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Anatomy > Renal System and Fluid Balance > Flashcards

Renal System and Fluid Balance Flashcards

1
Q

what processes occur as filtrate is converted to urine?

A
  • elimination of metabolic wastes, hormones, drugs
  • regulation of ion levels
  • regulation of acid base balance
  • regulation of bp
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2
Q

what is the function of the fibrous capsule of the kidney?

A
  • directly adhered to external surface of kidney
  • maintains kidneys shape, protects it from trauma, and prevents pathogen penetration
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3
Q

what is perinephric fat?

A

adipose CT external to fibrous capsule that cushions and supports kidney

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4
Q

what is the renal fascia?

A
  • dense irregular CT external to perinephric fat
  • anchors kidney to surrounding structures
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5
Q

what is paranephric fat?

A

adipose CT that is outermost layer surrounding kidney and cushions and protects it

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6
Q

what are renal pyramids?

A
  • portion of medulla divided by renal columns
  • wide base at external edge of medulla
  • apex is called renal papilla
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7
Q

what is the function of the renal sinus

A

medially located urine drainage area

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8
Q

what are the components of a nephron?

A

renal corpuscle and renal tubule

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9
Q

what is the renal corpuscle?

A
  • enlarged bulbous region of nephron within renal cortex
  • composed of glomerulus and glomerular capsule
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10
Q

what is the glomerulus?

A

tangle of capillary loops and glomerular capillaries

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11
Q

what is the glomerular capsule?

A
  • internal permeable visceral layer
  • external impermeable parietal layer
  • capsular space between two layers
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12
Q

what are the three sections of the renal tubule?

A
  • proximal convoluted tubule
  • nephron loop
  • distal convoluted tubule
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13
Q

what are the two types of nephrons?

A

cortical and juxtamedullary

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14
Q

what classifies a cortical nephron?

A
  • oriented near peripheral cortex
  • short nephron loop barely penetrates medulla
  • 85% of nephrons
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15
Q

what classifies a juxtamedullary nephron

A
  • renal corpuscles adjacent to corticomedullary junction
  • long nephron loop extend deep into medulla
  • help establish salt concentration gradient in interstitial space
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16
Q

how do nephrons drain?

A
  • nephrons drain into a collecting tubule
  • multiple collecting tubules empty into large collecting ducts
  • numerous collecting ducts empty into papillary duct within renal papilla
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17
Q

what is the juxtaglomerular apparatus?

A

helps regulate blood filtrate formation, systemic blood pressure

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18
Q

What are the components of the juxtaglomerular appartus?

A
  1. granular cells
    - modified smooth muscle cells of afferent arteriole that synthesize renin
  2. macula densa
    - modified epithelial cells in wall of DCT
    - detect changes in NaCl concentration of fluid and signal granular cells to secrete renin
  3. extraglomerular mesangial cells
    - just outside glomerulus in gap between each arteriole
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19
Q

how is filtrate formed?

A
  • blood flows through glomerulus
  • water and solutes are filtered from blood plasma
  • moves across wall of glomerular capillaries into capsular space
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20
Q

what is the new name for filtrate after it enters the PCT?

A

tubular fluid
- once it empties into larger collecting ducts it is called urine

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21
Q

How does urine flow out of the kindey?

A
  • enters papillary duct within renal papilla
  • flows within renal sinus to minor calyx to major calyx to renal pelvis
  • renal pelvis connects to ureter which connects to urinary bladder
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22
Q

What is the first step of urine formation?

A

glomerular filtration
- separates some water and solutes from blood plasma
- filtrate enters capsular space of renal corpuscle

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23
Q

what is the second stage of urine formation?

A

tubular reabsorption
- movement of components within tubular fluid
- move by diffusion, osmosis, or active transport
- return to blood within peritubular capillaries and vasa recta
- all vital solutes and most water reabsorbed

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24
Q

what is the third stage of urine formation?

A

tubular secretion
- movement of solutes usually by active transport
- move out of blood within peritubular and vasa recta capillaries into tubular fluid to be excreted

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25
Q

what are some characteristics of the filtration membrane?

A
  • porous, thin, negatively charged structure
  • formed by glomerulus and visceral layer of glomerular capsule
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26
Q

what are the layers of the filtration membrane? (from in to out)

A
  1. endothelium of glomerulus
    - fenestrations allow plasma and dissolved substances to pass but restricts large structures
  2. basement membrane of glomerulus
    - glycoprotein and proteoglycan molecules
    - restricts passage of large plasma proteins
  3. visceral layer of glomerular capsule
    - composed of podocytes which restrict passage of most small proteins
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27
Q

how much filtrate is produced daily?

A

180 L

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28
Q

what are the three categories of substances in blood?

A
  1. freely filtered: small substances
    - pass easily through membrane
  2. not filtered: large proteins
    - cannot pass through
  3. limited filtration: medium size proteins
    - usually blocked due to size or negative charge
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29
Q

how is blood pressure in the glomerulus different from bp in other systemic capillaries?

A
  • higher than bp of other systemic capillaries
  • required for filtration to occur
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30
Q

what is blood colloid osmotic pressure?

A

osmotic pressure exerted by dissolved solutes that opposes filtration and draws fluid back into glomerulus

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31
Q

what is capsular hydrostatic pressure?

A

pressure in glomerular capsule due to filtrate which impedes movement of additional fluid

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32
Q

what impact does increased net filtration pressure have?

A
  • increases glomerular filtration rate
  • increases solutes and water remaining in tubular fluid
  • increases substances in urine
  • decreases filtrate reabsorption
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33
Q

Which 2 mechanisms regulates constant bp and GFR in the kidney?

A

myogenic response and tubuloglomerular feedback mechanism

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34
Q

what is the myogenic response?

A

contraction or relaxation of smooth muscle of afferent arteriole in response to stretch
- compensates for high or low systemic bp

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35
Q

what is the tubuloglomerular feedback mechanism

A
  • “backup” to myogenic response to increased bp
  • if glomerular bp increased: amount of NaCl in tubular fluid also increases and results in further vasoconstriction of afferent arteriole
36
Q

what are some limitations to maintaining GFR?

A
  • renal autoregulation: mantains glomerular pressure when bp is 80-180mmHg
  • decrease in bp below 80: decrease in glomerular bp and GFR
  • increase in bp above 180: increase in glomerular bp and GFR which leads to increase urine production
37
Q

how does the sympathetic nervous system decrease GFR?

A
  • vasoconstriction of afferent and efferent arterioles
  • granular cells of JG apparatus releases renin, which results in angiotensin II production and contraction of mesangial cells which decreases surface area of glomerulus
38
Q

How does atrial natriuretic peptide increase GFR?

A

increases GFR through
- relaxation of afferent arteriole
- inhibits release of renin
- relaxation of mesangial cells increases filtration membrane area

39
Q

what is paracellular transport?

A

movement of substances between epithelial cells

40
Q

what is transcellular transport?

A
  • movement of substances across epithelial cells
  • must cross luminal membrane in contact with fluid
  • must cross basolateral membrane on basement membrane
41
Q

where does most reabsorption occur?

A

proximal convoluted tubule
- aided by microvilli which increase surface area

42
Q

what is transport maximum?

A

maximum rate of substance that can be reabsorbed or secreted across tubule epithelium per a certain time

43
Q

what is renal threshold?

A

max plasma concentration of a substance that can be transported in the blood without appearing in the urine

44
Q

How does sodium reabsorption occur?

A
  • 98% to 100% of Na+ reabsorbed from tubular fluid
  • reabsorbed along the entire nephron tubule, mostly in PCT
  • relatively high within tubule lumen and interstitial fluid
    -Na+/K+ pumps embedded in basolateral membrane
  • reabsorption regulated by hormones near end of tubule
45
Q

what role does aldosterone play in sodium reabsorption?

A
  • steroid hormone produced by adrenal cortex
  • stimulates protein synthesis of Na+ channels and Na+/K+ pumps
  • increase in Na+ reabsorption
  • water follows by osmosis
46
Q

what role does atrial natriuretic peptide play in sodium reabsorption?

A
  • inhibits reabsorption of Na+ in PCT and collecting tubules
  • inhibits release of aldosterone
  • more Na+ and water excreted in urine
  • increases GFR
47
Q

how does water reabsorption occur?

A
  • reabsorbed by paracellular transport between cells and transcellular transport through aquaporins
  • 65% reabsorbed in PCT
48
Q

How much water is filtered daily?

A

180 L filtered dailty with all but 1.5 L reabsorbed

49
Q

How much water is reabsorbed in the nephron loop

A

10% of filtered water

50
Q

what hormones regulate water absorption?

A

aldosterone and ADH

51
Q

what role does ADH play in water reabsorption?

A
  • increases migration of vesicles containing aquaporins to membrane and adds channels to increase water reabsorption
  • increases water reabsorption from filtrate to blood
  • results in smaller volume of more concentrated urine
52
Q

when would ADH levels be elevated

A

during dehydration

53
Q

Is potassium secreted or reabsorbed?

A
  • it is both reabsorbed and secreted
  • 60% to 80% reabsorbed in tubular fluid
54
Q

What influences the movement of potassium?

A
  • sodium reabsorbed across luminal membrane, water follows
  • increased concentration of remaining solutes in tubular fluid which creates gradient between tubular fluid and interstitial fluid
  • K+ moves down gradient from tubular fluid by paracellular route
55
Q

what role do intercalated cells and principal cells have in potassium secretion/reabsorption?

A
  • intercalated cells reabsorb K+ continuously
  • principal cells secrete K+ at varying rates based on aldosterone level
56
Q

how is calcium and phosphate balance regulated?

A
  • 60% in blood goes into filtrate
  • 90% to 95% filtered as blood passes through glomerular capillaries
57
Q

what role does parathyroid hormone play in calcium and phosphate balance?

A
  • regulates excretion of calcium and phosphate
  • inhibits phosphate reabsorption in PCT
  • stimulates calcium reabsorption in DCT
  • increases calcium blood levels
58
Q

how are bicarbonate ions filtered?

A
  • move freely across filtration membrane
  • if not reabsorbed, blood becomes too acidic
  • 80% to 90% reclaimed from tubular fluid
  • remaining 10% to 20% taken up from thick segment of ascending limb
59
Q

what happens if the blood becomes too acidic?

A
  • synthesized HCO3- reabsorbed into blood
  • H+ excreted within filtrate by type A intercalated cells
60
Q

what happens if the blood becomes too alkaline?

A
  • type B intercalated cells active
  • secrete HCO3- and reabsorb H+
61
Q

how is nitrogenous waste eliminated?

A
  • 50% of urea excreted in the urine
  • uric acid both reabsorbed and secreted
  • creatinine only secreted
62
Q

where does the secretion of most drugs and bioactive substances occur?

A

in PCT

63
Q

How is the pressure gradient established in the nephron loop?

A
  • positive feedback mechanism called countercurrent multiplier
  • descending limb permeable to water, impermeable to salts
  • ascending limb impermeable to water, salts pumped out
64
Q

how does the countercurrent exchange system work?

A
  • blood in vasa recta travels in opposite direction to tubular fluid of adjacent nephron loop
  • water diffuses out of vasa recta by osmosis
  • increases concentration of salt in vasa recta
  • vasa recta next runs along descending limb of nephron
65
Q

How is urea recycled?

A
  • urea remoced from tubular fluid in collecting duct but diffuses back into tubular fluid in thin segment of ascending lumb
  • remains within tubular fluid until it reaches collecting duct
66
Q

How can GFR be measured?

A
  • measured with inulin injection
  • GFR = (concentration of inulin in urine x volume of urine produced per minute)/concentration of inulin in plasma
  • normal is 125 mL/min
67
Q

what is the composition of water?

A

95% water, 5% solutes

68
Q

How does pH change in urine?

A
  • normally between 4.5 and 8.0
  • more acidic with larger amounts of protein or wheat in diet
  • less acidic with diet high in fruits and vegetables
69
Q

what is the specific gravity of urine?

A
  • density of a substance compared to density of water
70
Q

what are the tunics of the ureters?

A
  • mucosa: transitional epithelium and lamina propria, impermeable to urine
  • muscularis: inner longitudinal layer and outer circular layer of smooth muscle
  • adventitia: external layer of collagen and elastic fibers within areolar CT
71
Q

what is the trigone of the bladder?

A
  • posteroinferior triangular area of bladder wall
  • remains immobile as bladder fills and empties
72
Q

what are the tunic of the bladder?

A
  • muscosa: transitional epithelium with underlying lamina propria and mucosal folds for greater distension
  • submucosa
  • muscularis: 3 layers of smooth muscle
  • adventitia: areolar CT
73
Q

what are the two sphincters of the urethra?

A
  • internal urethral sphincter: involuntary
  • external urethral sphincter: voluntary
74
Q

what is micturition?

A

expulsion of urine from the bladder

75
Q

what two reflexes are associated with micturition?

A

storage reflex and micturition reflex

76
Q

what is the storage reflex?

A
  • continuous sympathetic stimulation which causes relaxation of detrusor to accommodate urine
  • stimulates contraction of internal sphincter which retains urine in bladder
77
Q

what is the micturition reflex?

A
  • volume of urine in bladder 200 to 300 ml
  • visceral sensory neurons signaled by baroreceptors
  • micturition center alters nerve signals down spinal chord
  • parasympathetic stimulation relaxes detrusor muscles and internal sphincter
78
Q

where is conscious control of urination initiated?

A

initiated from cerebral cortex through pundendal nerve

79
Q

what happens after the bladder is emptied?

A
  • detrusor muscles relaxes
  • micturition reflex inactivated
  • storage reflex activated
80
Q

what happens if urination is not activated at time of first reflex?

A
  • micturition reflex activated again after another 200 to 300 mL
  • urination occurs involuntarily between 500 ml and 600 ml
81
Q

what factors is blood composition dependent on three factors

A

dier, cellular metabolism, and urine output

82
Q

what roles do the kidneys play in maintaining blood composition?

A
  • excretion of nitrogen containing wastes
  • maintaining water balance of blood
  • maintaining electrolyte balance of blood
  • ensuring proper blood pH
83
Q

what makes up the majority of body fluid?

A

intracellular fluid (about 2/3)

84
Q

what are osmoreceptors?

A

cells in hypothalamus that react to small changes in solute blood composition by activating thirst center

85
Q

what is diabetes insipidus?

A
  • occurs when ADH is not released
  • leads to huge outputs of dilute urine
86
Q

what happens when blood pH rises?

A

bicarbonate ions are excreted and hydrogen ions are retained by kidney tubules

87
Q

what happens when blood pH falls?

A

bicarbonate ions are reabsorbed and hydrogen ions are secreted

Anatomy (10 decks)

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