L17

Question 1

Describe 3 components of The Ultrafiltration Barrier

Answer 1

1) Fenestrated endothelium
2) Basement membrane
3) Podocytes (pedicel- secondary process + Filtration slit)

Question 2

What’s the purpose of Fenestration (pore) of glomerular endothelial cell?

Answer 2

prevents filtration of blood cells but allows all components of blood plasma to pass through

Question 3

What’s the purpose of Basal lamina of glomerulus:

Answer 3

prevents filtration of larger proteins

Question 4

What’s the purpose of Slit membrane between pedicels:

Answer 4

prevents filtration of medium-sized proteins

Question 5

Describe the process of Micropuncture

Answer 5

• Animal anaesthetised
• Micropipette penetrates tubule
• Suck up fluid sample
• Chemical analysis

Question 6

What purpose does Mircopuncture serve?

Answer 6

to investigate ultrafiltration

Question 7

Variations on technique of Micropuncture:

Answer 7

• Tubule section separated by oil
• Test fluid injected (to investigate reab./secr.)
• Suck up fluid sample
• Chemical analysis

Question 8

…. described ultrafiltration. (ludzie z datą)

Answer 8

Wearn and Richards (1929)

Question 9

…. is formed by filtering out plasma proteins while allowing the free passage of ions (e.g. Na+) and small molecules (e.g. glucose)”

Answer 9

Capsular fluid

Question 10

The fluid formed by ultrafiltration is ….

Answer 10

GLOMERULAR FILTRATE

Question 11

•The rate at which the 2 kidney’s form ultrafiltrate is …..

Answer 11

GLOMERULAR FILTRATION RATE or GFR .

Question 12

The rate at which a single nephron forms ultrafiltrate is ….

Answer 12

SINGLE NEPHRON GFR or snGFR.

Question 13

Which substances are freely filtered?

Answer 13

Substances of a low molecular weight are freely filtered.

Question 14

Which substances are restricted?

Answer 14

Large molecules are restricted. e.g. hemoglobin, serum albumin

Negatively charged molecules are restricted. e.g. albumin

Question 15

What governs GFR?

Answer 15

“A balance of hydrodynamic forces”.

• Hydrostatic pressure (plasma leaves capillaries because of pressure)
• Plasma proteins remain in blood (because of size and charge). Produces osmotic pressure (plasma protein oncotic pressure)
• Oncotic pressure opposes hydrostatic force due to capillary pressure
• ALSO small oncotic pressure from Bowman’s space opposing hydrostatic pressure known as NET FILTRATION PRESSURE

Question 16

How can GFR be measured?

Answer 16

It can’t be measured, but it can be estimated.

•By measuring the rate of excretion of substances that are:

1. Freely filtered.
2. Not reabsorbed or secreted by tubules.
3. Have no influence on renal function (e.g. blood flow)

Inulin meets these criteria.

Question 17

The rate of excretion =

Answer 17

concentration in urine (UC) multiplied by amount of urine produced per min (Ů)

Rate of excretion = UC x Ů mg/min

Question 18

Przypomnienie

Answer 18

The rate of excretion also depends on its concentration in the plasma (PC)

Question 19

CLEARANCE -

Answer 19

The ratio between rate of excretion and PC is called CLEARANCE (C) and is expressed in ml/min

Thus: C = UC x Ů /PC in ml/min

Question 20

Definition of Renal Clearance:

Answer 20

the volume of plasma completely cleared of a given substance in 1 min.

Question 21

The clearance of inulin is used to estimate GFR. GFR for inulin clearance is …. ml/min for adult humans.

Answer 21

120-130

Question 22

In a single day that’s … litres of plasma that are filtered!

Answer 22

180

Question 23

If a substance has a clearance

Answer 23

reabsorbed (e.g. glucose) or not freely filtered (e.g. proteins).

Question 24

If a substance has a clearance >GFR it must be ….

Answer 24

secreted

Question 25

Why is Inulin not convenient for clinical purposes? What implications does it have?

Answer 25

as you need a steady concentration in plasma for accurate measurements. Thus use a substance, that fits the ‘criteria’, already found in plasma is used – creatinine. However, small amounts of creatinine are secreted into the proximal tubule!

Question 26

Glomerular filtration rate –

Answer 26

amount of filtrate formed in all the renal corpuscles of both kidneys each minute

Question 27

What happens when GFR is too high?

Answer 27

substances pass too quickly and are not reabsorbed

Question 28

What happens when GFR is too low?

Answer 28

nearly all reabsorbed and some waste products not adequately excreted

Question 29

Wymień 5 steps of maintenance of the internal environment

Answer 29

1) Filtration by Glomerulus 2) Obligatory reabsorption and secretion by PCT (Proximal Convoluted Tubule) 3) Generation of osmotic gradient by loop of Henle 4) Regulated reabsorption and secretion by DCT (Distal Convoluted Tubule) 5) Regulation of water uptake by collecting ducts

Question 30

Opowiedz o pierwszym etapie (co jest szczególnego we fluidzie)

Answer 30

The first stage in renal function is the transfer of fluid from the vascular space to the nephrons. Involves selective filtration of the plasma through the glomeruli into the Bowman’s capsule Fluid has a similar composition to plasma but with NO protein

Question 31

Regulation of plasma composition occurs via 3 key processes:

Answer 31

1. Ultrafiltration 2. Reabsorption 3. Secretion

Question 32

ULTRAFILTRATION -

Answer 32

Plasma flows through glomerular capillaries ~1/5 is forced through capillary walls (hydrostatic pressure of blood) into Bowman’s space

Question 33

The Glomerular filtrate -

Answer 33

cell and protein-free, the concentration of ions and small solutes are the same as in plasma (freely filtered). A filtration barrier restricts movement of solutes on a basis of size and charge.

Question 34

Molecules size in | Glomerular Filtrate :

Answer 34

Molecules 3.6 nm not filtered

Question 35

.... are more readily filtered than ..... for the same molecular radius

Answer 35

Cations | anions

Question 36

Serum albumin has a radius of about ... nm but its .... prevents its filtration

Answer 36

3.5 | negative charge

Question 37

Describe the structure of glomerulus and Bowman's capsule:

Answer 37

.

Question 38

what are the Evidences for ultrafiltration in glomerulus?

Answer 38

.

Question 39

explain Role of Starling forces in glomerular filtration:

Answer 39

.

Question 40

how to Measure GFR by inulin clearance?

Answer 40

.