golomular filtration - exam 2

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renal corpusule components
Composed of _______ and _______ capsule

Blood enters glomerulus by the___________ and leaves by the __________

Blood is filtered from glomerulus and the ultrafiltrate is collected in the ___________

glomerulus, Bowman's
afferent arteriole
efferent arteriole
Bowman's space

3 components of FILTRATION BARRIER

1 Fenestrated capillary- 1st layer of filteration have lots of pores that filter
2 Glomerular basement membrane- 2nd layer of filtration, secrete basil lamina that allow them to stick onto capilaries and help to filter
3 Slit diaphragm- last layer of filtration ( most outer) between pediciles, acts as a filter, filters on the bases of size and charge

Glomerular Filtration: Filtration Barrier
Capillaries:
SIZE - Fenestrations hold back ____ and larger __________ bigger than a certain size
CHARGE - The capillaries are are covered in laminin and fibronectin which repel ______charged molecules
Capillary epithelium is lined with ________
Capillary epithelium is perforated with large _______-

RBC,plasma proteins
negatively
polyanionic glycoproteins
pores

Glomerular Filtration: Filtration Barrier
Lamina rara:
CHARGE - Laminin, fibronectin and heparan sulphate repel ______ charged molecules
Contain proteins

negatively
polyanionic non-collagenous

Glomerular Filtration: Filtration Barrier

Lamina densa:
SIZE - Collagenous proteins filter ______only,
Contains collagenous ________

size
proteins

Glomerular Filtration: Filtration Barrier
Slit diaphragm: ________ (mostly nephrin) with holes in it.
SIZE - Holes filter based on ____ like Lamina densa
CHARGE - The supporting podocytes filter on basis of ______
Podocytes are covered with polyanionic glycoproteins
Slit diaphragm is perforated with ______ pores

Protein
size
charge
small

negatively charged molecules have a _______ time getting through the filtration barrier then positive charged molecules
plasma proteins ______ pass through protein barier because

harder
can not, they are large with a net negative charge
So conclusion, filtrate is therefore mostly protein free

which molecules will have the most difficult time crossing the filtration barrier

large and negatively charged molecules

WHAT DRIVES FLUID MOVEMENT OUT OF THE CAPILLARIES OF THE GLOMERULUS?

HYDROSTATIC AND ONCOTIC PRESSURE, THAT'S WHAT.

Hydrostatic pressure has the ______ influence on fluid movement. Blood pressure inside capillary pushes _____ but the fluid in Bowman's space also has a hydrostatic pressure and this pushes _____. However the Pc is ________ than Pbs so the net effect of hydrostatic pressure is to push plasma _____ of the glomerulus = drives filtration.

biggest
OUT
back IN
WAY bigger
out

Oncotic pressue is basically osmotic pressure caused by ___________. The filtration barrier prevents many proteins______the capillaries so therefore the protein concentration in the capillaries is _______ than the Bowman's space. This will generate an osmotic pull of fluid _______ the capillary (capillary oncotic pressure). Like hydrostatic pressure, this can go both ways

colloids (large proteins)
leaving
higher,INTO

HYDROSTATIC PRESSURE
is composed of

Capillary hydrostatic pressure (PC)
Bowman's space hydrostatic pressure (PBS)

ONCOTIC PRESSURE
is composed of what 2 preasures

Capillary oncotic pressure (πC)
Bowman's space oncotic pressure (πBS)- so small it barely matters

the net glomular filtration rate is determined by

forces pushing both IN and OUT and it is the balance of these forces which determines whether fluid moves into or out of the capillary.

why would cappillary onconic preasure increase

water is leaving cappillary but protein isn't leaving so force goes up

Use these numbers to work out the net filtration pressure at the feline glomerular capillary:

Pc = 58 mmHg
Pbs = 18 mmHg
πc = 22 mmHg
πbs = 0 mmHg

18 mmHg= net filtration preasure

____ is the biggest of Starling's Forces, and therefore the biggest determinant of ____. It makes sense, then, that the easiest way for the kidney to modulate GFR is to keep a tight handle on ____. It does this by carefully regulating blood flow through the _________.

Pc, GFR
Pc
glomerulus

If it's easier for blood to enter the glomerulus than leave it, this will __________and therfor ____________
If it's easier for blood to leave the glomerulus than enter it, this will ______________and therfor ____________

increase Pc and therefore increase GFR
reduce Pc and therefore reduce GFR

The thing that makes it "easier" or "harder" for blood to enter/leave the glomerulus is the resistance to blood flow provided by the ______________
so when afferent arterial dialates GFR _______
and dialation of the effererent arterial will __________GFR

afferent/efferent arterioles.
will increase
decrease

Disease states alter GFR because they change ___________

Starling's Forces

Disease states decrease GFR, consider the example of schistosomiasis. Changing the ____________ or ___________ of filtration apparatus will change GFR

permeablilty and/or surface area

if the filtration barrier gets chewed up it stops filtering and just lets anything through (ie proteins and RBC). This failure to filter = _________GFR = renal failure.

reduced

The key to realizing why a decreased Kf decreases GFR lies in the definition of GFR - it's the filtration rate across all FUNCTIONING glomeruli. If disease destroys the filtration apparatus, then __________ can't functionally filter, so overall GFR goes _______.

glomerulus
down

Kf CHANGES

Kf = (permeability of capillary) x (filtration surface area)
Most disease states decrease Kf
Glomerular disease is an excellent example

PC CHANGES

In acute renal failure, PC can decrease due to impaired renal perfusion. This causes decrease in GFR

πC CHANGES

Plasma protein levels can increase and decrease
↑ πC = ↓ GFR
↓ πC = ↑ GFR

PBS CHANGES

Obstructions (uroliths, plugs) can increase PBS
↑ PBS = ↓ GFR
↓ PBS = ↑ GFR

dialated aferent arteriole and normal efferent arteriole _____blood flow and _____GFR

increase, increase

Glomerular filtration is governed by forces pushing fluid out of the glomerulus and forces push fluid back into glomerulus. These forces are _________ and _____________.

hydrostatic pressure and oncotic pressure

_________________ pressure is the most important factor. Pc (and therefore GFR) can be changed by adjusting the resistance of afferent and efferent arterioles

Capillary hydrostatic

Autoregulation is the intrinsic ability of an organ to maintain___________at a nearly constant rate despite changes in __________ pressure

blood flow, arterial perfusion

Changes in BP can have 2 major consequences to the kidney and autoregulation helps to offset these consequences:
Autoregulation helps to prevent damage to kidneys by controlling the __________ to the glomeruli despite fluctuations in BP. ______remains relatively constant over a wide range of BP.
autoregulation controls RBF to PREVENT CHANGES IN _____.

blood flowing,RBF
GFR

Autoregulation works to maintain a steady state_________and _____ despite changes in systemic blood pressure.

blood flow,GFR

Goal of renal autoregulation
1. Prevent damage to _______caused by spiking BP (maintain constant blood flow despite changes in BP
2. Prevent fluctuations in BP from changing delivery of filtrate to ________ (maintain constant GFR despite changes in BP)

glomeruli
tubules

2 mechanisms
1. MYOGENIC MECHANISM
TRIGGER: Fluctuations in ___ change transmural pressure in _____ arteriole
Increased BP elicits ________ and decreased blood flow
Decreased BP elicits ___________ and increased blood flow
2. TUBULOGLOMERULAR FEEDBACK
TRIGGER: Fluctuations in___ change ____meaning distal tubule fluid composition is altered
1. Low/High GFR produces low/high___
2. Low/High ion concentration sensed by __________
3. JGA changes arteriole resistance to autoregulate ______
much slower

BP, AFFERENT
constriction
dilation
BP,GFR
ultrafiltrate
macula densa
GFR

Renin is an important molecule as it is critical to generating angiotensin II - this is one of the key molecules that change _________

arteriolar resistance!

function of ANGIOTENSIN II:
Systemic arteriolar ____________ to increase blood pressure
Increases __________ secretion (adrenal cortex)
Promotes _____secretion (pituitary) and thirst
Increases tubular_____uptake

vasoconstriction
aldosterone
ADH
NaCl

REDUCING GFR

If GFR is high, ____in the distal tubule fluid will be high and therefore more than usual will move to the cells of the _______.
_________ is the important mediator of this process
We know __________ in the extraglomerular mesangial cells are activated and that this increases ____. We think this Ca2+ then moves through gap junctions into afferent ________ cells (which causes them to contract) and into JG cells (inhibits renin release).
Finally, we know that ________ and _________can modulate this whole process

Cl- ,macula densa.
Adenosine
adenosine receptors
Ca2+
smooth muscle
nitric oxide and angiotensin II

INCREASING GFR
1. Low Na+ K+ and Cl- sensed by NKCC2 on apical surface of MD
2. MD releases _________
3. PGE2 causes afferent arteriole ________ (INCREASES GFR) and stimulates JG to release ______, increasing________
4. Angiotensin II in the bloodstream
Causes systemic ____________(INCREASES GFR)
Preferentially contracts _____________arteriole (INCREASES GFR)
Increases ______ production from MD (INCREASES GFR)
Negatively feedbacks onto contralateral kidney to stop ________release

prostaglandin E2 (PGE2
vasodilation, renin, angiotensin II
vasoconstriction
efferent over afferent
PGE2
renin

toxicity and acute renal failure
1. ________ depletion or systemic hypotension
2. systemic ____________
afferent ________
3. ______________ GFR
4. release __________
5. afferent ____________
6. normalized _________
toxisity prevent the release of _________which causes acute renal failure by preventing the negative feedback

volume
vasoconstriction
vasoconstriction
reduce
prostiglandin
vasodialation
GFR
prostiglandin

role of myogenic mechanism =
reponse time =
importance

protection aginst injury
fast
No myogenic mechanism, no autoregulation

role of Tubuloglomerular Feedback
reponse time=
importance

regulation of GFR
slower
Less important, works with other mechanisms to control GFR and fluid homeostasis

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