Renal I Flashcards
Historically, what are the 4 characteristics of urine that have been used as an indicator of health and functioning of the body?
Colour, clarity, odor, and taste
What is the cause of Blackwater fever?
Severe hemolysis, seen by black urine
What is the most prevalent pathology that used to be determined based on the taste of urine?
Diabetes
What is the overall function of the kidneys?
Homeostatic regulation of water and ion content of the blood (salt-water balance or fluid-electrolyte balance)
Here are the 6 more specific functions of the kidneys:
1. Regulation of extracellular ____ ____ and ____ ______
2. Regulation of ______: kidneys + behaviour
3. Maintenance of ___ balance: ___, ___, and ____
4. Homeostatic regulation of ___
5. Excretion of _____ : metabolic and xenobiotics
6. Production of _______: erythropoietin, renin
- fluid volume, blood pressure
- osmolarity
- ion, Na+, K+, Ca2+
- pH
- wastes
- hormones
You can lose up to ___ kidney function before affecting homeostasis
¾
What are xenobiotics?
Not naturally occurring in the body (preservatives, medications, etc)
___-___% of CO is directed towards the kidneys
20-25
What are the 4 main components of the urinary system?
Kidney, ureter, urinary bladder, urethra
The kidneys are located ________ at the level of the lower ribs
retroperitoneally
_______ are the functional unit of the kidneys
Nephrons
Of the nephrons in the kidney, 80% are _____ nephrons, and 20% are _______ nephrons
cortical, juxtamedullary
Cortical nephrons are located in the _______ while juxtamedullary nephrons are located within the ______
cortex, medulla
______ _______ : important for maintaining normal functioning within the nephrons
Juxtaglomerular apparatus
The region where the tubule passes the starting point again is the _______ ______
juxtaglomerular apparatus
The _____ contains all Bowman’s capsules, proximal and distal tubules. The ______ contains loops of Henle and collecting ducts
cortex, medulla
Kidneys are a ____ portal system
3rd
In juxtamedullary nephrons, they have a different name for the peritubular capillaries, they call it the _____ ____. This is specifically the portion of the capillaries that extends along the very long loop
vasa recta
Order these components according to “vascular components:”
efferent arterioles
afferent arterioles
renal vein
renal artery
peritubular capillaries
glomerulus (capillaries)
Renal artery ➞ afferent arterioles ➞ glomerulus (capillaries) ➞ efferent arterioles ➞ peritubular capillaries ➞ renal vein
_______ ____ take blood to the cortex
Renal arteries
One nephron has ___ arterioles and ___ sets of capillaries that form a portal system
2, 2
What are the 4 main steps of the kidney?
Filtration, reabsorption, secretion, and excretion
Where is the Bowman’s capsule?
The bulb portion
_______ _____: where the glomerulus makes contact with the nephron itself
Bowman’s capsule
The loop of Henle is divided into 2 sections: ?
ascending limb and descending limb
Order these components according to “tubular components:”
collecting duct
Bowman’s Capsule
descending loop of Henle
distal tubule
proximal tubule
ascending loop of Henle
Bowman’s Capsule ➞ proximal tubule ➞ descending loop of Henle ➞ ascending loop of Henle ➞ distal tubule ➞ collecting duct
The tubular component of the kidneys have a single layer of ______ cells
epithelial
________ : movement from blood to lumen in bulk flow
Filtration
______: from the blood to the lumen of the tubule
Secretion
________ : from the lumen into the blood
Reabsorption
_______ : from the lumen to outside the body
Excretion
What are the 3 processes that occur in the nephron?
Glomerular filtration, Tubular secretion, Tubular reabsorption
Approximately ___L of plasma is filtered at the glomeruli each day, >___% is reabsorbed, ~___L/day is excreted
180, 99, 1.5
~70% of reabsorption occurs in the ________ _____
proximal tubule
? : responsible for creating dilute urine
Loop of Henle
Distal tubule and collecting duct finely regulate salt and water balance under the control of _______
hormones
Glomerulus is generally ___-osmotic
iso
Reabsorption at the proximal tubule is ___-osmotic
iso
In the descending limb, water is being reabsorbed (___-osmotic)
hyper
In the ascending limb, way more solute to water is being reabsorbed (___-osmotic)
hypo
Solution entering the distal tubule is ___-osmotic
hypo
Final volume and osmolarity of urine excreted ______
varies
True or False: not all substances in plasma undergo filtration and/or reabsorption and/or secretion
true
How would you calculate the amount excreted?
Amount filtered - amount reabsorbed + amount secreted = amount excreted
A person filters 720 millimoles of K+ in a day and secretes 43 millimoles. She excretes 79 millimoles in her urine. What happened to the rest of the K+ and how much was it?
Filtered:720
Secreted: 43
Excreted: 79
Reabsorbed:?
720mmol-amount reabsorbed+43mmol=79mmol
Amount reabsorbed=684mmol
In filtration, RBC’s and plasma proteins remain in the _____, while plasma and dissolved solutes make up the ______
blood, filtrate
Of all the plasma that enters into the Bowman’s capsule, only ___% is filtered (filtration fraction), ___% continues on to the peritubular capillaries
20, 80
If 120mL of plasma filter each minute and the filtration fraction is 20%, what is the daily renal plasma flow?
Cardiac output is 5L/min
Kidneys receive ~20% of CO (1 L/min)
60% of blood is plasma (.6L/min)
20% of the plasma is filtered (0.12L/min)
0.12L/min x 60min/hour x 24 hour/day
~173 (180)L plasma filtered/day
125ml/min
_____ _____ : bowman’s capsule and the glomerular capillary
Renal corpuscle
______ : specialized epithetical cells that are found within the renal corpuscle that wrap around the glomerular capillary
Podocyte
________ : found in the middle and around the glomerular capillary tuft, and they can influence filtration itself by changing the amount of surface area that’s available for filtration. They are contractile cells
Mesangial
The renal corpuscle has a ______ filtration barrier
triple
What are the 3 components of the triple filtration barrier?
- capillary endothelial cells (fenestrated)
- basal lamina (extracellular matrix)
- podocyte endfeet
Podocyte foot processes surround each capillary, leaving _____ through which filtration takes place. Mesangial cells between the capillaries ______ to alter blood flow
slits, contract
Three pressures govern filtration from glomerular capillaries into the renal tubules: ?
Hydrostatic, colloid osmotic (oncotic), and Bowman’s capsule hydrostatic
______ pressure: of blood in the glomerular capillaries favors filtration (~55 mm Hg)
Hydrostatic
? pressure: of the blood is the pressure gradient due to the presence of plasma proteins and opposes filtration (~30 mm Hg)
Colloid osmotic (oncotic)
? pressure: the fluid that’s already been filtered that’s sitting in the nephron, opposes filtration (~15 mm Hg)
Bowman’s capsule hydrostatic
? : the volume of fluid that filters from the glomerular capillaries into the Bowman’s capsules per unit time
Glomerular filtration rate (GFR)
Glomerular filtration rate is normally ~___ml/min or ___L/day
125, 180
Our plasma volume is about __L meaning the kidneys filter our entire plasma volume approximately ___ times per day. If it was not reabsorbed we would run out of plasma in about 24 minutes
3, 60
Two factors influence GFR: ?
Net filtration pressure, and filtration coefficient
What determined filtration coefficient?
Slit surface area, and filtration barrier permeability
Slit surface area = ?
glomerular capillary surface area
GFR is relatively constant over a _____ range of blood pressures
wide
GFR is primarily regulated by ?
renal arterioles (afferent and efferent)
Autoregulation maintains a nearly constant GFR when mean arterial blood pressure is between ___-___ mmHg
80-180
_______ of the afferent arteriole increases resistance and decreases renal blood flow, capillary blood pressure (Ph), and GFR
Vasoconstriction
Renal blood flow is dependent on overall _________, which is determined by the resistance in both the _______ and ______ arterioles
resistance, afferent, efferent
What happens to capillary blood pressure, GFR, and RBF when the afferent arteriole dilates?
If afferent arteriole resistance decreased and efferent stayed the same then RBF would increase, hydrostatic pressure increase and GFR increase
Regulation mainly occurs at the ______ arterioles
afferent
True or False: RBF and GFR are always directly proportional?
False
What is the resulting GFR and RBF if: the afferent arteriole constricts?
⬇ GFR
⬇ RBF
What is the resulting GFR and RBF if: the efferent arteriole constricts?
↑ GFR
⬇ RBF
What is the resulting GFR and RBF if: the afferent arteriole dilates?
↑ GFR
↑ RBF
What is the resulting GFR and RBF if: the efferent arteriole dilates?
⬇ GFR
↑ RBF
Two auto-regulatory mechanisms maintain a relatively stable GFR in the face of normal blood pressure fluctuations: ?
- Myogenic response of the afferent arterioles (myogenic autoregulation)
- Tubuloglomerular feedback
What is the main purpose of the auto-regulatory mechanisms maintaining a relatively stable GFR?
To protect the filtration barriers from high blood pressures that would cause damage.
? : contraction in response to stretch of the vascular smooth muscle
Myogenic response of the afferent arterioles (myogenic autoregulation):
Order these statements according to “GFR regulation:”
1. Depolarization
2. ↑ Vessel wall tension and VSMC stretch
3. L-type Ca2+ channel activation and Ca2+ entry
4. VSMC contraction
5. ↑ Intraluminal pressure
6. Mechano-dependent event
5, 2, 6, 1, 3, 4
________ ______: local control pathway in which fluid flow through the tubule portion of the nephron influences GFR
Tubuloglomerular feedback
What are the two important pieces of the juxtaglomerular apparatus?
Macula dense cells, and granular cells
? : the specialized epithelial cells that line the wall of the ascending limb of Henle that’s coming into close contact with afferent and efferent arterioles. The interaction and feedback is mainly controlled by these cells, and can influence afferent arterioles. They release chemical substances that will influence the afferent arterioles and can help to regulate GFR
Macula densa cell
______ ___ : specialized smooth muscle cells, help maintain blood pressure, secrete renin
Granular cells
Macula densa cells help regulate GFR by sensing the amount of fluid and solute that is flowing through the latter portion of the ______
nephron
Order these statements according to “tubuloglomerular feedback helps GFR autoregulation:”
1. Flow past macula dense increases
2. Resistance in afferent arteriole increases
3. GFR increases
4. GFR decreases
5. Paracrine from macula dense to afferent arteriole
6. Flow through the tubule increases
7. Hydrostatic pressure in glomerulus decreases
8. Afferent arteriole constricts
3, 6, 1, 5, 8, 2, 7, 4
_______ neurons also influence GFR
Sympathetic
Integrating centers outside the kidneys are capable of overriding the local control mechanisms by _______ ______ or _______ ______
altering resistance, filtration coefficient
Sympathetic neurons release norepinephrine that acts on α1-adrenergic receptors on both afferent and efferent arterioles leading to __________
vasoconstriction
Sympathetic activation only really alters GFR when there is a sharp rapid ____ in blood pressure i.e. hemorrhage or severe dehydration when water needs to be conserved
drop
Afferent and efferent arterioles are innervated by _______ neurons
sympathetic
Two important hormones that modulate arteriole resistance are _________ ___, which is a potent vasoconstrictor and __________, which act as vasodilators
angiotensin II, prostaglandins
These hormones are also believed to alter the ________ ________ by acting on podocytes and/or mesangial cells
filtration coefficient,
Modulation of podocytes changes the ____ of the filtration slits altering ________ for filtration; contraction of mesangial cells alters capillary ______ ___ available for filtration
size, permeability, surface area
Regulated reabsorption allows kidneys to _________ return ions and water to the plasma to maintain homeostasis
selectively
Why bother filtering 180L if only excreting 1%, why not just filter and excrete the 1% that needs to be eliminated?
Many foreign substances are filtered into the tubules but not reabsorbed, this is a rapid way to remove unwanted materials
Frequent filtration of ions and water into the tubules simplifies regulation and allows it to occur rapidly.
True or False: reabsorption is active?
False, reabsorption may be active or passive
Reabsorption involves two types of transport: ?
Transepithelial (transcellular)
Paracellular transport
__________ transport: substances cross the apical and basolateral membranes of the tubule cells to enter into the ECF
Transepithelial (transcellular)
__________ transport: substances pass through the cell to cell junctions between two adjacent tubule cells.
Paracellular
The following paragraph describes reabsorption:
____ is actively pumped into the interstitial fluid with the use of ATP, which creates a ______ charged interstitial fluid in comparison to the filtrate, which will draw ______ (chloride primarily) to the fluid, which creates an _______ gradient, now we have a solute concentration gradient between the extracellular fluid and the _____
Sodium, positively, anions, osmotic, filtrate
_______ Na+ transport is always active transport via Na-K-ATPase
Basolateral
Secondary active transport: _______ with Na+
symport
What are 2 other reabsorption mechanisms?
Passive, and endocytosis
The majority of substances transported in the nephron use _______ _____
membrane proteins
The amount of solute that can be transported depends on the ______ of membrane proteins available
number
________: the maximum rate of transport that occurs when all available carriers are occupied
Saturation
The transport rate at saturation is the transport _______
maximum
_____ ______: is the plasma concentration of a solute when it first begins to appear in the urine, it occurs at the transport maximum
Renal threshold
How would you calculate the Amount Excreted?
Amount filtered - amount reabsorbed + amount secreted
Glucose appearing in your urine is known as ?
glucosuria or glycosuria
Gluco/glycosuria occurs with _______ blood glucose. It is a rare genetic disorder with reduced _______
elevated, transporters
Peritubular capillary pressures favors _______
reabsorption
Hydrostatic pressure at glomerulus is 55 mm Hg but after fluid is removed from the blood and resistance is encountered the hydrostatic pressure drops to ~___ mm Hg in the _______ ______
10, peritubular capillaries
_______ proteins are not filtered, the oncotic pressure remains at 30 mm Hg as blood travels into the peritubular capillaries, which now ______ the hydrostatic pressure which means fluids and solutes are drawn into the peritubular capillaries by ____ ____
Plasma, exceeds, bulk flow
The net pressure is 20 mm Hg driving fluid and solutes from the interstitial space back into the _______
capillaries
Secretion depends mainly on ?
membrane transport proteins
Secretion is an _____ process requiring the movement of substances against their concentration gradients
active
Homeostatic regulation of K+ and H+ (distal) and organic compounds (medications, food additives in proximal region) by _______ is important
secretion
Secretion enhances the _______ of a substance: if a substance is filtered and not reabsorbed, plus it is secreted then excretion of the substance will be very ____
excretion, high
The secretion of organic solutes, which use a multi-step (tertiary) active transport process:
First process: Hinges on active ______ transport, creating a very low concentration within the cell due to the Na-K ATPase pump on the ________ membrane.
Secondary process: moving _______ (used here – aKG) into the cell
Third process: using the created concentration gradient for dicarboxylates to move organic _____ across the basolateral layer
- sodium, basolateral
- dicarboxylates
- anions
By the time fluid reaches the end of the nephron it bears ______ resemblance to the filtrate
little
______, ______ _____, and useful ________ are reabsorbed
Glucose, amino acids, metabolites
Renal handling of a substance and GFR are often of clinical interest:
_____ as an indicator of overall kidney function
Renal _______/_______ information on new drugs is necessary
GFR, handling, clearance
How do we directly look at filtration, reabsorption and secretion at the level of an individual nephron?
Experimentally
Indirect methods using only analysis of urine and blood
? : a pipette for collection of fluid is inserted into a superficially located tubule in the kidney, in this case, the proximal tubule
Free-flow micropuncture
? : a droplet of oil is pipetted into the tubule through one barrel of a double-barreled pipette, and split by an aqueous solution introduced through the second barrel. Later, a second pipette with a single barrel samples the fluid that the tubule has modified
Stopped-flow microperfusion
? : the tubule undergoes continuous perfusion through a pipette, as does the adjacent capillary. A downstream pipette continuously collects the fluid. Voltage measurements are taken from either the tubule lumen or cell interior
Continuous microperfusion
? : one may isolate a tubule from any segment of any nephron. The lumen of the tubule, as well as its basolateral surface, are continuously perfused. While another pipette collects the fluid
Isolated perfused tubule
_______ is a noninvasive way to measure GFR
Clearance
________: of a solute is the rate at which a solute disappears from the body by excretion or metabolism
Clearance
How to calculate Clearance of x?
X = (excretion rate of x (mg/min)) / ([x]plasma (mg/mL plasma)), it gives mL/min
For a solute that is cleared only by renal excretion, clearance is expressed as ?. Looks at blood cleared of solute rather than amount excreted.
the volume of plasma passing through the kidneys that has been totally cleared of that solute in a given period of time (usually a minute)
Eg. 1 mg of solute Z in 100 ml of plasma, and you found 0.5 mg of Z appearing in the urine/ min, what is the clearance of Z?
Clearance of Z= (0.5mg/min) / (1mg/100ml) = 50 ml/min
The kidneys remove all of solute Z in a 50ml plasma sample in one minute
To most accurately calculate GFR we need to look at the clearance of a substance that is freely filtered and neither ________ or _______.
reabsorbed, secreted
________ clearance is also used as a measure of GFR
Creatinine
Clinicians commonly use creatinine clearance as a measure of GFR and indicator of renal function: freely filtered by the glomerulus, but it is _______ in very small amounts as well
secreted
Creatinine clearance slightly _________ GFR
overestimates
Example: a person has a plasma creatinine concentration of 0.01mg/ml and an excretion rate of 1.25mg/min (urine samples over 24hrs), what is the clearance?
(1.25mg/min) / (0.01mg/mL) = 125mL/min
Example: if plasma creatine = 1.8mg/100mL plasma, urine creatine = 1.5mg/mL urine, and urine volume is 1100mL in 24 hours, what is the creatine clearance? What is GFR?
Plasma creatinine: 1.8mg/100ml= 0.018mg/ml
Excretion rate: 1.5mg/ml x 1100ml in 24 hours = 1650mg/24 hrs = 1650mg/1440mins = 1.15 mg/min
GFR = (1.15 mg/min) / (0.018mg/ml) = 63.9 ml/min
Clearance helps to determine net _____ ______
renal handling
Once we know an individuals GFR we can look at their kidneys net handling of any solute by measuring the ?
solutes plasma concentration and excretion rate
How would you calculate the Filtered load of X?
Filtered load of X = [X]plasma x GFR
By comparing the filtered load (assuming the substance is filtered freely) with its excretion rate, we can tell ?
how the nephron handled that substance
If less of a substance appears in the urine than was filtered, what occurred?
net reabsorption
If more of a substance appears in urine than was filtered, what occurred?
net secretion
If GRF = Clearance:
Filtered ? excreted
What is the renal handling?
Filtered = excreted
Filtered, not reabsorbed, not secreted
If GRF > Clearance:
Filtered ? excreted
What is the renal handling?
Filtered > excreted
Filtered and net reabsorption
If GRF < Clearance:
Filtered ? excreted
What is the renal handling?
Filtered < excreted
Filtered and net secretion
