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URINARY > Lecture 4: Introduction to the glomerulus > Flashcards

Lecture 4: Introduction to the glomerulus Flashcards

1
Q

What is the role of the kidney?

A
  • maintain a steady internal environment
  • controls concentrations of key substances
  • excretes waste products
  • endocrine role: synthesis of renin, EPO, prostaglandins
  • metabolism: activeform of vit D, catabolism of insulin
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2
Q

What products are recovered in the kidney?

A

> 99% of filtered water
99% of filtered sodium and chloride ions recovered
100% of bicarbonate, glucose, AA’s removed
Just a few waste products not recovered

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3
Q

What is the role of the kidney in fluid balance?

A

Filters very large amount of ECF

  • forming ultrafiltrate: water, ions, all small molecules
  • 180L/day, recovering almost everything, leaving about 1.5L per day of urine
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4
Q

What does the kidney directly regulate?

A

All of the extracellular fluid (not intracellular)

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5
Q

What are the electrolyte compositions of intra/extra-cellular fluids?

A

Intra: high K+, low Na+, large organic anions
Extra: low K+, high Na+, main anion is Cl- and HCO3-
Maintained by sodium pumps (mainly Na+/K+)

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6
Q

What is the difference b/w osmolality and osmolarity?

A

Osmolality: solute per kilogram of solvent
Osmolarity: number of osmoles (charged particles) of solute per litre

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7
Q

What is oncotic force?

A

Osmotic force due to charged proteins

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8
Q

Where do you find the glomerulus in the kidney?

A

Cortex

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9
Q

What is the GFR?

A

140-180L of glomerular filtrate produced per day

= 125ml/min

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10
Q

What is the filtration fraction?

A

The proportion of fluid reaching the kidneys that passes into the renal tubules (normally 20%)
GFR/RPF=FF

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11
Q

What is the rough renal plasma flow (RPF) and the renal blood flow (RBF)?

A

RPF: 800 mL/min
RBF: 1100 mL/min

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12
Q

How much blood is filtered at a time from the renal artery?

A

20% of blood is filtered at any one time

80% of blood exits via efferent arteriole (unfiltered)

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13
Q

What is the normal range for GFR?

A

90-120 mL/min

  • contains now blood cells/platelets
  • contains no proteins
  • composed of mostly organic solutes with a low molecular weight and inorganic ions
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14
Q

What is the structure of the glomerular capillary membrane?

A
  • endothelial cells line the capillaries an dthey have gaps called fenestrations b/w them allowing filtrate to pass through
  • endothelial cells are attached to basement membrane
  • podocytes and podocyte processes line the basement membrane forming filtration slits
  • podocytes are also negatively charged to repel the negatively charged proteins in the blood
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15
Q

What is each foot of a podocyte called?

A

Pedicel (podocyte processes)

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16
Q

What is proteinuria?

A

The negative charge on the filtration barrier is lost, so therefore proteins are more readily filtered through. You end up with protein in the urine.

17
Q

What is haematuria?

A

Blood cells get filtered and appear in the urine

18
Q

What forces enable filtration?

A

PUSHING: mainly hydrostatic pressure in capillary (pushing plasma through the fenestrations)
PULLING: hydrostatic pressure in Bowman’s capsule, oncotic pressure difference (proteins in capillary draws water)
These all together give us the NET FILTRATION PRESSURE

19
Q

What is Starlings forces?

A
  • firstly at start of glomerulus is the hydrostatic pressure of the capillary pushing fluid out
  • then further along is the hydrostatis pressure in Bowman’s capsule pushing back in
  • lastly due to the loss of plasma to Bowman’s capsule, their is a higher concentration of charge proteins which then draws water back in
20
Q

What is the average net filtration pressure?

A

13 mmHg

21
Q

What factor can affect net filtration pressure?

A

-blood pressure

22
Q

What are the mechanisms involved in autoregulation to keep RBF/RPF/GFR constant?

A
  • myogenic mechanism

- tubuloglomerular feedback

23
Q

What is the myogenic mechanism?

A

Arterial smooth muscle responds to increases and decreases in vascular wall tension
-increase in renal arteriole pressure: afferent artery constricts to decrease GFR
(property of preglomerular vessels: arcuate, interlobular, afferent arteriole)

24
Q

How do you decrease the GFR?

A

Constrict the afferent arteriole, reducing the amount of blood reaching the glomerulus, reducing pressure

Dilating the efferent arteriole, easier for blood to leave glomerulus, reducing pressure

25
Q

How do you increased the GFR?

A

Constrict efferent arteriole, causing backup of blood in glomerular capillary, increasing the pressure

Dilate the afferent arteriole, allowing more blood to flow into the glomerular capillary, increasing the pressure

26
Q

How does tubuloglomerular feedback work?

A

Macula densa cells in DCT detect rate of movement of Na+/Cl- into the cells (higher flow of filtrate, higgher the Na+ conc)

  • macula densa cells detect flow of solutes which send signals to the juxtaglomerular cells, and then this causes constriction/dilation of the efferent or afferent arterioles
  • if BP increases, more signals of ATP are sent causing vasoconstriction
  • if BP decreases, less signals of ATP, causing less vasoconstriction
27
Q

Why is it not ideal if the flow in the tubules is faster than usual?

A

Won’t be able to reabsorb as much as normal

28
Q

What is the signalling molecule from the macula densa cells?

A

ATP

29
Q

Why is low blood pressure dangerous?

A

<60 mmHg

  • causing activation of sympathetic nerves, causing systemic constriction
  • lead to renal failure (as blood flow through glomarular apparatus is too slow)
30
Q

What happens when there is very low blood pressure to prevent acute renal failure?

A

-prostaglandins sent from macula densa cells causing vasodilation of the afferent arteriole
(if patient is on NSAIDS they are unable to produce prostaglandins)
-juxtaglomerular cells release renin: angiotensinogen>angiotensin 1>angiotensin 2= causes constriction of efferent arteriole
(if patients are on ACE inhibitors they won’t be able to produce angiotensin 2)

31
Q

What are the systemic effects when blood pressure is fatally low?

A

Constriction of the efferent arteriole means that the blood leaving the glomerular apparatus has a higher colloid osmotic pressure, so more water is reabsorbed back into blood= increasing blood pressure systemically
Angiotensin 2 causes an increase in aldosterone, which results in reabsorbing more NaCl, and therefore more water is reabsorbed= increase blood volume

32
Q

What is renin release stimulated by?

A
  • sympathetic nerve stimulation
  • decreased stretch of afferent arteriole
  • signals from macula densa

URINARY (9 decks)

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