Renal - filtration Flashcards
(90 cards)
1
Q
Although still ___, pressure is higher in these than in any other capillaries in the body
A
capillaries
2
Q
Characteristics of glomerulus
A
Larger surface area
Larger fenestrations for easier filtration
Efferent arteriole is smaller than the afferent
3
Q
This then requires more pressure to get plasma OUT of the glomerulus through the efferent arteriole
This pressure builds backwards into the glomerulus increasing filter pressure (positive pressure)
A
Efferent arteriole is smaller than the afferent
4
Q
Pressure in glomerulus pushing outward into capsular space
A
Glomerular blood hydrostatic pressure (GBHP)
5
Q
Glomerular blood hydrostatic pressure (GBHP) normal?
A
Usually 55mmHg
6
Q
Hydrostatic pressure exerted by the fluid in capsular space that pushes inward on the visceral glomerular membrane
A
Capsular hydrostatic pressure (CHP)
7
Q
“back pressure”
A
Capsular hydrostatic pressure (CHP)
8
Q
Normal Capsular hydrostatic pressure (CHP)?
A
15 mmHg
9
Q
Pressure due to proteins in blood plasma (mainly albumin)
A
Blood colloid osmotic pressure (BCOP)
“gravitational pull”
10
Q
Opposes filtration
A
Blood colloid osmotic pressure (BCOP)
11
Q
Pulls on fluid/solutes to keep them in the glomerulus if possible
A
Blood colloid osmotic pressure (BCOP)
Usually 30mmHg
12
Q
GBHP-CHP-BCOP
A
NFP
NFP= 55mmHg-15mmHg-30mmHg
13
Q
NFP
A
GBHP-CHP-BCOP
14
Q
As long as the NFP is a ___ number, filtration will occur
A
positive
15
Q
If NFP calculates into a ___ number, NO FILTRATION is occurring
A
negative
16
Q
Promoting filtration eventually leads to ___
A
urine production
17
Q
the amount of blood filtered by the kidneys’ glomeruli into capsular space per unit time
A
Glomerular Filtration Rate
18
Q
Glomerular Filtration Rate
A
the amount of blood filtered by the kidneys’ glomeruli into capsular space per unit time
19
Q
Normal GFR?
A
125 mL/min
20
Q
If GFR too fast?
A
filtrate may pass too quickly and required substances may not be reabsorbed
21
Q
If GFR too slow?
A
nearly all filtrate may be reabsorbed and certain wastes may not be excreted efficiently
22
Q
GFR is calculated as an estimated rate (no actual measurements).
Using what 5 components?
A
Creatinine
Age
Race
Weight
Gender
23
Q
waste from the breakdown of muscle (normal)
A
Creatinine
24
Q
As blood is filtered through the nephrons, the kidney neither reabsorbs or metabolizes this substance?
A
Creatinine
25
Should freely pass through the filtration membrane and be urinated out?
Creatinine
26
In a normal healthy adult, the serum level should be near or at the same level of the urine creatinine clearance (24hour urine collection)
Creatinine
27
If the urine level is low, this means the kidneys are not filtering the serum ___ properly (kidney damage)
creatinine
28
Usually means that the creatinine serum level will be elevated if what is low?
urine level (i.e., not be excreted thus held in the serum)
29
GFR directly related to pressures that determine ____
net filtration pressure
Ex: Severe blood loss reduces mean arterial pressure as well as glomerular blood hydrostatic pressure
30
If GBHP drops by even 10mmHg, filtration in the glomerulus ___ (remember the NFP is what is needed to force filtration)
stops
31
Mechanisms that regulate GFR
Renal autoregulation
Neural regulation
Hormonal regulation
32
Renal autoregulation
Neural regulation
Hormonal regulation
Mechanisms that regulate GFR
33
Innate actions that occur within the kidney
| Mechanisms that regulate GFR
Renal autoregulation
34
Sympathetic nervous system input (or reduction of input)
| Mechanisms that regulate GFR
Neural regulation
35
Angiotensin II
Atrial natriuretic peptide (ANP)
(Mechanisms that regulate GFR)
Hormonal regulation
36
GFR- Renal Autoregulation Mechanisms
Myogenic mechanism
Tubuloglomerular feedback
37
increased BP (as in exercise) causes stretching of afferent arteriole, this causes smooth muscle contraction of afferent arteriole, reduces renal blood flow, which reduces GFR
Myogenic mechanism
38
This helps to preserve nephron integrity with increased blood pressure
When threat of increased BP is reduced, afferent arteriole may vasodilate to increase GFR to balance out the system
Myogenic mechanism
39
When GFR increases, rate through the tubules increase
Reabsorption of Na+, Cl- and water reduce due to rate of flow
Macula densa cells sense the increased levels of these in filtrate
These levels inhibit the release of nitric oxide (NO; vasodilator)
If NO inhibited, afferent arterioles constrict, lowers GFR
Lowered GFR slows rate through tubules
Tubuloglomerular feedback
| GFR- Renal Autoregulation
40
DCT runs very close to the JGA... the macula densa cells (of DCT) sense a chemical shift in the JGA (through extraglomerular masangial cells cells)
leading to constriction... slide 91ish
41
A complex structure that has the ability to affect systemic blood pressure through the autoregulation of tubuloglomerular feedback
Juxtaglomerular Apparatus (JGA)
There is one JGA for every nephron
42
JGA contains?
Juxtaglomerular cells
Macula densa cells
Lacis cells (modified mesangial cells)
43
Found in the walls of the afferent arteriole
Juxtaglomerular cells
44
Found in the walls of the distal convoluted tubule
Macula densa cells
45
Located between afferent arteriole, efferent arteriole, and DCT
Lacis cells (modified mesangial cells
46
The afferent arterioles contain juxtaglomerular cells
Modified smooth muscle cells that have two functions
Detect when blood pressure is too low (by sensing the lack of stretch of the afferent arteriole wall)
They synthesize, store, then secrete hormone/enzyme Renin (described later in RAAS)
Renin causes a cascade of events that helps to increase blood pressure when needed
47
Modified smooth muscle cells that have two functions
Detect when blood pressure is too low (by sensing the lack of stretch of the afferent arteriole wall)
They synthesize, store, then secrete hormone/enzyme Renin (described later in RAAS)
Renin causes a cascade of events that helps to increase blood pressure when needed
juxtaglomerular cells
48
Detect increase in NaCl (Sodium Chloride) concentrations in the filtrate
In response to this concentration check, these cells release
ATP, Adenosine in various concentrations which act locally
These trigger contraction of afferent arteriole
This causes GFR to reduce, which reduces the rate tubule flow
macula densa of DCT (part of JGA)
49
located in between the afferent, efferent and distal convoluted tubule junction
Contract or relax to make small regulatory changes in response to the signals that the other JGA cells are sending
Lacis Cells (Modified Mesangial cells)
50
Together the macula densa, juxtaglomerular cells, and Lacis cells make the ____
Juxtaglomerular Apparatus
51
This is tubuloglomerular feedback
Together the macula densa, juxtaglomerular cells, and Lacis cells make the Juxtaglomerular Apparatus
52
Depending on the filtrate analysis at this location, the filtration performance of the glomerulus can be changed
Helps regulate blood pressure within the kidneys
This can eventually effect systemic blood pressure
This is tubuloglomerular feedback
53
Blood vessels of the kidney are supplied by __ nervous system fibers only
sympathetic
54
At rest, sympathetic stimulation is low, so?
Afferent and efferent arterioles are dilated
Blood flow into and out of the glomerulus is relatively equal
55
With greater sympathetic stimulation, what happens to the kidneys?
Vasoconstriction of the afferent arteriole occurs
Blood flow decreases into glomerulus
GFR decreases
We need blood elsewhere in the body during these times
This also protects the nephrons from the rapid rise in blood pressure
56
Two hormones control regulation of GFR
Angiotensin II
Atrial natriuretic peptide (ANP)-
57
Very potent vasoconstrictor
Mostly acts on efferent arterioles
Reduces renal blood flow
Angiotensin II- reduces GFR
58
reduces GFR (hormone)
Angiotensin II
59
Secreted by the atria (heart)
Usually secreted in response to increase in volume
Markedly vasodilates afferent and efferent arterioles
GFR increases
Atrial natriuretic peptide (ANP)-
60
increases GFR
| hormone
Atrial natriuretic peptide (ANP)
61
Glomerular filtration occurs from pressures alone, not from ATP expenditure
Passive Movement
62
Epithelial cells all along the renal tubule and ducts reabsorb, but the ___ make the largest contribution to reabsorption
PCT cells
63
Solutes that are both actively and passively reabsorbed include
Glucose, amino acids, urea, sodium, potassium, calcium, chloride, magnesium, bicarbonate, and phosphates
CCUBA GSMPP
64
Once fluid passes through the PCT, cells located more distally “fine tune” the reabsorption process. Where?
Loop of Henle, DCT, Collecting duct
65
If small proteins and peptides are passed through the glomerular filter, they are ____
reabsorbed by pinocytosis (usually in PCT)
66
between adjacent tubule cells
Passive movement only
Thought to account for up to 50% of reabsorption
Paracellular reabsorption
67
through the tubule cell itself
(e.g., active transport, pinocytosis)
Passive and Active movement
Transcellular reabsorption
68
the lumen side of the cell
Apical membrane
69
the interstitial side of the cell
Basolateral membrane
70
Solute reabsorption drives water reabsorption via osmosis
This is called obligatory water reabsorption
71
90% of actual water reabsorption by the kidneys occurs with the reabsorption of
Sodium (Na+)
Chloride (Cl-)
Glucose
72
These segments are always permeable to water!!!!!!!!!
PCT and the descending limb of the loop of Henle
73
facultative water reabsorption
Regulated by ADH
| Occurs in the late DCT and collecting ducts
74
Regulated by ADH
Occurs in the late DCT and collecting ducts
facultative water reabsorption
75
The transfer of materials from the capillaries (peritubular and/or vasa recta), interstitial spaces and tubule cells into the filtrate
Tubular Secretion
76
Secreted substances include (but not limited to)?
Hydrogen ions
Secretion of hydrogen ions helps to control the blood pH
Potassium
Ammonium ions
Creatinine
Certain drugs like penicillin
77
There is a constant turnover of new blood coming into the kidney’s
The body signals the need for certain elements to be reabsorbed or secreted based on an attempt for homeostasis
This constant movement generates an osmotic gradient as well as an electric gradient (+/-)
The body signals the need for certain elements to be reabsorbed or secreted based on an attempt for homeostasis
Because of this, there is constant movement of things across these membranes (tubule cell : interstitial fluid : capillary)
78
nitrogenous waste created when proteins are catabolized (broken down)
Ammonia
79
much less toxic than ammonia, but can still be deadly if left to accumulate
Urea
Urea plays a significant role in creating and maintaining the osmotic gradient in the renal medulla
80
Most of the ___ is reabsorbed in the PCT.
This “safeguards” the body’s supply of an important buffer
bicarb (HCO3-)
| slide 116
81
Largest amount of solute and water reabsorption from filtered fluid occurs in the PCT
100% of glucose, amino acids, vitamins
i.e., not in DCT
82
80-90% of filtered HCO3- (bicarb)
Proximal Convoluted Tubule
83
~65% of Na+, K+, and water
Proximal Convoluted Tubule
84
Sodium (Na+) is actively transported out of tubule and into interstitial fluid
Glucose and amino acids are co-transported with Na+
Proximal Convoluted Tubule
85
As Na+ moves into blood, this creates a significantly positive environment in blood, so ___ ions passively move from filtrate into interstitial fluid to help balance this
(PCT)
Cl-
86
Cells lining the PCT and the descending LOH are especially permeable to water because of the presence of
aquaporin-1 channels
87
These are protein water channels that increase the rate of water movement
aquaporin-1 channels
88
Movement of Na+ and Cl- into interstitium creates a significant osmotic imbalance now, so water is obligated to move out of filtrate and into interstitum by ___
osmosis
89
The osmosis of water will often bring K+ and Ca++ with it in a motion called ___
solvent drag
90
stimulates cells in the PCT to secrete phosphate
stimulates calcitriol (Vitamin D) to be made in PCT cells and then be absorbed into blood
stimulates cells in the DCT to reabsorb more calcium
Parathyroid Hormone (PTH)
