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PCS Unit 3 - Communication and Control > Week 8 - Kidney filtration, absorption and secretion > Flashcards

Week 8 - Kidney filtration, absorption and secretion Flashcards

1
Q

What % of cardiac output do the kidneys receive?

A

20-25%

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2
Q

What % of glomerular filtrate is reabsorbed?

A

99%

1% enters bladder to be excreted as urine

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3
Q

What are the two distinct areas of the kidney?

A

cortex and medulla

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4
Q

What are the features of the cortex?

A

extensive blood supply

medullary rays

cortical labyrinth

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5
Q

What are medullary rays?

A

aggregation of stright tubles and collecting ducts

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6
Q

What are renal columns?

A

between renal pyramids, extension of cortex

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7
Q

What is the capillary network of the medulla called?

A

vasa recta

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8
Q

What is the renal interstitium?

A

the connective tissue surrounding the nephrons, ducts and blood vessels

it comprises fibroblasts and collagen fibres

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9
Q

What artery supplies blood to the kidney?

A

renal artery

(branch of abdominal aorta below SMA)

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10
Q

Where do the kidneys lie in relation to the peritoneum?

A

retroperitoneum

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11
Q

At what vertebral level do the kidneys lie?

A

T12-L3

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12
Q

At the hilum of the kidney, which structure is most anterior?

a) renal artery
b) renal vein
c) renal pelvis

A

renal vein

hilum - entrance to space in kidney

vein is most anterior followed by artery and pelvis

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13
Q

What are two types of nephron?

A

juxtamedullary

cortical

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14
Q

What is the difference between the juxtamedullary and cortical nephrons?

A

juxtamedullary - loop of henle is longer and dips down into the inner medulla

constitute 15 - 25% of all nephrons

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15
Q

What is the renal corpuscle?

A

glomerulus and Bowman’s capsule

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16
Q

What structures comprise the glomerular filtration barrier?

A

fenestrated endothelium, glomerular basement membrane, visceral epithelial podocytes

fenestrated - ‘holey’

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17
Q

What is the inner visceral layer of Bowman’s capsule?

A

consists of cells called podocytes that have pedicels that wrap around glomerular capillaries

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18
Q

How are podocytes specialised?

A) positively charged

B) fenestrated

C) interdigitation of foot processes

D) possess a glycocalyx

A

C)

podocytes are the epithelial cells of Bowman’s capsule

they have projections from their cell body called ‘foot processes that interdigitate with each other and the spaces between are called slit pores

plasma passes through the slit pores

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19
Q

Describe the structure of Bowman’s capsule

A

parietal layer of simple squamous cells

Bowman’s space into which filtrate enters after passing through filtration slits in the podocytes

the visceral layer containing podocytes sitting on the glomerular basement membrane

20
Q

What feature of glomerular capillary endothelium makes it adapted for glomerular filtration?

A

they are fenstruated which allows small molecules to pass through them

fenstruated - ‘holey’

21
Q

Where do the renal arteries branch from the abdominal aorta?

A) superior to the coeliac trunk

B) superior to the middle suprarenal arteries

C) inferior to the superior mesenteric artery

D) At the level of L3

E) inferior to the gonadal arteries

A

C) - renal vessels branch at about L1-L2, below SMA

Coeliac trunk branches at T12, SMA at L1 and the gonadal arteries at L2

22
Q

Which vessels branch off renal arcuate arteries?

A) afferent arterioles

B) efferent arterioles

C) interlobular arteries

D) segmental arteries

E) interlobar arteries

A

C) also known as cortical radial arteries

The renal arteries branch of the abdominal aorta at the level of L1-L2 below the SMA and separate into 5 segmental arteries close to the hilum. Interlobar arteries ascend between renal pyramids to the level of the base of renal pyramids. They turn 90 degrees and become arcuate arteries that pass in parallel with the base of the pyramids. These give off the interlobular arteries that run downwards to nephrons and give off afferent arterioles.

Venous drainage is the same in the opposite direction

23
Q

What is the total body fluid for an average 70kg person?

A

42L

approx 60%

24
Q

Where is extracellular fluid distributed in the human body?

A

plasma, interstitial fluid, transcellular fluid

interstitial fluid - found in the interstitial spaces

25
Q

What is hydrostatic pressure?

A

pressure exerted by a liquid on the sides of a container

eg - pressure exerted on fluid on the insides of vessels

26
Q

What is oncotic pressure?

A

pressure exerted by proteins (albumin) in a blood vessels plasma

where plasma proteins are reduced there is a reduction in oncotic pressure

27
Q

How do Starling’s forces change from the afferent to efferent end of the glomerular capillaries?

A

Increase in capillary oncotic pressure because a large amount of fluid passes out into Bowman’s space, which increases hydrostatic pressure in Bowman’s space but reduces it in the capillaries

Due to fluid loss the capillary plasma proteins become more concentrated

There should be no change in oncotic pressure in Bowman’s space because normally no protein will pass through the filtration slits made by podocytes

28
Q

What is the mesangium?

A

the extracellular matrix that surrounds the mesengial cells and supports capillaries

29
Q

What determines glomerular filtration rate (GFR)?

A

hydrostatic pressure

osmotic pressure

properties of the barrier

30
Q

What is glomerular filtration rate (GFR)?

A

volume of fluid filtered by the glomerular capillaries per unit time

31
Q

What happens to cells when they are placed in a hypotonic solution?

A

cell increases in size

hypotonic - the amount of solute outside the cell is less than inside

water moves into the cell to try to balance the osmotic pressure difference and ensure both solutions are equally dilute

32
Q

Which part of the nephron is always impermeable to water?

A

the thich ascending limb of the loop of Henle is impermeable to both water and solutes except for the Na-K-Cl co-transpoter that acts to remove solutes

33
Q

How will water be distributed in the extracellular and intracellular fluid if a person drinks 60ml of tap water (assuming that all of the fluid is absorbed from the bowel)?

A

Body Fluid Compartments:

Intracellular - 2/3

Extracellular - 1/3

20ml ECF

40ml ICF

34
Q

What parts of the nephron are located in the cortex?

A

glomeruli, convoluted tubles, cortical collecting ducts

35
Q

Describe the flow of urine from the medullary pyramid to the renal pelvis

A

medullary pyramid forms a renal papilla that drains urine into a minor calyx. These unite to form a major calyx and from there urine enters the renal pelvis

36
Q

From which arteries in the kidney do afferent arterioles arise from?

A

cortical radial (interlobular) arteries

37
Q

What is responsible for most of the colloid osmotic pressure of the plasma?

A

plasma albumin

38
Q

What three processes are involved in forming urine?

A

glomerular filtration, tubular reabsorption and tubular secretion

39
Q

What is inulin clearence?

A

the volume of plasma that inulin is removed from in unit time

inulin is the substance used as a gold standard for measuring GFR because it passes through the kidneys without being synthesised or destroyed

it is not used in the clinic because it must be infused intravenously and the bladder is usually catheterised

creatinine is more commonly used

40
Q

Why are measurements of GFR using creatinine sometimes an overestimate (especially during renal disease)?

A

creatinine is not only filtered but also secreted by the kidney

urinary excretion of creatinine is elevated in renal disease

41
Q

What is the effect of GFR is there is an obstruction anywhere along the urinary tract?

A

GFR decreases

increased pressure upstream of the block, increases hydrostatic pressure in Bowmans capsule

this pressure opposes filtration

net filtration decreases

GFR = Kf x net filtration pressure

42
Q

What happens to GFR if a patient is given an intravenous infusion of a large volume of isotonic saline?

A

GFR increases

isotonic saline will decrease the plasma colloid osmostic pressure

this increases net filtration

43
Q

What two pressures oppose glomerular hydrostatic pressure?

A

bowmans capsule hydrostatic pressure

plasma oncotic pressure

44
Q

What physiological changes cause ADH secretion?

A
45
Q

Which part of the nephron in the kidney releases the enzyme renin in response to low blood pressure?

A

the juxtaglomerular apparatus

46
Q

What part of the loop of Henle is permeable to water but not ions?

A

descending limb

ascending limb is impermeable to water but permeable to ions

PCS Unit 3 - Communication and Control (15 decks)

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