the genitourinary system Flashcards
what are 5 functions of the kidney
1) excretion of metabolic products eg urea, uric acid and creatinine
2) excretion of foreign substances eg drugs
3) homeostasis of body fluids, electrolytes and acid-base balance
4) regulates blood pressure
5) secreted hormones eg erythropoietin and renin
what does erythropoietin do
protects RBCs against destruction
stimulates stem cells of the bone marrow to increase production of RBCs
what does renin do
it is released in response to low blood pressure or Na+ depletion
converts angiotensinogen to angiotensin 1
where does renal blood supply to the kidneys come from
peritubular capillaries (reabsorption - max SA, secretion and oxygen and nutrients for nephron function) tiny blood vessels in the kidney that filter and reabsorb
what is the pathway for blood travelling in the kidney
renal artery segmental artery interlobar artery arcuate artery interlobular artery afferent arteriole glomerular capillaries efferent arteriole peritubular capillaries interlobular vein arcuate vein interlobar vein renal vein
what is the function of detrusor muscle
contracts to build pressure in the urinary bladder to support urination
during urination this contracts
what is the function of the trigone
stretching of this triangular region to its limit signals the brain about need for urination
what is the function of the internal sphincter
Internal sphincter = Involuntary control
involuntary control to prevent urination - smooth muscle contracts
what is the function of the external sphincter
voluntary control to prevent urination (surrounds urethra - striated muscle)
what is the function of the bubourethral gland
produces thick lubricant which is added to watery semen to promote sperm survival
what is a nephron
a functional unit of the kidney
what is the structure for a nephron (chronological)
afferent arteriole
glomerulus - has capillaries
bowmans capsule
efferent arteriole
proximal convoluted tubule (epithelial rich in mitochondria - transport happens here)
thin descending loop of Henle
thin ascending loop of Henle (epithelial = low density of mitochondria - passive)
thick ascending loop of Henle (epithelial = rich in mitochondria - active reabsorption salt)
distal convoluted tubule (epithelial rich in mitochondia - active)
collecting duct (principal cells = low density mitochondria and intercalated cells = rich AT)
what is the ratio for superficial to juxtamedullary nephrons
~10:1
what is the juxtaglomerular apparatus
specialised structure formed by distal convoluted tubule and glomerular afferent arteriole
what are the constituents of the juxtaglomerular apparatus
macula densa (specialised cells lining the wall of the DCT) extraglomerular mesangial cells juxtaglomerular cells (afferent arteriole) - produce renin (conversion of angiotensinogen to angiotensin 1 - controls aldosterone production)
what is the function of the juxtaglomerular apparatus
GFR regulation through tubuloglomerular feedback mechanism
renin secretion for regulating blood pressure
what arteriole branches out to form peritubular capillaries surrounding the nephron
efferent arteriole
pathway for bringing in blood
afferent arteriole > glomerular capillaries > efferent arteriole > peritubular capillaries surrounding nephron
what are the 4 main processes that happen in the nephron
1) glomerular filtration (into bowmans capsule)
2) reabsorption (substances are reabsorbed - move from tubular filtrate into blood)
3) secretion (substances move from blood into filtrate)
4) excretion (through urine)
how is urine produced
different substances undergo a different combination of renal processes to produce urine
what is the passive process of glomerular filtration
fluid is “driven” through the semipermeable glomerular capillaries into the Bowmans capsule space by the hydrostatic pressure of the heart
hydrostatic = pushing
describe the filtration barrier
size and charge dependent
highly permeable to fluids and small solutes
impermeable to cells and proteins (blood cells and proteins)
what is the direction of filtration
glomerulus to bowmans capsule
what are the spaces between podocytes called
slits
made up of finger like projections creating very small spaces between them - only water and small solutes can pass through
what is the charge of the molecules the blood is mostly composed of
negatively charged molecules
what is hydrostatic pressure
pushing force
fluid exerts this pressure (outward pressure)
solute and fluid molecules are shoved out
what is oncotic pressure
pulling force
solute (eg proteins) exerts this pressure (inwards pressure)
fluid molecules drawn in across a semipermeable membrane
in the IF, in which direction does the hydrostatic and oncotic pressure go
IF hydrostatic goes into blood vessel
IF oncotic goes out of vessel
what is the equation for net ultrafiltration pressure (Puf)
Puf = HPgc - HPbw - 3.14159265359gc
HPgc = hydrostatic pressure in glomerular capillaries (pushing out) HPbw = hydrostatic pressure in bowmans capsule 3.14159265359gc = oncotic pressure of plasma proteins in glomerular capillaries
what is the definition for GFR
the amount of fluid filtered from the glomeruli into the bowmans capsule per unit time (mL/min)
sum of the filtration rate of all functioning nephrons - both kidneys
what is the equation for GFR
GFR = Puf x Kf
where Kf is an ultrafiltration coefficient (membrane permeability and SA available for filtration) - any changes in filtration forces or Kf = GFR imbalances
what is the GFR range for healthy males and females
males = 90-140 mL/min females = 80-125 mL/min
what does a fall in GFR suggest
it is a cardinal feature of a renal disease - with a build up of excretory products in the plasma
describe myogenic regulation of GFR if arterial pressure increases
arterial pressure increases > afferent arteriole stretches > smooth muscles lining the arteriole contracts > afferent arteriole contracts > vessel resistance rises > blood flow reduces > filtration decreases to stabilise GFR
how does tubulo-glomerular feedback mechanism regulate an increase in GFR
increase in GFR increased NaCl in loop of Henle change detected by macula densa cells increased ATP and adenosine discharged to afferent arteriole afferent arteriole constricts GFR stabilises
how does tubulo-glomerular feedback mechanism regulate an decrease in GFR
decrease in GFR decreased NaCl in loop of Henle change detected by macula densa cells decreased ATP and adenosine discharged to afferent arteriole afferent arteriole dilates GFR stabilises
what is renal clearance
the number of litres of plasma that are completely cleared of the substance per unit time
(only concerned with excretory roles played in the kidneys ie rate of removal of a substance X from the blood and excretion through urine)
each substance goes through a unique filtration
what is the equation for renal clearance
C = U x V/P
U = conc of substance in urine V = rate of urine production P = conc of substance in plasma
for eg if C = 50 mL/min this means that 50 mL of plasma has been cleared of that substance per minute
how can we practically determine GFR
if a molecule is freely filtered (and neither reabsorbed nor secreted in the nephron then the amount filtered = excreted - thus GFR can be measured by measuring renal clearance of this molecule
what is the ideal molecule and its properties
inulin
a plant polysaccharide freely filtered neither reabsorbed nor secreted not toxic measurable in urine and plasma however not found in mammals and needs to be transfused
what molecule is most commonly used as a measure of GFR
creatinine
waste product from creatin in muscle metabolism
amount released is fairly constant
if renal function is stable, then creatinine amount in urine is stable
low creatinine clearance or high plasma creatinine may indicate renal failure
what does freely filtered mean
conc of x in plasma = conc of x in glomerular filtrate
a freely filtered substance may be absorbed or secreted later on
freely filtered refers to the glomerulus - capillaries
what is renal plasma flow
volume of blood arriving at the kidney per unit time
how do you work out renal plasma flow
if the total amount of a molecule entering the kidney equals the amount excreted, then the renal clearance of this molecule equals the renal plasma flow (RPF)
what is PAH
para aminohippurate
all PAH is removed from the plasma passing through the kidney through filtration and secretion
what is the filtration fraction and the range
the ratio of the amount of plasma which is filtered, and which arrives via the afferent arteriole
range = 0.15-0.2
a value of 0.15 suggests that 15% of the plasma has been filtered
what does renal clearance equal to if the total amount of that substance entering the kidney is the total amount excreted
renal clearance = renal plasma flow
what is the equation for filtration fraction
FF = GFR/RPF
what happens when there is an electrical gradient difference
charged ions are able to travel to the side of the membrane which is of the opposite charge
what are the 3 types of active transport
primary active
endocytosis
secondary active
what is primary active transport
there is use of ATP straight away - eg sodium potassium pump found in nephron - uses 1 ATP to transport ions
what is endocytosis
small proteins are reabsorbed this way in the proximal convoluted tubule
what is secondary active transport
2 or more ions are coupled, one ion is moving downhill (high to low electrochemical gradient) providing energy for uphill movement (low to high) of another molecule
when both molecules travel in the same direction
symport
when molecules travel in opposite directions
antiport
what cells line the nephron tube
epithelial cells
what is the basolateral cell membrane
side facing the blood
what is the apical cell membrane
facing tubular filtrate
what is a tight junction
some substances are able to be transported from filtrate into blood from paracellular (between cells) pathways
what is a transcellular pathway
transport through a cell
eg water through aquaporins
how is sodium reabsorbed
Na/K ATPase pump - using 1 ATP to transport sodium out from cell into blood
is there a low conc of Na+ inside the cell? and if there is, what does it mean :)
yea lmao
sodium from tubular fluid travels downhill > low conc created from pump created the downhill gradient for Na+ travelling from tubular fluid into cell
when this is coupled with other transporters it provides energy for other molecules to move uphill
what happens in the early proximal convoluted tubule
region of high activity
sodium and bicarbonate reabsorption
- Na/K ATPase pump - pumps out Na+ of the cell - low conc in cell
- CO2 from tubular fluids enter by diffusion - by carbonic anhydrase converts CO2 and H2O > H+ and HCO3-
- H+ is pumped out through sodium hydrogen antiporter - sodium moving downhill and proton uphill (secondary AT) into tubular fluid
- bicarbonate is transported into blood by symporter - body wants to keep bicarbonate for acid balance
- angiotensin 2 regulates Na+ reabsorption by increasing Na+H+ antiporters
how is glucose reabsorbed in the early proximal convoluted tubule
wants to keep 100% glucose
ATPase pump - low conc of sodium inside cell - travels downhill gradient out of cell
providing energy for uphill transport of glucose by symptorter (SGLT2) - glucose is reabsorbed by glucose transporter
what are the substances reabsorbed in the early proximal convoluted tubule and their %
67% Na+ 67% Cl- 80% HCO3- 100% glucose 667% water 100% amino acids
what are the substances secreted from the early proximal convoluted tubule
drugs ammonia bile salts prostaglandins vitamins (folate and ascorbate)
what reabsorption happens at the Loop of Henle
fluid enters at ascending region - no water reabsorbed but a lot of salt is reabsorbed - passively in the thin region and actively in the thick region
- when a lot of salt = reabsorbed in the medullary region > increases osmolarity of medulla > helps passive reabsorption of water by simple osmosis
- high osmolarity surrounding the loop of henle
water = reabsorbed in the descending side - when filtrate reaches middle loop region = hyperosmotic and because of high salt being reabsorbed in ascending side - by the time it exits the loop - fluid becomes hypoosmotic
how does salt reabsorption actively occur in the thick ascending region
Na+/K+/Cl- symporter transports K+/Cl-/Na+ into the cell and Cl- and K+ are reabsorbed by K+/Cl- symporter
what are the substances reabsorbed and their %
25% Na+
25% Cl-
15% water
how does reabsorption occur in the early distal convoluted tubule
sodium and chloride reabsorption
Na+/K+ ATPase pump has created a sparsity of Na inside cell > allowing NA+/Cl- to be transported into the cell via symporter
- reabsorbed using K+/Cl- symporter
water channels are absent in the early region
how does active Ca2+ reabsorption happen in the early distal convoluted tubule
CA enters cell through calcium channels and are reabsorbed by
Na+/Ca2+ antiporter and Ca2+ ATPase pump
how does reabsorption happen in the late? DCT and collecting duct
in principal cells - Na+ reabsorption and K+ secretion through channels
important during hyperkalemia
aldosterone regulates Na+ absorption by increasing apical Na+ channels and basolateral Na+/K+ ATPase pumps
ADH regulates water reabsorption by increasing apical aquaporins - basolateral aquaporins almost always present - apical aquaporins are inserted as needed
what do intercalated cells do
maintaining acid base balance
how many intercalated cell types are there and what are they
there are 2 types
alpha and beta intercalated cells
what do alpha intercalated cells do
H+ secretion and HCO3- reabsorption
what do beta intercalated cells do
H+ reabsorption and HCO3- secretion
what happens in case of alkalosis
beta cells become more active to bring back homeostatic conditions
