb makes surrounding interstitial fluid more concentrated
  • Concentration multiplied due to descending limb
    • Passively permeable to H2O
    • Fluid concentration increases
    • As surrounding interstitial fluid becomes more concentration
  • Deepest region of medulla
    • 1,400mOsm
ascending limb loop of henle
Ascending Limb Loop of Henle
  • Thin segment in depths of medulla and thick segment toward cortex
  • Impermeable to H2O; permeable to salt
    • Thick segment Actively Transports NaCl out of filtrate
  • Active Transport of salt
    • filtrate becomes dilute (100 mOsm) by end of Loop of Henle
transport of ions in ascending limb
Transport of Ions in Ascending Limb
  • In thick segment – Na+ and K+ together with 2 Cl- enter tubule cells
  • Na+ then actively transported out into interstitial space, Cl- follows passively
  • K+ diffuses back into filtrate; some also enters interstitial space
active transport in ascending limb
Active Transport in Ascending Limb
  • Na+ – actively transported across basolateral membrane by Na+/ K+ pump
  • Cl- passively follows Na+ down electrical gradient
  • K+ passively diffuses back into filtrate
countercurrent multiplier system
Countercurrent Multiplier System
  • Countercurrent flow and proximity allow descending and ascending limbs of to interact
    • This causes osmolality to build in medulla
  • Salt pumping in thick ascending part raises osmolality around descending limb, causes more H2O to diffuse out of filtrate
    • This raises osmolality of filtrate in descending limb causes more concentrated filtrate to be delivered into ascending limb
    • As concentrated filtrate is subjected to Active Transport of salts, it causes even higher osmolality around descending limb (positive feedback)
    • Process repeats until equilibrium is reached when osmolality of medulla is 1400
vasa recta
Vasa Recta
  • For countercurrent multiplier system to be effective:
    • Most of the salt extruded from ascending limbs must remain in the interstitial fluid of the medulla
    • Most of the water that leaves descending limbs must be removed by the blood
  • This is accomplished by the vasa recta
    • Thin-walled capillaries parallel LH of juxtamedullary nephrons
    • Walls permeable to water because of aquaporins channels, NaCl, and urea but not plasma proteins
    • Therefore colloid osmotic (oncotic) pressure in vasta recta is higher than in surrounding tissue fluid
      • results in movement of H2O from interstitial fluid into ascending vasa recta that can be removed from the renal medulla
countercurrent exchange in vasa recta
Countercurrent Exchange in Vasa Recta
  • Important component of countercurrent multiplier
  • Permeable to salt, H2O (via aquaporins), and urea
  • Recirculates salt, trapping some in medulla interstitial fluid (maintains hypertonicity)
  • Reabsorbs H2O coming out of descending limb
  • Descending section has urea transporters
  • Ascending section has fenestrated capillaries
the role of urea in urine concentration
The Role of Urea in Urine Concentration

1. Urea diffuses out of inner collecting duct (in renal medulla) into interstitial fluid

2. Urea then passes into ascending limb

  • Recirculates in interstitial fluid of renal medulla
  • Urea and NaCl in interstitial fluid make it very hypertonic, so

3. Water leaves the CD by osmosis

collecting duct cd
Collecting Duct (CD)
  • Plays important role in water conservation
  • Is impermeable to salt in medulla
  • Permeability to H2O depends on levels of ADH
homeostasis of plasma concentration maintained by adh
Homeostasis of Plasma Concentration Maintained by ADH
  • Secreted by post pituitary in response to dehydration
  • Stimulates insertion of aquaporins PM of collecting duct (CD)
  • ADH high – H2O is drawn out of CD by high osmolality of interstitial fluid
    • And reabsorbed by vasa recta
adh stimulation of aquaporins
ADH Stimulation of Aquaporins
  • ADH absent – aquaporins located in membrane of IC vesicles within CD epithelial cells
  • ADH stimulates fusion of vesicles and
  • Insertion of aquaporins into PM
  • When ADH is withdrawn, PM pinches inward forms IC vesicle and removes aquaporin channels
osmolality of different regions of the kidney
Osmolality of Different Regions of the Kidney
  • Countercurrent multiplier system in LH and countercurrent exchange in vasa recta
    • Creates hypertonic renal medulla
  • Under influence of ADH CD becomes more permeable to H2O
    • Thus more H2O is drawn out by osmosis into hypertonic renal medulla and peritubular capillaries
secretion is the opposite of reabsorption
Secretion is the Opposite of Reabsorption
  • Secretion – active transport of substances from the peritubular capillaries into the tubular fluid
    • Secretion is opposite in direction to that which occurs in reabsorption
  • Reabsorption decreases renal clearance; secretion increases renal clearance
renal clearance
Renal Clearance
  • Excretion rate = (filtration rate + secretion rate) - reabsorption rate
  • If a substance in the plasma is filtered (enters filtrate in gomerular capsule) but is neither reabsorbed nor secreted
    • Its secretion rate must equal its filtration rate
  • This fact is used to measure volume of blood plasma filtered/min by the kidneys = glomerular filtration rate (GFR)
tubular secretion of drugs
Tubular Secretion of Drugs
  • Many drugs, toxins, and metabolites are secreted by membrane transporters in the PCT
    • Organic anion transporter(OAT)– major group of transporters
    • Eliminate xenobiotics, therapeutic and abused drugs
    • Located in basolateral membrane
    • Larger xenobiotics eliminated by OATS in the liver that transport xenobiotics into bile
  • Organic cation transporters–eliminate particular xenobiotics, such as nicotine
  • These carriers considered polyspecific—overlapping specificity (broad range of molecules)
inulin measurement of gfr
Inulin Measurement of GFR
  • Inulin – fructose polymer useful for measuring GFR
    • because it is neither reabsorbed or secreted
  • Rate at which a substance is filtered by the glomeruli can be calculated:
    • Quantity filtered= GFR x P
      • P = inulin concentration in plasma)
  • Quantity excreted(mg/min) = V x U
      • V = rate of urine formation in ml/min
      • U = inulin concentration in urine in mg/ml
  • Amount filtered = amount excreted

GFR(ml/min) = V(ml/min) x U(mg/ml)


renal clearance of inulin
Renal Clearance of Inulin
  • a) Inulin present in blood enters glomeruli , and b) some of this blood together with inulin is filtered
  • All filtered inulin enters the urine, most of filtered water is reabsorbed (returned to vascular system)
  • Blood leaving the kidneys in renal vein, therefore, contains less inulin than the blood that entered the kidneys in the renal artery
    • Because inulin is filtered but neither reabsorbed nor secreted, the inulin clearance rate equals GFR
renal plasma clearance rpc
Renal Plasma Clearance (RPC)
  • Volume of plasma from which a substance is completely removed/min by excretion in urine
  • If substance is filtered but not reabsorbed then all filtered will be excreted RPC = GFR
  • If substance is filtered and reabsorbed then RPC < GFR
  • If substance is filtered but also secreted and excreted then RPC will be > GFR (=120 ml/ min)

RPC = V x U V = urine volume/min

P U = concentration of substance in urine

P = concentration of substance in plasma

clearance of urea
Clearance of Urea
  • Urea is freely filtered into glomerular capsule
  • Urea clearance calculations demonstrate how kidney handles a substance: RPC = V X U/P
    • V = 2ml/min; U = 7.5 mg/ml of urea; P = 0.2 mg/ml of urea
  • RPC = (2ml/min)(7.5mg/ml)/(0.2mg/ml) = 75ml/min
    • Urea clearance is 75 ml/min, compared to clearance of inulin (120 ml/min)
      • Thus 40-60% of filtered urea is always reabsorbed
  • Passive process – presence of carriers for facilitative diffusion of urea
measurement of renal blood flow
Measurement of Renal Blood Flow
  • Not all blood delivered to glomerulus is filtered into glomerular capsule
    • 20% is filtered; rest passes into efferent arteriole and back into circulation
    • Substances that aren't filtered can still be cleared by active transport (secretion) into tubules
total renal blood flow using pah
Total Renal Blood Flow Using PAH
  • Para-aminohihppuric acid(PAH) – clearance used to measure total renal blood flow
    • Normally averages 625 ml/min
    • It is totally cleared by a single pass through a nephron
    • So it must be both filtered and secreted
    • Filtration and secretion clear only molecules dissolved in plasma
      • To get total renal blood flow, amount of blood occupied by erythrocytes must be taken into account
      • 45% blood is RBCs; 55% is plasma
      •  total renal blood flow = PAH clearance

= 625/0.55 = 1.1L/min 0.55

total renal blood flow using pah61
Total Renal Blood Flow Using PAH
  • a) Some PAH in glomerular blood b) is filtered into glomerular capsule; c) PAH present in unfiltered blood is secreted from peritubular capillaries into the nephron; d) so all of the blood leaving the kidneys is free of PAH
    • The clearance of PAH therefore equals the total renal blood flow
glucose and amino acid reabsorption
Glucose and Amino Acid Reabsorption
  • Filtered glucose and amino acids are normally 100% reabsorbed from filtrate
    • Occurs in PCT by carrier-mediated cotransport with Na+
      • Transporter displays saturation if ligand concentration in filtrate is too high
      • Transport maximum(Tm) – level needed to saturate carriers and achieve maximum transport rate
    • Glucose and amino acid transporters do not saturate under normal conditions
  • Presence of glucose in urine
  • Occurs when glucose > 180-200mg/100ml plasma = renal plasma threshold
    • Glucose is normally absent because plasma levels stay below this value
    • Hyperglycemia: exceeds renal plasma threshold
    • Diabetes mellitus: occurs when hyperglycemia results in glycosuria
electrolyte balance
Electrolyte Balance
  • Kidneys regulate levels of Na+, K+, H+, HCO3-, Cl-, and PO4-3 by matching excretion to ingestion
  • Control of plasma Na+ is important in regulation of blood volume and pressure
  • Control of plasma of K+ is important in proper function of cardiac and skeletal muscles
role of aldosterone in na k balance
Role of Aldosterone in Na+/K+ Balance
  • 90% filtered Na+ and K+ reabsorbed before DCT
    • Remaining variably reabsorbed in DCT and cortical collecting duct according to bodily needs
      • Regulated by aldosterone (controls K+ secretion and Na+ reabsorption)
      • In the absence of aldosterone, 80% of remaining Na+ is reabsorbed in DCT and cortical collecting duct
      • When aldosterone is high all remaining Na+ is reabsorbed
k is reabsorbed and secretion
K+ is Reabsorbed andSecretion
  • K+ almost completely reabsorbed in PCT
  • Under aldosterone stimulation – K+ secreted into cortical collecting ducts
  • All K+ in urine is from secretion
juxtaglomerular apparatus jga
Juxtaglomerular Apparatus (JGA)
  • Specialized region in each nephron where afferent arteriole comes in contact with thick ascending limb LH
renin angiotensin aldosterone system
Renin-Angiotensin-Aldosterone System
  • Activated by release of renin from granular cells within afferent arteriole
    • Renin converts angiotensinogen to angiotensin I
      • ACE in lungs converts angiotensin I to angiotensin II
      • Angio II stimulates release of aldosterone
regulation of renin secretion
Regulation of Renin Secretion
  • Inadequate intake of NaCl always causes decreased blood volume
    • Because lower osmolality inhibits ADH, causing less H2O reabsorption
    • Low blood volume and renal blood flow stimulate renin release
      • Via direct effects of BP on granular cells and
      • By sympathetic activity initiated by arterial baroreceptor reflex
macula densa
Macula Densa
  • Located where tubule cells make contact with granular cells
  • Act as sensor for tubuloglomerular feedback – needed for autoregulation of GFR
    • Signals afferent arteriole to constrict
    • Signals granular cells to decrease secretion of renin when blood Na+ increased
atrial natriuretic peptide anp
Atrial Natriuretic Peptide (ANP)
  • Produced by atria due to stretching of atrial walls
  • An aldosterone antagonist
  • Stimulates salt and H2O excretion
  • Acts as an endogenous diuretic
reabsorption of na and secretion of k
Reabsorption of Na+ and Secretion of K+
  • In DCT, K+ and H+ secreted in response to potential difference produced by reabsorption of Na+
    • High concentration of H+ may therefore decrease K+ secretion, and vice versa
renal acid base regulation
Renal Acid-Base Regulation
  • Kidneys help regulate blood pH by excreting H+ and/or reabsorbing HCO3-
  • Most H+ secretion occurs across walls of PCT in exchange for Na+ (Na+/H+ antiporter)
  • Normal urine is slightly acidic (pH 5 – 7) because kidneys reabsorb almost all HCO3- and excrete H+
reabsorption of hco 3 in pct
Reabsorption of HCO3- in PCT
  • Indirect because apical membranes of PCT cells are impermeable to HCO3-
  • When urine is acidic, bicarbonate combines with H+ to form carbonic acid
  • Carbonic acid in filtrate is converted to carbon dioxide and water in a reaction catalyzed by carbonic anhydrase (CA)
    • located in apical cell membrane of PCT in contact with filtrate
reabsorption of hco 3 in pct78
Reabsorption of HCO3-in PCT
  • When urine is acidic, HCO3- combines with H+ to form H2CO3 (catalyzed by CA on apical membrane of PCT cells)
  • H2CO3 dissociates into CO2 + H2O
  • CO2 diffuses into PCT cells and forms H2CO3 (catalyzed by CA)
  • H2CO3 splits into HCO3- and H+ ; HCO3- diffuses into blood
urinary buffers
Urinary Buffers
  • Nephron cannot produce urine with pH < 4.5
  • Excretes more H+ by buffering H+s with HPO4-2 or NH3 before excretion
  • Phosphate enters tubule during filtration
  • Ammonia produced in tubule by deaminating amino acids
  • Buffering reactions
        • HPO4-2 + H+ H2PO4-
        • NH3 + H+ NH4+ (ammonium ion)
  • Used to lower blood volume due to hypertension, congestive heart failure, or edema
    • Increase volume of urine by increasing proportion of glomerular filtrate that is excreted
  • Loop diuretics – most powerful
    • inhibits active transport of salt in thick ascending limb of LH
  • Thiazide diuretics – inhibit NaCl reabsorption in first part of DCT
  • Carbonic anhydrase inhibitors–prevent H2O reabsorption in PCT when HCOs- is reabsorbed
  • Osmotic diuretics – increase osmotic pressure of filtrate
renal function tests and kidney disease
Renal Function Tests and Kidney Disease
  • Renal plasma clearance of PAH – measures total blood flow to the kidneys
  • Measurement of GFR by inulin clearance
  • Plasma creatinine concentration provides index of renal function
  • Urinary albumin excretion rate – commonly performed test
    • Detect slightly higher than normal excretion rate of albumin (microalbuminuria)
    • First manifestation of renal damage caused by diabetes or hypertension
kidney diseases
Kidney Diseases
  • Acute renal failure – impaired ability of kidneys to excrete wastes and regulate blood volume, pH, and electrolytes
    • Rise in blood creatinine and decrease in renal plasma clearance of creatinine
    • Can result from atherosclerosis, inflammation of tubules, kidney ischemia, or overuse of NSAIDs
  • Glomerulonephritis – inflammation of glomeruli
    • Autoimmune attack against glomerular capillary basement membranes
      • Causes leakage of protein into urine resulting in decreased colloid osmotic pressure and resulting edema
kidney diseases85
Kidney Diseases
  • Renal insufficiency – nephrons have been destroyed as a result of a disease (diabetes mellitus)
    • Clinical manifestations include salt and H2O retention and uremia (high plasma urea levels)
      • Uremia accompanied by high plasma H+ and K+ which can cause uremic coma
    • Treatment includes hemodialysis
      • Patient's blood passed through a dialysis machine – separates molecules on basis of ability to diffuse through selectively permeable membrane
      • Urea and other wastes are removed
kidney diseases86
Kidney Diseases
  • Diabetes insipidus– may be caused by:
    • Drinking too much water (polydipsia)
    • Inadequate secretion of ADH (central diabetes insipidus)
    • Inadequate ADH action due to genetic defect in ADH receptors or aquaporins (nephrogenic diabetes insipidus)
  • Without adequate ADH (secretion or action) the collecting ducts are not very permeable to H2O
    • Why would this cause a problem?
the kidneys and chf
The Kidneys and CHF
  • Congestive Heart Failure – inability of the heart to deliver an adequate blood flow (CO is low)
    • Body becomes congested with fluid
    • Due to heart disease or hypertension
    • Associated with breathlessness, salt and water retention, and edema
  • How are the kidneys affected?
  • What is the role of the kidneys in CHF?