Glomerular filtrations

Question 1

Glomerulus structure

Answer 1

capillary knot that is supplied by the afferent arteriole, a division of the renal artery and drained by the efferent arteriole

enveloped in the Bowman’s capsule

Question 2

brief blood vessels after glomerulus

Answer 2

efferent arteriole takes blood to peritubular capillaries of the vasa recta, finally ending in the renal vein

peritubular capillaries lie alongside the renal tubule

vasa recta form hair pin capillary loops

Question 3

who described the microscopic structure of the glomerulus?

Answer 3

Bowman

Question 4

Who proposed the theory of capillary ultrafiltration?

Answer 4

Ludwig, influenced Starling’s laws depicting the movement of fluids

Question 5

filtrate versus blood key difference

Answer 5

Filtrate has no proteins

Question 6

hydrostatic pressure in the glomerulus

Answer 6

45mmHg

Question 7

stages of moving from glomerulus into the bowman’s capsule

Answer 7

1. move through the fenestrated endothelial cell wall of the capillaries, preventing only the movement of cells
2. endothelium cell wall
3. between the pedicels of podocytes

Question 8

component of endothelial cell wall + function

Answer 8

negatively charged glycosaminoglycans, preventing the movement of positive molecules

Question 9

structure of podocytes

Answer 9

extensions of the podocytes called pedicels, which interdigitate to form slit pores

nephrins present in the pedicels interdigitate to form the pores - negatively charged

Question 10

nephrotic syndrome definition

Answer 10

damage to basement membrane occurs resulting in proteinuria

Question 11

what does the filtration rate depend on?

Answer 11

net filtration pressure= pressure out - pressure in

Question 12

what forms the pressure out of the capillary?

Answer 12

hydrostatic pressure in capillary and oncotic pressure of filtrate in bowman’s capsule

Question 13

what forms the pressure into the capillary?

Answer 13

hydrostatic pressure in the bowman’s capsule and oncotic pressure in the capillary

Question 14

different expressions for the different values

Answer 14

PGC- hydrostatic pressure in capillary

PBS- hydrostatic pressure in Bowman’s capsule

PiGC- oncotic pressure of glomerular capillary plasma

PiBS- oncotic pressure of bowman capsule filtrate

Question 15

what value should PiBS be?

Answer 15

0 as there should not be any proteins in the filtrate

Question 16

what value should be low+why?

Answer 16

PBS- hydrostatic pressure in Bowman’s capsule, as the space acts like a sink, with the filtrate moving into the proximal tubule

Question 17

rate of formation filtrate

Answer 17

GFR- Kf x PUF

Kf= the filtration coefficient, which is permeability x surface area

PUF- is the net filtration pressure

Question 18

how is the driving force sustained?

Answer 18

greater afferent arteriole and smaller efferent arteriole, so there is a high hydrostatic pressure in the capillary

Question 19

what changes along the length of the glomerulus capillary?

Answer 19

net filtration pressure diminishes, as less water in the capillaries

oncotic pressure rises, more fluid moves out and the concentration of proteins remaining in the blood rises

Question 20

what can lead to an increase in pressure in the bowman’s capsule?

Answer 20

kidney stones in the ureter, urine can’t pass, back log of fluid, fills bowman’s capsule

Question 21

how can the GFR be modified?

Answer 21

sympathetic nervous system leads to the vasodilation or contraction of either the efferent or afferent arteriole

Question 22

what other cells surround the glomerulus? + function

Answer 22

mesangial cells which are contractile cells that can contract to change the surface area of the capillary wall and thus alter GFR

Question 23

what is the glomerulus pressure range?

Answer 23

80-180 mmHg

Question 24

2 main autoregulatory mechanisms of GFR

Answer 24

myogenic Bayliss mechanism and tubuloglomeruluar feedback

Question 25

myogenic Bayliss mechanism explained

Answer 25

1. increased pressure, arteriole smooth muscle stretched
2. activates stretch mediated ion channels, leading to depolarisation
3. induces voltage gated calcium channels, leading to contraction of afferent to reduce volume in kidney

Question 26

explain tubuloglomerular feedback

Answer 26

macula densa in the juxtaglomerular apparatus detects distal flow rate in the renal tubule

if flow rate is increased, signal is released to constrict the afferent arteriole

Question 27

clearance definition

Answer 27

the volume of plasma from which substance X is completely removed in a minute by the kidneys. the minimum volume of plasma which could have contained the filtered substance

Question 28

GFR in humans

Answer 28

125 ml per minute

Question 29

filtration fraction definition

Answer 29

ratio of glomerular filtration rate to renal plasma flow

represents the proportion of the fluid reaching the kidneys that passes into the renal tubules

Question 30

normal filtration fraction

Answer 30

20%

Question 31

renal plasma flow definition

Answer 31

the amount of plasma flowing into the kidneys

Question 32

renal plasma flow figure

Answer 32

600ml/min

Question 33

what can be used to approximate the glomerular filtration?

Answer 33

creatine or inulin

Question 34

why does creatine approximate the GFR?

Answer 34

endogenous chemical that is excreted only by filtration

produced by breakdown of creatine phosphate

only secreted by the peritubular capillaries in small amounts

Question 35

what is inulin?

Answer 35

group of naturally occurring plant polysaccharides

Question 36

why does inulin approximate the GFR?

Answer 36

Inulin is not reabsorbed nor secreted by the kidneys

so rate of excretion is directly proportional to the rate of filtration of water and solutes