Final: Cont. Flashcards
Hydrostatic P in glomerular capillaries
45 mm HG
Hydrostatic P in Bowman’s space
10 mm HG
Glomerular filtration rate
180 L day = 125 ml/min
Filtered load
Amount of substance filtered across glomerular capsule
Tubular fluid
Fluid in Bowman’s space and lumen of nephron
Mechanisms of action for reabsorption
Transporters in membrane of tubular epithelial cells
Most important function of kidneys and why
Reabsorb Na -> drives reabsorption of everything else
Major cation in ECF
Na
Increase in Na intake = increase in
Volume
Examples of substances secreted from peritubular blood into tubular fluid via tubular epithelium
Organic acids
Organic bases
K+
Cellular mechanism for glucose reabsorption
Carrier mediated along with Na in early PT
- from tubular fluid into tubular cell via Na/glucose symporter SGLT
- 2 Na (downhill) and 1 glucose (uphill)
- Na/K pump on peritubular capillaries side keeps Na low in ICF
- secondary active transport
Glucose transported from tubular cell into peritubular blood by
Facilitated diffusion
GLUT 1 and 2 ( insulin dependent)
Splay on glucose titration curve
Bending of reabsorption curve
Threshold - not all glucose reabsorbed
Reasons for splay
Low affinity of Na glucose cotransporter
Heterogeneity of nephrons
Glucosuria definition and observed in what conditions
High plasma glucose >200 mg/dL (DM)
Pregnancy (increased GFR which increases filtered load)
Congenital abnormalities of Na/glucose cotransporter
___ freely filtered across glomerular capillaries
Urea
__ transported in most segments of nephron
Urea
Concentration of urea increases in tubular fluid as water is
Reabsorbed from tubule
Urea secreted in
Thin descending limb
Structures impermeable to urea
Thick ascending limb
Distal tubule
Cortical CD
Outer medullary CD
More urea is secreted than was reabsorbed by
PCT
Inner medullary collecting ducts have urea transporter 1 which is activated by
ADH
Urea can by __ at high levels
Toxic
__ and __ help create osmotic gradient at loop of Henle so water can be reabsorbed
Urea and salt
Para-aminohippuric acid (PAH)
Used to measure renal plasma flow
90% of PAH in blood bound to
Plasma proteins - not filterable
Only ___ of PAH is filterable
10%
PAH secretion
Transporters in peritubular membranes of PT cells
Inhibited by probenecid
Excretion of PAH
Rises sharply as unbound plasma PAH levels rise
Weak acids
PAH
Salicylic acid
Weak bases
Quinine
Morphine
Only ____ species of weak acids and bases can diffuse across tubular cells
Uncharged species
Aspirin reabsorption
HA form = salicylic acid - reabsorbed
A- form = salicylate = not reabsorbed
Positive Na balance
Excretion < intake
Negative Na balance
Excretion > intake
Positive Na balance; excess Na accumulates where
ECF = Increase BV and BP
Possible edema
Negative Na balance; Na lost from
ECF
Maintenance of ___ essential for normal function of excitable tissue
K
Most (98%) of K is where
ICF
___ major cation that exchanges for H
K
Shifts of K from ICF to ECF
Insulin deficiency Beta 2 adrenergic antagonists Alpha adrenergic agonists Acidosis Hperosmolariry Cell lysis Exercise
Shifts of K from ECF to ICF
Insulin Beta 2 adrenergic agonsits Alpha adrenergic antagonsits Alkalosis Hypoosmolarity
___ increases activity of Na/K ATPase
Insulin
High levels of insulin can result in
Hypokalemia
Type 1 DM can result in
Hyperkalemia
Insulin helps move ingested ___ into cells to prevent ____ after K rich meal
K
Hyperkalemia
Acid base abnormalities are often associated with
K abnormalities
K disturbances do not occur in ___ or ___
Respiratory acidosis or alkalosis
K is not bound and freely filtered at
Glomerular capillaries
___ reabsorbed 67% fo filtered load of K
PCT
__ reabsorbs 20% of filtered load of K
Thick ascending limb
Final adjustments to K secretion occurs in
Distal tubule and collecting duct
K reabsorption occurs via
Alpha intercalated cells
K secretion occurs by
Principe cells
Loop diuretics and thiazide diuretics
Increase K excretion leading to hypokalemia
Produce profound kaliuresis and hypokalemia
Thick AL impermeable to
Water
Increase plasma osmolarity stimulates osmole receptors in
Anterior hypothalamus
Vasa recta
Capillaries that serve medulla and papilla
3 actions of ADH on renal tubule
- Increase water permeability of principal cells in Lae DT and CD
- Increase activity of Na/K/Cl cotransporter of TAL
- Increase urea permeability in inner medullary CD
In nephron free water generated in
Diluting segment
ADH low and effect on free water clearance
All free water excreted -> cannot be reabsorbed by collecting ducts
Free water clearance positive
ADH high and effect of free water clearance
All free water reabsorbed by late distal tubule and CD
Free water clearance is negative
Normal body pH
7.4
Normal range of arterial pH
7.37-7.42
Ph range compatible with life
6.8 to 8
___ important as buffer in tubular fluid of kidney and intracellular buffer
Phosphate buffer
All enzyme systems and body functions are altered by
H concentration
Acidosis
Suppresses neuronal excitability —> coma
Alkalosis
Excessive neuronal excitability —> convulsions
3 mechanisms to maintain pH
Buffering (immediate) Respiratory compensation (rapid) Renal compensation (slower)
Acidosis if blood»>
< 7.37
Alkalosis if pH of blood…
> 7.42
H secretion and HCO3 reabsorption occur in all parts of tubule except
TAL and TDL of loop of henle
Most HCO3 reabsorption occurs in
Proximal tubule
3 buffering systems
Bicarbonate
Phosphate
Proteins
Powerful intracellular buffers
Proteins
Most powerful regulators of pH
Kidneys
Kidneys regulate ECF H concentration by 3 mechanisms
Secretion of H
Reabsorption of filtered HCO3
Production of new HCO3
Secretion of H by secondary active transport occurs in
PT
TS of AL
Early DT
H is combined with buffers in tubular fluid, and 2 main buffers
Phosphate
Ammonia
Normal P co2
40
Acidosis due to increase in PCO2
Respiratory acidosis
Acidosis due to fall in HCO3
Metabolic acidosis
2 forms of acid on body
Volatile
Fixed
Example of volatile acid
CO2
Examples of fixed acids
Sulfuric acid
Phosphoric acid
Kidneys play 2 major roles in maintenance of normal acid base balance
Reabsortion of HCO3
Excretion of fixed H
