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Kidneys Kidneys

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									            The Urinary System
       Fluid, Electrolyte & Acid-Base
                   Balance


   Karen Marshall, Associate Professor
          Montgomery College
         Takoma Park Campus




                           Kidneys
   maintain constancy of fluids
   filter ~200 L of fluid from bloodstream
     – daily
           •   toxins
           •   metabolic wastes
           •   excess ions
           •   return needed substances (blood)




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                           Kidneys
   major excretory organ
     – regulate blood volume & chemistry
     – maintain balance
           • water and salt
           • acids and bases
   add’l excretory organs
     – lungs
     – skin


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                           Kidneys
   role in gluconeogenesis
    – prolonged fasting
           • ~1/5th as much glucose as liver
   act as an endocrine gland
    – produces
           • renin (enzyme)
              – regulates BP & kidney function
           • erythropoietin (hormone)
              – stimulates RBC production (RBCs)
    – metabolizes
9/3/2003
           • vitamin D to its active form          4




     Organs of the Urinary System
   kidneys
     – form urine
   urinary bladder
     – temporary storage site for urine
   paired ureters
   urethra
     – tubelike organs
     – transport channels for urine
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                          Fig. 26.01




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       Internal Anatomy of Kidney
   three distinct regions
     – renal cortex
     – renal medulla
     – renal pelvis




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       Internal Anatomy of Kidney
   renal cortex
     – most superficial region
     – light in color
     – granular appearance




9/3/2003                                                       10




       Internal Anatomy of Kidney
   renal medulla
    – deep to cortex
    – darker, reddish brown color
    – medullar pyramids
           • cone shaped tissue masses
              – formed almost entirely of collecting tubules
           • apex of pyramid
              – papilla




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       Internal Anatomy of Kidney
   renal pelvis
    – flat, funnel shaped tube
    – continuous w/ ureter
    – branching extensions
           • surround & collect urine
              – draining from papillae (pyramid)
           • major calyces
              – subdivide
                  » minor calyces



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                           Fig. 26.03a




9/3/2003                                           13




                           Fig. 26.03b




9/3/2003                                           14




                  Kidney Infections
   pyelitis
    – infection of renal pelvis and calyces
   pyelonephritis
    – infection or inflammation of entire kidney
    – severe cases
           • kidney swelling
           • abscess formation
           • pus formation (pelvis)
    – trt
           • antibiotics
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           Pathway of Renal Vasculature
                   (fig 26.3b)




9/3/2003                                      16




           Pathway of Renal Vasculature
   no lobar or segmental veins
   abdominal aorta
     – located to left of midline
           • right renal artery
              – longer than left

   inferior vena cava
     – located on right of vertebral column
           • left renal vein
              – twice as long as the right

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  Internal Anatomy of Kidney (fig 26.3b)




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Fig. 26.04




             9/3/2003                                          19




                                       Nephrons
                blood processing units
                tiny
                millions
                carry out processes that form urine




             9/3/2003                                          20




                                       Nephrons
                glomerulus
                  – high pressure capillary bed
                renal tubule
                  – subdivisions
                        •   glomerular capsule (Bowman’s)
                        •   proximal convoluted tubule (PCT)
                        •   loop of Henle
                        •   distal convoluted tubule (DCT)


             9/3/2003                                          21
                      Nephrons
   second capillary bed
     – low pressure peritubular capillary bed
     – closely associated w/ renal tubule
           • each nephron




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  Structure of Nephrons (fig 26.4)




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 Anatomy of Nephrons (fig 26.5)




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Fig. 26.05a




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Fig. 26.05b




              9/3/2003                                    26




                 Juxtaglomerular Apparatus (JGA)

                 region in each nephron
                 consists of
                   – juxtaglomerular cells
                   – macula densa cells
                 assoc w/ afferent & efferent arteriole




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           Juxtaglomerular (JG) Cells

   located in arteriole walls
   enlarged smooth muscle cells
     – secretory granules
           • contain renin
              – act as mechanoreceptors
                  » directly sense blood pressure in arterioles




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                 Macula Densa Cells

   group of tall, closely packed distal
   tubule cells
   lie adjacent to JG cells
   chemoreceptors (osmoreceptors)
     – respond to changes in solute content
           • filtrate in tubule lumen




9/3/2003                                                          29




    Juxtaglomerular Apparatus (fig 26.7)




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                       Fig. 26.06a




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                       Fig. 26.06b




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            Filtration Membrane
   porous membrane
     – actual filter
   allows free passage of water and
   solutes
     – smaller than plasma proteins
   lies between the blood and interior of
   glomerular capsule

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              Filtration Membrane (fig 26.8)




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Fig. 26.08a




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                         Fig. 26.08b




      9/3/2003                                 36
Fig. 26.10




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                               Filtrate
       contains same substances as blood
       plasma
        – except
             • proteins
       courses collecting ducts
        – removal
             • water
             • nutrient
             • essential ions
        – left w/ urine
                – metabolic wastes
                – unneeded substances
  9/3/2003                                  38




                     Urine Formation
       three major processes (nephron)
         – glomerular filtration
             • glomeruli
         – tubular reabsorption
             • renal tubules
         – tubular secretion
             • renal tubules
       assistance from collecting tubules
         – concentrate or dilute urine
  9/3/2003                                  39
              Glomerular Filtration

   function of glomeruli
     – acts as mechanical filters
     – fed and drained by arterioles
     – contain filtration membrane
     – highly pressurized
   passive, nonselective filtration process
           • fluids and solutes forced through a membrane


9/3/2003                                                    40




              Tubular Reabsorption

   function of renal tubules
   needed substances are removed from
   filtrate
     – tubule cells
   returned to peritubular capillary blood




9/3/2003                                                    41




                 Tubular Secretion

   function of renal tubules
   addition of substances to filtrate from
   blood or tubule cells
   aids in elimination of unwanted
   substances




9/3/2003                                                    42
                  Single Uncoiled Nephron (fig 26.9)




       9/3/2003                                        43




Fig. 26.07




       9/3/2003                                        44




       Glomerular Filtration Rate (GFR)
             total amt of filtrate formed per minute
             – kidneys
             normally 120-125 ml/min
             (7.5L/hr or 180 L/day)




       9/3/2003                                        45
           Factors that Govern GFR
   1) total surface area available for filtration
   2) filtration membrane permeability
   3) net filtration pressure




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                         Diuretics
   chemicals that enhance urinary output
   any substance
     – not absorbed
     – exceeds the ability of reabsorption
           • renal tubules
   act as an osmotic diuretic
     – carry water out with it


9/3/2003                                            47




                         Diuretics
   alcohol
     – essentially a sedative
     – inhibits release of ADH




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                              Diuretics
   caffeine
     – found in coffee, tea, and colas
     – inhibits Na+ reabsorption
            • (water also follows)
     – acts like most diuretics prescribed for HTM




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                                 Urine
   color and transparency
   specific gravity
   pathological causes of abnormal urine
    –      specific gravity
    –      pH
    –      glucose
    –      proteins
    –      ketones
    –      blood
    –      bilirubin
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              Color and Transparency
   freshly voided urine
     – clear and pale to deep yellow in color
            • pigment urochrome
                – due to destruction of Hgb via bilirubin or bile
                  pigments




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           Color and Transparency
    abnormal color
     – pink, brown or smoky
     – causes
           •   certain foods (beets, rhubarb)
           •   presence of bile pigments
           •   blood in the urine
           •   commonly prescribed drugs or vitamin
               supplements



9/3/2003                                              52




               Color and Transparency
   concentrated urine
     – a deeper yellow color
   cloudy urine
     – indicative of an infection
           • some part of the urinary tract




9/3/2003                                              53




                    Specific Gravity
      relative wt of a specific volume of liquid
      compared with an equal volume of
      distilled water




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                    Specific Gravity
      water
       – 1.000
       – 1 ml of water weighs 1 g
      urine
       – ranges from 1.001 - 1.030
       – contains dissolved solutes
       – weighs more than water


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                    Specific Gravity
   concentrated urine
     – high specific gravity
     – common
           • drink limited amounts of
           • fever
           • pyelonephritis




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                    Specific Gravity
   dilute urine
     – specific gravity of less than 1.001
     – contains few solutes
     – common
           •   drink excessive amounts of water
           •   use diuretics
           •   diabetes insipidus (DI)
           •   chronic renal failure



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                   Specific Gravity
   excessively concentrated urine
     – precipitation or crystallization
           • calcium, magnesium, or uric acid salts
              – formation of kidney stones ~ renal calculi




9/3/2003                                                     58




                     Kidney Stones
    AKA renal calculi
    ~ very small stones
     – pass through the urinary tract without
       causing problems
    larger stones
     – obstruct a ureter and block urine drainage




9/3/2003                                                     59




                     Kidney Stones
    pain
     – increasing pressure within the kidney
     – contracting ureter wall closes in on the
       sharp calculi during peristalsis
    predisposing conditions
     – frequent bacterial infections (UT)
     – urinary retention
     – alkaline urine

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                     Kidney Stones
    trt
     – surgical removal
     – shock wave lithotripsy
     – acidify urine
           • cranberry juice
     – dilute urine
           • water



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                                 pH

   usually slighty acidic
     – ~pH 6
     – changes in relation to body metabolism or diet
           • ranges 4.5 to 8.0




9/3/2003                                                     62




                                 pH
   acidic urine
     – acid-ash diet
           • large amounts of protein and whole wheat products


   alkaline urine
     – alkaline-ash (vegetarian) diet
     – prolonged vomiting
     – bacterial infection


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    Pathological Causes of Abnormal
                  Urine
      Substance            Name of Condition   Possible Pathological
                                               Condition

      Glucose              Glycosuria          Diabetes Mellitus


      Proteins             Proteinuria         Heart Failure, HTM,
                                               Glomerulonephritis,
                                               Renal Ds

      Ketone Bodies        Ketonuria           Diabetes Mellitus

      Erythrocytes         Hematuria           Bleeding urinary tract


      Bile Pigments        Bilirubinuria       Liver Ds- hepatitis,
                                               cirrhosis



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                      Urinary Bladder
   smooth, collapsible, muscular sac
   stores urine temporarily
   interior
     – openings
           • ureters (inlets)
           • urethra (outlet)




9/3/2003                                                                65




                      Urinary Bladder
   trigone
     – smooth, triangular region of the wall
     – between the openings of the two ureters
       posteriorly and the urethra anteriorly




9/3/2003                                                                66
                       Urinary Bladder
   three layered wall
    – mucosa
           • transitional epithelium
    – thick muscular layer
           • AKA detrusor muscle
           • intermingled smooth muscle fibers
           • arrangement
              – inner and outer longitudinal layers
              – middle circular layer
    – fibrous adventitia
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                        Urine Storage

   bladder is very distensible
     – uniquely designed for urine storage
   little or no urine
     – the bladder collapses
           • basic pyramidal shape
           • walls are thick and thrown into folds (rugae)




9/3/2003                                                              68




                        Urine Storage
   urine accumulates
     – bladder expands
           • pear-shaped
           • rises superiorly in the abdominal cavity
           • muscular wall stretches and thins, and rugae disappear
           • allows the bladder to store more urine
               – without a significant rise in internal pressure
               – (at least until 300 ml have accumulated)




9/3/2003                                                              69
                    Urine Storage

   moderately full bladder
     – about 5 inches long
     – holds approximately 500 ml (1 pint of urine)
           • can hold more than double this amount if
             necessary




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           Urinary Bladder (fig 26.19)




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                           Fig. 26.21




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                              Urethra

   thin-walled muscular tube
   drains urine from the bladder and conveys it
   out of the body
   differs in the sexes




9/3/2003                                                    73




                              Urethra
   Females
     – 1.5 inches (3-4 cm) long
     – tightly bound to the anterior vaginal wall by
       fibrous connective tissue
     – conducts ONLY urine




9/3/2003                                                    74




                              Urethra
   Females
     – external opening
           •   AKA external urethral orifice-meatus
           •   anterior to the vagina
           •   posterior to the clitoris
           •   shortness of urethra and closeness of external
               orifice to the anal opening
                – contribute to frequent UTI’s




9/3/2003                                                    75
                             Urethra
  female
    – UTI
           • affects 40% of all women
           • most occur in sexually active young women
              – intercourse drives bacteria from the vagina and
                external genital region toward the bladder
           • also caused by improper toilet habits
              – wiping back to front after defecation




9/3/2003                                                          76




                             Urethra
  male
    – 8 inches (20 cm) long
    – double function
           • transports urine AND semen




9/3/2003                                                          77




                              Urethra
   contains two sphincters
     – formed from muscle
           • 1) internal urethral sphincter
           • 2) external urethral sphincter




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            Internal Urethral Sphincter
   involuntarily controlled
   located at the bladder-urethral junction
     – at the proximal opening of the urethra
   formed by the thickening of the detrusor
   smooth muscle
   keeps the urethra closed
     – when urine is not being passed
     – prevents leaking of urine between voidings
   controlled by the parasympathetic NS

9/3/2003                                            79




           External Urethral Sphincter
   AKA sphincter urethrae
   voluntarily controlled
   formed of skeletal muscle
   located inferior to the internal sphincter
   and encircles the urethra
   we are always consciously contracting this
   sphincter (even during sleep)
    – exception - during micturition

9/3/2003                                            80




                    Micturition
   voiding or urination
     – act of emptying the bladder




9/3/2003                                            81
                Micturition Reflex
   when one chooses not to void
     – reflex bladder contractions subside within
      approximately one minute and urine
      continues to accumulate




9/3/2003                                                  82




                Micturition Reflex
   external sphincter & levator ani muscles
     – voluntarily controlled
           • we can choose to keep the sphincter closed
             and postpone bladder emptying temporarily




9/3/2003                                                  83




                Micturition Reflex
   the micturition reflex occurs again
     – after 200 - 300 ml have collected
   micturition reflex continues to occur and
   then dampen
     – as long as urination is delayed
   micturition occurs
     – when the urge to void become irresistible


9/3/2003                                                  84
           Homeostatic Imbalances
   Incontinence
     – the inability to control micturition voluntarily
     – causes
           • emotional problems
           • physical pressure during pregnancy
           • nervous system problems
              – stroke
              – spinal cord lesions




9/3/2003                                                    85




           Homeostatic Imbalances
   incontinence
     – normal in infants who to do yet know how
       to control their urethral sphincter
           • reflex voiding occurs each time a baby’s
             bladder fills enough to activate the stretch
             receptors




9/3/2003                                                    86




           Homeostatic Imbalances
   Stress incontinence
     – a sudden increase in intra-abdominal
       pressure
           • during laughing and coughing
     – forces urine through the external sphincter
     – common in pregnancy




9/3/2003                                                    87
            Homeostatic Imbalances

    Overflow incontinence
     – urine dribbles from the urethra whenever
       the bladder overflows




9/3/2003                                                           88




            Homeostatic Imbalances
   urinary retention
     – bladder unable to expel its contained urine
     – normal after general anesthesia
           • it takes time for the detrusor muscle to regain
             activity
     – in men
           • reflects hypertrophy of the prostate gland
              – narrows the urethra making it difficult to void




9/3/2003                                                           89




            Homeostatic Imbalances

   Urinary retention
     – trt
           • catheter (a slender rubber drainage tube) is inserted
             through the urethra
              – drain the urine
              – prevent bladder trauma from excessive stretching




9/3/2003                                                           90
             Flow of Urine
   urine travels through the collecting
   ducts within each renal pyramid
   urine exits through the renal papillae
   into the minor calyces and into the
   major calyces
   once in the renal pelvis, urine drains
   into the ureter
   ureter located in the kidney’s hilus
   carries urine to the urinary bladder
9/3/2003                                    91




                  Fig. 26.03a




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                 Dialysis
   process of cleansing of blood of
   metabolic wastes and adjusting its ionic
   composition




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                           Dialysis
   blood is diffused through a semipermeable
   membrane
     – to remove toxic materials
     – to maintain fluid, electrolyte and acid-base
       balance
     – in cases of impaired kidney function or absence




9/3/2003                                                 94




                      Hemodialysis

   the use of an artificial kidney to clear
   urea, metabolic waste products, toxins,
   and excess fluid from the blood




9/3/2003                                                 95




                             CAPD
   continuous ambulatory peritoneal
   dialysis
     – dialysis in which fluid is infused into the
       peritoneum through an implanted catherer
       and then drained from the body
     – the peritoneal lining serves as the dialytic
       membrane
     – alternative to hemodialysis
           • but is less efficient

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              Effects of Aging
   only 3% of elderly individuals have
   histologically normal kidneys
   kidney function declines with age
     – kidneys shrink as the nephrons decrease
       in size and number
     – tubule cells become less efficient




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              Effects of Aging

   by age 70, GFR is only half that of
   middle-aged adults
     – due to narrowing of the renal arteries by
       atherosclerosis




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                Aging Effects

   diabetics are at risk for renal disease
   urinary bladder shrinks to less than half
   the capacity of a young adult
     – 250 ml vs 600 ml
   loss of bladder tone
     – leads to frequent micturition and often
       incontinence

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           Glomerular Filtration




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             Kidneys (fig 26.3)




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   Filtration Membrane (fig 26.8)




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   Glomerular Capsule (fig 26.10)




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               Fig. 26.09




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           Nephron (fig 26.9)




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              Tubular Reabsorption




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  Structure of Nephrons (fig 26.4)




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           Single Uncoiled Nephron (fig 26.9)




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           Figure 26.12




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           Figure 26.7




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 Anatomy of Nephrons (fig 26.5)




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 Anatomy of Nephrons (fig 26.5)




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            Figure 26.7




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 Anatomy of Nephrons (fig 26.5)




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             Figure 26.7




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  Structure of Nephrons (fig 26.4)




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 Anatomy of Nephrons (fig 26.5)




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           Tubular Secretion




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           Nephron (fig 26.9)




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                   Figure 27.12




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Fig. 26.20




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