Section 6: Renal System Flashcards
(217 cards)
1
Q
External anatomy of kidneys
A
Renal capsule (innermost layer) Adipose capsule Renal fascia (outermost layer)
All made of CT - provides padding, protection and packaging
2
Q
Kidneys: Renal capsule
A
Physical barrier; protection against trauma
Maintains shape of kidneys
3
Q
Kidneys: Adipose capsule
A
Padding; physical protection
Maintains position of kidneys
4
Q
Kidneys: Renal fascia
A
Anchors kidneys to surrounding structures
5
Q
Parenchyma of kidney
A
Functional portion
Contains ~1 million nephrons (functional units)
Focusing on juxtamedullary nephrons
6
Q
Kidneys: Renal corpuscle - components
A
Glomerulus (blood) - endothelium
- input: afferent arterioles
- output: efferent arterioles
Glomerular (Bowman’s) capsule - epithelium
- visceral: podocytes (modified epithelium)
- parietal: from outer wall of capsule (simple squamous)
7
Q
Kidneys: Filtration membrane - parts
A
Fenestration (pore) of glomerular endothelial cell
Basal lamina of glomerulus
Slit membrane between pedicles
Differential filtering
8
Q
Kidneys: Filtration membrane - fenestration
A
Prevents filtration of blood cells, but allows all components of blood plasma to pass
9
Q
Kidneys: Filtration membrane - basal lamina
A
Prevents filtration of larger proteins
10
Q
Kidneys: Filtration membrane - slit membrane
A
Prevents filtration of medium-sized proteins
11
Q
Filtration unit and substrate
A
Filtration unit = nephrons
Substrate = blood supply
12
Q
Kidney mass
A
~150g
13
Q
Kidneys: Renal columns
A
Extension of cortex into medulla
Lots of blood vessels and tissue embedded here
14
Q
Kidneys: Interlobar
A
Between 2 lobes
15
Q
Kidneys: Nephrons - arrangement
A
Not randomly arranged
Very tightly packed in organised ways and all collect into a bunch (bouquet)
16
Q
Kidneys: Calyces
A
Cup-like structures that collect urine from papillary
Start with smaller cups which merge to form bigger cups
17
Q
Kidneys: Interlobar artery
A
Red blood vessel found between 2 lobes
18
Q
Kidneys: Nephrons - classes
A
Some located higher up near cortical area
Others located lower down near medulla
19
Q
Kidneys: Juxtamedullary nephrons
A
Nephrons close to cortical-medullary junction
Responsible for helping us make concentrated urine
20
Q
Kidneys: Arcuate artery
A
Where renal artery arches as it comes up to the cortex at cortical-medullary junction
Gives rise to interlobular arteries
21
Q
Kidneys: Interlobular arteries
A
Feed the lobules
22
Q
Kidneys: Glomerulus / glomerular capillaries - form an important part of…
A
The filtration barrier
23
Q
Afferent arteriole is ____ of the filtration apparatus
A
Upstream
24
Q
Efferent arteriole - pathways
A
Can stay in cortex and feed cells that make up tubular parts of nephron
Or can delve deep into medulla and feed cells of tubular parts of nephron located here
25
Ascending vs descending vasa recta
Ascending: venous blood; relatively O2-poor blood
Descending: arterial blood; relatively O2-rich blood
26
Peritubular capillaries of medulla
Where gas exchange happens
| O2 is absorbed by cells of nephron and CO2 is transported back into blood in peritubular capillaries
27
Kidneys: Where does blood transition from arterial to venous
In the peritubular capillaries
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Peritubular capillaries: Venous blood - pathway
Travels into interlobular veins --> arcuate vein --> interlobar vein --> converge and exit kidney by renal vein --> IVC --> heart
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Where does filtration begin
Renal corpuscles
30
Corpuscles
Capsulated structures
31
Interaction between what enables filtration to take place
Podocytes and underlying glomerular capillaries
| Tgt they form the filtration barrier
32
Kidneys: Capsular / urinary space
Space between visceral and parietal epithelium
| Where filtrate accumulates and eventually flows out the renal corpuscle into the tubular portion
33
Kidneys: What is the basal lamina made up of
BM secreted by podocyte
| BM secreted by endothelial cells
34
Kidneys: Glomerular capillaries - texture
Not a smooth surface because has pores
35
Kidneys: Differential filtering - what happens to the proteins that get trapped
Either bounce back into blood circulation or are phagocytosed and recycled
36
Kidneys: Proximal convoluted tubule - cells
Have microvilli on apical membrane
| Involved in transport
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Kidneys: Distal convoluted tubule of many nephrons...
Combine and feed into a single collecting duct
38
Kidneys: Distal convoluted tubule - function
Monitors how things are going and provide feedback to influence the beginning of the process
39
Main functions of kidney
Regulation of water and electrolyte balance
Regulation of arterial pressure
Filters blood
40
Kidney - homeostasis
Blood pressure
Water and electrolyte balance
pH
Waste product removal
41
Kidney is part of ______ system
Circulation
42
Kidney: When things go wrong - symptoms
```
Swelling
High blood pressure
Shortness of breath
Fatigue
Nausea
```
43
Dialysis
Prevents build up of waste products
| e.g. build up of high K+ --> heart rhythms go bizarre --> sudden death
44
Osmosis
The movement of water through a selectively permeable membrane
From an area of lower solute conc (high water conc) to higher solute conc (low water conc)
45
Osmotic pressure
The pressure required to prevent net water movement, i.e. pressure generated by the water moving inside a cell
46
Osmolarity
A measure of the osmotic pressure exerted by a solution across a semi-permeable membrane compared to pure water
Dependent on no of particles in solution (but independent of nature of particles)
Basically a measure of the conc of all the components in the solution
47
Osmolarity =
Molarity x dissociation factor
48
150mL NaCl + 1L water dissociates to give...
150 mM/L Na+ + 150 mM/L Cl-
| = 300 mOsm/L
49
300mM urea + 1L water gives..
300 mOsm/L
50
Osmolarity usually refers to...
A container / beaker, not necessarily a cell
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Hyperosmotic
A solution with a higher Osm than another
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Isosmotic
2 solutions with the same Osm
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Hyposmotic
A solution with lower Osm than another
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Tonicity
Takes into account the conc of a solute *and* the ability of the particle to cross a semi-permeable membrane
i.e. ability of a solution to change shape of a cell
'effective osmolarity'
55
NaCl - permeability
Low permeability
56
Urea - permeability
Higher permeability
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Hypertonic
A solution with a higher POsm than another
| Water will leave cell --> shrinkage
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Isotonic
2 solutions with same POsm
| Not net water movement
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Hypotonic
A solution with a lower POsm than another
| Water will move into cell --> swelling (and burst)
60
Disturbances in water balance: Dehydration
Loss of H2O from ECF
ECF osmotic pressure rises
Cells lose H2O to ECF --> cells shrink
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Disturbances in water balance: Hydration
H2O enters ECF
ECF osmotic pressure falls
H2O moves into cell --> cells swell
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Why maintaining osmolarity is important
Sets MP
Generates electrical activity in nerve and muscle
Provides energy for uptake of nutrients and expulsion of waste
Generation of intracellular signalling cascades
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Fluid distribution in body - average 70kg male
```
60% fluid = 42L
2/3 intracellular = 28L
1/3 extracellular = 14L
- 20% plasma = 2.8L
- 80% interstitial = 11.2L
```
64
Major sources of water intake
Metabolism 8%
Foods 28%
Beverages 64%
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Major sources of water output
Feces 4%
Lungs 12%
Skin 24%
Urine 60%
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Electrolyte composition: High extracellular conc
Na+, Cl-, Ca2+ ions have high extracellular conc
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Electrolyte composition: High intracellular conc
K+ ions have high intracellular conc
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Electrolyte composition - similarities?
Amount in blood plasma and interstitial fluid are usually very similar
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About ___L of fluid enters the renal tubules each day
180L
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In the average adult, the entire extracellular fluid V is filtered about __ times a day
12
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How much fluid that enters the renal tubules is reabsorbed
~178.6L reabsorbed
| ~1.4L urine produced each day
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Excretion = ?
Filtration + secretion - reabsorption
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Renal handling of water and solutes: Water
```
Filtration = total
Reabsorption = most of total
Excretion = small amount of total
```
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Renal handling of water and solutes: Sodium
```
Filtration = total
Reabsorption = most of total
Excretion = small amount of total
```
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Renal handling of water and solutes: Glucose
```
Filtration = total
Reabsorption = total
Excretion = 0
```
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Renal handling of water and solutes: Creatinine
```
Filtration = total
Reabsorption = 0
Excretion = total
```
77
What is reabsorption
The idea that you're taking fluid out of your nephron and back into blood
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Nephrons - pathway
```
Glomerulus
Proximal tubule
Loop of Henle: descending limb
Loop of Henle: ascending limb
Distal convoluted tubule
Collecting duct
```
79
Glomerular filtration rate %
~25% of total renal plasma flow
180 L/day
Very constant, especially over a mean pressure of 80-140
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Glomerulus has a similar solute conc to...
Plasma
81
Glomerulus lacks..
Proteins and other high molecular weight compounds
| Free from blood cells
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Glomerulus - coming in and going out
Have an arteriole coming in, a capillary bed, and an arteriole going out
The only place in body to have an arteriole before and after a capillary bed
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Glomerulus: Capillaries - holes
Capillaries in capillary bed have big holes in them - easy for fluid to be filtered out
84
Glomerulus: Podocytes sit on top of _____
Capillaries
85
Blood flow to kidneys - regulation
Tightly regulated, thus glomerular filtration rate is relatively constant
86
Urine output is directly proportional to....
Renal/blood pressure
87
Kidneys - autoregulation
Good autoregulation
| Pressure and blood flow through glomerulus is relatively constant
88
What is kidney autoregulation due to
Ability of arterioles to constrict - means flow through kidneys doesn't change much
Particularly afferent arterioles
89
Glomerular blood hydrostatic pressure (GBHP)
The major force pushing fluid and solutes out the glomerular capillaries, i.e. BP inside glomerulus
Mechanical P between afferent and efferent arterioles
90
GBHP: Vasoconstriction of afferent vs efferent arterioles
Increases in arterial P can be buffered by vasoconstriction of afferent a
Decreases in P can be buffered by vasoconstriction of efferent a
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GBHP: Pressure at afferent vs efferent arteriole
P at afferent arteriole slightly higher than at efferent arteriole
92
GBHP: Normal pressure inside glomerulus and arterioles
Glomerulus: 55 mmHg (halfway between afferent and efferent a)
Afferent: 60 mmHg
Efferent: 50 mmHg
93
GBHP: Afferent arteriole vasoconstriction - pressures
i.e. constricts before glomerulus
Glomerulus: decreases
Afferent: decreases
Efferent: same
94
GBHP: Efferent arteriole vasoconstriction - pressures
i.e. constricts after glomerulus
Glomerular: increases
Afferent: same
Efferent: increases
95
GBHP: What happens if BP drops
Efferent arteriole constricts --> increases P before constriction --> efferent P and glomerular BP increases
96
Glomerular filtration is dependent of...
Pressure gradients
97
NFP = ?
GBHP - CHP - BCOP
| ~10 mmHg
98
Net filtration pressure (NFP)
Determines how much water and small dissolved solutes leave the blood
99
Capsular hydrostatic pressure (CHP)
Pressure exerted on plasma filtrate by elastic recoil of glomerular capsule
~15 mmHg
100
Blood colloid osmotic pressure (BCOP)
The osmotic force which is the proteins left in the plasma - exert an increasing osmotic 'pull' on the water in plasma filtrate
~30 mmHg
101
GBHP vs CHP
```
GBHP = pressure inside capillaries
CHP = pressure inside capsule (opposes)
```
102
Kidney stone affects which pressure
Fluid in kidney builds up --> increases CHP
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Which pressure drives fluid back into capillaries
BCOP
104
Regulation of glomerular filtration - types
Autoregulation
Neural
Hormonal
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Regulation of glomerular filtration: Autoregulation
Myogenic autoregulation or tubuloglomerular feedback
| Blood vessels themselves respond to changes in pressure
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Regulation of glomerular filtration: Neural
Increased sympathetic nerve activity --> (afferent) vasoconstriction --> reduces filtration
107
Regulation of glomerular filtration: Hormonal
Angiotensin II
Atrial natriuretic peptide
Longer term
108
Regulation of glomerular filtration: Hormonal - angiotensin II acts via...
Vasoconstriction of afferent and efferent arterioles
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Regulation of glomerular filtration: Hormonal - atrial natriuretic peptide (ANP)
Responds to stretch of atria by relaxation of mesangial cells --> increases SA for filtration
110
Regulation of glomerular filtration: i.e. anything that...
- alters the GBHP (e.g. P in afferent artery)
| - alters the SA available for filtration
111
Regulation of glomerular filtration: If you stretch a blood vessel...
It tends to constrict around it
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Regulation of glomerular filtration: Which arterioles receive innervation from sympathetic nerves
Both afferent and efferent arterioles
113
Regulation of glomerular filtration: BP and sympathetic activity
High BP = high sympathetic activity
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Natriuresis
The excretion of sodium
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Diuresis
Getting rid of lots of water
116
Premature children and BP
Tend to develop high BP because SA available for filtration is reduced --> less glomeruli
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Tubuloglomerular feedback - cycle
Increased GFR -->
Increased tubular flow rate (ascending limb) -->
Increased tubular Na+, Cl-, water content sensed by macula densa cells -->
Juxtaglomerular apparatus NO release decreased -->
Afferent arteriole vasoconstriction -->
Back to top
118
Macula densa
Sense amount of Na+ in ascending limb of nephron loop
Can give info to afferent arterioles - if lots of Na+, means there's lots of fluid passing through tubules --> tells afferent arterioles constrict
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Juxtamedullary vs cortical nephrons
Cortical: dilute urine, shorter
Juxtamedullary: important in production of concentrated urine (regulating Na+ and H2O balance), extends down into medulla
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Where is interstitial fluid is very concentrated
Medulla
121
Where is there high conc of urea
Tip of nephron
122
Nephron structure and function
Cells in diff areas look diff and have diff functions
123
Where does the largest amount of solute and water reabsorption from filtered fluid occur
Proximal convoluted tubule
~60% glomerular filtrate
~60% NaCl and water
~100% glucose (except diabetes)
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What area of the nephron is closest to the glomerulus
Proximal convoluted tubule
125
Do we urinate glucose
Generally no - all stored for later use
| Exception is diabetes
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Nephron: Proximal convoluted tubule - function
Highly active in membrane transport processes with reabsorption of water, ions and glucose
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Nephron: Proximal convoluted tubule - structure
Highly developed brush border (microvilli) --> increases SA
128
Na+/K+ ATPase - location
Located on basal surface
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Na+/K+ ATPase - function
Pumps Na+ into interstitial place
| Maintains low Na+ in cell
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Na+ movement into tubule cells
Occurs via symporters (e.g. Na+/glucose symporter) and antiporters (Na+/H+)
131
Nephron: Proximal convoluted tubule - glucose
Glucose and other solutes can diffuse down their conc gradient
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Nephron: Proximal convoluted tubule - water
Na+ movement allows water movement via osmosis
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Nephron: Proximal convoluted tubule - osmolarity
Similar to plasma
134
Na+/Glucose sympoter
Na+ moves in cell down its conc gradient and glucose moves with it
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Nephron: Proximal convoluted tubule - diabetes
High levels of glucose --> saturate symporters --> urinate glucose
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Nephron: Descending loop of Henle - permeability
Low permeability to ions and urea
| Highly permeable to water
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Nephron: Descending loop of Henle - water movement
Interstitial fluid is highly concentrated in medulla of kidney --> water moves out of tubule via osmosis --> urine becomes more concentrated
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Nephron: Descending loop of Henle - bottom
By the bottom of the loop, the filtrate is v concentrated
| ~1200 mOsmol/L, whereas ECF ~300 mOsmol/L
139
Nephron: Thick ascending limb - permeability
Impermeable to water
| Na+, K+ and Cl- actively reabsorbed
140
Nephron: Thick ascending limb (of Henle) - top
By the time the filtrate gets to top of loop, conc of ECF decreases --> gets rid of ions via Na/K/Cl symporter --> very dilute
~100 mOsmol/L
141
Nephron: Thick ascending limb - junctions
Very tight junctions --> water moves out
142
Loop of Henle: Countercurrent mechanism
Descending limb impermeable to NaCl
| Ascending limb impermeable to water
143
Nephrons: Thick ascending loop provides...
Environment for thin ascending loop by pumping out ions
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Nephrons: Loop of Henle is helped by...
Blood vessels
145
Nephrons: Descending loop of Henle is close to...
Descending side of capillary network
146
Nephrons: Thick ascending loop is close to...
Ascending side of loop of Henle
147
Nephrons: Does the ECF become diluted
Anything pumped out of the thick ascending loop is taken to thin descending loop and water coming out is taken away by veins --> doesn't dilute the ECF
148
Loop of Henle vs vasa recta
Vasa recta moves in an opp direction to loop of Henle to take fluid away --> keeps a high concentration medulla
149
Nephron: Distal convoluted tubule and collecting duct - function
Additional reabsorption of NaCl
150
Nephron: Distal convoluted tubule and collecting duct - ADH
Water permeability is dependent on antidiuretic hormone
In absence of ADH, area is impermeable to water --> more reabsorption of Na+ and Cl- --> urine produced has little Na+ and Cl- --> urine dilute
151
Fluid dynamics: Water
Rapidly equilibrates throughout ICF and ECF
| Decreases osmolarity
152
Fluid dynamics: Isotonic solution
Remain in ECF
No effect on plasma osmolarity
No gradient in isotonic solution for H2O to move into cell - not effective for dehydration
153
Antidiuretic hormone (ADH) - precursor
Made in hypothalamus and stored in vesicles in posterior pituitary
154
ADH release: Osmoreceptors
Innervate the hypothalamus, sense:
- increase in Na+ conc
- increase in osmolarity
Signal is sent to posterior pituitary and in response to APs, ADH is released into bloodstream
155
Where is ADH made
Nerve cells in hypothalamus
156
ADH: Osmoreceptors detect osmolarity in ____
ECF
157
Osmoreceptors - structure
Have 'stretch-inhibited' cation channels
| Like a pyramid tethered with long arms - when cell shrinks, lots of stretch on arms --> opens stretch-activated channels
158
Osmoreceptors - channels
When cell shrinks due to hypertonic stimulus, cation channels open
Na+ enters cells and triggers APs
159
ADH AKA
Arginine vasopressin (AVP)
160
Plasma ADH and osmolarity
Plasma ADH increases as osmolarity increases
161
ADH release - blood volume
Increased blood volume = less ADH
162
ADH - threshold
Threshold for ADH release ~280 mOsm
Normally plasma osmolality is 290 mOsm
So, we usually have ADH circulating in our body with ability to increase or decrease
163
ADH - increased threshold results in...
Thirst (dehydration)
164
What hormone is most sensitive to osmolarity
ADH
165
What does ADH act on
The last part of the convoluted distal tubule and the collecting duct (i.e. end of nephron)
166
ADH - storage vesicles
ADH stimulates insertion of aquaporin-2 containing vesicles into the apical membrane
Aquaporin-2 is a water channel, so water can move from tubule into cell (water pore)
167
ADH - basolateral membrane
Always relatively permeable to water, so water can move via osmosis back into blood
168
ADH - steps
1. ADH binds to membrane receptor
2. Receptor activates cAMP second messenger system
3. Cell inserts aquaporin-2 water pores into apical membrane via exocytosis
4. Water is absorbed by osmosis into blood
169
ADH - ADH receptors
Detect and bind to ADH and sends a message into cell
170
ADH - apical vs basolateral membrane permeability
Normally apical membrane not permeable to water (but presence of water pores allows permeability)
Basolateral permeable to water
171
ADH - urine
ADH facilitates reabsorption of water in distal tubule and collecting duct --> concentrated urine
172
Collecting ducts move through the ____ of the kidney
Medulla
173
As we move down the collecting duct, there's a gradient for water to...
Move out of it, so water pores allow them to easily move out to dilute the medulla
174
End of collecting duct - osmolarity
Can get up to 1200 mOsm
175
ADH release - types of baroreceptors
Both arteriole and cardiopulmonary baroreceptors
176
ADH release - baroreceptors, blood P and blood V
Decreased baroreceptor activity, decreased blood V or P = ADH release
177
Overall, what factors affect ADH release
Anything that causes an increase in osmolarity, an increase in conc, or a decrease in blood V
178
Renin-Angiotensin-Aldosterone (RAA) system - functions
Maintaining Na+ balance
| BP regulation
179
ADH: Dehydration
Increase in osmolarity and change in blood V = ADH increases
180
ADH: Drinking too much water
ADH decreases
181
Juxtaglomerular apparatus
Where distal tubule borders the glomerulus
182
Juxtaglomerular apparatus: Macula densa cells
Respond to a decrease in NaCl content by increasing prostaglandins
Baseline regulation to keep it even - not involved in blood P regulation, just prevents damage of kidneys
183
Juxtaglomerular apparatus: Juxtaglomerular (granular) cells
In afferent arteriole
| Release renin
184
Juxtaglomerular apparatus: Pressure
Decrease in pressure in afferent arteriole acts on juxtaglomerular cells --> release renin
185
Juxtaglomerular apparatus: Macula densa cells - fast or slow
Buffers quick changes
186
Juxtaglomerular apparatus: Renin release - fast or slow
Slow - long-term effect that respond to more subtle changes
187
Renin is released primarily due to...
Low Na+ in nephron
188
Hormones - speed
Usually take a while
189
Triggers for renin release from juxtaglomerular (granular cells
Low NaCl conc in distal tubule (Na+ depletion)
Decreased perfusion pressure (by granular cells, afferent arteriole)
Increased sympathetic activity (e.g. via baroreflect)
i.e. low BP, low BV, low Na+
190
Renin release: Macular densa cells are sensing...
Low Na+
191
Renin-Angiotensin System: Active hormone
Angiotensin II
| Others (angiotensinogen and angiotensin I) are precursors
192
Renin is a(n) _______
Enzyme
193
Renin-Angiotensin System: Rate limiting step
Renin is the rate limiting step of the production of angiotensin II
194
Renin-Angiotensin System: ACE
Usually lots present
| Usually the target when wanting to reduce angiotensin II because less side effects
195
Aldosterone - release
From adrenal cortex in response to angiotensin II
196
Aldosterone - what does it act on
Distal tubule and collecting ducts to increase transcription of Na/K ATPase pumps --> increases Na+ reabsorption and K+ excretion
197
Aldosterone - water
Water reabsorption may also increase via osmosis if ADH is present
198
Aldosterone - main functions
Na+ and water retention
199
Angiotensin II - high levels
Quite a potent vasoconstriction in kidney and smooth muscle
| Can stimulate thirst
200
RAA system summary - dehydration
Na+ deficiency and haemorrhage --> decrease blood V --> increase renin --> increase angiotensin II --> vasoconstriction of arterioles --> increase BP until norm
OR:
increase aldosterone --> increase Na+ (and water) reabsorption in --> increase blood V -> BP increase until norm
201
Angiotensin II and salt
Increased salt --> reduced angiotensin II --> reduced renin because of change in arteriole P
202
Chips (increased salt) - effects
Increased intake of NaCl in ECF --> water moves out of cell --> increased blood V and osmolarity (?)
203
ADH and chips
Increase in blood V is major trigger so ADH doesn't help much
204
Salt vs water balance
ADH: important in maintaining water balance
RAA system: important in maintaining salt balance
2 systems allow for independent control of water and salt levels in body
205
Haemorrhage - fluid loss is...
Isosmotic
| Lose both water and salt so need both RAA system and ADH
206
Blood loss is...
Hypovolemic / isotonic
207
What is blood loss sensed by
Juxtoglomerular cells and arterial baroreceptors
208
Blood loss leads to increased...
Sympathetic activity
ADH
Renin / angiotensin II / aldosterone
--> vasoconstriction and conservation of water and Na+
209
Atrial natriuretic peptide (ANP) - acts to..
Reduce renin, ADH and aldosterone release
Increase GFR
Reduces Na+ and water reabsorption
210
Timescale:
Baroreceptors = second
Osmolarity = ~1-2 min
ADH at least half an hour, 3 hours before any change in blood levels
Aldosterone ~4 hours
211
Where are glomerular capillary endothelial cells found
In renal corpuscle
212
Gradient for transport of many substances is produced by...
The Na/K ATPase pump
213
Perfusion P and blood flow
Decreased perfusion P --> decreased NV --> decreased renal blood flow
214
Renin and GFR
Decreased GFR = increased renin
215
Selective vasoconstriction of the efferent arteriole leads to....
Increased P in glomerular capillary network
216
Dehydration - aquaporins
Dehydration --> more aquaporins inserted into membrane collecting ducts
217
The countercurrent exchange in the vasa recta maintains..
High conc of NaCl in ECF
