Genitourinary System Flashcards
What are the 4 functions of the kidneys?
- Excretion —> metabolic products: urea, uric acid,
creatinine
—> foreign substances: drugs - Homeostasis —> body fluids
—> electrolytes
—> acid-base balance - Regulate blood pressure
- Hormone secretion —> erythropoietin
—> renin
What are the 7 main components of the kidneys?
- Cortex - outside
- Medulla - inside
- Major calyx - join to ureter
- Minor calyx - branches of major calyx
- Renal artery
- Renal vein
- Ureter
What is the pathway of blood through the kidneys?
In:
Renal artery
Segmental artery
Interlobar artery
Arcuate artery
Interlobular artery
Afferent arteriole
Glomerular capillaries
Out:
Efferent arteriole
Peritubular capillaries —> supply kidney
Interlobular vein
Arcuate vein
Interlobar vein
Renal vein
Which blood vessels supply the kidney?
Peritubular capillaries
What are the 5 parts of the bladder?
- Detrusor muscle
- outside
—> contraction for urination
- outside
- Trigone
—> signals brain when bladder full (stretch) - Internal sphincter
- end of bladder
—> involuntary control to prevent urination
- end of bladder
- External sphincter
- urogenital diaphragm
—> voluntary control to prevent urination
- urogenital diaphragm
- Bulbourethral glands
- males only
- urogenital diaphragm
—> produce and secrete lubricant to semen for
sperm survival
What are the 6 parts of a nephron?
- Glomerulus
- Bowman’s capsule
- Proximal convoluted tubule
- Loop of Henle - ascending and descending
- Distal convoluted tubule
- Collecting duct
Where is mitochondria found in high vs low densities in a nephron?
High —> active transport:
1. PCT
2. DCT
3. Thick ascending loop of Henle
4. Intercalated cells of collecting duct
Low —> passive transport:
1. Thin descending loop of Henle
2. Thin ascending loop of Henle
3. Principal cells of collecting duct
What are the 2 types of cells that make up the collecting duct?
- Principle cells —> Na+ reabsorption and K+
secretion - Intercalated cells —> maintain acid-base balance
What are the 2 types of nephron?
- Superficial
- glomerulus in outer cortex
- loop of Henle trough at inner-outer medulla
border
- Juxtaglomerular
- glomerulus near cortex-medullar border
- loop of Henle trough deep in inner medulla
Nephron —> 10:1 (superficial : juxtaglomerular)
Why is the cortex granular and medulla striated?
Cortex —> contains many glomeruli (dots)
Medulla —> contains many tubules (lines)
What is the juxtaglomerular apparatus?
Where glomerulus is next to DCT
- Macula densa - cells of DCT that meet glomerulus
—> GFR regulation (tubulo-glomerular
feedback mechanism)
- Extraglomerular mesangial cells - between DCT and
efferent arteriole
- Juxtaglomerular cells - on afferent arteriole
—> secrete renin —> regulates
blood pressure
What are the 4 renal processes?
- Glomerular filtration
- Reabsorption
- Secretion
- Excretion
How does glomerular filtration occur?
- Blood plasma pushed through glomerular
fenestrae- due to heart’s hydrostatic pressure
- 70nm gaps in basement membrane —> sieve
- Through Bowman’s capsule space
- Through Bowman’s capsule membrane
- -ve proteins in membrane —> repel proteins
- Through slit diaphragm
- between epithelial podocytes
- thin and porous —> sieve
Which 4 pressures affect glomerular filtration?
Push fluid out:
1. Blood hydrostatic pressure
2. Fluid oncotic pressure
Pull fluid in:
1. Blood oncotic pressure
2. Fluid hydrostatic pressure
What are the 4 equations for renal action?
- Net Ultrafiltration Pressure:
Puf = HPgc - HPbw - πgc - Glomerular Filtration Rate:
GFR = Puf x Kf - Renal Clearance:
C = (U x V) / P - Filtration Flow:
FF = GFR / RPF
What is Puf and how is it calculated?
Net Ultrafiltration Pressure
- pressure exerted on blood to force fluid out at
glomerulus
Puf = HPgc - HPbw - πgc
- HPgc = hydrostatic pressure in glomerular capillaries
- HPgc = hydrostatic pressure in bowman’s capsule
- πgc = oncotic pressure of plasma proteins in
glomerular capillaries
What is GFR and how is it calculated?
Glomeruar Filtration Rate
- volume of fluid pushed filtered through the
glomeruli per unit time (indicative of renal failure)
- mL/min
- males —> 90-140
females —> 80-125
GFR = Puf x Kf
- Puf = net ultrafiltration pressure
- Kf = ultrafiltration coefficient
- depends on membrane permeability and surface
area
What are the 2 mechanisms for GFR regulation?
- Myogenic mechanism:
- arterial pressure inc —> afferent arteriole
contracts —> blood flow dec
- arterial pressure inc —> afferent arteriole
- Tubulo-glomerular feedback mechanism:
- GFR inc —> inc NaCl in loop of Henle —> macula
densa detects —> inc ATP and adenosine
secreted —> afferent arteriole contricts - GFR dec —> dec NaCl in loop of Henle —> macula
densa detects —> dec ATP and adenosine
secreted —> afferent arteriole dilates
- GFR inc —> inc NaCl in loop of Henle —> macula
What is C and how is it calculated?
Renal Clearance
- volume of plasma cleared of a specific substance via
the kidneys per unit time
- mL/min
C = (U x V) / P
- U = conc of substance in urine
- V = rate of urine production
- P = conc of substance in plasma
Which 2 substances are used to determine GFR and why?
- Inulin - must be transfused from plants —> less use
- Creatine - muscle metabolism waste —> common
- Freely filtered (no reabsorption or secretion)
- Non-toxic
What is FF and how is it calculated?
Filtration Factor
- proportion of filtered plasma fluid that reaches the
afferent arteriole
- 0.15-0.2 (15-20% filtered)
- use PAH to measure - all removed from plasma
through kidney
FF = GFR / RPF
- GFR = glomerular filtration rate
- RPF = renal plasma flow
Which substance is used to calculate FF and why?
PAH = Para AminoHippurate
- all removed from plasma —> amount entering
kidney = amount excreted —> RPF = C
What are the 5 transport mechanisms used in renal tubules?
Passive:
1. Diffusion
2. Osmosis
3. Electrochemical gradient
Active:
4. Primary —> Na+/K+ ATPase pump
—> endocytosis
5. Secondary (coupled) —> symport eg. Na+/glucose
—> antiport eg. Na+/H+
What are the 2 transport pathways used in renal tubules?
- Transcellular —> across basolateral membrane
cells via transport proteins - Paracellular —> via tight junctions between
basolateral membrane cells
Which substances are reabsorbed and secreted in the early PCT?
Reabsorbed:
- Water —> 67%
- Na+ —> 67%
- Cl- —> 67%
- HCO3- —> 80%
- Urea —> 50%
- Glucose —> 100%
- Amino Acids —> 100%
Secreted:
- Drugs
- Ammonia
- Bile salts
- Prostaglandins
- Vitamins (B+C)
How does Na+ and HCO3- reabsorption occur in the early PCT? (4)
- Na+/K+ ATPase pump (b) —> Na+ out, K+ in —> low
Na+ in cells - CO2 diffuses in —> react with water (CO2 + H2O —>
HCO3- + H+) using carbonic anhydrase —> high H+
in cells - Na+/H+ antiporter (b) —> Na+ in, H+ out (regulated
by angiotensin II) - Na+/3 HCO3- symporter (b) —> Na+ out, 3 HCO3-
out —> reabsorbed to blood
How does glucose reabsorption occur in the early PCT? (3)
- Na+/K+ ATPase pump (b) —> Na+ out, K+ in —> low
Na+ in cells - SGLT2 (Na+/glucose symporter) (a) —> Na+ in,
glucose in - GLUT2 (b) —> glucose out —> reabsorbed to blood
How is Na+ reabsorption regulated in the early PCT?
Angiotensin II —> inc Na+/H+ antiporters
What happens at the loop of Henle? (4)
- No aquaporins in ascending limb —> no water out
- Na+ and Cl- out ascending limb —> passive in thin
—> active in thick - Outside loop —> v. low water potential (salty)
- Water out descending passively
No Na+ or Cl- transporters —> no ions out
How does Na+ and Cl- reabsorption occur in the thick ascending limb of the loop of Henle? (3)
- Na+/K+ ATPase pump (b) —> Na+ out, K+ in —> low
Na+ in cells - K+/Cl- symporter and channels (b) —> K+ out, Cl-
out —> low Cl- in cells - Na+/K+/2 Cl- symporter (a) —> Na+ in, K+ in, Cl- in
—> out via transporters above —> reabsorbed
Which substances are reabsorbed in the loop of Henle?
- Na+ —> 25%
- Cl- —> 25%
- Water —> 15%
How does Na+ and Cl- reabsorption occur in the early DCT? (4)
- Na+/K+ ATPase pump (b) —> Na+ out, K+ in —> Na+
reabsorbed - No aquaporins (a) —> no water in
- Na+/Cl- symporter (b) —> Na+ in, Cl- in
- K+/Cl- symporter + Cl- channels (b) —> K+ out, 3 Cl-
out —> Cl- reabsorbed
How does Ca2+ reabsorption occur in the early DCT? (3)
- Na+/K+ ATPase pump (b) —> Na+ out, K+ in —> low
Na+ in cells - Ca2+ channels (a) —> Ca2+ in —> high Ca2+ in cells
- Na+/Ca2+ antiporter + Ca2+ ATPase pump (b) —>
Na+ in, Ca2+ out —> Ca2+ reabsorbed into blood
How does Na+ reabsorption and K+ secretion occur in the distal DCT and collecting duct? (4)
Principle cells:
1. Na+ channels (a) —> Na+ in
2. K+ channels (a+b) —> K+ out
3. Na+/K+ ATPase pump (b) —> Na+ out, K+ in —> Na+
reabsorbed and K+ secreted
4. Aquporins (a+b)—> water in —> out —> water
reabsorbed
How is blood and urine pH maintained by the collecting duct? (3x2)
Acidosis —> α-intercalated cells (urine too alkaline):
1. Cl- channels (b) —> Cl- out —> low Cl- in cells
2. Cl-/HCO3- antiporter (b) —> Cl- in, HCO3- out —>
HCO3- reabsorbed
3. H+ ATPase pump (a) —> H+ out —> H+ secreted
Alkalosis —> β-intercalated cells (urine too acidic:
1. Cl- channels (b) —> Cl- out —> low Cl- in cells
2. H+ ATPase pump (b) —> H+ out —> H+ reabsorbed
3. Cl-/HCO3- antiporter (a) —> Cl- in, HCO3- out —>
HCO3- secreted
How is Na+ reabsorption in the distal DCT and collecting duct regulated?
Aldosterone —> inc apical Na+ channels
—> inc basolateral Na+/K+ ATPase pump
- inc Na+ reabsorption —> dec Na+ loss
How is water reabsorption in the distal DCT and collecting duct regulated?
ADH —> inc apical aquaporins
- inc water reabsorption —> dec water loss
What occurs at the early PCT? (2)
- Na+ and HCO3- reabsorption
- Glucose reabsorption
What occurs at the early DCT? (2)
- Na+ and Cl- reabsorption
- Ca2+ reabsorption
What occurs at the distal DCT and collecting duct? (2)
- Na+ reabsorption and K+ secretion
- Maintaining acid-base balance
