Genitourinary System Flashcards
What are the 5 main functions of the kidneys?
- EXCRETION of metabolic products e.g. urea, creatine
- EXCRETION of foreign tings e.g. drugs
- REGULATION of body fluids, electrolytes and acid-base balance
- CONTROL of blood pressure
- SECRETES hormones
What is the anatomical structure of the kidney?
CORTEX-outer layer
MEDULLA-inner bit
RENAL ARTERY
RENAL VEIN
URETER-urine out
-MINOR + MAJOR CALYX- chambers that urine passes through
Describe the pathway of blood supply in the kidney?
What happens when urine enters the bladder?
- Urine enters Bladder via Urethra
- once the bladder fills to 200ml the DETRUSER MUSCLES start to contract =pressure
- pressure is sensed in the TRIGONE region
- leads to relaxing of the INTERNAL SPHINCTER (involuntary control to usually prevent leakage)
- voluntary control of the external sphincter
- PEE
What is the difference between the male and female Urethra?
Male one is much longer as it spans the length of the penis (so depends how big the D is)
What are the functions of 5 different parts of the bladder and urethra?
DETRUSER MUSCLE-contracts to build pressure inn t he bladder to support peeing
TRIGONE-strethcing of this triangular region to its limit send signals tot he brain that you need to pee
INTERNAL SPHINCTER-involuntary control to prevent peeing
EXTERNAL SPHINCTER-voluntary control to stop peeing
BULBOURETHRAL GLAND-produces thick lubricant which is added to watery semen to promote sperm survival
What is the structure of the nephron?
Describe water and sodium absorption from the Nephron?
PROXIMAL DISTAL TUBULE: sodium, most solutes like GLUCOSE, and water reabsorbed into the capillaries (via active transport) from the PROXIMAL CONVOLUTED TUBULE
LOOP OF HENLE is a COUNTER CURRENT: salt is AT out of the top of the ascending loop (epithelial cells are rich in mitochondria here). This means the interstitual fluid now has a low water content. So water leaves the bottom of the decending limb via osmosis(as the ascending limb is impermeable to water)
DISTAL CONVOLUTED TUBULE: Start is impermeable to water, some salt is reabsorbed into the capillaries
COLLECTING DUCT: Na+ reabsorbed and water follows
What cell types in the nepohron are rich/not rich in mitochondria?
EPITHELIAL CELLS(of distal convoluted tube)- rich in mitochondria
INTERCALATED CELLS(collecting duct)-rich in mitochondria
PRINCIPAL CELLS(collecting duct)-not so rich in mitochondria
What are the 2 types of nephron?
SUPERFICIAL NEPHRON- loop only dips into the OUTER MEDULLA
JUXTAMEDULLARY NEPHRON-loop dips deep into the inner medulla
10:1 ratio of superficilal: juxtamedullary nephron
What are the 3 main Consituents and 2 main function of the Juxtaglomerular apparatus?
Constituents:
- MARCULA DENSA(dct)
- EXTRAGLOMERULAR MESANGIAL CELLS
- JUXTAGLOMERULAR CELLS (afferent arteriole)
Function:
- GFR regulation through tubulo-glomerular feedback mechanism
- Renin secretion for regualting bloood pressure
Which renal blood vessel branches out to form the peritubular capillaries?
efferent arteriole
Describe Glomerular filtration?
-Fluid driven through SEMI-PERMEABLE glomerular capillaries into the bowmans capsule by hydrostatic pressure of the heart
only small tings and fluids can get through not large tings and proteins
What is the structure of the Glomerulus filtration system?
-Capillary endothelium with fenestrations between them (small proteins and ions can pass through)
-Basement membrane below
-Epithelial Podocytes below which have Slits between them
(allow small solutrs and water to pass through)
What are the pressures involved in Glomerular filtration?
Blood Hydrostatic pressure-fluid exerts this pressure, solute and fluid pushed out of the blood due to this
Blood Oncotic pressure-proteins and solutes exert this pressure, draws fluid in across a semi permeable membrane into the blood capillaries
Interstitual Fluid Hydrostatic Pressure-exerts high pressure on the blood cappilaries causing fluid and soulutes to move in
Interstitual fluid oncotic pressure-low pressure in IF as there are less solutes in IF than in the blood so water moves out of the blood capillaries
Hydrostatic pressure-pushing caused by fluid
Oncotic pressure-pulling caused by solutes
What is the net ultrafiltration pressure of glomerular filtration?
Hydrostatic pressure in Glomerular capillaries- Hydrostatic pressure in Bowmans Capsule-Oncotic pressure of solutes in Glomerular Capillaries
What is Glomerular filtrartion rate?
How do we calculate it?
Amount of Fluid filtered from the glomeruli into the Bowmans Capsule per unit of time mL/min
Thsi is the sum of filtration rate of all functioning nephrons
GFR=K(f) x P(uf)
Kf=ultrafiltration constant calculated by the membrane permeability and surface area
Puf=overall pressure of the system
What is the Glomerular Filtration Rate(GFR) in healthy adults?
Males: 90-140ml/min
Females: 80-125ml/min
Whatv does a low GFR indicate?
Renal disease(with a build up of excretory products in the plasma
What 2 mechanisms keep GFR regulated(KEPT THE SAME)?
MYOGENIC REGULATION:
Arteriole pressure increases-> arteriole stretches->arteriole contracts -> resistance increases-> this causes blood flow to be reduced -> which means the GFR is maintained the same
TUBULAR-GLOMERULAR FEEDBACK MECHANISM:
Increase/ decrease in GFR->increased/decreased sodium(NaCl )in the loop of Henle->chadetected by the MACULA DENSA which porduces more/ less RENIN-> increased/ decreased ATP and adenosoine discharged -> affererent arteiole constricts/ dialates->GFR stabilises
What is Renal Clearence?
How is it used?
- The volume of plasma completely cleared of a substance
- Used to calculate GFR, Renal plasma flow(RPF) and to understand the excretory route of a substance (that is filtered or fuiltered and secreted)
What is the Renal plasma flow equal to?
What happens when things are absorbed into/ secreted out of the kidney?
The rate of blood into the kidney is = to the renal plasma flow rate
The renal plasma flow rate= out for excretion into the bladder and out for recirculation
-If something is NOT secreted or reabsorbed the rate at which it comes out of the renal tubule(GFR) will match the rate at which it enters the bladder
- If substances are REABSORBED into the kidney – the rate at which it comes out of the bladder will be lower than the GFR
- if substances are SECRETED and REABSORBED the rate at which it leaves the kidney depends on the proportion of absorption and secretion
- If it is SECRETED from the kidney – the rate at which it leaves the kidney to enter the bladder will = the rate at which it comes in (the renal plasma flow rate)
What is the calculation for renal clearence?
C=(UxV)/P ml/min
U= concentration of substance in the urine
V= rate of urine production
P= concentration of urine in the Plasma
If C =50ml that means 50ml of plasma had been cleared of that particular substance per min
What is completely reabsorbed from the kidney?
Glucose
What are the features of the substsnce that we would use to measure/estimate the GFR?
Features:
- FREELY FILTERED
- NEITHER REABSORBED OR SECRETED in the nephron -because the rate at which it comes out of the nephon will then = the rate at which it entered(the GFR)
What is the ideal molecuel we will use to measure the GFR?
What are the pros and cons?
INULIN:
PROS:
- Freely filtered
- A plant polysaccharide neither absorbed or secreted
- Not toxic
- measurable in plasma and urine
CONS:
-NOT found in mammals so has to infused
What is commonly used to measure GFR?
What are the features?
Why is it not an ideal molecule?
CREATINE:
FEATURES:
- If you muscle mass remains consistant the amount of creatine in your urine also remains stable
- amount creatine released is fairly constant
- If renal function is stable the amount of creatine in the urine is stable
- freely filtered
NOT IDEAL:
- a small amount is SECRETED
- chronic conditions of muscle wasting willl cause an elevation in the levels of creatine because you’re losing muscle mass
What are the features of the substance you would use to measure Renal Plasma Flow rate?
-something that is completely secreted e.g. PAH
How do you calculate the filtration Fraction?
What is the Filtration fraction?
What is the normal value of the filtration fraction?
What fraction of the plamsa entering the kidneys has been filtered
FF=GFR/RPF
Ranges from 0.15-0.25 meaing 15-25% is usually filtered
How do you calculate renal plasma flow rate?
Measure something that is completely secreted formthe pasma flowing throught he kidney e.g PAH-para-aminohippurate
Why does something moving down its electrical gradient count as both passive transport and secondary active transport?
because when something moves down its electrical gradient it provides energy thatv can be used to move another solute against its concentration gradient(secondary active transport)
What are the different transport pathways in the renal tubules?
-Passive Transport- down conc gradient
-Active transport- against conc gradient using energy from ATP or energy from something moving down its electrical gradient
Paracellular pathway-stuff goes between cells- water moves this way and drags other things with it e.g urea, cl-, K+
Transcellular pathway-water moves through cells via AQUAPORINS
Transcellular Na+ reabsorption- sodium moving dow its electrochemical gradient after being exchanged with K+ brings things back innto the cell with it.
Describe sodium Bicarbonate reabsorption in the Proximal Convoluted tubule?
sidenote: Low blood volume/ salt= RENIN released = Angiotensin II released = increases Na+ reabsorption by increasing amount of Na+-H+ antiporters
1-CARBONIC ANHYDRASE converts H+ and HCO3- into H2O and CO2
2-These products enter the cells and are converted back to bicarbonate and a proton
3-The proton is exchanged for Na+, so Na+ enter and H+ leaves via sodium-proton antiporter
4-Sodium is then exchanged for k+ via Na+ k+ ATPase pump
5-HCO3 -Na+ symporter is used to pump both substances out
6-Bicarbonate and sodium are now in high concentrations in the Tubular fluid surrounding the PCT and can therefore move down concentration gradient into the blood ( reabsorbed)
What gets reabsorbed on the Proximated Convuluted Tubule?
What get secreted here?
Reabsorbed:
- 50% urea
- 67% of Na+
- 67% of Cl-
- 67% of water
- 90% of HCO3-
- 100% glucose
- 100% amino acids
Secreted:
- Drugs
- ammonia
- bile salts
- prostoglandins
- vitamins(folate, ascorbate)
Describe glucose reabsorption from the Proximal Covuluted Tubule?
1-Sodium and glucose brought into the cells of PCT via Na+-glucose symporter
2-Na+ is transported out of the cell into the Tubular fluid via the Na+-K+ ATPase pump
3-Glucose is transpoted out of the cell into the Tubular fluid via GLUT 2 transporter
4-Na+ and Glucose move down their concentration gradients intot he blood capillaries
Describe reabsorption in the loop of Henle?
1-Na+CL- actively pumped out of the top of the ascending limb- thcik ascending limb ( descending limb is impermaeable to Na+Cl-) higher concentration outside the loop
2- water passively leaves the bottom of the descending limb which is permaeable to water (descending limb is not )
3-As fluid moves from the bottom up the ascending limb Na+ leaves passively
25% of the Na+ and Cl- is reabsorbed into the blood
15% of water is reabsorbed into the blood
Describe what happens in the thick ascending limb (at the top of the ascending limb)?
Describe reabsorption in the early Distal Convuluted tubule?
Na+ and Cl- reabsorption:
1-It is impermeable to water
2-There is a Na+Cl- symporter that allows them to enter the cell
3-Na+ leaves via the Na+K+ ATPase pump and the K+ and Cl- leaves via K+Cl- antiporter
4-Na+ and Cl- are reabsorbed in to the blood
Active Ca2+ reabsorption:
1-Ca2+ enters the cells of the DCT
2-Na+K+ ATPase pump, pumps Na+ out and K+ in
3-Na+Ca2+ pumps Na+ back in and Ca2+ out
4-Ca2+ ATPase pump also pumps Ca2+ out
5-Ca2+ can then be reabsorbed intot he blood
What is reabsorbed and secreted via the Principle cells of the DCT?
1-Na+K+ ATPase pump sodium out and K+ in
2-Due to there being less Na+ in the cell Na+ can now passively enter from the other side
3-ALDESTERONE regulates Na+ absorption by increasing the amountof Na+K+ ATPase basolaterally and Na+ channels apically
4-ADH regulates water reabsorption by increasing the amount of aquaporins in the cell membrane
How is acid basebalance maintained in the DCT and Collecting Duct
In Alpha INTERCALATED CELLS:
H+ ATPase pump to pump H+ out
In Beta INTERCALATED CELLS:
CL-HCO3- Antiporter
What happens via alpha/beta intercalated cells?
ALPHA- HCO3- reabsorption and H+ secretion
BETA- H+ reabsorption and HCO3- secretion
