renal Flashcards
1
Q
what are the main functions of the kidneys?
A
- regulation of water, Na/K balance and blood pH
- removal of metabolic from the blood and their excretion in the urine
- removal of foreign chemicals from the blood
- hormone/enzyme production
2
Q
what types of hormones are produced by the kidneys?
A
erythropoietin
renin
1,25 dihydroxyvitamin D3
3
Q
what is the function of erythropoietin?
A
production of RBC
4
Q
What is Renin
A
enzyme that controls the formation of angiotensin and influence sodium balance.
5
Q
what is the function of vitamin d in the kidneys
A
influences calcium balance, precursor enters the kidneys to be activated
6
Q
how big are each kidney?
A
size of fist, 150g
7
Q
where are the kidneys located?
A
Behind the peritoneum on either side of the vertebral column against the posterior abdominal wall
8
Q
what is the outer layer of the kidneys?
A
renal cortex
9
Q
what is the inner layer of the kidneys?
A
renal medulla
10
Q
how is the renal medulla divided into?
A
pyramids
11
Q
what do the renal pyramides converge into?
A
renal pelvis
12
Q
where is the renal A relative to the renal vein?
A
A is above V
13
Q
what is the first arterial branch of the renal a
A
interlobar A
14
Q
how does the interlobar A travel?
A
turns 90 degrees and artery, turns back 90 degrees
15
Q
what does the interlobar A branch off into?
A
into the interlobular
16
Q
what branch gives blood to the nepheron
A
afferent arteriole
17
Q
how many nepherons are contained in each kidnet
A
~1 million
18
Q
what is the nepheron composed of?
A
tubule renal corpuscule (glomerulus and bowman’s capsule)
19
Q
how does the nephron get blood supply?
A
afferent arteriole –> glomerulus –> efferent arteriole
20
Q
where is the bowman’s spae located?
A
around the glomerulus in the bowman’s casule
21
Q
in what does urine travel through?
A
through the tubule
22
Q
how does urine travel through the tubule
A
proximal tubule in the cortex will then enter the medulla in the loop of henle, will leave the medulla and will come in contact with the arterioles and enter the distal convoluted tubule which will merge with other nephrons into a collecting duct system found in both the cortex and the medulla.
23
Q
where is renin formed in the kidneys?
A
Juxtaglomerular apparatus
24
Q
what are the holes found in the glomerular capillary wall?
A
Fenestrae
25
what covers the holes of the glomerular capillary wall?
podocytes
26
what is the function of the glomerular capillary wall?
acts as a filtration barrier
27
where are the fenestrae located?
in the endothelial cells of the glomerular capillary wall
28
how does blood circulate through the glomerular capillary wall (pathway)
capillar lumen > endothelial cells > glomerular basement membrane > visceral glomerular epithelial cells
29
what is another name given to the glomerular epithelial cells?
podocytes
30
what is the function of the glomerulus?
filter blood to produce urin
31
what is another name given to the tubule epithelial cells?
peritubular capillaries
32
what are the 3 basic processes of urine formation?
1. glomerular filtration
2. tubular secretion
3. tubular reabsorption
33
what is the function of glomerular filtration?
filtration of plasma from the glomerular capillaries into Bowman’s space
34
what is glomerular filtrate ?
fluid found in bowman’s space which is cell free but contains substances or plasma except for large proteins
35
what is the function of tubular secretion?
peritubular capillaries to tubules blood becomes urine
36
what happens are the glomerular filtrate passes through the tubules?
As the glomerular filtrate passes through the tubules, its composition is altered by movements of substances.
37
what does tubuar reabsorption invole
reabsorbin urine into the blood by the tubule to the peritubular capillaries
38
what is the amount of urine excreted?
its the sum of the amount filtered + amount secreted - amount reabsorbed
39
where does everything get filtered?
at the glomerular capillaries.
40
how is glucose filtered?
100% reabsorbed
41
how is sodium and water filtered?
reabsorbed to some extent and then the rest is secreted
42
how is PAH filtered?
what isnt filtered continues in the blood and gets fully secreted
43
what does the rate of filtration, reabsorption and secretion depend on?
physiological state of the body such as (When the body content of a substance goes above or below normal, homeostatic mechanisms can regulate the substance’s bodily balance by changing these rates)
44
what gets filtered in the bowman’s space of the glomerulus?
filtrate
45
what type of molecules are freely filtered?
Water and low-molecular weight substances
46
what type of molecules are not freely filtered?
Not freely filtered: cells, proteins (i.e. albumin, globulins), protein-bound substances (i.e. 1/2 of Ca ion, fatty acids)
47
what are the main forces involved in filtration?
```
PGC = glomerular capillary blood pressure is the favoring filtration force.
PBS = fluid pressure in bowman’s space, an opposing filtration force.
piGC = Oncotic pressure = osmotic force due to proteins in plasma, the other opposing filtration force.
```
48
what is the net glomerular fitration pressure?
PGC – PBS – piGC
| ~16 mm Hg
49
what is the Glomerular filtration rate (GFR)?
the volume of fluid filtered from the glomeruli into
| Bowman’s space per unit time
50
how if GFR regulated?
net filtration pressure (only one accounted for in this class but also memebrane permeabiluty and surface area availible for filtration)
51
what is the normal GRF in a standard patient?
180L/day
52
how often is the entire plasma of a person filtered daily?
over 50 times
53
how can GRF be decreased?
1. Constrict the afferent arteriole, thus less blood flowing per time, decreasing PGC.
important)
2. Dilate efferent arteriole, thus decreasing the PGC
54
how can GRF be increased?
1. Constrict Efferent arteriole, slowing down the blood flow away from glomeruli, increasing PGC. 2. Dilate afferent arteriole, more blood arrives at the same time, increasing PGC.
55
what is the filtered load?
total amount of any freely filtered substance per unit time. GFR x plasma concentration of the substance (if freely filtered)
56
what happens if filtered load > amount excreted?
net reabsorption has occurred
57
what happens if filtered load < amount excreted?
net secretion has occurred
58
where does reabsorption take place?
from the tubular lumen to the peritubular capillary
59
what keeps the tubular epithelial cells together?
tight junctions
60
what faces the tubular lumen?
the tubular membrane
61
what faces the peritubular capillaries
basolateral membrane
62
how do parcellular solvents travel?
go between the cells from tubular lumen to peritubular capillary
63
how do transcellular solvents travel?
go through the cells from tubular lumen to peritubular capillary
64
what has the highest percentage of reabsorption?
Water, sodium and glucose
65
why are urine and potassium not fully reabsorbed?
urine is a waste product (44% reabsorbed)
| potassium if found in large doses may be toxic (86.4%)
66
is reabsorption of waste products complete?
no, relatively incomplete
67
is reabsorption of most useful plasma components complete?
yes
68
is the regulation of glucose and AA regulated?
no
69
is the reabsorption of water and inorganic ions regulated?
yes
70
are the filtered loads big or small?
they are enormous
71
through what process does reabsorption occur?
diffusion and mediated trabsort
72
how does reabsorption by diffusion function/?
ften across the tight junctions connecting the tubular epithelial cells. Secondary to sodium diffusion.
73
what happens when urea is reabsorbed through the proximal tubules?
- ->In the proximal tubule, water reabsorption occurs and urea follows water.
- ->Urea concentration in the tubular fluid becomes higher.
- ->Urea diffuses into the interstitial fluid and peritubular capillaries.
74
how does reabsorption by mediated transport function?
occurs across tubular cells Requires the participation of transport proteins in the plasma membrane of tubular cells.
75
what is reabsorption by mediated transport usually coupled with?
Na+ reabsorption
76
how does mediated transport function?
Na/K-atpase pumps Na from the cell into the capillary and K from the capillary to the cell. Low Na in the cell drives Na+ in the lumen of the cell
Na/glucose cotransporter allows for Na and Glucose to drive into the cell
Na/AAs channels allow Na to drive in with AAs
Glucose/AAs channels let glucose and AAs diffuse out into the ISF and eventually back into the capillaries
77
what is the transport maximum attained?
When the membrane transport proteins become saturated causing the tubule to be unable to reabsorb anymore
78
how is Tm exceeded in diatbetic patients?
uncontrolled diabetes= high [glucose] in plasama, where filtered load > capacity of tubules to reabsorb glucose causing glucourea
79
what is moved by tubular secretions?
moves substances from peritubular capillaries into the tubular lumen
80
what is tubular secretion mediated by?
diffusion and transcellular mediated transport.
81
what are the most important substances secreted by the tubules?
H+ and K+
82
what is tubular secretion generally coupled with?
eabsorption of sodium
83
what is the function of the proximal tubule?
reabsorbs most of this filtered water and solutes. It is also a major site of secretion for various solutes, except K+.
84
what is the function of Henle’s loop of the tubules?
eabsorbs relatively large quantities of the major ions (less water).
85
what is the function of DCT/CD of the tubules?
Fine-tuning. Determines the final amounts excreted in the urine by adjusting the rates of reabsorption, and, in a few cases, secretion.
86
where does most homeostatic controls take place int he tubuules
DCT/CD
87
what is clearence?
the volume of plasma from which that substance is completely removed (“cleared”) by the kidneys per unit time.
88
what does clearence dependent on?
Mass of S excreted in urine per unit time/
| Plasma concentration of S (Ps)
89
what equation is used to calculate clearence?
Mass of S excreted per unit time = Urine concentration of S (Us) x Urine volume per unit time (V).
Cs = UsV / Ps
90
what is inulin?
polysaccharide that gets freely filtered at the glomerulus but isn’t reabsorbed, secreted or metabolized by the tubule
91
what is the clearance of inulin equal to?
is equal to the volume of plasma originally filtered (GFR).
92
what is the most accurate marker for GFR?
INULIN CLEARENCE
93
Why is inulin clearence not ideal?
requires to keep patient on IV over a certain time period
94
what is creatinine?
Creatinine is a waste product produced by muscle.
95
is creatinine filtered and reabsorbed by glomerulus?
It is filtered freely at glomerulus and is NOT reabsorbed.
96
is creatinine metabolized by the tubule?
no
97
what is an advantage of measuring creatinine clearence?
naturally found in the body hence doesnt need to be administered to patient
98
how to calculate creatinine clearence?
Urine concentration of creatinine (UCr)*Urine volume (V)/Plasma concentration of creatinine (Pcr)
99
what happens when clearence > GFR
secreted at the tubule
100
what happens when clearence < GFR
its reabsorbed at the tubule
101
how can partial reabsorption or total absorption be described as?
clearence < GFR
102
What needs to be maintained to sustain normal BP and life?
total body balance of Na and water
103
how do we intake water?
food, liquids and metabolism
104
how does water leave our bodies?
insensible losses of the skin and lungs
urine
feces
105
how do we intake Na
through food
106
how does the body excrete sodium?
sweat
feces
mostly urine
107
how much can sodium and water intake vary daily?
h20 can vary from 0.4 L/day to 25 L/day
| sodium chloride output can vary from 0.05 g/day to 25 g/day
108
is sodium and water secreted?
no, both are freely filtered and ~99% gets reabsorbed
109
where does the majority of sodium and water reabsorption occur?
2/3 occurs in the proximal tibule
110
where does the hormonal control of reabsorption of sodium and water take place?
DCT and CD
111
where does Na reabsorption take place?
tubular segments except for he descending thin limb of Henle’s loop
112
where does H20 reabsorption take place?
occurs via diffusion
113
what is H20 reabsorption dependent on?
on Na reabsorption
114
where does Na active reabsorption take place?
cortical collecting duct
115
how does Na/K atpase function in Na reabsorption?
allows for Na to be reabsorbed into the tubular lumen
116
what does Na diffuse through in the cortical collecting duct to reach the tubular lumen?
sodium channels
117
what is the role of Na/K-atpase on the basolateral membrane?
pumps sodium out of the cell and keeps the intracellular concentration of sodium low
118
what happens to sodium on the apical (lumenal) side of the membrane
Na moves downhill from the tubular lumen into the tubular epithelial cells
119
what is different about each tubular segment in regards to Na reabsorption
function under different mechanisms in different segments
120
what happens when sodium intake goes uo?
urinary sodium excretion goes up
121
what happens when sodium intake goes down?
urinary sodium excretion goes down
122
what is the body’s major extracellular solute?
Na
123
what do changes in the body’s sodium result in?
similar changes in the Body’s ECF volume
124
what is the total body sodium sensed by?
baroreceptors in the cardiovascular system.
125
what is the total body sodium sensed as?
sensed as intravascular fillin (amount of plasma in the blood vessels)
126
is plasma concentration of sodium a marker for total body sodium?
no
127
what does Pna reflect?
relative relationship of the total body Na and water
128
what is the amount of sodium excreted?
sodium filtered-sodium reabsorbed
129
what regulates sodium excretion
GFR (minor) sodium reabsorption (major)
130
what happens when the body loses a high amount of sodium or water?
1) decrease plasma volume
- decrease venous pressure which gets sensed by the baroreceptor reflex
- increases activity of the renal sympathetic nerves
2) decreased venous return thus the heart doesnt which devreases atrial pressure, EDV, SV and thus the heart cannot pump enough blood which triggers baroreceptor reflex to increase activity of the sympathetic nerves
131
what happens when the baroreceptor reflex to increase activtiy of the sympathetic nerves
Causes an increased constriction of afferent arterioles and then a decrease of the net GF pressure which decreases GFR thus decrease is Na and H20 excretion
132
what is the main hormone responsible for controling Na reabsorption?
aldosterone
133
aldosterone stimulates Na reabsorption where?
stimulates reabsorption in DCT and CD
134
how much of the filtered load is excreted when no aldosterone?
~2% thus ~35g NaCl
135
how much of the filtered load is excreted when high aldosterone?
~0% of filtered load gets excreted
136
reabsorption of Na in CCD is under what control?
hormonal control
137
where does Na absorption take place? in what proportions
Proximal = 67%, TAL = 25%, DT = 4%, CCD = 3%, IMCD = 1%
138
what gets activated/upregulated by aldosterone?
the activity of ATPases and Na channels
139
what system is responsible for the regulation of aldosterone secretions?
Renin angiotensin system
140
where does angiotensinogen begin?
in the liver and gets secreted into the blood
141
how is angiotensinogen converted once its in the blood? by which hormone?
angiotensin 1 by renin
142
what organ secretes renin?
kidneys
143
what is angiotensin 1 converted into? by what enzyme?
angiotensin 2 by angiotensin converting enzyme
144
where does angiotensin 2 go and what does it stimulate?
enters the adrenal cortex and stimulates aldosterone secretion
145
what may increase secretion of aldosterone?
increase plasma K or ACTH
146
what can inhibit secretion of aldosterone?
ANP
147
what are the juxtaglomerular cells wound tightly around?
afferent arteriole
148
what innervates the juxtaglomerular cells?
sympathetic nerves
149
what can be stimulated by the sympathetic nerves?
renin secretion
150
how can the juxtaglomerular cells be activated other than by innervation?
low afferent arteriole tension allows blood to pass through and thus can be sensed by the cells
151
what does the ascendinh part of the loop of henle come in touch with?
the glomerula
152
what is the name of the cells that touch the sude of the tube of glomerula?
macula densa
153
what can be detected by macula densa
when there is not enough Na and send signal to the juxtaglomerular cells
154
what are some other factors that may influence renal na excretion?
- arterial natriuretic peptide
| - BP
155
what is ANP?
peptide hormone secreted by cells in the cardiac atria.
156
what does ANP act on?
acts on the tubules to inhibit sodium reabsorption thus increases GFR
157
What stimulates ANP secretion?
Increased total body sodium
158
what does increased blood pressure cause?
increased sodium excretion
159
what is osmolarity?
total solute concentration of a solution,
160
what is a hypoosmotic solution?
solution where the total solute concentration is less than that of the ECF (300 mOsm)
161
what is a isoosmotic solution?
solution where the total solute concentration is equal to that of normal ECF (300 mOsm)
162
what is a hyperosmotic solution?
having total solute concentration greater than that of normal ECF (300 mOsm)
163
what are the 3 crucial aspects of water balance?
- Water is freely filtered but ~99% is reabsorbed, no secretion.
- The majority of water reabsorption (~2/3) occurs in the proximal tubule.
- But the major hormonal control of reabsorption occurs in the CD.
164
what does water reabsorption depend on?
Na absorption
165
where is water reabsorbed into from the tubular lumen?
into the ISF across the epithelial cells
166
what happens to the osmolarity in the lumen and interstitium as Na is reabsorbed in the tubular lumen?
The local osmolarity in the lumen decreases (water conc becomes high), while the local osmolarity in the interstitium increases.
167
what does the difference in the tubular lumen and interstitium
auses net diffusion of water from the lumen into the interstitial fluid.
168
how does water move into the interstitium
via tubular cells’ plasma membranes
| via tight junctions
169
through what mechanism does the interstitum move
bulk flow in peritubular capillaries
170
what happens in the when the water intake is small
the kidney reabsorbs more water
171
what happens in the when the water intake is large
the kidney reabsorbs less water
172
where does dynamic regulation of water take place?
in the CD
173
what are the 2 critical components of dynamic regulation of water?
1. High osmolarity of the medullary interstitium.
| 2. Permeability of CD to water (regulated by vasopressin)
174
what mechanisms maintains high osmolarity in the medulla of the kidneys?
countercurrent multiplier system
175
how much urine can the kidney’s concentrate
up to 1400 mOsm/L.
176
where does urinary concentration take place?.
takes place as tubular fluid flows through the medullary collecting
ducts.
177
what does urinary concentration depend on?
the hyperosmolarity of the interstitial fluid
178
what happens to water in the presence of vasopressin
water diffuses out of the ducts into the interstitial fluid in the medulla
179
what happens to the osmolarity of the medulla as it passes through Henle’s loop
hyperosmotic
180
what is the function of the ascending limb of the countercurrent multiplier system?
reabsorbs NaCl but is impermeable to water
181
what happens to the osmolarities of the ascending limb of the countercurrent multiplier system
since Na is absorbed but not water, the fluid Osm goes from 300 to 200 and the ISF increases to 400 mOsm
182
what is the function of the descending limb of the countercurrent multiplier system?
Doesn’t reabsorb NaCl, permeable to water
183
what happens to the osmolarities of the descending limb of the countercurrent multiplier system
ISF=400 mOsm but water moves until it equilibrates and tubule fluid=400 mOsm
184
how does the fluid move in the from the tubule, descending and ascending limb?
Fresh fluid comes from proximal (300), fluid in descending limb moves down, turns and starts to go up (400), fluid in in the ascending limb continues up and starts to leave (200)
185
what are the main steps of the countercurrent multiplier system?
Step 1 NaCl is reabsorbed, changing the osmolarities
| Step 2 water diffuses again to keep up with the change in interstitial osmolarity.
186
what is equilibrated by the descending limb
The fluid surrounding it is equilibrated with the descending limb
187
what are the blood vessels surround the medulla?
vasa recta
188
what does the hair-pin loop minimize?
minimizes excessive loss of solute from the interstitium
189
what factors contribute to medulla hyperosmolarity?
NaCl, urea
190
what does water reabsorptiin in the tubules depend on?
depends on the water permeability of the tubules
191
what does permeabilty of the epithelium depend on?
depends on the tubular segment
192
what is the permeability of water in the proximal tubule?
high permeability
193
what does permeability largely depend on?
ermeability largely depends on the presence of water channels
194
what is the key hormone that controls water permeability in the MCD, CD?
vasopressin
195
what is vasopressin?
Peptide hormone, also called anti-diuretic hormone (ADH)
196
what produces vasopressin?
posterior pituituary
197
what type of receptors interact with vasopressin
Couples to G-coupled Protein CReceptors V1 (smooth muscle) and V2 (kidney)
198
how does vasopressin function?
Vasopressin stimulates the insertion of aquaporins in the luminal membrane of the collecting duct cells and increases the water permeability.
199
what happens to collecting ducts when vasopressin is present?
When vasopressin is present, collecting ducts become permeable to water
200
what happens to collecting ducts when vasopressin is absent?
water diuresis
201
what my cause diabetes insipudus?
malfunction of the vasopressin system
202
what happens to fluid in the presence of vasopressin by the time it reaches the CCD?
Fluid is hypoosmolar by the time it gets to the cortical collecting duct. If there is vasopressin, It starts to get reabsorbed.
203
what happens to the fluid when it enters the medullary collecting duct?
nterstitial fluid becomes more and more hyperosmotic, until it reaches the max (1400).
204
what happens to fluid in the absence of vasopressin in the CD?
Fluid stays hypoosmotic through the whole collecting duct (50).
205
what rate is regulated by vasopressin?
Water excretion is mainly regulated by the rate of water reabsorption from the tubules
206
what regulates vasopressin secretion?
1. Osmoreceptor control (most important)
| 2. Baroreceptor control (less sensitive)
207
what process happens in osmoreceptor control?
excess water consumption > body fluid osmolarity decreases > supresses firing of hypothalamic osmoreceptors > decrease in vasopressin secretion > decrease of vasopressin in plasma > decrease tubular permeability to water >decrease in water reabsorption > increase inwaterexcretion.
208
what process happens in baroreceptor control?
plasma volume decreases > decrease in venous, atrial and arterial pressures > reflexes mediated by cardiovascular baroreceptors activated > increase in vasopressin secretion > increase in vasopressin in plasma > increase in tubular permeability to water > increase in water reabsorption > decrease in water excretion
209
what factors cause us to feel thirsty?
1. dry mouth, throat
2. metering of water intake by GI tract
3. decrease of plasma volume detected by
baroreceptors
4. high plasma osmolarity detected by
osmoreceptors
