Module 8 - Renal Flashcards
Exam 3
What are the big 3 function of the renal system?
Filtration, reabsorption, and secretion
Where does filtration occur?
Renal Corpuscle - Glomerular capillaries / Bowman’s capsule
Where does reabsorption occur?
PCT, Loops of Henle, DCT, collecting ducts
Anything that moves from the filtrate in Bowman’s Capsule back to the peritubular capillaries is _____
Reabsorption
Anything that moves from the peritubular capillaries and into the filtrate is called _____
Secretion
The kidneys are located at which ribs?
11th and 12th
Purpose of ureters is ____
transport urine from the kidneys to the bladder
The purpose of the bladder is to ____
store urine until voided from the body
____ carries urine from the bladder to the outside of the body
Urethra
The tubular parts of the nephron include what 3 structures?
PCT, Loop of Henle, DCT (collecting ducts somewhat)
What are the two types of nephrons?
Juxtacortical and juxtamedullary
Which type of nephron is more prevalent?
Juxtacortical
Which nephron type has longer loops of Henle?
Juxtamedullary
How does blood enter the kidneys?
Through the renal artery
The renal artery attaches to what structure?
Afferent arteriole
Where is the key site of filtration?
Glomerular capillaries
What are the two layers of Bowman’s capsule?
Visceral (inner)
Parietal (outer)
Why is the glomerulus so good for filtration?
Highly porous, very fenestrated; high permeability makes it easy to filter things
What materials can pass through glomerular fenestrations?
(1) water
(2) glucose
(3) amino acids
(4) electrolytes
(5) proteins
What materials should NOT pass through the glomerulus (ideally)?
Proteins
What prevents proteins from passing through the fenestrations of the glomerulus?
The negative charge of the visceral layer of the Bowman’s Capsule - will repel the protein.
What makes up the juxtaglomerular apparatus?
Juxtaglomerular cells, Macula densa
What are juxtaglomerular cells?
Specialized cells of the afferent arteriole that produce renin
What are Macula densa?
Specialized chemoreceptors on the epithelial cells of the DCT
What is the function of the Juxtaglomerular apparatus?
Regulation of blood into the glomerulus for filtration
What are the factors / variables of glomerular filtration?
Permeability
Surface Area
Net filtration pressure (NFP)
Why is surface area typically high in the nephrons?
Because of the capillaries that are wound / bunched up
What does GFR indicate?
Flow rate of filtrate / the volume of fluid filtered from the glomerulus that enters into Bowman’s Space
We have a relatively stable GFR of ____
125 mL per minute
What happens when the GFR is too high?
Lots of fluid, but not able to reabsorb enough.
What happens when GFR is too low?
We are unable to filter out metabolic waste and electrolytes out of the blood.
T/F: We should not find protein or blood in our urine.
True.
If there is blood or protein in the urine, then there is a problem with _____
filtration membrane
What are the 3 Starling forces that determine NFP?
(1) Hydrostatic pressure of the glomerular capillaries (PGC)
(2) Osmotic force d/t protein in plasma (piGC)
(3) Fluid pressure in Bowman’s Space (PBS)
What factor in NFP favors filtration?
PGC favors pressure to move everything OUT of the blood that needs to and INTO Bowman’s Capsule
What factors oppose filtration re: NFP?
PBS - repels the movement of fluid from the vascular space to Bowman’s space
piGC - more plasma proteins, means increase in osmotic pressure –> we will pull fluid back or repel the movement of fluid from the vascular space to Bowman’s Space
PGC means?
Hydrostatic pressure of glomerular capillaries
PBS means?
fluid pressure in Bowman’s Space
piGC means?
Osmotic force due to protein in plasma
What is the most important factor in net filtration pressure?
The amount of blood that goes into the afferent arteriole and into the glomerulus on a minute-by-minute basis
What is the equation for NFP?
NFP = PGC - PBS - piGC
What’s the equation for GFR?
Flow = change in pressure / resistance
What are the two ways we decrease GFR (arterioles)?
(1) Constrict afferent arteriole
(2) Dilate efferent arteriole
What are the two ways we increase GFR (arterioles)?
(1) Dilate afferent arteriole
(2) Constrict efferent arteriole
What is the key to resistance and GFR?
Radius of the arterioles
what are two forms of autoregulation that can alter PGC?
(1) Myogenic
(2) Tubuloglomerular feedback
What are two extrinsic ways to modify PGC?
(1) SNS
(2) Angiotensin II
What is the stimulus for the myogenic response?
Increase in GFR d/t afferent arteriole being stretched.
What is the stimulus for tubular glomerular feedback?
Increase in GFR through Macula Densa
How does renal artery stenosis impact hydrostatic pressure of glomerular capillaries (PGC)?
Decreases PGC because less blood –> less water –> less pressure
Where is angiotensinogen produced?
Liver
Name the key functions of angiotensin II (4)
(1) preferentially bind to the efferent arteriole, causing vasoconstriction
(2) increase aldosterone production from the adrenal cortex
(3) increase ADH / vasopressin production from the posterior pituitary
(4) increase systemic vasoconstriction
What is one consequence / downside of angiotensin II?
It can contribute to systemic hypertension
Where does the majority of reabsorption occur in the body?
PCT
Where does fine tuning of reabsorption occur?
DCT and collecting ducts
Hormonal controls target which areas for reabsorption?
DCT and collecting ducts
Name the general pathway of reabsorption through the PCT
Tubular lumen - tubular epithelial cells apical - tubular epithelial cells basolateral - interstitial fluid - peritubular capillaries
Which two solutes are completely reabsorbed in the PCT?
Glucose and amino acids
What does isosmotic reabsorption mean with regards to the PCT?
It means that there is no change in solute concentration at any point throughout the reabsorption process (starts and ends with 300 mOsm)
What causes movement of materials from the interstitium to the peritubular capillaries?
Bulk Flow
The descending loops of Henle are ____ to water and _____ to solute
permeable, impermeable
The ascending loops of Henle are ____ to solute and _____ to water
permeable, impermeable
The medullary interstitium is (1) hypotonic, (2) hypertonic, (3) isotonic?
hypertonic
Why is reabsorption at the ascending loop of Henle important?
It helps to create an osmotic gradient for water reabsorption at the descending loop of Henle
What is the role of the Na/K/2Cl Symporter?
Chemoreceptor and symport protein that moves solutes across the apical membrane and into ICF
What is the driving force for water being reabsorbed through the Descending Loop of Henle?
Keeping the medullary interstitium hypertonic
What is countercurrent exchange?
The difference in flow down through the descending limb and the upward flow back into the cortex via the ascending loop of Henle
What type of hormone is aldosterone?
Steroid
Where does aldosterone diffuse through?
Epithelial cells called Principle Cells
What are Principle Cells?
Specialized epithelial cells of the DCT and collecting ducts
Aldosterone affects _____ because it’s a steroid hormone
gene transcription
What is one major stimulus for aldosterone release?
Elevated extracellular K+ levels
Vasopressin / ADH stimulates the translocation of _____ on the ____ membrane of the ____ convoluted tubule and _____ ____.
AQP-2, apical, distal, collecting ducts
T/F: Vasopressin / ADH translocates AQP-3 and AQP-4 on the basolateral membrane.
False. AQPs on the basolateral membrane of the DCT and collecting ducts are not under hormonal control
Where does renal regulation of Calcium and Phosphate reabsorption occur?
DCT
Renal regulation of Calcium and Phosphate reabsorption is controlled by what hormone?
parathyroid hormone
How does PTH increase Ca reabsorption?
Through translocation of Ca channels on the apical membrane
What does renal clearance (RC) mean?
The volume of plasma that is cleared of a substance in one minute (mL/min)
What is the equation for renal clearance (RC)?
RC = UV/P
U - concentration of the substance in the urine (mg/mL)
V - flow rate of urine formation (mL/min)
P - concentration of the substance found in the plasma (mg/mL)
If serum creatinine levels are increasing, what does this tell us?
There is some type of damage at the glomerulus (filtration process)
As serum creatinine levels increase, what happens to eGFR?
eGFR will decrease
Name three causes of a high serum creatinine level.
(1) reduced filtration capacity
(2) high protein diet
(3) high muscle mass
Name three causes of low serum creatinine levels
(1) being elderly and having reduced muscle mass
(2) pregnancy, which can increase filtration
(3) pregnancy and hypovolemia
If we find proteins in the urine, where does this indicate damage?
To the visceral layer of Bowman’s Capsule
What does Blood Urea Nitrogen (BUN) indicate?
The amount of urea nitrogen found in the blood
What does a high BUN indicate about filtration?
Inability to filter urea out of the blood and excrete in the urine
What is the main function of a loop diuretic?
To block the Na/K/2Cl symporter
Where is the Na/K/2Cl symporter found?
The macula densa of the thick ascending loop of Henle
How do loop diuretics generally work?
They block the reabsorption of ions, which means you will also reabsorb less water because it does not have as many ions to follow / dilute.
Which diuretic is considered the most potent?
Loop
Why is the loop diuretic considered a more potent diuretic than others?
because it affects an area where you naturally see more reabsorption of NaCl
Name a potential side effect of loop diuretics
Hypokalemia
What is the function of thiazide diuretics?
Inhibit Na/Cl symporter
How do thiazide diuretics generally work?
If you can’t reabsorb NaCl, you can’t reabsorb water at the distal part of the nephron –> result: pee out Na, Cl, and water
What is the function of aldosterone blockers?
Block the effects of aldosterone on Principle Cells of the DCT
What happens when you block the effects of aldosterone on principle cells?
Fewer Na/K leak channels on the apical membrane and fewer Na/K ATPase on the basolateral membrane –> less Na and water reabsorbed
Aldosterone blockers are also called what?
Potassium-sparing diuretics
