URINE TRANSPORT, STORAGE, AND ELIMINATION
Filtrate modification and urine production end when the fluid enters the renal
pelvis. The remaining parts of the urinary system (the ureters, urinary
bladder, and urethra) are responsible for the transport, storage, and
elimination of urine. A pyelogram (PI-el-o-gram) is an image of the urinary
system, obtained by taking an X-ray of the kidneys after a radiopaque
compound has been administered. Such an image provides an orientation to
the relative sizes and positions of these organs.
General Characteristics of Normal Urine
Characteristics
Normal Range
pH
6.0 (range: 4.5-8)
Specific gravity
1.003-1.030
Osmolarity
855-1335 mOsm/l
Water content
93-97 %
Volume
1200 ml/day
Color
Clear yellow
Odor
Varies w/composition
Bacterial content
Sterile
Compound
Primary Source
Typical Values from Standard Urine Testing
Daily
Concentration
Excretion
Remarks
Nitrogenous
wastes
Urea
Deamination of amino acids at liver & kidneys
21g
1.8 g/dl
Rises if negative nitrogen balance
exists
Creatinine
Breakdown of creatinine phosphate in skeletal
muscle
1.8g
150 mg/dl
Ammonia
Deamination by liver & kidney; absorption from
intestinal tract
0.68g
60 mg/dl
Uric acid
Breakdown of purines
0.53g
40 mg/dl
Hippuric acid
Breakdown of dietary toxins
4.2 mg
350 µg/dl
Urobilin
Urobilinogens absorbed at colon
1.5mg
125 µg/dl
Gives urine yellow color
Bilirubin
Hemoglobin breakdown product
0.3 mg
20 µg/dl
Increase my indicate problem w/
liver excretion or excess production;
causes yellow skin color in jaundice
Carbohydrates
0.11g
9 µg/dl
Primarily glucose; glycosuria
develops if Tm is exceeded
Ketone bodies
0.21g
17 µg/dl
Ketouria may occur during
postabsorptive state
Lipids
0.02g
1.6 µg/dl
May increase in some kidney
diseases
Amino acids
2.25g
287.5 µg/dl
Note relatively high loss compared to
low Tm; excess (aminoaciduria)
indicates Tm problem
Sodium
4.0g
333 mg/dl
Varies w/ diet, urine pH, hormones,
etc.
Chloride
6.4g
533 mg/dl
Potassium
2.0g
166 mg/dl
Varies w/ diet, urine pH, hormones,
etc.
Calcium
0.2g
17 mg/dl
Hormonally regulated (PTH/CT)
Magnesium
0.15g
13 mg/dl
RBC’s
130,000/day
100/ml
WBC’s
650,000/day
500/ml
Proportional to muscle mass;
decreases during atrophy or muscle
disease
Increases in gout, liver diseases
Nutrients and
metabolites
Ions
Blood cellsŦ
Representative values for a 70 kg male.
Excess (hematuria) indicates
vascular damage
Excess (pyuria) indicates renal
infection or inflammation
Ŧ
Usually estimated by counting the cells in a sample of sediment after urine centrifugation.
1
Segment
Renal Corpuscle
Proximal convoluted tubule
Loop of Henle
Distal convoluted tubule
Collecting system
Peritubular capillaries
Vasa recta
Renal Segments and Their Functions
General Function
Specific Function
Mechanism
Filtration of plasma; generates
approximately 180 liters/day of filtrate
similar in composition to blood plasma
without plasma proteins
Filtration of water, inorganic &
organic solutes from plasma;
retention of plasma proteins &
blood cells
Glomerular hydrostatic (blood)
pressure working across capillary
endothelium, lamina densa; &
filtration slits
Reabsorption of 60-70% of the water
(approximately 180 liters/day), 99100% of the organic substrates, and
60-70% of the Na+ and Cl- in the
original filtrate
Reabsorption: Active: glucose,
other simple sugars, amino acids,
vitamins, ions (including Na+, K+,
magnesium, phosphate, and
bicarbonate); Passive: urea, Cl-,
lipid-soluble materials, water
Secretion: H+, ammonium ions,
creatinine, drugs, and toxins (as at
DCT)
Carrier-mediated transport,
including, facilitated transport
(glucose, amino acids), cotransport
(glucose, ions)or countertransport
(w/secretion of H+)
Diffusion (solutes) or osmosis
(water)
Countertransport w/ Na+
Reabsorption of 25% of the water (45
liters/day) & 20-25% of the Na+ & Clpresent in the original filtrate; creation
of the concentration gradient in the
medulla
Reabsorption: Na+ and Cl-
Active transport via Na+-K+/2 Cltransporter
Water
Osmosis
Reabsorption of a variable amount of
water (usually 5%, or 9 liters/day),
under ADH stimulation, & a variable
amount of Na+, under aldosterone
stimulation
Reabsorption: Na+ & Cl-
Cotransport
Na+ (variable)
Countertransport w/ K+;
aldosterone regulated
Calcium ions (variable)
Carrier-mediated transport
stimulated by parathyroid hormone
& calcitriol
Water (variable)
Osmosis: ADH-regulated
Secretion: H+, ammonium ions
Creatinine, drugs, toxins
Countertransport w/ Na+
Carrier-mediated transport
Reabsorption: Na+ ions (variable)
Countertransport w/ K+ or H+;
aldosterone regulated
Bicarbonate ions (variable)
Diffusion, generated w/in tubular
cells
Water (variable)
Osmosis: ADH regulated
Urea (distal portions only)
Diffusion
Secretion: K+ and H+ (variable)
Carrier-mediated transport
Redistribution of water & solutes
reabsorbed in cortex
Return of water & solutes to the
general circulation
Osmosis and diffusion
Redistribution of water & solutes
reabsorbed in the medulla &
stabilization of the concentration
gradient of the medulla
Return of water and solutes to the
general circulation
Osmosis and diffusion
Reabsorption of variable amount of
water (usually 9.3%, or 16.8
liters/day), under ADH stimulation,
and a variable amount of Na+, under
aldosterone stimulation
Above tables and information taken from Martini; 4 th Ed. 1998. Fundamentals of Anatomy and Physiology.
2
Kidney Regulation of Osmolarity Expected Results
Solution
Action in Body
800 ml distilled water
Hypotonic
Incr. blood volume
Decr. osmotic pressure
Incr. blood pressure
800 ml water w/
7g NaCl
Creates an osmotic
problem with rapid
adjustment
Approx. isotonic
Incr. blood volume
Osmotic pressure mainly
unchanged
Incr. blood pressure
80 ml water w/
7g NaCl
Creates an ECF volume
problem complicate by
equivalent NaCl conc. –
slow adjustment
Hypertonic
Incr. blood volume, slightly
Incr. osmotic pressure
Incr. blood pressure, due to
incr. osmotic pressure
₤
ADH Level
©
Aldosterone Level
Urine Output
Volume
NaCl in Urine
Urine Specific
Gravity
(incr.s water excretion)
(incr.s water excretion)
(incr.s Na+ excretion)
Creates an ECF volume
problem combined w/ an
(decr.s water excretion) (incr.s Na+ excretion)
osmotic problem – very
slow adjustment
1. Decreased water excretion means increased retention of water and decreased osmotic pressure.
2. Increased Na+ excretion means excess NaCl elimination.
3. Once osmotic problem is corrected, a very small water excretion is made to restore normal blood volume.
₤
ADH = antidiuretic hormone
 produced by the posterior pituitary gland, under stimulation from hypothalamus
©
Aldosterone is a hormone released from the adrenal cortex, which increases Na+ reabsorption in the kidneys
3