9b UrinSystem II-FluidEleclytpH

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Transcript 9b UrinSystem II-FluidEleclytpH

 Slender tubes attaching the
kidney to the bladder
• Continuous with the renal
• Enter the posterior aspect
of the bladder
 Runs behind the peritoneum
 Peristalsis aids gravity in urine
Urinary Bladder
 Function
• Smooth, collapsible, muscular sac
• Temporarily stores urine
 Trigone Structure
 Bladder Wall
• Three layers of smooth muscle
(detrusor muscle)
• Mucosa made of transitional
• Walls are thick and folded in an
empty bladder
• Bladder can expand significantly
without increasing internal pressure
• Internal and external sphincters
Figure 15.6
 Thin-walled tube that carries urine from the bladder to
the outside of the body by peristalsis
 Release of urine is controlled by two sphincters
Internal urethral sphincter (involuntary)
External urethral sphincter (voluntary)
 Length and Location
Females – 3–4 cm (1 inch), along wall of the
Males – 20 cm (8 inches) through the prostate and
 Function
Females – only carries urine
Males – carries urine and is a passageway
Micturition (Voiding)
 Both sphincter muscles must open to allow
• The internal urethral sphincter is relaxed
after stretching of the bladder
• Activation is from an impulse sent to the
spinal cord and then back via the pelvic
splanchnic nerves
• The external urethral sphincter must be
voluntarily relaxed
Urinary System I: Kidneys and Urine Formation
 Functions of the Urinary System
 Organs of the Urinary System
 The Kidney
• Coverings and Regions
• Blood Flow
• Nephrons: Glomeruli and Renal Tubules
• Urine Formation
 Urinalysis
 Ureters, Bladder, and Urethra
Characteristics of Urine Used for Medical Diagnosis
 Colored somewhat yellow due to the pigment
urochrome (from the destruction of hemoglobin)
and solutes; darker if patient dehydrated, lighter
if over hydrated.
 Sterile
 Slightly aromatic
 Normal pH of around 6
 Specific gravity of 1.001 to 1.035; higher if
concentrated, lower if dilute.
 Checking for
Glycosuria (excessive sugary food intake or diabetes)
Proteinuria (intense exercise, pregnancy, hypertension)
Pyuria (pus from urinary tract infections)
Hemoglobinuria (from transfusion reactions or
hemolytic anemia)
Bilirubinuria (hepatitis)
Pyelonephritis (high specific gravity)
Urinary System II: Fluid, Electrolyte, and Acid/Base Balance
 Distribution of Body Fluid
 Maintaining Water Balance
 Hormornal Regulation of Water and
 Acid-Base Balance
• Blood Buffers
• Regulation by Lung Respiration
• Regulation by Kidney on
 Developmental Aspects of the Urinary
Most Body Fluid is Within Cells
 Intracellular fluid (inside
 Extracellular fluid
(outside cells)
• Interstitial fluid
• Blood plasma
 Normal amount of water in the human
• Young adult females – 50%
• Young adult males – 60%
• Babies – 75%
• Old age – 45%
•Low Na+ and Cl–
•Major cation: K+
•Major anion HPO42–
Maintaining Water Balance
 Water intake must equal water output
• Sources for water intake
o Ingested foods and fluids
o Water produced from metabolic processes
• Sources for water output
o Vaporization out of the lungs
o Lost in perspiration
o Leaves the body in the feces
o Urine production
 Urine Output
• Dilute urine is produced if water intake is excessive
• Less urine (concentrated) is produced if large amounts of water are lost
• Proper concentrations of various electrolytes must be present
Maintaining Water and Electrolyte Balance
Maintaining Acid-Base Balance in Blood
 Blood pH must remain between 7.35 and 7.45 to maintain
• Alkalosis – pH above 7.45
• Acidosis – pH below 7.35
 Most ions originate as byproducts of cellular metabolism
 Acid-base control
• Blood buffers (immediate, first line regulator of pH)
• Respiration rate (reacts in 1-3 minutes)
• Renal/Kidney mechanisms exert strongest effect but
slow (hours-days)
Chemical Buffer Systems of the Body
 Buffers react to prevent dramatic changes in hydrogen ion (H+) concentrations
• Bind to H+ when pH drops
• Release H+ (or bind OH-) when pH rises
1. Bicarbonate buffer system
Major buffer for the extracellular fluid, also intracellular fluid
H2O + CO2 <--> H2CO3 <--> HCO3- + H+
Phosphate buffer system
Effective buffer in urine and ICF, where phosphate concentrations
are high
(H3PO4 <--> H2PO4– + H+ <--> HPO42– + H+),
Protein buffer system
Mostly active within cells, some effects in plasma
Amino groups bind H+ (-NH2 + H+ <--> NH3+)
Carboxyl groups remove OH- (-COOH + OH- <--> -COO- + H2O
The Bicarbonate Buffer System
Renal Mechanisms of Acid-Base Balance
 Excrete bicarbonate ions if needed
 Conserve or generate new bicarbonate ions if needed
• Bicarbonate conservation or production causes rise in blood pH
• Bicarbonate excretion causes fall in blood pH
• H+ excretion in the urine
 Urine pH varies from 4.5 to 8.0
CO2 + H2 O
H2 CO3
H+ + HCO3
Acidosis and Alkalosis: Why It Matters
 Acidosis
• Blood pH below 7  depression of CNS 
coma  death
• Enzymes denature
 Alkalosis
• Blood pH above 7.8  excitation of nervous
system  muscle tetany, extreme nervousness,
convulsions, respiratory arrest
• Enzymes denature
Metabolic Acidosis and Alkalosis
 Any pH imbalance not caused by abnormal blood CO2 levels;
indicated by abnormal HCO3– levels
 Metabolic Acidosis
• Caused by ingestion of too much alcohol ( acetic acid),
excessive loss of HCO3– (e.g., persistent diarrhea)
• Causes by accumulation of lactic acid, shock, ketosis in
diabetic crisis, starvation, and kidney failure
 Metabolic Alkalosis (much less common than metabolic
• Indicated by rising blood pH and HCO3–
• Caused by vomiting of the acid contents of the stomach
or by intake of excess base (e.g., antacids)
Developmental Aspects of the Urinary System
 Fetal Development and Newborns
Functional kidneys are developed by the third
Urinary system of a newborn
Bladder is small
Urine cannot be concentrated
Control of the voluntary urethral sphincter does not
start until age 18 months
Urinary infections are the only common problems
before old age
 Effects of Aging on Urinary System
There is a progressive decline in urinary function
The bladder shrinks with aging
Urinary retention is common in males
 Congenital Abnormalities of the Urinary System
Polycystic kidney
Urinary System II: Fluid, Electrolyte, and Acid/Base Balance
 Distribution of Body Fluid
 Maintaining Water Balance
 Hormornal Regulation of Water and
 Acid-Base Balance
• Blood Buffers
• Regulation by Lung Respiration
• Regulation by Kidney on
 Developmental Aspects of the Urinary