an intro to the kidney (mini learning) Flashcards
1
Q
Where in the kidney does blood filtration occur ?
A
Renal cortex
the boarder around the renal pyramids
2
Q
In which layer of the kidney are renal pyramids found ?
A
medullary layer
3
Q
Roughly how many renal pyramids does each kidney have ?
A
8-10 is average
could be 7-18
4
Q
Where does the urine drain into from the renal pyramids ?
A
minor calyx
5
Q
Where does urine drain into after the minor calyx ?
A
major calyx
6
Q
Where does the urine accumulate after leaving the major calyx ?
A
renal pelvis
7
Q
Where does the urine go after the renal pelvis ?
A
leaves the kidney, via the ureter, to be stored in the bladder
8
Q
What are the main functions of the kidney ?
A
- maintain ECFV (extracellular fluid volume)
- maintaining acid-base balance
- excretion of metabolic waste (urea, creatinine)
- endocrine secretion
9
Q
How does the kidney maintain ECFV ?
A
regulates Na in the blood, causing osmotic action to follow
10
Q
Which endocrine systems does the kidney regulate ?
A
- renin-angiotensin system
- erythropoietin production
- vitamin D activation
11
Q
What effect does the number of nephrons in a persons kidney have on blood pressure ?
A
fewer nephrons = higher hypertension risk
12
Q
Where does selective reabsorption of glomerular filtrate occur in the kidneys ?
A
- Proximal convoluted tubule
- Distal convoluted tubule
13
Q
Where does ultrafiltration of glomerular filtrate occur in the kidneys ?
A
bowman’s capsule
14
Q
Which arteriole of the glomerulus has a wider diameter ?
A
afferent in-coming arteriole
15
Q
Which molecules are forced out of the glomerulus into the bowman’s capsule ?
A
small molecules
- water
- glucose
- urea
- ions
16
Q
Which molecules do not leave the glomerulus in ultrafiltration ?
A
- proteins
- blood cells
17
Q
What type of cells form the inner epithelial layer of the bowman’s capsule
A
podocytes
18
Q
Where is 85% of glomerular filtrate reabsorbed ?
A
proximal convoluted tubule
19
Q
What % of the glomerular filtrate is reabsorbed in the proximal convoluted tubule ?
A
85%
20
Q
Does the PCT epithelium have microvilli or not ?
A
yes, there are microvilli
21
Q
Name all the arterial divisions within the kidney from the renal artery to the afferent arteriole…
A
- renal artery
- segmental arteries
- interlobar arteries
- arcuate arteries
- interlobular arteries
- afferent arterioles
22
Q
Which arteries travel between the medullary pyramids ?
A
interlobar arteries
23
Q
Which arteries travel along the top of the medullary pyramids ?
A
arcuate arteries
24
Q
Which arteries project into the renal cortex, alongside the nephrons ?
A
interlobular arteries
25
Which arteries give off the afferent arterioles ?
**interlobular** arteries
26
What is the capillary network called that surrounds the nephron ?
vasa recta
27
Does the vasa recta drain into the renal artery or vein system ?
**vein system** to return the reabsorbed nutrients back into general circulation
28
Roughly, how much blood per minute is supplied to the kidneys?
1 litre/min
*about 20% of cardiac output*
29
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
30
What is the name of the smallest protein found in blood ?
albumin
31
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**
32
What type of cells make up the outer epithelium of the bowman’s capsule ?
parietal cells
33
Where does blood from the efferent arteriole go ?
into **vasa recta** to rejoin circulation
34
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**
35
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*
36
Does glomerular capillary hydrostatic pressure favour or oppose ultrafiltration?
favours filtration
*pressure in the glomerulus pushing out into the bowman’s capsule*
37
Does bowman’s capsule hydrostatic pressure favour or oppose ultrafiltration?
opposes filtration
*pressure in the capsule pushing back against the filtrate leaving the glomerulus*
38
What are the 3 types of pressure used in the GFR (glomerular filtration rate) equation ?
1. glomerular capillary hydrostatic pressure
2. bowman’s capsule hydrostatic pressure
3. glomerular capillary oncotic pressure
39
What is the average glomerular hydrostatic pressure ?
~ 55 mmHg
40
What is the average bowman’s hydrostatic pressure ?
~ 30 mmHg
41
What is the average glomerular oncotic pressure ?
~ 15 mmHg
42
Roughly how many litres of plasma gets filtered by the kidneys each day ?
180 L/day
43
What is the process called that maintains a steady GFR and RBF regardless of blood pressure fluctuations?
auto regulation
44
What are the mechanisms of auto regulation ?
- myogenic tone
- tubuloglomerular feedback
45
What is myogenic tone ?
property of **vascular smooth muscle** that means it **responds to stretch by vasoconstricting**
46
What is tubuloglomerular feedback ?
the **flow through the DCT** (distal convoluted tubule) **regulates vasoconstriction/dilation** as necessary
47
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**
48
Which neurotransmitter is released onto the afferent arterioles to cause constriction when increased flow is detected in the distal convoluted tubule ?
adenosine
49
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
50
Which cells detect the flow rate within the distal convoluted tubule ?
macula densa cells
51
Which transmitter does the macula densa cells release in response to **increased** flow through the DCT ?
increased GFR = **adenosine** = constriction of **afferent** arteriole
52
What receptors on the afferent arteriole does adenosine interact with to cause vasoconstriction?
a1 receptors
53
Which transmitter does the macula densa cells release in response to **decreased** flow through the DCT ?
decreased GFR = **prostaglandin E2** = constriction of **efferent** arteriole
54
What stimulates
RAAS (renin-angiotensin system) ?
drop in BP
55
What renal transmitter stimulates
RAAS (renin-angiotensin system) ?
prostaglandin E2
56
Which arteriole does RAAS act to constrict ?
**constricts efferent** arteriole to raise pressure within glomerulus
57
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*
58
Which 2 markers are used to measure renal clearance/GFR ?
- inulin *gold standard (not inSulin!!)*
- creatinine
59
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**
60
Why might creatinine not be the best marker of renal clearance/GFR ?
affected by:
- age
- ethnicity
- gender
- diet
61
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.*
62
What is the substance currently being tested as a good marker for measuring GFR ?
Cystatin C
63
What marker is primarily used in clinical settings to measure GFR?
creatinine
64
What marker is considered the gold standard for measuring GFR?
inulin
65
What happens to efferent arteriole resistance as renal arterial pressure increases ?
efferent arteriole resistance **decreases**
66
What is the average plasma sodium concentration of blood ?
140 mmol/L
67
Roughly how much sodium is filtered out the blood per day ?
25,200 mmol/day
*1.5 kg salt per day - most is reabsorbed*
68
Roughly how much salt is found in urine per day ?
9g salt per day
69
Why is it important to regulate Na in the blood?
Na levels determine…
- **extracellular fluid volume**
- **arterial BP**
70
What kind of sodium reabsorption occurs in the proximal convoluted tubule ?
**bulk reabsorption**
= unregulated
71
What kind of sodium reabsorption occurs in the distal convoluted tubule ?
**fine tuning**
72
What % of sodium is reabsorbed in the proximal convoluted tubule ?
67%
*two thirds of Na*
73
What % of sodium is reabsorbed in the loop of Henlé ?
25%
74
What % of sodium is reabsorbed in the distal convoluted tubule ?
8%
75
What % of sodium is lost in the urine ?
2%
76
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
77
What is the name of the receptor involved in bulk reabsorption in the proximal convoluted tubule ?
NHE-3
*SLC9A3 is another name for it*
78
Where does ‘fine tuning’ reabsorption occur in the nephron ?
late distal convoluted tubule/collecting ducts
79
Is ‘fine tuning’ reabsorption of Na under
a) ionic gradient control ?
b) osmotic potential control ?
c) hormonal control ?
hormonal control
80
Which hormone controls ‘fine tuning’ reabsorption of Na in the nephron ?
Aldosterone
*steroid hormone*
81
Where is Aldosterone produced ?
adrenal cortex
82
What causes/stimulates the release of aldosterone ?
- angiotensin 2
- plasma potassium conc
