the kidney Flashcards
(71 cards)
1
Q
what are the key functions of the kidney
A
filtration and collection
2
Q
why is urinary excretion needed
A
- to remove excess water, electrolytes and metabolic waste products
- removes toxic waste so we can maintain bodily regulation
3
Q
what is the blood flow rate to the kidney
A
- 20-25% of cardiac output
- high due to anatomical positioning off the descending aorta
4
Q
what is the venous and arterial blood supply to the kindys
A
- renal artery
- renal vein
5
Q
where is filtration in the kidney
A
- starts in the pyramids in the renal medulla
6
Q
stages of absorption into the kidneys
A
- filtration of the blood
- reabsorbed wanted ions/ water
- excrete waste/ excess in urine
7
Q
how does the kidney filter the blood
A
- blood is directed into the renal cortex where it then subdivides into the glomerulus for ultrafiltration
8
Q
what is the glomerulus
A
a tubular epithelium that collect filtrate and then begins the process of reabsorption
9
Q
what are the kidneys capillary beds
A
- dual capillary bed or cortical nephron of juxta medullary nephron
10
Q
what are the cortical nephrons
A
- these nephrons travel out through an efferent arterial and then form a secondary capillary bed the Perry Tubular capillaries
- loop of Henley into the medullary region
11
Q
what is the role of the cortical nephron
A
absorbing solutes that are taken up in the cortex
12
Q
what are the juxta medullary nephrones
A
capillaries leaving the efferent arterial leave into long loops called the vasorector
13
Q
what do the juxta medullary nephrons do
A
supply the blood supply to the medullary region
14
Q
what is the purpose of the bowans capsule
A
- a layer of epithelial cells that envelops the glomerulus
- collects the filtrate into the tubular epithelium
- it helps slow down blood flow so filtration can occur and be sent into the urine
15
Q
what is the glomerular filtration rate
A
the rate of fluid filtration from the renal capillaries into the bowmans space
16
Q
what is the filtration coefficient
A
the permeability of the capillary to water
17
Q
what is the reflection coefficien
A
how impermeable to capillary is to proteins
18
Q
what does starlings force calculate
A
the glomerular filtration rate
19
Q
what does a low glomerular filtration rate indicated
A
kidney failure
20
Q
how does glomerular filtration occur
A
- the higher glomerular capillary pressure which is caused by the glomerular shape, causing more resistance and having a higher blood flow than needed
- osmotic pressure of the capillaries causes solute back into the glomerular capillaries
21
Q
what is the capillary structure on the kidneys
A
fenestrated which allows for high filtration rate as it makes it easier to move water. so faster filtration and faster toxin removal
22
Q
what is the function of podocytes
A
- create an interlocking mesh that cover the outside of the endothelium
- tight sieving space to make sure large proteins don’t cross
23
Q
what is the function of the basement membrane
A
selects what crosses the filtration barrier based upon molecular weight and electrical charge as it is negatively charged so proteins are repelled
24
Q
how are wanted ions reabsorbed
A
through the tubular epithelium in each segment of the nephron
25
what are the different sections of the nephron and where are they found
- bowmen's capsule - cortex
- loop of Henley - medullary region
- distal convoluted tubal - cortex
- collecting ducts - cortex, outer medullar and inner medulla
26
how does transcellular transport work
- uses a transporter for both membrane either primary or secondary active transport
- gives control over what can be reabsorbed as some minerals can't go through both barriers
the luminal and basolateral membrane are permeable to water or the solute of interest
27
what is paracellular transport
transport between the cells depending on the junction between the 2 cells
28
how does reabsorption work in the proximal tubule
1. the pressure decreases in the nephron due to a decrease in the volume, slow down flow rate for reabsorption through transporter channels
2. proximal tubual transported take up bicarb so plasma concentration stays constant
3. amino acids are reabsorbed
4. all glucose is taken back up
29
how does isosmotic reabsorption work
1. transcellular reabsorption of glucose and amino acid drive Na uptake
2. Na reabsorption creates positive electrochemical gradient
3. triggers cl reabsorption through leaky junctions
4. cl travels down the electrochemical gradient
5. creates nacl which creates an osmotic gradient for paracellular water reabsorption
30
what is the function of having dual capillary beds
- glomerulus is for absorption
- peritubular capillaries are for reabsorption of interstitial fluids
31
what is the main function of ADH
increase water reabsorption
32
what is the main function of parathyroid hormone
increase Ca and decrease Pi absorption
33
what is the main function of calcitriol
increase Ca and Pi absorption
34
what is the main function of atrial natriuretic peptide
decrease Na absorption
35
what is the main function of noradrenaline
increase Na absorption
36
what is the main function of angiotensin II
increase Na absorption
37
what is the main function of of aldosterone
increase K secretion
38
what is an osmol
the combined total of all different solutes that can exert and osmotic gradient across any membrane
39
what is an isotonic cell
one that has a net volume of 0
40
what is a hypertonic cell
- osmoregulatory of the cell extracellular fluid is higher outside the cell than inside
- draws water from inside to outside making a shrunk cells
41
what is a hypotonic cell
- cell takes up water as they have more concentrated osmolytes inside the cell than outside
- causes cell to swell as they take in more water
42
what is the isosmotic fluid reabsorption
- proximal tubule
- lose sodium chloride, draws out water so no osmotic gradient
- little change to omolarity of urin
43
what occurs in the thin descending limb
- water permeable, absorbed small amounts of water
44
what occurs in the thick ascending limb
- no passive sodium reabsorption, but does in presence of signals
- actively pumps sodium chloride
more sodium than water uptake
- hypotonic fluid leaving loop of henely
45
how does the ascending limb reabsorb sodium chloride
- sodium potassium ATPase couple with sodium 2 chloride potassium transporter
46
what occurs are the distal convoluted tubule and collecting ducts
reabsorbs sodium chloride but not enough for dilute urine
47
what are the stages of the negative feedback loop
1. change in plasma osmolarity
2. transduction
3. sensors respond to osmilarity of 290mOsml
4. signals to kidney
5. kidney responds to this signal
6. change in cellular activity
48
what is trasnduction
cell or sensor that can sense the change in osmolarity
49
how do osmoreceptors work
they change there neuronal firing and rate of action potentials depending on the plasma osmolarity
50
what to stetch inhibited ion channels do
open when the cell shrinks so depolarising the cell increases the frequency of action potential firing in the sensor neurons
51
what do osmoreceptor neural signals do
trigger the hypothalamus to increase thirst, increase ADH secretion from posterior pituitary
52
what are the stages in transduction
1. neurones are bathed in interstitue from plasma so detect osmolarity changes
2. become hypertonic to pull more water out of cells to shrink neuronal cells
3. reduces tension in plasma membrane of osmoreceptors
4. opens stretch inhibited ion channels
5. sodium enters neuron increasing depolarisation
6. hypothalamus activate ADH at synapse, increasing release
53
how is water transcellularly absorbed
- through aquaporins on both the luminal and basolateral membrane
- through leaky junctions only in proximal convoluted tubule
- needs an osmotic gradient to drive water movement
54
stages of reabsorption in the convoluted tubule
1. loop of Henley increases NaCl, counter current multiplication, more sodium out than reabsorbed water (descending)
2. increased NaCl conc in peritubular fluid, increasing the osmolarity
3. creates osmotic gradient to draw water from collecting ducts by osmosis
4. creates concentrated urine
55
what is the counter current multiplication
mechanisms used to maximise the amount of sodium chloride out of the loop of henely
56
what happens in the thin ascending limb
is permeable to water due to aquaporin 1 expression and interstitial fluid is isosmotic to plasma
57
what is the counter current multiplication in the thick ascending limb
- actively pumps NaCl into interstitial fluid so is hyperosmotic to incoming tubular fluid
58
stages of fluid entering the proximal tubular
1. fluid enters that is isosmotic to blood plasma
2. water goes up thick ascending limb and can actively transport NaCl
3. as the ascending limb NaCl is removed and pumped into the medullary fluid (highly osmotic)
4. hypotonic fluid leaving the ascending limb
59
how does new fluid enter the tubule
- NaCl pumping creates an osmotic gradient for water to leave thin descending limb
- higher osmolarity due to NaCl pumping
- means water can be reabsorbed down the osmotic gradient
60
what happens when there is an increase is water reabsorption
there is an increase in the NaCl of the tubual fluid in the thin descending limb so more NaCl can be pumped from the thick ascending limb
61
why is there an increase in the thick ascending thick pumping NaCl
higher NaCl in interstitial fluids from descending limb maximises the osmolarity of the interstitial fluid so more can be pumped out
62
what is the overall purpose of the countercurrent multiplication
- the descending limb removes water and pre-concentrates the tubular fluids which creates a greater pump out of the thick ascending limb
- more NaCl out means more water in
63
how does ADH work
1. bind to ADH receptors
2. causes G protein coupled cascade to causes activation of adenyselcyclase
3. turns ATP to cAMP binding to active protein kinase A
4. phosphorylates protein aquaporin 2 triggering exoytosis
5. makes membrane permeable to water
6. water moves through luminal membrane
7. AQP3 and 4 are able to absorbed water so it can move out and be reabsorbed
64
what changes in permeability with ADH
- the collecting ducts are permeable to water and the inner medulla collecting ducts are permeable to urea
- makes concentrated urine and decreases blood plasma osmolarity
65
how is a concentration gradient created with urea
as there is further reabsorption of water there is an increase in urea, ends with a limit to water reabsorption
66
how does urea recycling work
1. moves down the concentration gradient into medullary fluids across collecting duct
2. urea is greater in collecting ducts than thin ascending limb so it diffuses into tubule
3. increase tubule urea concentration
4. when it reaches the inner medullary collecting duct it allows more to leave into the interstitum
67
how does ADH stop a very high urea concentration
- allows medullary interstitial fluids to equilibrate with tubular fluids so no osmotic pressure is exerted
68
why is urea recycling needed
so that high urea in the tubular fluid is build up to help maximise urea loss in the urine
69
how does urea enhance the countercurrent multiplication
increased urea of interstitial fluid helps enhance the reabsorption of NaCl from loop of henly to allow more water reabsorption
70
stages of urea enhancing countercurrent multiplication
1. absence of urea in intertitium, water drawn out of thin descending limb
2. increases NaCl pumped out by thick ascending limb
3. water pulled out of thin descending until interstitium and tubule NaCl is balanced
4. increased urea in medullary interstitium drawn more water out from thin descending
5. causes tubular to become more concentrated
6. gradient across thin ascending allowing passive NaCl diffusion out of tubules
7. create more preconcentrated tubule fluid to reach thick ascending limb
71
what is the overall effect of urea enhancing the countercurrent multiplication
increases the maximum concentration of the urine to allow greater water reabsorption form the collecting ducts
