an intro to the kidney (mini learning) Flashcards
Where in the kidney does blood filtration occur ?
Renal cortex
the boarder around the renal pyramids
In which layer of the kidney are renal pyramids found ?
medullary layer
Roughly how many renal pyramids does each kidney have ?
8-10 is average
could be 7-18
Where does the urine drain into from the renal pyramids ?
minor calyx
Where does urine drain into after the minor calyx ?
major calyx
Where does the urine accumulate after leaving the major calyx ?
renal pelvis
Where does the urine go after the renal pelvis ?
leaves the kidney, via the ureter, to be stored in the bladder
What are the main functions of the kidney ?
- maintain ECFV (extracellular fluid volume)
- maintaining acid-base balance
- excretion of metabolic waste (urea, creatinine)
- endocrine secretion
How does the kidney maintain ECFV ?
regulates Na in the blood, causing osmotic action to follow
Which endocrine systems does the kidney regulate ?
- renin-angiotensin system
- erythropoietin production
- vitamin D activation
What effect does the number of nephrons in a persons kidney have on blood pressure ?
fewer nephrons = higher hypertension risk
Where does selective reabsorption of glomerular filtrate occur in the kidneys ?
- Proximal convoluted tubule
- Distal convoluted tubule
Where does ultrafiltration of glomerular filtrate occur in the kidneys ?
bowman’s capsule
Which arteriole of the glomerulus has a wider diameter ?
afferent in-coming arteriole
Which molecules are forced out of the glomerulus into the bowman’s capsule ?
small molecules
- water
- glucose
- urea
- ions
Which molecules do not leave the glomerulus in ultrafiltration ?
- proteins
- blood cells
What type of cells form the inner epithelial layer of the bowman’s capsule
podocytes
Where is 85% of glomerular filtrate reabsorbed ?
proximal convoluted tubule
What % of the glomerular filtrate is reabsorbed in the proximal convoluted tubule ?
85%
Does the PCT epithelium have microvilli or not ?
yes, there are microvilli
Name all the arterial divisions within the kidney from the renal artery to the afferent arteriole…
- renal artery
- segmental arteries
- interlobar arteries
- arcuate arteries
- interlobular arteries
- afferent arterioles
Which arteries travel between the medullary pyramids ?
interlobar arteries
Which arteries travel along the top of the medullary pyramids ?
arcuate arteries
Which arteries project into the renal cortex, alongside the nephrons ?
interlobular arteries
Which arteries give off the afferent arterioles ?
interlobular arteries
What is the capillary network called that surrounds the nephron ?
vasa recta
Does the vasa recta drain into the renal artery or vein system ?
vein system to return the reabsorbed nutrients back into general circulation
Roughly, how much blood per minute is supplied to the kidneys?
1 litre/min
about 20% of cardiac output
Compared to other organs in the body, how many times larger is renal blood supply ?
the kidneys receive 10-50 times more blood than other organs
What is the name of the smallest protein found in blood ?
albumin
In a healthy patient, is albumin filtered out the blood into the bowman’s capsule via ultrafiltration ?
Some is filtered out into the bowman’s capsule, as it is the smallest protein, but not large quantities
What type of cells make up the outer epithelium of the bowman’s capsule ?
parietal cells
Where does blood from the efferent arteriole go ?
into vasa recta to rejoin circulation
What does ‘oncotic pressure’ mean ?
the osmotic pressure of plasma due to the presence of proteins, specifically albumin, that causes the pull of fluid back into capillaries
Does oncotic pressure favour or oppose ultrafiltration in the golmerulus ?
opposes filtration
molecules leave the blood, increasing oncotic pressure due to the more concentrated protein cone creation, which acts to pull fluid back into the glomerulus
Does glomerular capillary hydrostatic pressure favour or oppose ultrafiltration?
favours filtration
pressure in the glomerulus pushing out into the bowman’s capsule
Does bowman’s capsule hydrostatic pressure favour or oppose ultrafiltration?
opposes filtration
pressure in the capsule pushing back against the filtrate leaving the glomerulus
What are the 3 types of pressure used in the GFR (glomerular filtration rate) equation ?
- glomerular capillary hydrostatic pressure
- bowman’s capsule hydrostatic pressure
- glomerular capillary oncotic pressure
What is the average glomerular hydrostatic pressure ?
~ 55 mmHg
What is the average bowman’s hydrostatic pressure ?
~ 30 mmHg
What is the average glomerular oncotic pressure ?
~ 15 mmHg
Roughly how many litres of plasma gets filtered by the kidneys each day ?
180 L/day
What is the process called that maintains a steady GFR and RBF regardless of blood pressure fluctuations?
auto regulation
What are the mechanisms of auto regulation ?
- myogenic tone
- tubuloglomerular feedback
What is myogenic tone ?
property of vascular smooth muscle that means it responds to stretch by vasoconstricting
What is tubuloglomerular feedback ?
the flow through the DCT (distal convoluted tubule) regulates vasoconstriction/dilation as necessary
What is glomerulotubular balance ?
an increased/decreased flow through the PCT (proximal convoluted tubule) increases/decreases reabsorption in the PCT and loop of Henle, respectively, which has the opposite feedback effect on the system
Which neurotransmitter is released onto the afferent arterioles to cause constriction when increased flow is detected in the distal convoluted tubule ?
adenosine
How does tubuloglomerular feedback cause vasoconstriction to regulate GFR in the event of increased arterial pressure ?
- increased pressure = increased GFR
- increased GFR = increased filtration
- increased filtration = increased oncotic pressure
- increased oncotic pressure negatively feedbacks to decrease GFR - increased GFR = increased flow through PCT
- increased PCT flow = increased reabsorption
- increased reabsorption negatively feedbacks to decrease GFR via glomerulotubular balance - increased PCT flow = increased DCT flow
- increased DCT flow = transmitter (adenosine) released from macula densa
- adenosine release = vasoconstriction of afferent arteriole
- afferent constriction = decreased GFR
Which cells detect the flow rate within the distal convoluted tubule ?
macula densa cells
Which transmitter does the macula densa cells release in response to increased flow through the DCT ?
increased GFR = adenosine = constriction of afferent arteriole
What receptors on the afferent arteriole does adenosine interact with to cause vasoconstriction?
a1 receptors
Which transmitter does the macula densa cells release in response to decreased flow through the DCT ?
decreased GFR = prostaglandin E2 = constriction of efferent arteriole
What stimulates
RAAS (renin-angiotensin system) ?
drop in BP
What renal transmitter stimulates
RAAS (renin-angiotensin system) ?
prostaglandin E2
Which arteriole does RAAS act to constrict ?
constricts efferent arteriole to raise pressure within glomerulus
What is renal clearance ?
the removal of substance from the blood via the glomerulus
= the amount of a substance in a given volume of plasma that passes the kidneys and ends up in urine
Which 2 markers are used to measure renal clearance/GFR ?
- inulin gold standard (not inSulin!!)
- creatinine
Why are creatinine and inulin good markers of real clearance/GFR?
- freely filtered by glomerulus
- not reabsorbed in nephron
- not secreted into DCT at later stage of process
- excreted in urine
Why might creatinine not be the best marker of renal clearance/GFR ?
affected by:
- age
- ethnicity
- gender
- diet
what is the downside to inulin as a marker for GFR ?
it isn’t endogenous
it comes from a plant so to use it, it has to be infused into the blood until you reach a constant plasma conc.
What is the substance currently being tested as a good marker for measuring GFR ?
Cystatin C
What marker is primarily used in clinical settings to measure GFR?
creatinine
What marker is considered the gold standard for measuring GFR?
inulin
What happens to efferent arteriole resistance as renal arterial pressure increases ?
efferent arteriole resistance decreases
What is the average plasma sodium concentration of blood ?
140 mmol/L
Roughly how much sodium is filtered out the blood per day ?
25,200 mmol/day
1.5 kg salt per day - most is reabsorbed
Roughly how much salt is found in urine per day ?
9g salt per day
Why is it important to regulate Na in the blood?
Na levels determine…
- extracellular fluid volume
- arterial BP
What kind of sodium reabsorption occurs in the proximal convoluted tubule ?
bulk reabsorption
= unregulated
What kind of sodium reabsorption occurs in the distal convoluted tubule ?
fine tuning
What % of sodium is reabsorbed in the proximal convoluted tubule ?
67%
two thirds of Na
What % of sodium is reabsorbed in the loop of Henlé ?
25%
What % of sodium is reabsorbed in the distal convoluted tubule ?
8%
What % of sodium is lost in the urine ?
2%
Describe how Na is absorbed into the cells of the late proximal convoluted tubule …
- Na actively pumped out basolateral membrane, K pumped into cell = sets the Na gradient
- Na diffuses in from lumen via NHE-3 receptor in exchange for Hydrogen
On basolateral membrane…
- Na-K pump sets Na gradient
- Na moves into cell via NHE-1 in exchange for H out cell
- Cl moves through channel out cell
On apical membrane…
- Na moves into cell via NHE-3 in exchange for H out
- Bicarbonate leaves cell in exchange for Cl in
What is the name of the receptor involved in bulk reabsorption in the proximal convoluted tubule ?
NHE-3
SLC9A3 is another name for it
Where does ‘fine tuning’ reabsorption occur in the nephron ?
late distal convoluted tubule/collecting ducts
Is ‘fine tuning’ reabsorption of Na under
a) ionic gradient control ?
b) osmotic potential control ?
c) hormonal control ?
hormonal control
Which hormone controls ‘fine tuning’ reabsorption of Na in the nephron ?
Aldosterone
steroid hormone
Where is Aldosterone produced ?
adrenal cortex
What causes/stimulates the release of aldosterone ?
- angiotensin 2
- plasma potassium conc