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Physiology > Renal 4 > Flashcards

Renal 4 Flashcards

1
Q

Tubular Reabsorption (3)

A 
 High capacity & variable; 
very selective
 Many electrolytes and 
nutrients almost 
completely reabsorbed
 Most waste products 
poorly reabsorbed.
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2
Q

Tubular Secretion (2)

A

 Variable
 Important for certain
electrolytes (K+, H+), drugs,
toxins.

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3
Q

Once fluid is reabsorbed across the tubule epithelium

into the interstitial fluid, it enters

A

peritubular capillaries

via Bulk Flow

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4
Q

Reabsorption =

A

Kf (Net Reabsorptive force)
= Kf (Reabsorptive Force)-(Filtration force)
=Kf ((πC + Pif) – (PC + πif))

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5
Q

Normal rate of Peritubular Capillary Reabsorption =

A

124 ml/min (GFR?)

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6
Q

Normal rate of Peritubular Capillary Reabsorption = 124 ml/min (GFR?)
Large: (2)

A

 Large Kf (high surface area and permeability)

 Large πC (due to volume lost during filtration)

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7
Q

> —% of filtered sodium

reabsorbed

A

99

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8
Q

> 99% of filtered sodium
reabsorbed
 All along —

A

nephron

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9
Q

Sodium Reabsorption can

occur via both (2)

A

Transcellular

and Paracellular

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10
Q

Transcellular pathways (2)

A 
- Passive across apical and 
active across basolateral 
membranes
- Apical Na+ transport may 
be secondary active and 
tied to reabsorption of 
other substance (ex. 
Glucose)
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11
Q

Transport maximum

A

Maximum rate some substances
can be transported across the
epithelium (absorption or
secretion)

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12
Q

transport maximum is due to

A

saturation of transport

proteins

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13
Q

Renal Threshold is the

A

plasma
concentration that saturates the
carrier (tubular load)

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14
Q

Once the transport maximum is

reached for all nephrons,

A

further
increases in tubular load are not
reabsorbed and are excreted.

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15
Q

examples of transport max (6)

A

glucose, amino acids,
phosphate, sulfate, urate,
(creatinine, PAH)

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16
Q

As [Glucose] plasma increases, the [Glucose] filtrate —, Glucose tubular load —.

A

increases

increases

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17
Q

Reabsorption of Water: Passive But Influences Many Solutes

 Strictly —

A

passive

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18
Q

As Na+ reabsorbed, creates
gradient for — reabsorption via
osmosis

A

H2O

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19
Q

Proximal tubule highly permeable

to —

A

H2O

20
Q

As H2O moves via osmosis: (2)

A 
- Carries other solvents along = 
Solvent drag (size restricted)
- Creates gradients for the passive 
reabsorption of other solute (ex. 
Cl- and Urea)
21
Q 
H2O Permeability varies as  move 
through nephron (2)
A
  • Ex. Ascending limb of Loop of
    Henle (not permeable to H2O
  • Collecting duct (regulated; ADH)
22
Q

PT Reabsorption of Na+, Cl-, Urea

and H2O exhibit

A

Gradient-Time

Transport

23
Q

The concentrations of solutes in different parts of the tubule depend on relative reabsorption of the solutes compared to water: (2)

A

 if water is reabsorbed to a greater extent than the solute, the solute will become more concentrated
in the tubule (e.g., creatinine, inulin)
 if solute is reabsorbed to a greater extent than
water, the solute will become less concentrated in the tubule (e.g., glucose, amino acids)

24
Q

Regional Tubular Transport (5)

A
  1. Early Proximal Tubule (early PT or PCT) and
    Late Proximal Tubule (late PT or PST)
  2. Loop of Henle
  3. Early Distal Tubule (early DT)
  4. Late Distal Tubule and Cortical Collecting
    Duct (Late DT and CCD)
  5. Medullary Collecting Duct (MCD)
25
Q

Loop of Henle (3)

A

Thin descending limb
Thin ascending limb
Thick ascending limb

26
Q

Proximal Tubule

PT =

A

PCT + PST

27
Q

Cells have High capacity for Active

and Passive Reabsorption (4)

A
  • Large # mitochondria
  • Large surface area on both apical
    and basolateral membranes
  • Large number of membrane
    proteins
  • High permeability for H2O.
28
Q

PT Reabsorbs (2)

A

– ~ 65% of filtered Na+, Cl-, HCO3-,
and K+
– All filtered glucose and amino
acids.

29
Q

PT Secretes (3)

A
  • metabolic waste products such as H+ ions ,
    organic acids, and bases such as: bile salts,
    oxalate, urate, and catecholamines
  • Harmful drugs or toxins
  • Para-Aminohippuric Acid (PAH)
30
Q

Early PT (3)

A

Paracellulary
 Passive down ΔEC
 Solvent drag

31
Q

Late PT (4)

A

 Transcellular
 Apical 2° active Formate/Cl- antiporter
 Basolateral facilitated diffusion
 Paracellularly

32
Q

*SGLT2 inhibitors used in

treatment of

A

T2DM (ex.

Glifozins; Invokana).

33
Q 
Δ in [Solute] as 
Filtrate Passes 
through 
Proximal Tubule
Tx = [solute] in filtrate
Px = [solute] in plasma (4)
A 
Na+ and H2O - Isotonic 
Solution Reabsorbed
Proximal portions reabsorb 
all Glucose, Amino Acids 
and 65% HCO3-
Distal Portion reabsorbs 
more Cl- and urea
Creatinine not actively 
reabsorbed
34
Q
  1. Thin Descending Limb (tDL) (3)
A 
 High H2O permeability (Contain AQP-1 
channels): major role in 
concentration/dilution of urine
 No active solute transport
 Urea secretion via facilitated diffusion
35
Q
  1. Thin Ascending limb (tAL) (3)
A

 does not reabsorb significant amounts of any
solutes
 impermeable to water
 Urea secretion via facilitated diffusion

36
Q
  1. Thick Ascending Limb (TAL) (4)
A

 Impermeable to H2O and Urea
 Major site of Na+, K+, Cl- reabsorption, H+ secretion
 By end of Loop of Henle, more solute reabsorbed
than H2O
 Distal End of TAL forms part of JG apparatus

37
Q

Early Distal Tubule (6)

A 
 Parallels TAL in that it absorbs 
solute w/out H2O
 Impermeable to H2O (and urea).
 Reabsorbs ions
 Na+-Cl- co-transporter in apical 
membrane moves Na+ and Cl- 
into cells from tubule lumen
 Na+-K+-ATPase transports Na+ 
into interstitium.
 Cl- diffuses into the interstitium 
through channels in basolateral 
membrane.
38
Q

 Reabsorbs ions (3)

A
  • 5% of Na+ & Cl-
    – Further dilutes filtrate
    – Diluting Segment
39
Q

Late Distal/Cortical Collecting Duct (CCD)

Two Cell Types

A
  1. Principal Cells

2. Intercalated Cells

40
Q
  1. Principal Cells (4)
A 
60-70% of cells
Site of Aldosterone  and ADH 
action
–Reabsorb Na+  and H2O
–Secrete K+
41
Q 
Late Distal/Cortical Collecting Duct (CCD)
These 
segments are 
completely 
impermeable to ---
A

Urea

42
Q 
2. Intercalated Cells 
cell types (2)
A

Alpha Intercalated Cells

Beta Intercalated Cells

43
Q

Alpha Intercalated Cells (4)

A 
Function important during acidosis
Secrete H+
Reabsorb K+ and HCO3-
1° Active Transport of H+ across 
apical membrane can secrete H+ 
against a great ΔC (1000:1)
44
Q

Beta Intercalated Cells (3)

A

Function important during alkalosis
Secrete K+ and HCO3-
Reabsorb H+

45
Q

Medullary Collecting Duct (MCD) (4)

A 
 Processes < 10% of Na+ and 
H2O but very important (10% 
of 180 L).
 Site of Aldosterone  and ADH 
action
 Urea reabsorbed via 
facilitated diffusion
 Secretes H+ using same 
mechanism as α-intercalated 
cells.
46
Q

Regional Tubular Transport

Tx/Px) (5

A 
1. Proximal Convoluted 
Tubules (PCT)
2. Loop of Henle
3. Early Distal Convoluted 
Tubules (DCT)
4. Late Distal Tubule and 
Cortical Collecting Duct
5. Medullary Collecting 
Duct (CT)

Physiology (53 decks)

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