Genitourinary system Flashcards
What are the four functions of the kidney?
Excretion : Metabolic products and foreign substances
Homeostasis : body fluids ,electrolytes and acid-base balance
Regulation : blood pressure
Secretion : hormones
Which Hormones do the kidneys secrete?
Erythropoietin and renin
Which metabolic products and foreign substances do kidneys excrete?
Urea, uric acid, creatinine
Drugs
Describe the supply of blood pathway from the renal artery to the renal vein?
Renal artery –> Segmental Artery –> Interlobar artery –> Arcuate Artery –> Interlobular artery –>
Afferent arteriole –> GLOMERULAR CAPILLARIES –> Efferent arteriole –> Peritibular capillaries –>
Interlobular vein –> Arcuate Vein –> Interlobar vein –> Renal Vein
Function of peritubualr capillairess
peritubular capillaries are tiny blood vessels
Travel alongside nephrons allowing reabsorption and secretion between blood and the inner lumen of the nephron
Which muscles lines the bladder and contracts during urination?
Detrusor muscle
What does the Trigone do?
Stretching of this triangular region to its limit signals the brain about the need for urination
What does the internal spincter do?
Involuntary control to prevent urination.
What does the external sphincter do?
Voluntary control to prevent urination.
What does the bulboutheral gland do?
Produces thick lubricant which is added to watery semen to promote sperm survival
What is a functional unit of the kidney?
The nephron
Why do the epithelial cells in the PCT have more mitochondria than the ones in the Descending loop of Henle?
Proximal convolated tubule : absorption of salt, glucose, bicarbonate etc,
Descending loop : passive reabsorption of salt and water
Why is the cortex of a kidney granular looking and medulla striated?
Loop of Henle and ducts go through medulla = striated
Whats the difference in the superficial nephron and Juxtamedullary nephron?
Superficial : have their glomeruli in the outer cortex. They have shorter loops of Henle, which dip only into the outer medulla
Juxtamedullary nephrons’ loops of Henle dip deeper into the inner medulla and papilla, and are vital in the concentration of urine.
What constitutes the juxtaglomerular apparatus?
Macula Densa (Distal convoluted tubule)
Extraglomerular mesangial cells
Juxtaglomerular cells (Afferent arteriole
What are the functions of the juxtaglomerular apparatus?
GFR regulation through tubulo-glomerular feedback mechanism.
Renin secretion for regulating blood pressure
What passive processes are happening in the glomerular?
Fluid is ‘driven’ through the semipermeable glomerular capillaries into the Bowman’s capsule space by the hydrostatic pressure of the heart.
What is the slit diaphragm?
Thin and porous, water and small solutes can pass
Why is the filtration barrier charge dependent?
The glomerular basement membrane is negatively charged to repel the majority of proteins which are also negatively charged
How to calculate the net ultrafiltration pressure happening in glomerular filtration?
Puf = HPgc – HPbw – πgc
HPgc = Hydrostatic pressure in glomerular capillaries
HPbw = Hydrostatic pressure in bowman’s capsule
πgc = Oncotic pressure of plasma proteins in glomerular capillaries
What is the glomerular filtration rate GFR?
It is the amount of fluid filtered from the glomeruli into the Bowman’s capsule per unit time (mL/min).
( Sum of filtration rate of all functioning nephrons across the two kidneys )
- a fall in GFR is the cardinal feature of renal disease
How to calculate GFR?
GFR = Puf x Kf
Where Kf is an ultrafiltration coefficient (membrane permeability and surface area available for filtration
Female : 90-140 mL/min
Male : 80-125 mL/min
What is the myogenic mechanism and how does it regulate GFR?
Arterial Pressure increases –> afferent arterioles stretch –> arteriole contracts –> vessel resistance rises –> blood flow reduces –> GFR stays the same
How does the Tubulo-glomerular feedback mechanism work to regulate GFR?
Increase in GFR –>
Increase in NaCl in loop of Henle –>
Change detected by macula densa –>
Increase ATP and Adenosine discharged –>
Afferent arteriole constricts –>
GFR stabalises
( For a decrease in DGR Nacl decreases, ATP and adenosine decreases and arterioles dilates.
What is Renal clearance?
is the number of litres of plasma that are completely cleared of the substance per unit time.
- only concerned with the excretory role played by the kidneys
What is the calculation for renal clearance?
𝐶=(𝑈 𝑥 𝑉)/𝑃 mL/min
U = Concentration of substance in urine V = Rate of urine production P = Concentration of substance in plasma
C = 50mL/min for a substance, this means 50mL ?
this means 50mL of plasma has been cleared of that substance per minute.
What does it mean if a molecule is freely filtrered?
The amount filtered is equal to its amount excreted.
Renal clearance would = the GFR
Which two molecules are freely filtered and which one do we use?
Inulin and Creatinine
Waste product from creatine in muscle metabolism.
Amount of creatinine released is fairly constant.
If renal function is stable, creatinine amount in urine is stable.
Low creatinine clearance or high plasma creatine may indicate renal failure.
- refer to slide to understand why inuln is the better option but cannot use it because it is not found in mammals
If the total amount of a molecule entering the kidney equals amount excreted?
The renal clearance of this molecule equals the renal plasma flow (RPF).
What is used for renal plasma flow?
PAH (Para aminohippurate) is used as all the PAH is removed from the plasma passing through the kidney through filtration and secretion.
What is the filtration fraction?
FF = 𝐺𝐹𝑅/𝑅𝑃𝐹
The ratio of the amount of plasma which is filtered, and which arrives via the afferent arteriole is defined by the Filtration fraction (FF).
Its value ranges from 0.15-0.20 normally. A value of 0.15 implies 15% of the plasma has been filtered.
What is Primary active transport?
Uses ATP directly in a pump to transport e.g. K in and Na out of cell
What is secondary active coupled transport?
Movement of one solute along its electrochemical gradient provides energy for the other solute to move against it.
(Secondary active coupled transport types)
What is Symport transportation ?
Antiport?
Both molecules travelling in same direction. ( one molecule will be moving along its gradient to provide energy for the other to move against )
Antiport- opposite directions
What is a paracellular pathway in tubules?
Through tight junctions eg, Ca, K Cl, urea
What is the transcellular pathway in tubules?
Pathway through the cell into blood reabsorption e.g. Na is reabsorbed from tubular fluid into cells while the Na already in the cell is pumped into blood
How is sodium and bicarbonate reabsorbed in the early PCT?
Na+ K pump created low Na concentration in cell
CO2 enters cell by diffusion to form carbonic acid and hydrogen
Na+ and H+ antipose transporter allows H+ to be pumped out as Na comes into cell passively
How does Angiotensin II regulated Na+ reabsorption?
Angiotensin II regulates Na+ reabsorption by increasing Na+ - H+ antiporters
How is Glucose reabsorbed in the early Proximal Convoluted Tubule
Na+ K+ pump used to remove Na
Na+ glucose symporter in the cell allows both glucose and Na to come into tubular cell as Na+ moved in passively
Characteristics of descending limb?
Salt cannot be pumped out
Water moved out passively due to activity of ascending limb
Characteristics of ascending limb
Secrete Na and Cl PASSIVELY making the medulla salty, water cannot leave
What happens in the thick ascending limb?
Na+ K ATPase pump removes Na into blood
Na+ K+ 2CL- symporter moves them all in along Na+ passive movement
K+ CL- symporter moves Cl- out into blood along K+ passive movement
What occurs in the early Distal Convoluted Tubule?
Na+ Cl- reabsorption:
Calcium reabsorption
How is calcium reabsorbed?
Na+ K+ pump moves Na+ into blood
Calcium passively moved in from fluid to cell
Ca2+ moved into blood by Na+ Ca2+ antiporter as Na+ moves into cell passively
Ca2+ ATPase pump into blood too
How is Salt reabsorbed?
Na+ K+ pump moved Na+ out
Na+ Cl- Symporter brings Cl- into cell alongside passive Na+
Ka+ Cl- symporter bring Cl- into blood alongside K+
Cl- moved into blood passively too
What do the Principle cells do?
Na+ reabsorption & K+ secretion
Na+ K+ pump moves Na+ into blood and K+ into cell
Na+ passively moves from fluid into cell and K+ moves passively into Tubular fluid
Water moved across into blood through aquaporins along gradient
( Hypercalaemia correction? * )
What does aldosterone do?
Aldosterone regulates Na+ reabsorption by increasing apical Na+ channels & basolateral Na+ - K+ - ATPase pumps.
What does ADH do?
Anti-Diuretic Hormone regulates water reabsorption by increasing apical aquaporins.
What does the intercalated cell do?
Maintaining acid-base balance
Alpha : HCO3- reabsorption & H+ secretion.
Beta : HCO3- secretion & H+ reabsorption ( minority but needed in e.g, alkilosis )
- Check slide diagram to see transporters involved
