1. Unit IV: Regulation Urinary System II
Chapter 23: pp

2. Urine Storage and Elimination
Ureters (about 25 cm long)
small flap of mucosa that acts as a valve into bladder
3 layers:
adventitia
muscularis
urine enters, it stretches and contracts in peristaltic wave
mucosa
lumen very narrow, easily obstructed
Lamina propria
Transitional epithelium
Mucosa
Connective tissue layer
Smooth muscle

3. Urinary Bladder Located in pelvic cavity, posterior to pubic symphysis
3 layers
parietal peritoneum, superiorly; fibrous adventitia rest
muscularis: detrusor muscle
mucosa: transitional epithelium
rugae:
trigone:
capacity: moderately full ml, max ml
The wall of the urinary bladder
Peritoneum
Detrusor muscle
Submucosa
Lamina propria
Transitional epithelium
Mucosa

4. Urinary Bladder and Urethra - Female

5. Female Urethra 3 to 4 cm long External urethral orifice
between vaginal orifice and clitoris
Internal urethral sphincter
smooth muscle
External urethral sphincter
skeletal muscle

6. Male Bladder and Urethra
18 cm long
Internal urethral sphincter
External urethral sphincter
3 regions
prostatic urethra
during orgasm receives semen
membranous urethra
passes through pelvic cavity
spongy urethra
to external urethral orifice

7. Urine Formation Stages: Fluid names thru nephron: Glomerular filtrate
Capsular space
Tubular fluid
PCT  DCT
Urine
Collecting duct

8. Glomerular Filtration Filtration Membrane
Capsular space
Filtration slit < 3nm
Filtration pore nm
Basement membrane
>8nm
Passed through filter: W
ater
Electrolytes
Glucose
Amino acids
Fatty acids
Vitamins
Urea
Uric acid
Creatinine
Turned back:
Blood cells
Plasma proteins
Large anions
Protein-bound
Most molecules
> 8 nm in
diameter
Bloodstream
Endothelial cell of
glomerular capillary
Foot process of
podocyte
minerals and
hormones
Glomerulus
Podocyte

9. Glomerular Filtration
Damage causes:
Proteinuria – presence of albumin
Hematuria - presence of blood

10. Filtration Pressure

11. Glomerular Filtration Rate (GFR)
Filtrate formed per minute
GFR = 125 ml/min or 180 L/day, male
GFR = 105 ml/min or 150 L/day, female
depends on permeability and surface area of filtration barrier
99% of filtrate reabsorbed, 1 to 2 L urine excreted/day

12. Effects of GFR Abnormalities
GFR, urine output rises  dehydration, electrolyte depletion
GFR  wastes reabsorbed (azotemia possible)
GFR controlled by adjusting glomerular blood pressure
autoregulation
sympathetic control
hormonal mechanism: renin and angiotensin

13. Renal Autoregulation of GFR
 BP  constrict afferent arteriole, dilate efferent
 BP  dilate afferent arteriole, constrict efferent
Function of the Juxtaglomerular Apparatus
Cannot compensate for extreme BP (<70mmHg)

14. Sympathetic Control of GFR
Strenuous exercise or acute conditions (circulatory shock) stimulate afferent arterioles to constrict
 GFR and urine production, redirecting blood flow to heart, brain and skeletal muscles

15. Enzyme Regulation of GFR

16. Tubular Reabsorption and Secretion: Proximal Convoluted Tubules (PCT)
Reclaims water and solutes from tubular fluid and returns them to the blood
Reabsorbs 65% of GF to peritubular capillaries
active transport
6% of resting ATP and calorie consumption
Reabsorbs greater variety of chemicals than other parts of nephron
transcellular route - through epithelial cells of PCT
paracellular route - between epithelial cells of PCT

17. Mechanisms of Reabsorption in the PCT
Peritubular
capillary
Tissue
fluid
Tubule epithelial cells
Tubular fluid
Sodium–glucose
transport protein
(SGLT) (Symport)
Glucose
Na+
ATP
Na+
Glucose
Na+–K+ pump K+
Na+
Na+–H+ antiport
ADP + Pi H+ K+
Cl–
Cl––anion antiport
Cl–
Anions
K+–Cl–
symport
H2O
Aquaporin
Tight junction
Solvent drag
Transcellular route
Brush
border
H2O, urea, uric acid,
Na+, K+, Cl–, Mg2+, Ca 2+, Pi
Paracellular route
Blood in Peritubular capillaries has a high Colloid Osmotic Pressure

18. Tubular Secretion of PCT and Nephron Loop
Process by which renal tubules extract chemicals from capillary blood and secrete them into the tubular fluid.
Waste removal
urea, creatine, bile salts, ammonia, catecholamines, many drugs
Acid-base balance
secretion of hydrogen and bicarbonate ions
Primary function of nephron loop
water conservation
Counter-current multiplication

19. Water Conservation DCT and Collecting Duct
Function
fluid reabsorption (water conservation)
DCT reabsorbs Na, Cl, and water
Collecting Duct only conserves water
regulated by hormonal action (Aldosterone, ANP, ADH, PTH)
Principal cells – receptors for hormones; involved in salt/water balance
Intercalated cells – involved in acid/base balance

20. Voiding Urine - Micturition
Involuntary micturition reflex
To pons
From pons 1
Stretch receptors detect filling
of bladder, transmit afferent
signals to spinal cord. 5 6 7 2
Signals return to bladder from
spinal cord segments S2 and S3
via parasympathetic fibers in
pelvic nerve.
Pelvic nerve 3
Efferent signals excite
detrusor muscle.
Sensory
fiber
Motor
fiber 4
Efferent signals relax internal
urethral sphincter. Urine is
involuntarily voided if not
inhibited by brain.
Full
urinary bladder
Sacral segments
of spinal cord S2
Voluntary control 2 5
For voluntary control, micturition
center in pons receives signals
from stretch receptors. 1 S3 6
If it is timely to urinate,
pons returns signals to
spinal interneurons that
excite detrusor and relax
internal urethral sphincter.
Urine is voided.
Para-
sympathetic
ganglion in
bladder wall S4 3
Stretch receptors 7
If it is untimely to urinate,
signals from pons excite
spinal interneurons that
keep external urethral
sphincter contracted. Urine
is retained in bladder.
Motor fibers to
detrusor muscle 4
Urethra
Internal urethral
sphincter (involuntary)
External urethral
sphincter (voluntary) 8
Somatic motor fiber
of pudendal nerve 8
If it is timely to urinate, signals
from pons cease and external
urethral sphincter relaxes. Urine
is voided.

21. Test IV - Regulation Chapters 16 and 23 Chapter 24: 885-891 Lab:
Identify organs of endocrine and urinary system
Slides and models
Roles of those organs
Tissue types of urinary system