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RUSVM Physio II *TWO* > Renal > Flashcards

Renal Flashcards

1
Q

What are the functions of the kidney

A 
Filtration of the blood 
Production of urine
Reabsorption of filtered substances 
Excretion of metabolic waste and xenobiotics 
Water and acid-base balance 
Production of glucose (gluconeogenesis) 
Endocrine functions
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2
Q

What hormones are produced by the kidneys ?

A

Calcitorol - stimulated by PTH in response to hypocalcemia (increase reabsorption)
Renin- BP regulator (increase H2O reabsorption)
Erythropoietin - erythropoiesis

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3
Q

What is the functional unit of the kidney?

A

Nephron

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4
Q

What are the two types of nephrons?

A

Cortical nephrons - short loops supplied by peritubular capillaries

Juxamedullary nephrons- cortex and medulla supplied by vasa recta (essential for urine concentration)

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5
Q

What is the Malpighian body?

A

The glomerulus surrounded by the Bowmans capsule.

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6
Q

Trace filtrate flow through the nephron and the main function of that part of the nephron.

A

Malpighan body- glomerulus and bowmans capsule-> production of primary ruin through filtration

Proximal convoluted tubule- reabsorption of solute and water, excretion of drugs

Loop of Henule - thick and thin descending limb, and ascending limb (only in juxtamedullary nephrons have thin acceding limbs)
Urine concentration

Distal convoluted tubule- reabsorption of solutes

Collecting duct - water balance

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7
Q

What is the sequence of renal blood supply ?

A

Abdominal aorta -> renal artery -> interlobar arteries ->arcuate artery -> interlobular arteries (into renal capsule) -> afferent arterioles -> globular capillaries -> efferent arterioles -> peritubular capillaries / vasa recta

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8
Q

Why is urine production a highly energy consuming process?

A

Active transport of solutes across membranes

ATP-dependant transport

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9
Q

What are examples of renal IR?

A

Organ transplants
Cardiac and vascular surgeries
Acute renal failure
Toxins

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10
Q

Renal ischemia has what affect on the kidney?

A

Inflammatory response to O2 deprivation
-> production of ROS -> damage DNA, Lipids, and proteins => Loss of cell polarization => Apoptosis

Impaired renal function

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11
Q

What is the regenerative capacity of the kidney?

A

Nephrons cannot be replaces but tubular cells have some regenerative capacity

Migration and proliferation of surrounding cells to mesechymatic phenotype

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12
Q

What is the glomerulus?

A

Compact network of capillaries that retains cellular components and proteins

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13
Q

What is the glomerular filtration rate dependent on?

A

Renal plasma flow (RPF) - rate the kidney is perfused with blood

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14
Q

What percentage of blood plasma is filtered through the glomeruli?

A

20% is filtered

99% of this filtrate is reabsorbed

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15
Q

Epithelial cells covering the glomerulus?

A

Podocytes

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16
Q

What are the components of the filtration barrier?

A 
Capillary endothelium (fenestrated) 
Glomerular basement membrane (glycoproteins) 
Visceral epithelium (podocytes)
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17
Q

What are the three layers of the glomerular basement membrane?

A

Lamina rara interna
Lamina densa
Lamina rara externa

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18
Q

What is the lamina densa made up of?

A

Glycoproteins (laminins, type IV collagens, proteoglycans)

Impermeable to proteins

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19
Q

Filterability of substances is dependent on what factors?

A

Size (radius and molecular weight)

Electrical charge - negative charged large molecules are filtered less easily than positively (cationic) charged molecules of the same molecular size

Plasma protein binding

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20
Q

What is the main driving force for filtration

A

Hydrostatic pressure

Oncotic pressure of blood plasma opposes the hydrostatic pressure

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21
Q

How does the pressure of the glomerular capillaries change over the length of the glomerulus?

A

Hydrostatic is relatively constant

Oncotic pressure increases gradually along the length

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22
Q

What are methods used to determine renal function?

A 
Urine strips - proteins 
Centrifuge + microscope -crystals 
Refractometer -concentration/SG
Protein detection tests 
Urine concentration test 
Clearance
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23
Q

What properties does an indicator substance for GRF have?

A

Freely filterable
Amount filtered must not change due to restoration/secretion in the tubule
Must not be metabolized in the kidney
Must not alter renal function

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24
Q

What is renal clearance ?

A

Clearance = GFR

Rate the plasma is cleared of a substance if the substance is freely filterable

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25
Q

How is blood flow regulated in the kidney ?

A

Auto regulatory window between 80-180mmHg

Myogenic reflex
RAAS
Tubuloglomerular feedback

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26
Q

Where is renin produced?

A

Wall of the cells of afferent arterioles

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27
Q

What is the myogenic reflex (Baylis effect) ?

A

Detects changes in glomerular perfusion

Increase tension of arteriolar wall -> depolarization of vascular smooth muscle -> Ca2+ enters cell -> muscle cell contraction -> constriction of afferent arteriole

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28
Q

What is the tubulogomerular feedback mechanism?

A

Increase GFR -> increased tubular fluid -> NaCL in macula densa -> depolarization of cells and ATP release -> suppression of renin release from juxtaglomerular cells -> mesangial cells contraction increase resistance of afferent arteriole -> reduced GFR

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29
Q

Describe the RAAS?

A

Decreased arterial presssure -> kidney releases renin-> coverts antiogentinogen to angiotensin I -> ACE coverts angiotensin I to angiotensin II-> increase water retention -» increase BP

30
Q

What affect does the sympathetic system have on renin?

A

B-adrenergic stimulation induces renin release

31
Q

What are vasodilator agents ?

A

NO (NOS)
PGE2- modulate mesagnial cell contraction

Counteract constriction to maintain oxygenation

32
Q

What are constricting factors

A

Endothelin,
TXA2
ANG2
B-adrenergic stimulation

33
Q

What is primary urine?

A

Ultrafiltrate in the Bowmans capsule space (same concentration of solutes as plasma)

34
Q

How can you determine rental tubule function?

A

Fractional excretion rate - net rate of reabsorption and secretion of a filtered substance

FEx = Ux/Px / Ucre/Pcre

35
Q

Describe cells of the proximal tubule ?

A

Polarized (apical and basolateral membrane)
Brush borders (microvilli)
Tight junctions

36
Q

By what two ways can tubule fluid components be moved back into the blood?

A

Transcellular pathway- carrier mediated across basolateral and apical

Paracellular pathway - through tight junctions (passive diffusion/ solvent drag)

37
Q

Primary active transport

A

Fueled directly by ATP consumption

Eg Na/K ATPase to establish Na gradient

38
Q

Secondary Active transport

A

Driven by the electrochemical gradient produced by the primary active transporter (eg Na cotransporter)

39
Q

Tertiary active transport

A

Carrier is driven by the gradient generated by a secondary active transport

H+ gradient can be used to move a third substance like tri and dipeptides into the cell

40
Q

Secondary transport systems are important for what substances?

A

Glucose, amino acid, prostate, sulfate, and citrate

41
Q

How are peptides reabsorbed in the kidney?

A

Tertiary active transport -di and tripeptides
H+ gradient

Oligopeptides are hydrolyzed by extracellular peptidaes
Na symporter -> secondary active transport

42
Q

How are low molecular weight proteins reabsorbed int the kidney?

A

Receptor-mediated endocytosis

Protein binds to receptor -> endocytosis -> fusion with lysosomes and degraded -> vesicle recycled back to plasma membrane

Saturation of these receptors -> unrecovered proteins -> proteinuria

43
Q

How can proteinuria be classified?

A

Pre-renal - concentration freely filterable proteins in blood is increased

Intrarenal -glomerular filter is damaged

Post-renal- tubular loss of protein (inflammatory process)

44
Q

Where and how is bicarbonate reabsorbed in the kidney??

A

Proximal tubule

Sodium gradient drives Na/ H transporter. H+ out to tubular lumen and combines with HCO3 to form Co2

Co2 enters cell through aquaporins and is covered back to HCO3 by carbonic anhydrase

45
Q

How is chloride ion reabsorbed in the proximal tubule?

A

Paracellular

46
Q

How is calcium reabsorbed in the proximal tubule?

A

Uptake by paracellular and solvent drag

47
Q

What substances are secreted into the proximal tubule?

A 
Organic ions (endogenous or exogenous) 
-if protein bound-> poorly filtered
48
Q

How are organic ions secreted?

A

Basolateral uptake and apical secretion (carrier mediated)

49
Q

What proteins are involved in organic anion secretion and where are they located on the PT?

A

Organic anion transporter ( OAT) - basolateral

Multrdrug Resistance Protein 2 (MRD2) -apical and linked with ATP

50
Q

What proteins are involved in secretion of organic cations and where are they located on the PT?

A

Organic cation transporter (OCT) - basolateral

Multidrug resistance - (MDR1) - apical and linked with ATP

51
Q

How is glucose reabsorbed and where?

A

Sodium-dependent transporter (SGLT) -secondary active transport
In the proximal tubule

52
Q

High levels of plasma glucose (>10-15mmol) has what effect on reabsorption of glucose?

A

Carriers become saturated -> excess glucose secreted in urine.

Glucose is osmostically active so it pulls water with it => polyuria

53
Q

What are the segments of the loop of Henule?

A

Thick descending limb ( sometimes concidered part of PT)

Thin descending limb

Thin ascending limb ( not present in cortical nephrons)

Thick ascending limb

54
Q

What type of nephrons are especially important for urine concentration

A

Juxtamedullary ( long loops) nephrons

55
Q

The thin descending limb is highly permeable to ________ and has reduced permeability to __________.

What is the overall effect of this?

A

Water (aquaproins on apical membrane)

Sodium, chloride, and urea

Tubular fluid becomes more concentrated (increased osmolality)

56
Q

The ascending limbs are impermeable to _____________. The thick ascending limb reabsorbed high amounts of _________.

What is the net effect of this?

A

Water.

Solutes (sodium, chloride, potassium, calcium, bicarbonate, magnesium)

Dilution of tubular fluid .

57
Q

The descending limb ________ tubular fluid and the ascending limbs ________ tubular fluid

A

Concentrate

Dilute

58
Q

What is the most significant transport system in the thick ascending limb?

A

Na, K Cl cotransporter (NKCC) - move solutes from the lumen back to interstitium

59
Q

How are Ca, Mg and Na reabsorbed from the ascending limb?

A

Paracellular - lumen is positively charged, forces ions to move back to interstitium

60
Q

What is the main process in the distal convoluted tubule?

A 
Reabsorption of solutes 
Ca channels (TRPV)-apical
Na/Cl cotransporter (NCC)-apical
K channels-basolateral
Ca/Na exchanger (NCX)- basolateral
61
Q

What is the main function of the late DT and cortical collecting duct?

A

Water reabsorption through aquaporins

62
Q

What is the main process in the inner medullary collecting ducts?

A

Urea reabsorption - urea transporters

63
Q

What are the two types of cells in the collecting duct?

A

Principal cells and intercalated cells

64
Q

What are the important transport systems of the CD principal cells?

A

NaCl reabsorption by ENaC

K secretion by ROMK

65
Q

Type A intercalated cells secretes _____ and reabsorbs _______

A

H+

HCO3-

66
Q

Type B intercalated cells secrete _____ and reabsorb _______

A

HCO3-

H+

67
Q

What effect does PTH have on transporters in the kidney?

A

Inhibits apical NaPi transporters (phosphate not reabsorbed)

Stimulates apical uptake of Ca2+

Vitamin D hormone synthesis in the kidney -> increased Ca reabsorption from intestines

68
Q

What hormones stimulate solute reabsorption in the kidney?

A

Antigotensin II
Aldosterone
ADH

Work on transporters

69
Q

What hormones inhibit solute reabsorption in the kidney?

A

NO
Endothelin -1
ANP

Inhibiting sodium transporters

70
Q

How does ANP inhibit solute reabsorption?

A

Inhibit aldosterone and renin release

Increase Na+ excretion

RUSVM Physio II *TWO* (11 decks)

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