CVPR Week 7: Water & Sodium Balance Flashcards
1
Q
Objectives
A
2
Q
Question 1
A
3
Q
Question 2
A
4
Q
Question 3
A
5
Q
Basic role of the kidneys
A
Body fluid composition
6
Q
How do the kidneys change body fluid composition?
A
- Ideal environment for cellular function
- water and electrolyte excretion and retention controlled
- Composition of extracellular water and plasma tightly regulated by renal function
7
Q
Primary processes of the kidneys
5 listed
A
- Filtration
- Reabsorption
- Secretion
- Excretion
- Endocrine function
8
Q
What structure in the kidney is responsible for filtration?
A
Bowman’s Capsule
9
Q
Glomerulus AKA
A
Bowman’s Capsule
10
Q
Bowman’s Capsule AKA
A
Glomerulus
11
Q
What function is the glomerulus responsible for?
A
Filtration
12
Q
What function is the proximal tubule responsible for?
A
Reabsorption
13
Q
What function is responsible for reabsorption in the kidney?
A
Proximal tubule
14
Q
What function is responsible for descending water reabsorption and ascending solute reabsorption in the kidney?
A
Loop of Henle
15
Q
What function is responsible for regulated solute reabsorption in the kidney?
A
Distal tubule
16
Q
What function is responsible for regulated water reabsorption in the kidney?
A
Collecting duct
17
Q
What function is the proximal tubule responsible for?
A
Reabsorption
18
Q
What function is the Loop of Henle responsible for?
A
- Water reabsorption (descending)
- Solute reabsorption (ascending)
19
Q
What function is the distal tubule responsible for?
A
Regulated solute reabsorption
20
Q
What function is the collecting duct responsible for?
A
Regulated water reabsorption
21
Q
Identify
A
22
Q
Types of nephrons
A
- Superficial nephrons
- Juxtamedullary nephrons
23
Q
Juxtamedullary nephrons
A
- 10% of nephrons
- Long loop
24
Q
Superficial nephrons
A
- Short loop
- 90% of nephrons
25
Identify
26
The filtration process
1. Blood is "filtered" as it passes through the glomerular capillaries
2. ~20% of plasma entering the glomerulus is filtered into Bowman's Space and enters the proximal tubules
3. Plasma is filtered ~60 times/day to control water, sodium and waste product levels
27
Blood is filtered as it passes through?
The glomerular capillaries
28
How much filtrate is Reabsorbed
99% of filtrate is reabsorbed
29
Reabsorbed filtrate moves into
The peritubular capillaries
30
How is reabsorption regulated?
By hormones
31
The importance of urine excretion
important route of excretion for many toxic substances
32
How is secretion in the kidney mediated?
By transporters
33
Endocrine function of the kidneys
The kidney is an important site of synthesis for three hormones
34
Renal hormones
3 listed
* Erythropoietin
* 1, 25-dihydroxy vitamin D3
* Renin
35
1, 25-dihydroxy vitamin D3 AKA
Calcitriol
36
Calcitriol AKA
1, 25-dihydroxy vitamin D3
37
Erythropoietin function
Erythrocyte formation
38
1, 25-dihydroxy vitamin D3 function
Ca2+ homeostasis
39
Renin function
Na+ and H2O balance
40
Location of renin synthesis
Synthesized in juxtaglomerular cells (JCC) of the afferent arteriole (granular cells)
41
What is renin
Renin is an enzyme the regulates the formation of angiotensin II
42
Renin regulation
Renin is regulated by sympathetic nerves, salt intake and blood pressure
43
What stimulates the release of renin?
Decreased renal blood flow or sodium delivery stimulates renin release
44
Renin function
regulates the formation of angiotensin II
45
Angiotensin II function in fluid composition
it is a sodium-retaining hormone
46
Identify
47
EGMC AKA
Extraglomerular mesangial cell
48
What is erythropoietin?
a glycoprotein hormone
49
Location of erythropoietin synthesis
Erythropoietin is synthesized and secreted from renal epithelial cells
50
Erythropoietin function
stimulates erythrocyte synthesis
51
erythropoietin AKA
EPO
52
EPO AKA
erythropoietin
53
Renal failure and erythropoietin
Renal failure decreases erythropoietin synthesis leading to anemia
54
Location of calcitriol synthesis
* The inactive 25-hydroxyvitamin D (Calcidiol) is synthesized in the skin and liver
* Calcidiol is then taken up by proximal tubule cells hydroxylated to active calcitriol (1, 25-dihydroxy vitamin D)
55
Calcitriol is reabsorbed
from the proximal tubule into the blood stream
56
Calcitriol function
increases Ca2+ reabsorption from the gut and from the renal tubules and inhibits PTH release
57
Calcitriol synthesis pathway
58
Renal regulation of body fluids: Out
* Urine
* Sweat
* Feces
59
Renal regulation of body fluids: In
* Food
* metabolism
60
Renal regulation of body fluids
61
Body fluid compartments
* Intracellular compartment
* Extracellular compartment
62
Total body water compartmentalization
40% ICW
20% ECW
63
Intracellular water % of body weight
40% of the body weight
64
Extracellular water % of body weight
20%
65
Intracellular compartment water consists of?
Water inside cells
66
Electrolyte composition of the intracellular compartment
* High [K+]
* Low [Na+] & [Ca2+]
67
How does water move in the intracellular compartment
* movement across cell membranes through channels and pumps
* water moves freely in and out of cells
68
Extracellular compartment electrolyte composition
* Low [K+]
* High [Na+] & [Ca2+]
69
Extracellular compartment water consists of?
plasma and interstitial water
70
Extracellular compartment movement of water
* Relatively large changes in volume
* water moves from the plasma to interstitium across capillaries (back in lymph)
71
Electrolyte distribution in fluid compartments
72
How to calculate compartment size
Dilution principle
73
Substances used to estimate body compartment sizes
* Total body water
* Extracellular fluid
* plasma
* Intracellular fluid
* Interstitial water
74
TBW AKA
Total Body water
75
ECF AKA
Extracellular fluid
76
VP
Plasma volume
77
ICF AKA
Intracellular fluid
78
Vinst AKA
Interstitial water volume
79
Vinst =
ECF - VP
80
ICF =
TBW - ECF
81
VP =
Evans blue or 131I-albumin
82
ECF =
Inulin or mannitol
83
TBW =
Antipyrine
Titrated water (3H2O) or deuterium (D2O)
84
The simplest and cheapest method for quickly assessing fluid balance
Body weight
85
Plasma osmolarity =
2 x PNa + [glucose]/18 + BUN/2.8 = plasma osmolarity
86
Considerations of estimating plasma osmolality
* Protein is ignored since it usually contributes less than 1 mOsm
* [glucose] is divided by 18 and BUN by 2.8 to convert from mg/dL to mmol/L
* PNa is multiplied by 2 to account for the accompannying anion (usually Cl- or HCO3-)
* 2 x PNa gives an estimate of plasma osmolality
* (will give a low value if glucose, BUN or organic acids are elevated)
87
Na intake alters?
ECF volume
88
Osmosis description
Solvent moves towards high solute concentration from a lower solute concentration
89
Osmosis solute considerations
Only non-permeant solute contributes to osmotic pressure
90
Osmosis rate is dependent on?
osmotic gradient and permeability of the membrane
91
What determines the final size of a compartment?
the amount of non-permeant solute in that compartment
92
How is cell volume regulated?
Osmolality regulates cell volume
93
Types of volume expansion
* Isosmotic
* Hyperosmotic
94
Hyposmotic volume expansion
