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Physiology 150 > Unit 10 - Urinary Physiology > Flashcards

Unit 10 - Urinary Physiology Flashcards

1
Q

Kidney Function

A
  1. regulate water, fluid and electrolyte balance (H+, K+, NA+, electrolyte and water balance)
  2. regulate blood volume and blood pressure
  3. regulate acid base balance (H+ & HCO3-)
  4. Excretion of foreign compounds (drugs, presticides, food additives) and waste products (urea, uric acid, creatinine)
  5. Secrete hormones
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2
Q

Urinary System consists of

A

Urine forming organs ( 2 kidneys)
Structures carry urine from kidneys to outside for elimination (2 ureters L slightly longer than R, 1 urinary bladder, 1 urethra) 2 adrenal glands

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3
Q

Renal Structures

A

Renal cortex: filters blood
Renal medulla: contain 8-12 renal pyramids, empties into cuplike calyx, calyces channel urine into renal pelvis.
Renal pelvis: urine travels from renal pelvis to bladder for storage

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4
Q

Process of urine

A

Renal pyramid projects into a minor calyx
3 Minor calyces form 1 major calyx
Minor calyx accepts tip of pyramid where urine is dripping off papillary duct in pyramid.
Major calyx empty into pelvis which is at top of ureter
Urine enters ureter
Variability between kidneys

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5
Q

Renal papula

A

apex of the pyramid and projecting into the calyx

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6
Q

Nephron

A

Functional unit of the kidney
Filter blood to remove water and substances
Then necessary fluid and electrolytes reabsorbed back into blood
removes unnecessary molecules
approximately 1 million nephrons/kidney
each nephron has two components (vascular & tubular)

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7
Q

Vascular Component

A

From aorta, each renal artery subdivided into afferent arterioles
1 afferent arteriole supplies 1 nephron -> glomerular capillaries
Glomerular capillaries rejoin to form efferent arteriole
Forms peritubular capillaries
Wrap around tubular structures
Supply renal tissue with blood

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8
Q

Vasa recta

A

Series of straight capillaries in medulla

Slow rate of blood flow allows concentration of urine

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9
Q

Juxtaglomerular Apparatus JGA

A

between glomerulus and DCT to regulate function of nephron
Contains:
1. the macula densa, at start of DCT (Sensitive to concentration of NaCl of fluid flowing by
2. Juxtaglomerular cells that secrete renin
3. Extraglomerular mesangial cells (unknown function)

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10
Q

Tubular Component

A

Blood from afferent arteriole into glomerulus
Fluid that is formed -> proximal convoluted tubule (PCT)
Down descending limb of Henle, which dips into medulla
Urine from DCT to collecting duct->renal pelvis->bladder->elimination

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11
Q

Glomerulus

A

network of capillaries that sit in bowman’s capsule

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12
Q

Distal Convoluted tubule DCT

A

ascending limb of Henle returns to cortex

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13
Q

Three steps of Renal Process

A
  1. Glomerular filtration
  2. Tubular reabsorption
  3. Tubular secretion
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14
Q

Glomerular Filtration

A

First step to form urine
20% of blood that enters glomerulus is filtered and goes into BC
Filtered blood components (most of the water, most/all of the salts, glucose and urea
80% of unfiltered blood then travels in efferent arteriole

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15
Q

GFR

A

Males- 125ml/min
Females- 115ml/min
180 L/day

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16
Q

Three physical forces affect GFR

A
  1. Glomerular capillary blood pressure
  2. Plasma-colloid osmotic pressure
  3. Bowman’s capsule hydrostatic pressure
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17
Q

Glomerular capillary blood pressure

A

Pressure exerted by blood in glomerular capillaries
afferent arteriole diameter>efferent diameter
therefore, pressure of blood inside glomerulus is increased
this increased blood pressure forces the components of blood out of glomerular capillaries
elevated pressure favours fluid entering bowman’s capsule (favours GFR)

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18
Q

Plasma-colloid osmotic pressure

A

caused by more proteins in glomerulus than is BC

water moves from high conc. BC to low conc glomerulus (opposes filtration)

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19
Q

Bowman’s capsule hydrostatic pressure

A

pressure that pushes fluid out of BC (opposes filtration)

Net filtration pressure (change force favouring filtration, 1 - (2+3)

20
Q

Regulation of GFR

A

two major control mechanisms
1. Autoregulation (prevent spontaneous GFR changes) myogenic mechanism, tubuloglomerular feedback TGF
Neuron control aimed at long-term regulation of BP ( SNS effect on afferent arterioles)

21
Q

Myogenic mechanism (autoregulation)

A

Increase in BP (afferent arteriole automatically constricts -> decreased dismeter and flow into glomerulus -> less blood filtered and lover GFR)
Decrease in BP (afferent arteriole automatically dilates -> increased diameter and flow into glomerulus -> more blood filtered higher GFR

22
Q

Tubuloglomerular feedback mechanism

A

Increased BP increases GFR
Elevation of BP and GFR-> more fluid and salt filtered -> macula densa release ATP and adenosine -> afferent arteriole contricts -> lowers glomerular blood flow and lowers GFR
Reduction of BP and GFR -> less fluid and salt filtered -> less ATP released and adenosine made -> afferent arteriole dilates -> raise glomerular blood flow and raise GFR

23
Q

Regulatory mechanisms

A

myogenic and TGF regulations work together
prevent inappropriate fluctuations in GFR and dangerous imbalances of fluid, electrolytes and waste (lose too much water, electrolytes if GFR too high, retain wastes if GFR too low)
Work within MAP 80-180 mm Hg ( changes outside range cause GFR to increase/decrease)

24
Q

Neural Regulation of GFR

A

Kidney’s blood vessels also regulated by sympathetic fibers
If blood voume decreased (hemorrhage) -> BP reduced -> baroreceptors -> CV control centre in brain stem -> raise sympathetic stimulation -> vasoconstriction of afferent arterioles that reduces GFR -> less fluid filtered -> lowers urine output -> concerves fluid to help increase BP

25
Q

Hormonal Regulation of GFR

A

Atrial natriuretic peptide ANP

26
Q

Atrial natruoretic peptide ANP

A

incease in BO -> atria stretch and release ANP
Inhibits Na+ reabsorption
Promotes (natriuretic more Na excreted, Diuretic more H2O excreted, reduces BP hypotensive effect)
increase GFR -> more urine formed -> less blood volume -> reduces BP

27
Q

Renin-Angiotensin-Aldosterone-System RAAS

A

starts lower BP -> juxtaglomerular cells secrete renin
Follow flow chart
at end, angiotensin II reduces GFR (potent vasoconstrictor that narrows both afferent and efferent arterioles reducing GFR, less urine formed -> more blood volume -> increase BP)

28
Q

Tubular Reabsorption

A

involves the transfer of substances from tubulat lumen into peritubular capillaries ( move substances from filtered fluid back into blood, body needs these substances)
Most substances reabsorbed

29
Q

Reabsorbed substances must cross what five barriers

A
  1. leave tubular fluid by crossing luminal membrane of tubular cell
  2. pass through cytosol from one side of tubular cell to the other
  3. cross basolateral membrane of the tubular cell to enter interstitial fluid
  4. diffuse through interstitial fluid
  5. penetrate capillary wall to enter blood plasma
30
Q

Renal threshold

A

maximum ability of kidney to reabsorb a specific substance
required specific carrier for each substance
Any substance beyond Tm is not reabsorbed
the glucose carrier mechanism can reabsorb a maximum of 375 mg of glucose per minute (Tm)

31
Q

Glycosuria

A

when 375 mg/ml reached and carriers fully saturated, excess glucose excreted in urine

32
Q

Renal threshold

A

point at which glucose begins to spill into the urine

33
Q

Tubular secretion

A

transfer of selective substances from peritubular capillaries (blood) back into tubular lumen (to urine)

34
Q

Tubular secretion is important for two reasons

A

H+

K+

35
Q

H+

A

important in regulating acid-base balance
when body fluids are too acid -> more H+ is secreted
when body fluids too alkaline -> less H+ secreted
Secreted in proximal, distal, and collecting tubules

36
Q

K+

A

secreted only in DCT and collecting tubules under control of aldosterone
normal plasma K+ concentration maintains normal membrane excitability in muscles and nerves

37
Q

Tubular secretion

A

organic ions
secreted only in the proximal tubule (efficient elimination of foreign compounds from body)
certain drugs (penicillin)
environmental pollutants such as pesticides

38
Q

Regulation of urine concentration

A

countercurrent mechanism
urine concentration mechanism completed in loop of henle
The concentrtion of tubular fluid (urine) is progressively increasing in the descending limb and progressively decreasing in the ascending limb
benefits of countercurrent mechanism
effective water reabsorption
final adjustment of urine concentration

39
Q

Regulation of Urine Concentration

A

Descending limb

Ascending limb

40
Q

Descending limb

A

thin epithelium
water flows out into interstitial fluid
no Na+ reabsorption

41
Q

Ascending limb

A

thick epithelium
impermeable to water
actively transports NaCl out of the tubular lumen into interstitial fluid

42
Q

Vasopressin ADH

A

DCT and collecting tubule not permeable to water
become permeable if ADH present
released when ECF too concentrated (need more water for body_ -> conc urine
inhibited when ECF too dilute (need less water for body) -> urine dilute

43
Q

Renal endocrine functions

A

erythropoietin : increased release with hypoxia and decreased circulating red cell mass

44
Q

Excretion

A 
the end product of the renal process (excess ions, H2O, molcules, toxins, NH4+ and extra urea [nitrogenous wastes])
urine output (1.0-1.5L/day, high volume less concentrated uring, low volume more concentrated urine, depending on body's state of hydration)
45
Q

Micturition

A

urine in bladder stimulates stretch receptors
PNS neurons stimulate stretch receptors to signal smooth muscle in bladder wall
contraction of bladder urine out of the body
micturition reflex (relaxation of external urethral sphincter muscle allowing urine to pass through urethra and out of the body)
under voluntary control but connot be delayed indefinitely

Physiology 150 (11 decks)

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