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PHYSIOLOGY-Y2S2 > renal hemodynamics > Flashcards

renal hemodynamics Flashcards

1
Q

what are the functions of kidney?

A

Excretion of metabolic waste productions ( urea, uric acid, creatinine, urobilinogen )

Excretion of foreign chemicals ( pesticides , toxins )

Secretion, metabolism and excretion of hormones ( erythropoietin , vitamin D activations )

Regulation of acid base balance

gluconeogenesis : glucose synthesis from amino acids ( in prolonged fasting )

Control of arterial pressure ( renin system and regulate fluid volume )

Regulation of water and electrolytes excretion

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2
Q

How does the kidneys regulates ECF?

A

via glomerulus

Tubules

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3
Q

describe how does glomerulus regulate ECF?

A

Filtration

provide the tubules with fluid so that THE VOLUME AND COMPOSITION CAN BE MODIFIED

Filtration is the first step in urine formation , blood is going to the glomerulus and gets filtered resulting in formation of ultrafiltrate in bowmans capsule

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4
Q

Describe how Tubules regulate ECF?

A

Modify the composition of ECF by reabsorbing what is needed

Secrete substances into fluid

Modification of ultrafiltrate happens in the tubules by reabsorbing what body needs secreting other substances which the body doesnt need

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5
Q

what is the functional unit of the kidney?

A

Nephrons

1-1.2 million nephrons per kidney

nephrons cannot be regenerated

With normal aging the number of nephrons decreases but kidneys have strong adaptive ability, person can live with one kidney

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6
Q

what are the 2 components of nephrons ?

A

vascular components

Tubular components

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7
Q

what are the vascular components?

A

Glomerulus

Afferent arterioles

Efferent arterioles ( we have 2 sets of capillaries connected by the efferent arterioles, this makes vascular system of the kidneys unique )

Peritubular capillaries

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8
Q

describe tubular components ?

A

Bowmans capsule

Proximal tubule

Loop of henle

Distal tubule

Collecting ducts

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9
Q

what is glomerulus?

A

capillary network emerging from afferent arterioles

the glomerulus capillaries are surrounded by bowmans capsule or space

IN this space

THE BLOOD IS ULTRAFILTRERED INTO THIS SPACE ( FIRST STEP IN THE FORMATION OF URINE

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10
Q

what are the types of nephrons ?

A

superficial cortical nephron

Juxtamedullary nephrons

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11
Q

describe superficial cortical nephron ?

A

80%

glomeruli in outer cortex hairpin loops barely reaches medulla

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12
Q

describe juxtamedullary nephrons?

A

20%

glomeruli near corticomedullary border

long loop of henle descending deep into inner medulla and papilla and is essential for urine concentration

present at the junction between cortex and medulla

very long loop of henle

vasa recta

make concentrated urine ( why they have to reach the medulla )

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13
Q

what supplies superficial cortical nephrons?

A

peritubular capillaries for supplying nutrients to epithelial cells

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14
Q

what supplies juxtamedullary nephrons?

A

Peritubular capillaries —> KNOWN AS VASA RECTA

Which are long hairpin like following the loop of henle —> FOR CONCENTRATING URINE

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15
Q

describe the structures of juxtaglomerular apparatus?

A

Ascending limb of henle passes through a fork formed by afferent and efferent arterioles of the same nephrons

Vascular and tubular cells at this junctures are both specialized to form the JUXTRAGLOMERULAR APPARATUS

Juxtaglomerular cells in the wall of afferent and efferent arterioles and MACULA DENSA cells in the initial portion of distal tubule constitutes JUXTAGLOMERULA APPARATUS

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16
Q

where are juxtaglomerular apparatus found?

A

specialized type of cells located in the distal convoluted tubule DCT

outer lining of the afferent and efferent arterioles

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17
Q

how are juxtaglomerular apparatus formed?

A

when the DCT starts it goes back to the cortex it comes in contact with arterioles because they are in the cortex too

we need this for autoregulation and blood pressure regulations

in the DCT cells are called macula densa and in the walls of the arterioles the cells are called juxtaglomerular cells together they form juxtaglomueral apparatus

their function is to sense the composition of the urine and respond accordingly , mainly sense sodium chloride they can produce renin ( when low sodium, low bp, hypovolemia )

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18
Q

what pressure is higher in glomerular capillaries?

A

High hydrostatics pressure

they are filtering capillaries

19
Q

why is hydrostatic pressure high ?

A

Because efferent arterioles are narrow and have high resistances

20
Q

what is the function of peritubular capillaries?

A

reabsorbing capillaries

Very low hydrostatic pressure to allow reabsorption

21
Q

what happens to blood flow past glomerular capillaries to peritubular capillaries?

A

Large pressure drop because the hydrostatic pressure is high at glomerular but low at peritubular capillaries

22
Q

what is the composition of glomerulus?

A

Glomerulus is composed of capillary loops

invaginated in bowmans capsule

Bowmans capsule joins the proximal tubule a single layer of epithelial cells lying on a basement ( bowmans is a tubular component and glomerular capillaries is vascular component )–> together = glomerulus

23
Q

what are the layers blood has to go through in order to reach bowmans capsule ?

A

1- endothelium of BV ( fenestrated 50-100 nm )

2- basement membrane of BV

3- epithelium of bowmans capsule ( podocytes )

all these 3 together form filtration apparatus

24
Q

what does the first layer exclude ?

A

capillary endothelium ( fenestrated )

excludes BLOOD CELLS, high permeable

25
what does the second layer allow pass?
basement membrane lamina rara interna, lamina densa, lamina rara externa Proteoglycan gel , negative charge ----> ALLOW CATIONS TO PASS
26
what does the 3rd layer allow pass?
capsular epithelial cells, podocytes and foot processes filtration slits , slit diaphragm size, selective porous membrane NEGATIVELY CHARGED ---> makes this layer selective to size but allow cations to pass SO WHEN SUBSTANCES WANT TO PASS THROUGHT : SHOULD BE LOW IN SIZE COMPARED TO THE SLIT THEY SHOULDNT BE NEGATIVE UNBOUND
27
What are the stuff freely filtered?
Na CL Crystalloids K HCO3 Urea Cr INSULIN PAH GluAA organic acids HB myoglobin water freely pass
28
what are the stuff that are not freely filtrated?
albumin plasma protiens lipid soluble sb attached to protiens T4 BILIRUBIN UNBOUND LIPIDS SOLUBLES SUBSTANCES SUCH AS FREE CORTISOL CAN BE FILTRERED COLLOIDS
29
describe filtration of anions?
at any molecular weight filtration of anions is selectively restricted LOSS OF ANION COAT RESULTS IN INCREASE OF SOME SUBSTANCES FILTERED , like proteins ---> when a disease happens, the first thing lost from filtration membrane is the anion coat which results in loss of negative charge So any substances that has negative charge can easily pass such as albumin, later on pores are distorted and become bigger allowing bigger proteins to pass
30
what decreases filterability?
negative charge SIZE as the size increases the filterability deceases anions are difficult to pass even if they are small in size ( opposite applies to cations )
31
what determines glomerular filtration rate?
Net filtration pressure ( NFP ) X Filtration coefficient ( Kf)
32
what is net filtration pressure ?
sum of staling forces : Glomerular hydrostatic pressure PG glomerular colloid osmotic pressure Hydrostatic pressure in bowmans capsule bowmans capsule colloid osmotic pressure colloid one is the opposing forces of the glomerular
33
which force is favored and is 0?
bowmans colloid pressrue is favored but it is 0 cuz no protein in this fuild so not considered it is supposed to pull fluid to the bowmans capsule
34
what is the major determinant of GFR?
glomerular hydrostatic if it increases GFR will increase
35
what is GFR proportional too?
filtration coefficienct which changes in pathologies
36
what happens to the osmotic pressure of Glomerulus ?
progressively increases as fluid is filtered cuz as fluid goess into the capsule , this causes the concentration of proteins increaese in blood ---> increases the glomerular colloid pressure So by the time blood reaches efferent arteriolar end of filtration stops and pressure is 0 filtration equilibrium is attained and net ultrafiltration pressure is zero ( filtration stops )----> OCCUR AT THE BEGNINNING OF CAPILARRIES ( efferent arterioles )
37
what is the difference between Kf of kidney capillaries and body capillaries ?
400 times higher
38
what controls filtration coefficient ?
Water permeability or hydraulic conductance Total surface area
39
what could affect the water permeability /hydraulic conductance and decrease the filtration coefficient ?
chronic hypertension Diabetes increased thickness of glomerular capillary basement membrane
40
what could affect the the total surface area and decrease filtration coefficient ?
chronic renal failure chronic pyelonephritis number of functional nephrons are destroyed total surface area decrease ---> decrease KF
41
describe the regulations of GFR?
GFR remains relatively constant due to autoregulation despite arterial pressure fluctuations A decrease in arterial pressure to 70 mm HG and INCREASE TO 180 mm HG changes the GFT only LESS THAN 10% IN ABSENCE OF AUTOREGULATION WITH SMALL INCREASE IN BP GFR will increase up to 25% and urine output WOULD INCREASE MORE THAN 30 FOLDS SO ITS AFFECTED HIGHLY BY BP BUT UUSALLY NOT DUE TO AUTOREGULATION
42
What happens if u constrict afferent arterioles?
AFFERENT ARTERIOLES RESISTANCE INCREASE blood coming to the glomerulus will decrease ----> decrease hydrostatic pressure and GFR and decrease renal blood flow
43
what happens if constrict efferent arterioles?
Resistance in EFFERENT INCREASES blood wont leave so it will pool in the glomerular capillaries INCREASING THE HYDROSTATIC PRESSURE ---> INCREASE GFT but after long time , the GFR will decrease ---> Decreasing renal blood flow
44
why does mild constriction in efferent increase GFR and severe constriction lead to decrease in GFR?
its called biphasic effect moderate constriction ---> slight increase in GFR cuz glomerular hydrostatic pressure increase severe constriction ----> GFR decrease cuz the plasma protein concentration in the glomerular capillaries increases CUZ THE BLOOD POOLS in to the glomerulus and filtration is going on this ( fluid is lost but proteins still there and more blood is coming and more proteins is coming ) ---> and as this is going on the plasma protein concentration increases in the glomerular osmotic pressure this will reduce the net filtration pressure and cause GFR to reduce

PHYSIOLOGY-Y2S2 (16 decks)

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