L20– Glomerular Filtration and Tubular Transport Flashcards Preview

MBBS I CPRS > L20– Glomerular Filtration and Tubular Transport > Flashcards

Flashcards in L20– Glomerular Filtration and Tubular Transport Deck (79):
1

How is water content controlled by urine?

By urine volume (if water in deficit > concentrated urine > smaller loss of water)

2

What three things are controlled by urine composition?

 Electrolyte balance (Na+, K+, Ca2+, Cl-, PO43-

 Acid/base balance (pH of body fluids)

 Excretion of nitrogenous/metabolic waste

3

How is blood pressure related to urine production?

Indirectly, by blood volume which is related to urine volume

4

What is the distribution of nephrons in the kidney's medulla vs cortex?

 90% = cortical
 10% = juxtamedullary

5

Each nephron has which 2 capillary beds?

Glomerulus + Peritubular capillary and Vasa Recta (formed from efferent arterioles exiting glomerulus)

6

In the two types of nephrons, are both renal corpuscles in the cortex?

Yes, one in cortex, other in juxtamedullary cortex

7

Which type of nephron has a longer Loop of Henle?

Juxtamedullary

8

Which two tubules lie adjacent to the glomerulus?

PCT and DCT

9

What are the three basic functions of a nephron?

Glomerular filtration

Tubular reabsorption

Tubular secretion

10

In which vessels do tubular secretion and tubular reabsorption take place?

Peritubular capillaries and Vasa Recta

11

What 2 cells are important in the glomerulus capillaries?

Endothelial cells
Mesangial cells

12

What are the modified cells on the visceral layer of the Bowman's capsule?

podocytes

13

What is the role of the Mesangial cells in glomerulus?

Specialized smooth muscle cells
Do not collapse, structural role
Contract/ relax to control blood flow to glomerulus (contract = reduce filtration rate)

14

3 components of renal corpuscle filtration barrier?

Fenestrated endothelium of glomerular capillaries

Fused basal lamina of endothelial cells and podocytes

Filtration slits of podocytes

15

What forms filtration slits? What is size of slit?

Podocytes' feet interdigitate
Slits only 20-30nm wide

16

What is ultrafiltration dependent on? (think properties of what goes through)

Molecules ultra-filtrated under HIGH PRESSURE based on SIZE and CHARGE

17

Glomerular capillaries have fenestrations that does what?

Allow macro-molecules to pass
Prevent cells to pass

18

What component of the renal corpuscle filtration barrier sort molecules by charge?

2. membrane (GBM): made of collagen
negatively charged = repels negatively charged proteins)

19

What is the role of glomerular basement membrane?

 Prevents filtration of large plasma proteins (radius = 7-10nm)
 Slows passage of smaller plasma protein

20

What is the final glomerular filtration barrier?

Glomerular epithelial cells + slit diaphragm

21

What are some substances that can pass through the glomerular filtration barrier?

ions e.g. Na+, Cl-, H+, K+
Glucose
Water
Urea
Small proteins

22

Does filtration barrier have much effect on small charged particles

No

23

Are molecules larger than 8nm filtered?

No

24

Why is albumin not filtered?

Due to negative charge repelled by GBM and size

25

What is a sign of chronic kidney disease associated with protein in urine? How does it occur? (think what chronic diseases and how the micro-structure is changed)

Proteinuria/ albuminuria or urine albumin >300mg/24 hours

Result from diabetes, hypertension, kidney inflammation...

Fusion or collapse of podocyte foot process, splitting of GBM, altered exoskeleton of podocyte

26

How much protein/ time is considered severe nephrotic syndrome?

>3.5g/24 hours

27

Pressure favouring filtration?

Glomerullar blood
hydrostatic capillary pressure = 55
mmHg

28

Pressures opposing filtration?

Glomerular capillary oncotic pressure (due to suspension in plasma e.g. albumin)

Bowman's capsule hydrostatic pressure ( = 15
mmHg)

29

What does rate of ultrafiltration depend on?

Balance of forces favouring and opposing filtration

30

How is high pressure generated in ultrafiltration?

Blood pressure from Afferent arteriole

Efferent arteriole narrower than Afferent arteriole

31

How is net filtration pressure calculated?

glomerular capillary blood
hydrostatic pressure (GBHP) - Bowman’s capsule hydrostatic pressure (CHP) - Glomerular/blood capillary oncotic pressure (BCOP)

32

How does the composition of glomerular filtrate compare to plasma?

 Composition of water, electrolytes, wastes is almost identical to plasma

 Exception: proteins, RBCs are kept out from filtrate

33

How much glomerular ultrafiltrate is made each day and how much is reabsorbed?

kidney makes ~180 L of glomerular ultrafiltrate per day
~179 L is retained

34

What is the normal Glomerular Filtration Rate? GFR

Total volume of filtrate formed by BOTH kidneys per minutes
GFR (90-140 mL/min)

35

How can net filtration pressure (NFP) increase?

Increase by: Vasodilation of AFFERENT arteriole and Vasoconstriction of EFFERENT arteriole

36

What is the effect of vasodilating afferent arteriole?

Increase blood flow to glomerular > increase capillary blood pressure > Increase net filtration pressure

37

What is effect of vasocontricting Efferent arteriole?

Increase capillary pressire
Increase NFP

38

How can NFP be decreased?

Vasoconstrict Afferent arteriole or

Vasodilate Efferent arteriole

39

What is the effect of Vasoconstricting afferent arteriole?

Decrease blood flow to glomerulus
Decrease glomerular capillary blood pressure
Decrease NFP

40

What is the effect of Vasodilating Efferent arteriole?

Decrease glomerular capillary blood pressure
Decrease NFP

41

What 3 things does GFR depend on?

Net filtration pressure

Permeability of filtration membrane

Surface area available for filtration

42

What are the stages of GFR?

Stage 1 >90mL/min Structural kidney damage with normal function

Stage 2 60-89mL/min
Kidney damage with mild loss of function

Stage 3 30-59mL/min Mild > Moderate> Severe Kidney damage

Stage 4 15-29mL/min Severe kidney damage

Stage 5 <15mL/min Kidney Failure

43

How can GFR be determined by a substance?

Renal clearance of a substance NEITHER reabsorbed NOR secreted by kidneys can be used to determine GFR

44

How is clearance calculated?

Excretion amount of substance (mass per minute)/ Concentration of substance in body (conc.)

45

What substance is used for good estimating GFR?

Inulin (and sinistrin)
Freely filtered, Not reabsorbed nor secreted

So diuretic drug would have no effect on inulin clearance

46

Why is creatinine used as a rough measure for eGFR?

Inulin administration is time consuming

Creatinine is slightly secreted so eGFR is slightly higher than actual

47

How does excretion relate to filtration, reabsorption and secretion?

Filtration - reabsorption + secretion = excretion

48

What affects GFR?

age, gender, food intake, muscle mass...etc

49

What is the formula for GFR?

GFR= (urine concentration (of inulin) x urine flow)/ Plasma concentration (of inulin)

50

What are the two routes for reabsorption pathways in Renal tubule?

Transcellular route and Paracellular route

51

In which tubule does most reabsorption happen?

70% reabsorption in PCT

52

Sequence of movement in transcellular route? (think what to cross)

Transport across Apical membrane of tubule cell > Diffuse through cytoplasm > Transport across basolateral membrane > Move through interstitial fluid > Move through capillary endothelium

53

Sequence of movement through paracellular route?

Directly bypass cell via leaky tight junctions through lateral intercellular space

or

Transport through apical membrane > move out of cell to lateral intercellular spaces

54

What is the epithelium of all tubules in kidney except collecting duct (*not collecting tubule)?

Simple cuboidal

Collecting duct has simple columnar

55

What transport mechansim for paracelullar route movement?
What substances use paracellular?

Diffusion down concentration gradient

e.g. urea, Ca2+, K+...

56

What transport mechanisms for transcellular route?What substances use transcellular?

Primary active transport, secondary a.t. , facillitated diffusion, osmosis

e.g. glucose, water, glucose... etc

57

Give examples of symport, antiport on the apical membrane of tubules.

Symport = same direction of transport as Na+
e.g. Glucose and Na+

Antiport: opposite direction to Na+ movement
e.g. Na+/ H+ pump

58

What causes Na+ deficiency inside tubule cell and allows apical membrane secondary active transport?

Na+/K+ pump on basolateral membrane generates Na+ concentration gradient inside tubule cell

59

How does glucose move through tubule cell?

Symport at apical membrane

Facillitated diffusion at basolateral membrane

60

What is the name of channels involved in glucose movement in tubule cells?

Na+/glucose cotransporter/ symport channel = SGLT2

Facil. diffusion channel/ Uniporter at basolateral membrane = GLUT2

61

What is the anitport channel on apical membrane of tubule cells ?

Na+/H+ exchanger = NHE3

62

What is the primary active transport carrier name on basolateral membrane in tubule cells?

Na+/K+ ATPase

63

What is the name of Cl-/Base exchanger on apical membrane in tubule cells?

Pendrin

64

How does DCT absorb NaCl?

absorbs NaCl mainly via an Na+-Cl- cotransporter

65

In which tubule is paracellular route observed?

PCT only

66

Is the fluid leaving PCT iso-osmotic to plasma?

Yes

67

What follows Na+ movement generated by Na+/K+ ATPase on basolateral membrane?

water

68

What is tubular transport maximum (Tm)?

For substances reabsorbed via transporters (mainly secondary active transport), the number of available carriers determines Tm

69

Relationship between concentration gradient and reabsorption rate for active transport substances?

Completely reabsorbed until all available carriers become
saturated > reach tubular maximum > no further increase in resorption even if concentration gradient increases more

70

What substances are abosorbed by secondary active transport?

Ca2+, Cl-, H+, organic solutes, phosphate

71

How does Glycosuria occur?

Amount of glucose in filtrate exceed maximum number of transporters/Transport maximum of PCT

72

How does filtration rate and conc. grad. relate?

Filtration normally increases in proportion to plasma
concentration (freely filtered)

73

Talk through processes of movement for Na+

Na+ reabsorption
Apical: Facillitated Diffusion/ involved in cotransport

Basolateral: Active transport with K+

74

Process of mvt. for Water

Osmosis on apical and basolateral
(follows Na+)

75

Process of mvt. for Ca2+

Diffusion on apical

Osmosis on basolateral
(Transport of Na+ creates an osmotic gradient > H2O follows (transcellular / paracellular) > leads to
concentration gradient for Ca2+ > resorption of Ca2+ (transcellular)

76

Process of mvt. for Cl-?

Apical: Diffusion (mostly paracellular)

Basolateral: Electrochemical gradient (with H20 and Na+)

77

Process of mvt. for K+

Reabsorption

Apical: Paracellular diffusion

Basolateral: Facillitated Diffusion

78

Glucose, amino acid, HPO4_ reabsorption?

Apical: Facillitated co-transport with Na+

Basolateral: Diffusion (Na+/K+ pump)

79

What is transport maximum of glucose in men and women?

Men: 375 mg/ml
Women: 300 mg/ml

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