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Foundations 511 > Renal > Flashcards

Renal Flashcards

1
Q

What is the purpose of kidneys

A

-filtration system for the removal of wastes
->excretion in urine

-reabsorption of water, glucose and amino acids

-production of hormones
->renin0angeiotensin-aldosterone system
->calcitrol
->erythropoietin

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2
Q

Are kidneys located retroperitoneally

A

-yes

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3
Q

What is the hilum

A

-the medial indentation of each kidney

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4
Q

Does each kidney have an outer cortex and inner medulla

A

-yes
->the outer cortex features glomeruli and portions of the renal tubuli

-the inner medulla features portions of the renal tubule, loops of Henle and medullary collecting ducts

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5
Q

Describe renal pyramids in the medulla

A

-tip of each pyramid forms a renal papilla
->renal papilla drains into a minor calyx
->minor calyces form a major calyx
->guides urine into the renal pelvis

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6
Q

How is urine guided down the ureter

A

-it is guided through peristalsis

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7
Q

How is blood flow supplied in the kidney

A

-supplied by a renal artery
->artery branches successively within the kidney
->eventually branches into afferent arterioles which supply the glomerula capillaries
->glomerular capillaries drain into efferent arterioles
->efferent arterioles then supply peritubular capillaries that surround the renal tubules

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8
Q

What happens to the blood from the peritubular capillary

A

-it drains into venules
->blood passes into successively larger veins before reaching the renal vein and draining into the vena cava

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9
Q

What kind of nervous innervation does the kidney receive

A

-it receives extensive sympathetic innervation and some sensory innervation
->sympathetic activation induces renal vascular vasoconstriction decreasing renal blood flow
->innervate tubular epithelia cells to stimulate sodium reabsorption
->stimulate renin release from juxtaglomerular cells

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10
Q

What is the functional unit of the kidney

A

-they are nephrons
->each kidney features about 1 million nephrons
->nephrons cannot be regenerated
->there is the natural and gradual loss with aging

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11
Q

What is the structure of each nephron

A

-tuft of glomerular capillaries
-long tubule for conversion of filtered fluid to urine

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12
Q

Do glomerular capillaries have high hydrostatic pressure to other capilarries

A

-yes
->approximate double

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13
Q

What are glomerular capillaries covered in? What type of cells specifically?

A

-it is covered in epithelial cells

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14
Q

What are cortical nephrons surrounded by

A

-peritubular capillaries

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15
Q

What are juxtamedullary nephrons surrounded by

A

-a specialized peritubular capillary called the vasa recta

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16
Q

Describe the 4 key renal processes

A
  1. Filtration
    ->Blood comes through afferent arteriole and flows through glomerular capilarries
    ->fluid crosses glomerula capillaries into the Bowman’s capsule
  2. Reabsorption
    ->fluid can come out of the nephron into the peritubular capillaries
  3. Secretion
    ->Substances that leave the capilarries and enter the renal tubule

4.Excretion
->whatever remains in the tubules at the end is removed

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17
Q

How is excretion calculated

A

Excretion=Filtration-Reabsorption+Secretion

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18
Q

What has excretion rate less than filtration

A

-sodium and chloride

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19
Q

What are substances freely filtered but all reabsorbed and not excreted

A

-amino acids and glucose

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20
Q

What is an example of a substance not reabsorbed but additional parts are secreted into the peritubular capillaries

A

-creatinine
-uric acid

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21
Q

Are foreign drugs poorly reabsorbed and secreted

A

-yes
->because we want these things removed from the body
->we don’t want them to build up in our body

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22
Q

What is glomerular filtrate

A

-it is the fluid filtrated from glomerullar capilarries to Bowman’s capsule
->filtrate is protein free
because glomerullar capillaries are impermeable to proteins
->composition of solutes is similar to plasma

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23
Q

What is the difference between filtrate and the composition of solutes in the plasma?

A

-no proteins in the filtrate
-calcium and fatty acids are bound to plasma proteins and not freely filtered into the Bowman’s capsule

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24
Q

What factors determine GFR

A

-hydrostatic pressure(major component)
-Bowman’s capsule pressure
-Glomerular oncotic pressure
-capillary filtration coefficient
->capillary permeability
->filtering surface area(how many glomerular capillaries do we have)

25
Q

What are the three major layers of the glomerular capillaries

A

-endothelium of the capillary
-basement of membrane
-layer of epithelial cells(podocytes)
->they surround the outer surface of the basement membrane

26
Q

Why is the epithelial cells surrounding the outer surface of the basement membrane negatively charged in the glomerulus?

A

-so proteins dont cross the glomerulus into the Bowman’s capsule

27
Q

What happens to glomerular filtration rate as you increase afferent arteriolar resistance

A

-you are reducing the glomerular filtration rate
->because you are getting less blood to the glomeruli
->reduced hydrostatic pressure in the glomeruli as well

28
Q

What happens to glomerular filtration rate as you increase efferent arteriolar resistance?

A

-blood accumulates in glomerular capillaries and increases hydrostatic pressure, increasing the glomerular filtration rate
->but this doesn’t increase forever because you increase renal blood flow over time
->so glomerular filtration rate eventually plateaus and goes down

29
Q

Why do we need a high cardiac output for the kidneys

A

-so we can supply enough plasma for high GFR needed to regulate body fluid volume and solute concentration

30
Q

How do we regulate renal blood flow and GFR

A

-hormones and autacoids influence GFR

-norepinepherine, epinepherine and endothelin vasoconstrict increase afferent arteriole resistance, reducing GFR

-endothelial-derived nitric oxide and prostaglandins have a vasodilation at the afferent arteriole increasing the blood to the glomerulus increasing GFR

-angiotensin 2 can act on afferent and efferent arteriole but is preferential for efferent
->helps to preserve GFR and prevent it from falling too low

31
Q

What is autoregulation

A

-it keeps renal blood flow and GFR constant with changing pressure
->while allowing for renal excretion and water/solutes as well

32
Q

How to kidneys perform autoregulation

A

-they need a feedback mechanism
->that links changes to NaCl concentration at the macula densa with control of renal arteriolar resistance

-the amount of sodium chloride that reaches the distal tubule is sensed by that tubule and helps to regulare bloodflow

33
Q

Describe the process that occurs in the kidneys when arterial pressure decreases

A

-well that leads to glomerular hydrostatic pressure and filtrate flows more slowly in the nephrons and is reabsorbed more readily
->this means less NaCl reaches the macula densula

-this less NaCl results in renin from the juxtaglomerular cells being released
->which also increases angiotensin 2 formation and increases the efferent arteriolar resistance

-as well, the afferent arteriolar resistance is increased too

34
Q

What happens when arterial blood pressure increases

A

-increased delivery of NaCl to macula densula
->so afferent arteriolar constriction, resulting in less blood to glomerulus reducing glomerular hydrostatic pressure

35
Q

What are the two steps of reabsorption

A
  1. Transport across tubular epithelial membranes into renal interstitial fluid
  2. Then the filtrate goes through peritubular capillary membrane back into blood

-dependant on active or passive transport mechanisms

-also dependent on transcellular route through cell membrane

-paraceulluar route is another approach as well
->through spaces between cell junctions

36
Q

How are water and solutes transported from the peritubular capillaries back into the blood

A

-through ultrafiltration
->mediated by Starling forced

37
Q

How does the Na-K ATPase work on the proximal tubular membrane to help with sodium reabsorption

A

-Na-K ATPase
->moves sodium out of epithelial cells into interstitial fluid and potassium back into epithelium
->water will follow sodium, just following solute

38
Q

What is secondary active transport in relation to the Na-K ATPase on the tubular cells

A

-transport of sodium down an electrochemical gradient help another substance like glucose move against its gradient

-sodium glucose transporters carry glucose across proximal tubule cells
->then glucose transporters help diffusion of glucose out of epithelial cells into interstitial fluid

-this can be done with sodium and amino acids as well

39
Q

What is secondary active secretion

A

-involves counter transport of a substance with sodum ions
->energy liberated from sodium moving downhill on its electrochemical gradient helps the uphill movement of a second substance towards secretion

-this can help us maintain acid base balance

40
Q

Is there passive water reabsorption by osmosis coupled to sodium reabsorption?

A

-yes
->this happens mostly through tight junctions between epithelia cells and through cells themselves

41
Q

How does water and solutes enter the peritubular capillaries by bulf flow? Talk about Starling forces

A

-lower peritubular capillary hydrostatic pressure and much higher oncotic pressure drives net reabsorption into capillaries

42
Q

What is pressure natriuresis(salt loss) and pressure diuresis(water loss)

A

-it happens because of increased blood pressure, increasing urine excretion

-also slight increase in peritubular capillary hydrostatic pressure, especially in vasa recta
->this leads to subsequent increase in renal interstitial fluid hydrostatic pressure

43
Q

Describe the reabsorption in the proximal tubule

A

-bulk of water and sodium reabsorption(65%)

-epithelia cells are highly metabolic, supporting active transport processes(large amount of mitochondria)
-extensive luminal brush border
-large surface area on luminal and basolateral epithelia
-loaded with protein carrier molecules

44
Q

Does the concentration of sodium change in the proximal tubule due to water loss

A

-no because water follows sodium
-so yes you lose sodium, but you also lose water balancing out that concentration of sodium and keeping it consistent

45
Q

Is there secretion of organic acids and bases into the proximal tubule?

A

-yes

46
Q

Describe the thin descending/ascending loop of henle in terms of reabsorption. As well you can mention the thick ascending portion as well

A

-thin epithelial membranes, no brush borders, few mitochondria, minimal metabolic activity

-the thin descending specifically have high permeability to water
->moderate permeability to most solutes
->20% of filtered water is reabsorbed in Loop of Henle, mostly in the thin descending portion

-the thin ascending/thick ascending are virtually impermeable to water
->filtrate becomes hypotonic because water can’t leave

47
Q

Describe the thick ascending loop of henle transport mechanisms

A

-we have the Na-K ATPase
->this can be used to drive Cl and K transport
-drugs(loop)direutics target Na-K ATPase transporters
->accumulate ions in filtrate and water is not reabsorbed

-there is also paracellular diffusion of other solutes such as magnesium, calcium, sodium and potassium
->because potassium can accumullate in the filtrate due to leak channels

-there are also potassium leak channels

48
Q

Describe the reabsorption processes of the early distal tubule

A

-the first portion of the macula densa
-similar reabsorptive characteristics of the thick ascending limb of loop of Henle
-very permeable to solutes but not water so filtrate becomes diluted

49
Q

Why would Na-Cl co-transporters be inhibited in the distal tubules

A

-to help treat hypertension

50
Q

Describe the reabsorption process of the late distal tubule and collecting tubule

A

Two cell types
-principal cells which help reabsorb Na and water from the lumen and secrete K into lumen
->site of action of aldosterone for Na reabsorption

-intercalated cells
->help reabsorb K and secrete hydrogen into tubular lumen
->contribute to acid-base balance

51
Q

How is the water permeability of the late distal tubule and cortical collecting duct controlled

A

-by ADH
->if we are volume depleted, we can help reabsorb the water back into the blood

52
Q

Why are principal cells important

A

-because of sodium reabsorption and potassium secretion
-low intracellular Na favors sodium diffusion into cell from lumen through sodium channels

-potassium secretion happens in two steps
->first potassium enters cell due to Na-K ATPase action
->resulting in high intracellular potassium
->once in cell, potassium diffused down the concentration gradient into a tubular fluid

53
Q

What are aldosterone antagonists and sodium channel blockers(potassium-sparing direutics)

A

-they block sodium reabsorption and water reabsorption
->as well they decrease K transport into cells and reduces K secretion into tubules

54
Q

Describe the reabsorption process in the medullary collecting duct

A

-reabsorbs less than 10% of filtered water and sodium
-final site for processing urine
-epithelial cells feature few mitochondria
-permeability to water controlled by ADH
-permeable to urea and urea transporters present
->raises osmolarity in medullary intestitium helping form concentrated urine

55
Q

What happens with excessive water consumption

A

-osmolarity of renal medullary interstitium is decreased
->ability to concentrate urine is impaired

56
Q

What converts angiotensin 1 into angiotensin 2

A

-in the lungs through ACE enzymes

57
Q

What does angiotensin 2 do?

A

-blood vessel vasoconstriction, which increased total peripheral resistance
->result in increased blood pressure

-increased release of aldosterone which acts on principal cells
->helps with sodium reabsorption

-acts on brain and helps release AVP or ADH, increase permeability of latter tubules to water
->increasing reabsorption here as well

-as well, thirst increases too

58
Q

What happens when there is volume overload

A

-there is an atrial stretch at the heart
->there is release of atrial natriuretic peptide(ANP)

ANP has multiple effects
->works to oppose aldosterone release
->vasodilates blood vessels and reduces pressure
->opposes the release of renin and angiotensin 2 as well

-ANP increases total urine output, resulting in naturasis and direusis

59
Q
A

Foundations 511 (8 decks)

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