Urinary System

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Urinary System
Ch 26
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Function

1. Remove nitrogenous wastes
2. Maintain electrolyte, acid-base, and fluid
   balance of blood
3. Homeostatic organ
4. Acts as blood filter
5. Release hormones calcitriol erythropoietin

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Kidneys as Filters

• Diuretic- lose water coffee, alcohol
• Antidiuretic- retain water ADH
• Aldosterone- sodium water reabsorption, and K
  excretion
• GFR 180 liters (50 gal) of blood/day
• 178-179 liters are reabsorbed back into blood
• Excrete a protein free filtrate

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Each kidney contains over 1 million nephrons and
thousands of collecting ducts
DCT
Glomerulus
PCT
Collecting duct
Loop of Henle
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• Nephrons functions
• glomerular filtration
• tubular reabsorption
• tubular secretion

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Histology of a renal corpuscle
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Pressures that drive glomerular filtration
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The filtration membrane
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Nephron
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Composition of Glomerular Filtrate

• Water
• Small Soluble Organic Molecules
• Mineral Ions

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Proximal Convoluted Tubule
Reabsorbs water, glucose, amino acids, and
sodium.

• 65 of Na is reabsorbed
• 65 of H2O is reabsorbed
• 90 of filtered bicarbonate (HCO3-)
• 50 of Cl- and K

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Loop of Henle
Creates a gradient of increasing sodium ion
concentration towards the end of the loop within
the interstitial fluid of the renal pyramid.

• 25 Na is reabsorbed in the loop
• 15 water is reabsorbed in the loop
• 40 K is reabsorbed in the loop

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Distal Convoluted Tubule
Under the influence of the hormone aldosterone,
reabsorbs sodium and secretes potassium. Also
regulates pH by secreting hydrogen ion when pH of
the plasma is low.

• only 10 of the filtered NaCl and 20 of water
  remains

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Collecting Duct
Allows for the osmotic reabsorption of water.
ADH (antidiuretic hormone)- makes collecting
ducts more permeable to water-- produce
concentrated urine
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Urine

• Water- 95
• Nitrogenous waste
• urea
• uric acid
• creatinine
• Ions
• sodium
• potassium
• sulfate
• phosphate

From the original 1800 g NaCl, only 10 g appears
in the urine
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Nitrogenous Wastes
urea
uric acid
ammonia
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Hormonal Control of Kidney Function
ADH
ANP
Renin-Aldosterone-Angiotensin
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Fig. 18.09
ADH
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Hormonal Control of Kidney Function
hypothalamus
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ANP
aldosterone
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Regulation of Aldosterone secretion by
renin-angiotensin-aldosterone (RAA) pathway
Fig. 18.16
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Hormonal Control of Kidney Function
reduced blood pressure and glomerular filtrate
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Hormonal Control of Kidney Function
renin
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Hormonal Control of Kidney Function
angiotensin II
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Urinary Bladder
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Bladder

1. Mucosa (transitional epithelium)
2. Muscular layer (detrusor muscle) 3 layers of
   smooth muscle
3. Fibrous adventia

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Sphincter Muscles on Bladder

• Internal urethral sphincter
• Smooth muscle
• Involuntary control
• More superiorly located
• External Urethral sphincter
• Skeletal muscle
• Voluntary control
• Posteriorly located

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Diuresis (Micturition)
When bladder fills with 200 ml of urine, stretch
receptors transmit impulses to the CNS and
produce a reflex contraction of the bladder (PNS)
When is incontinence normal?
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Urinalysis
Why do doctors ask for a urine sample?       

• characteristics
• smell- ammonia-like
• pH- 4.5-8, ave 6.0
• specific gravity more than 1.0 1.001-1.030
• color- affected by what we eat salty foods,
  vitamins

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Odor
odor- normal is ammonia-like diabetes mellitus-
smells fruity or acetone like due to elevated
ketone levels diabetes insipidus-
yucky asparagus---
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pH- range 4.5-8 ave 6.0 vegetarian diet- urine
is alkaline protein rich and wheat diet- urine
is acidic
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Color
Color- pigment is urochrome Yellow color due to
metabolic breakdown of hemoglobin (by bile or
bile pigments) Beets or rhubarb- might give a
urine pink or smoky color Vitamins- vitamin C-
bright yellow Infection- cloudy
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Specific Gravity
Water s.g. 1g/liter Urine s.g. 1.001 to
1.030
Pyelonephritus- urine has high s.g. form kidney
stones Diabetes insipidus- urine has low s.g.
drinks excessive water injury or tumor in
pituitary
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Abnormal Constitutes of Urine

•  Glucose- when present in urine condition called
  glycosuria (nonpathological) glucose not
  normally found in urine
• Indicative of
• Excessive carbohydrate intake
• Stress
• Diabetes mellitus

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Abnormal Constitutes of Urine
Albumin-abnormal in urine its a very large
molecule, too large to pass through glomerular
membrane gt abnormal increase in permeability of
membrane Albuminuria- nonpathological conditions-
excessive exertion, pregnancy, overabundant
protein intake-- leads to physiologic
albuminuria Pathological condition- kidney trauma
due to blows, heavy metals, bacterial toxin
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Abnormal Constitutes of Urine
Ketone bodies- normal in urine but in small
amts Ketonuria- find during starvation, using fat
stores Ketonuria is couples w/a finding of
glycosuria-- which is usually diagnosed as
diabetes mellitus RBC-hematuria Hemoglobin- Hemogl
obinuria- due to fragmentation or hemolysis of
RBC conditions hemolytic anemia, transfusion
reaction, burns or renal disease
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Abnormal Constitutes of Urine
Bile pigments- Bilirubinuria (bile pigment in
urine)- liver pathology such as hepatitis or
cirrhosis WBC- Pyuria- urinary tract infection
indicates inflammation of urinary tract Casts-
hardened cell fragments, cylindrical, flushed out
of urinary tract WBC casts- pyelonephritus RBC
casts- glomerulonephritus Fatty casts- renal
damage
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INQUIRY

1. List several functions of the kidneys.
2. What does the glomerulus do?
3. What are several constitutes you should not find
   in urine?
4. What is specific gravity?
5. What two hormones effect fluid volume and sodium
   concentration in the urine?
6. Where are the pyramids located in the kidney?
7. What vessel directs blood into the glomerulus?
8. Where does most selective reabsorption occur in
   the nephron?

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Moment of Zen
KIDNEY