1. Formation of Urine
Figure 15.5

2. Characteristics of Urine
Yellow due to pigment urochrome (from break-down of hemoglobin) & solutes
Sterile
Slightly aromatic
Normal pH of ~ 6
Specific gravity of to 1.035
~1500 ml daily

3. Chemical Composition of Urine
95% water and 5% solutes
Nitrogenous wastes: urea, uric acid, and creatinine
Other normal solutes
Na+, K+, PO43–, and SO42–,
Ca2+, Mg2+ and HCO3–
Abnormally high concentrations of any constituent may indicate pathology

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

5. Ureters
As bladder pressure increases, distal ends of the ureters close, preventing backflow of urine

6. Lumen Adventitia Circular layer Longitudinal layer Transitional
epithelium
Lamina
propria
Figure 25.20

7. Renal Calculi Kidney stones form in renal pelvis
Crystallized calcium, magnesium, or uric acid salts
Larger stones block ureter, cause pressure and pain in kidneys
May be due to chronic bacterial infection, urine retention, Ca2+ in blood, pH of urine
Lithotripsy

8. Urinary Bladder Smooth, collapsible, muscular sac
Temporarily stores urine
Trigone – 3 openings
- Two from ureters
- One to urethrea

9. Urinary Bladder
Retroperitoneal, on pelvic floor posterior to pubic symphysis
Males—prostate gland surrounds the neck inferiorly
Females—anterior to the vagina and uterus

10. Urinary Bladder Wall Detrusor muscle – pushes down
3 layers of smooth muscle
Walls - thick & folded in empty bladder
Transitional epithelium - expands without increasing internal pressure

11. Urethra Thin-walled tube Carries urine from bladder by peristalsis
Release controlled by 2 sphincters
Internal urethral sphincter (involuntary)
External urethral sphincter (voluntary)

12. Urethra Gender Differences
Length
- Females – 3–4 cm (1 inch)
- Males – 20 cm (8 inches)
Location
- Females – along wall of the vagina
- Males – through the prostate and penis
Function
- Females – only urine
- Males –urine and sperm

13. Micturition Urination or voiding Three simultaneous events
Contraction of detrusor muscle by ANS
Opening of internal urethral sphincter by ANS
Opening of external urethral sphincter by somatic nervous system

14. Maintaining Water Balance
Normal amount of water in humans (~1/2)
- Adult females – 50%
- Adult males – 60%
- Babies – 75%
- Old age – 45%
Water is necessary for many functions and levels must be maintained
Water intake = water output
Sources for water intake
- foods and fluids
- metabolic processes
Sources for water output
- Vaporization from lungs
- perspiration
- feces
- Urine

15. Distribution of Body Fluid
Intracellular fluid (inside cells)
Extracellular fluid (outside cells)
- Interstitial fluid
- Blood plasma

16. Link Between Water and Salt
Changes in electrolyte balance causes water to move from one compartment to another. Water follows salt!
- Alters blood volume & blood pressure
- Can impair the activity of cells

17. Regulation of Reabsorption
Hormones
- Antidiuretic hormone (ADH) prevents excessive water loss in urine
Aldosterone regulates sodium
Triggered by the renin-angiotensin mechanism
Monitored by kidneys and hypothalamus

18. Maintaining Blood pH Normal Blood pH
- Alkalosis – pH above 7.45
- Acidosis – pH below 7.35
Most ions are metabolic byproducts
Most pH balance is maintained by kidneys
Other acid-base controlling systems
- Blood buffers
- Respiration

19. Blood Buffers Molecules to prevent dramatic changes in [H+]
- Bind to H+ when pH drops
- Release H+ when pH rises
Three major chemical buffers
Bicarbonates
Phosphates
Proteins

20. Buffering Systems

21. Fetal/Newborn Developmental Aging Functional kidneys by 3rd month
Bladder is small in newborn
Urine cannot be concentrated
Developmental
Control of voluntary sphincter ~ 18 mos
Urinary infections - common problems
Aging
Bladder shrinks
Decline in function
Retention if prostate enlarges (males)

22. Conditions
UTI (urinary tract infection) - caused E.coli. Frequent urgency to urinate, cloudy urine, dysuria (trouble / painful urination)
Prostate Enlargement (Hypertrophy) – causes dysuria due to pressure on urethra
Incontinence – normal for children, heavy sleepers, during pregnancy or infection, old age

23. Renal Calculus – kidney stones; urine too concentrated and substances crystalize; causes oliguria (decreased urine)
Addison’s Disease (hypoaldosteronism) – causes polyuria