1. Ureters Slender tubes attaching the kidney to the bladder
Continuous with the renal pelvis
Enter the posterior aspect of the bladder
Runs behind the peritoneum
Peristalsis aids gravity in urine transport

2. 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 epithelium
Walls are thick and folded in an empty bladder
Bladder can expand significantly without increasing internal pressure
Internal and external sphincters
Figure 15.6

3. Urethra
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 vagina
Males – 20 cm (8 inches) through the prostate and penis
Function
Females – only carries urine
Males – carries urine and is a passageway

4. Micturition (Voiding)
Both sphincter muscles must open to allow voiding
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

5. 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

6. 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 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)

7. Urinary System II: Fluid, Electrolyte, and Acid/Base Balance
Distribution of Body Fluid
Maintaining Water Balance
Hormornal Regulation of Water and Salt
Acid-Base Balance
Blood Buffers
Regulation by Lung Respiration
Regulation by Kidney on Bicarbonate
Developmental Aspects of the Urinary System

8. Most Body Fluid is Within Cells
Intracellular fluid (inside cells)
Extracellular fluid (outside cells)
Interstitial fluid
Blood plasma
Low Na+ and Cl–
Major cation: K+
Major anion HPO42–
Normal amount of water in the human body
Young adult females – 50%
Young adult males – 60%
Babies – 75%
Old age – 45%

9. Maintaining Water Balance
Water intake must equal water output
Sources for water intake
Ingested foods and fluids
Water produced from metabolic processes
Sources for water output
Vaporization out of the lungs
Lost in perspiration
Leaves the body in the feces
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

10. Maintaining Water and Electrolyte Balance

11. Maintaining Acid-Base Balance in Blood
Blood pH must remain between 7.35 and 7.45 to maintain homeostasis
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)

12. 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
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

13. The Bicarbonate Buffer System

14. 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

15. Acidosis and Alkalosis: Why It Matters
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

16. 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 acidosis)
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)

17. Developmental Aspects of the Urinary System
Fetal Development and Newborns
Functional kidneys are developed by the third month
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
Hypospadias
Hypospadias

18. Urinary System II: Fluid, Electrolyte, and Acid/Base Balance
Distribution of Body Fluid
Maintaining Water Balance
Hormornal Regulation of Water and Salt
Acid-Base Balance
Blood Buffers
Regulation by Lung Respiration
Regulation by Kidney on Bicarbonate
Developmental Aspects of the Urinary System