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Human physiology > Chapter 19: The Kidneys > Flashcards

Chapter 19: The Kidneys Flashcards

1
Q

what are the functions of the urinary system?

A
  • Regulate plasma ionic composition
  • Regulate plasma volume
  • Regulate plasma osmolarity
  • Regulate plasma pH
  • Remove metabolic waste products and foreign substances from plasma (creatinine, uric acid, urobilinogen, xenobiotics)
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2
Q

what are other functions of the urinary system?

A
  • Secrete erythropoietin and renin
  • Activate vitamin D3 to calcitriol
  • Gluconeogenesis
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3
Q

-form urine
-located retroperitoneally
at the level of the lower ribs.

A

kidneys

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4
Q

transport urine from kidneys to bladder

A

ureters

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5
Q

store urine

A

bladder

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6
Q

excrete urine from bladder to outside of body

A

urethra

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7
Q

functional unit of kidney

A

nephron

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8
Q

consists of glomerulus and Bowman’s capsule

A

renal corpuscle

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9
Q

capillary network for filtration

A

glomerulus

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10
Q
  • Receives the filtrate

- Inflow to renal tubules

A

Bowman’s capsule

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11
Q

what are the parts of renal tubules?

A
  • proximal tuble
  • loop of Henle
  • distal convoluted tubule
  • collecting duct
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12
Q

consists of descending limb, thin ascending limb, and thick ascending limb

A

Loop of Henle

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13
Q

divided into an outer cortex and an inner medulla

A

the kidney in cross section

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14
Q

flows into the renal pelvis prior to passing through the ureter into the bladder

A

urine leaving the nephrons

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15
Q
  • enter the kidney at the hilus
  • receive 20% of cardiac output at rest
  • function is to filter blood
  • account for 16% of ATP usage by the body
  • take blood to the cortex
A

renal arteries

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16
Q

exit at the hilus

A

renal veins

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17
Q
  • short loop of henle
  • most numerous, 80-85%
  • produce urine
A

cortical nephrons

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18
Q
  • long loop of henle extends into medulla
  • responsible for the medullary osmotic gradient
  • produce urine
A

juxtamedullary nephron

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19
Q

contains all bowmans capsules, proximal and distal tububles

A

cortex

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20
Q

contains loops of henle and collecting ducts

A

medulla

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21
Q

has two arterioles and two sets of

capillaries that form a portal system

A

one nephron

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22
Q

from glomerulus to Bowman’s capsule

A

glomerular filtration

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23
Q

from tubules to peritubular capillaries

A

reabsorption

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24
Q

from peritubular capillaries to tubules

A

secretion

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25
Q

from tubules out of the body

A

excretion

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26
Q

-must cross three barriers to enter Bowman’s capsule

A

glomerular filtrate

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27
Q

Movement of protein-free plasma from glomerulus to Bowman’s capsule

A

GFR = 125 mL/min or 180 L/day

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28
Q

what are the 3 barriers glomerular filtrate must cross to enter bowman’s capsule?

A
  • Capillary endothelial layer
  • Surrounding epithelial layer
  • Basement membrane sandwiched between these two layers
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29
Q

what are the filtration fractions?

A 
1. Plasma volume
entering afferent
arteriole = 100%.
2. 20% of volume filters
3. >19% of fluid is reabsorbed 
4. >99% of plasma 
entering kidney
returns to systemic 
circulation.
5. <1% of
volume is
excreted to
external
environment
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30
Q

what are the forces favoring filtration?

A
  • Glomerular capillary hydrostatic pressure

- Bowman’s capsule colloid osmotic pressure

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31
Q
  • 55 mm Hg

- High due to resistance of efferent arteriole

A

Glomerular capillary hydrostatic pressure

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32
Q
  • 0 mm Hg

- Low due to lack of protein in filtrate

A

Bowman’s capsule colloid osmotic pressure

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33
Q

what are the forces opposing glomerular filtration?

A
  • Bowman’s capsule hydrostatic pressure

- Glomerular colloid osmotic pressure

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34
Q
  • 15 mm Hg

- Relatively high due to large volume of filtrate in closed space

A

Bowman’s capsule hydrostatic pressure

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35
Q
  • 30 mm Hg

- Higher than in systemic capillaries due to plasma proteins in smaller volume of plasma

A

Glomerular colloid osmotic pressure

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36
Q

= (PGC + πBC) – (PBC + πGC)

= (55 + 0) – (15 + 30) = 10 mm Hg

A

filtration pressure

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37
Q

what is the amount of renal plasma flow?

A

625 mL/min

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38
Q

what is the filtration pressure and rate in systemic capillaries?

A
  • Filtration pressure = 2 mm Hg

- Filtration rate = 3 L/day

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39
Q

is the glomerular filtration rate constant?

A

relatively constant

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40
Q

what are the two factors that influence glomerular filtration rate (GFR)?

A
  • net filtration pressure

- filtration coefficient

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41
Q

what is involved in net filtration pressure?

A

Hydrostatic pressure – colloid osmotic pressure – fluid pressure

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42
Q

what is involved in the filtration coefficient?

A
  • Surface area of glomerular capillaries available for filtration
  • Permeability of interface between the capillary and Bowman’s capsule
43
Q

the epithelium around glomerular capillaries is modified into…..

A

podocytes

44
Q

-surround each capillary, leaving slits through which filtration takes place

A

podocyte foot processes

45
Q
  • between the capillaries

- contract to alter blood flow

A

mesangial cells

46
Q

-create a 3-layer filtration barrier

A
  • glomerular capillary endothelium
  • basal lamina
  • Bowman’s capsule
47
Q

pass through endothelial pores and filtration slits

A

filtered substances

48
Q

what is involved in the intrinsic regulation of the glomerular filtration rate?

A
  • myogenic reguation

- Tubuloglomerular feedback

49
Q
  • Smooth muscle in wall of afferent arteriole

- Contracts in response to stretch

A

myogenic regulation

50
Q
  • macula densa cells

- smooth muscles of arterioles contract in response to paracrines

A

Tubuloglomerular feedback

51
Q

-secrete paracrine factors in response to an increase in flow of fluid past them
-sense distal tubule flow
and release paracrines that affect afferent
arteriole diameter.

A

Macula densa cells

52
Q
  • takes place over a wide range of blood pressures

- maintains a nearly constant GFR when mean arterial blood pressure is between 80 and 180 mmHG

A

autoregulation of glomerular filtration rate

53
Q

loops back on itself so that the ascending limb of the loop of Henle passes
between the afferent and efferent arterioles

A

nephron

54
Q

secrete renin, an enzyme

involved in salt and water balance.

A

granular cells

55
Q

how does the tubuloglomerular feedback help GFR autoregulation?

A
  1. GFR increases
  2. flow through tubule increases
  3. flow past macula densa increases
  4. Paracrine from macula densa to afferent arteriole
  5. afferent arteriole constricts —-> resistance in afferent arteriole increases—-> hydrostatic pressure in glomerulus decreases—-> GFR decreases
56
Q

how do hormones and autonomic neurons help with GFR regulation?

A
  • By changing resistance in arterioles

- by altering the filtration coefficient

57
Q

how is the resistance in arterioles altered?

A
  • sympathetic neurons
  • angiotensin II
  • prostaglandins
58
Q
  • constrict afferent and efferent arteries

- decrease GFR

A

sympathetic neurons

59
Q

vasoconstrictor

A

angiotensin II

60
Q

vasodilators

A

prostaglandins

61
Q

how is the filtration coefficient altered?

A
  • podocytes filtration slits

- contraction of mesangial cells

62
Q

Extrinsic control of GFR and renal vascular resistance during fluid loss due to…..

A

hemorrhage or sweating

63
Q
  • Movement from tubules into peritubular capillaries (returned to blood)
  • occurs most in proximal tubules
  • not regulated for the most part
A

reabsorption

64
Q
A

Transepithelial transport (transcellular transport)

65
Q
  • Substances pass through the cell–cell junction between two adjacent cells
  • other solutes move through junctions between epithelial cells
A

paracellular pathway

66
Q

how does tubular reabsorption of solutes work?

A
  1. Na+ is reabsorbed by active transport
  2. Electrochemical gradient drives anion
    reabsorption.
  3. Water moves by osmosis, following solute reabsorption. Concentrations of
    other solutes increase as fluid volume
    in lumen decreases.
  4. Permeable solutes are reabsorbed by
    diffusion through membrane transporters
    or by the paracellular pathway.
67
Q

what is involved in re-absorption?

A
  • active transport of sodium
  • secondary active transport: symport with sodium
  • passive reabsorption of urea
  • plasma proteins and receptor mediated endocytosis
68
Q

what are the steps of sodium reabsorption in the proximal tubule: active transport?

A 
1. Na+ enters cell through various 
membrane proteins, moving 
down its electrochemical 
gradient.
2. Na+ is pumped out the 
basolateral side of cell by the Na+-K+-ATPase
69
Q

Rate of transport when carriers are saturated

A

transport maximum

70
Q

when can saturation of carriers occur?

A

When solute is transported across epithelium by carrier proteins

71
Q

Solute in plasma that causes solute in filtrate to saturate carriers and spill over into urine

A

renal threshold

72
Q

what happens if filtrate saturates carriers?

A

some solute is excreted in urine

73
Q
  • freely filtered at glomerulus

- normally 100% actively reabsorbed in proximal tubules

A

glucose reabsorption

74
Q

should glucose appear in the urine?

A

no

75
Q

what are the carrier proteins for glucose reabsorption?

A
  • Apical membrane: secondary active transport

- Basolateral membrane: facilitated diffusion

76
Q

what are the steps of sodium linked reabsorption: indirect (secondary) active transport?

A 
1. Na+ moving down its electro-
chemical gradient uses the 
SGLT protein to pull glucose 
into the cell against its 
concentration gradient. 
2. Glucose diffuses out the 
basolateral side of the cell 
using the GLUT protein.
3. Na+ is pumped out by 
Na+-K+-ATPase.
77
Q

shows the relationship between filtration, reabsorption, and excretion of glucose

A

composite graph

78
Q

in secretion, in what direction does solute move?

A

from peritubular capillaries into tubules

79
Q

what are some secretion substances?

A
  • Potassium
  • Hydrogen ions
  • Choline
  • Creatinine
  • Penicillin
80
Q

takes place in proximal tubules

A

nonregulated reabsorption

81
Q

in the distal tubules and collecting ducts

A

Regulated reabsorption and secretion

82
Q

where does water conservation take place?

A

loop of henle

83
Q
  • the mass reabsorber
  • 70% sodium and water
  • 100% glucose
A

proximal tubule

84
Q

what are the features of the proximal tubule that allows it to be the mass reabsorber?

A
  • Brush border provides for large surface area
  • Large numbers of mitochondria
  • Leaky tight junctions allow paracellular transport
85
Q

how is transport regulated across the epithelium in the distal tubules and collecting ducts?

A
  • Tight junctions limit paracellular transport

- Receptors for hormone that regulate the transport of water and several solutes

86
Q
  • establishes conditions necessary to concentrate urine

- Minimizes water loss

A

Loop of Henle

87
Q

Amount of substance excreted =

A

amount filtered + amount secreted – amount reabsorbed

88
Q

what are the 3 factors that the amount of substance secreted depends on?

A
  • Filtered load (GFR x plasma concentration of x)
  • Secretion rate
  • Reabsorption rate
89
Q
  • Volume of plasma from which a substance has been removed by kidneys per unit time
  • Noninvasive way to measure GFR

=excretion rate/plasma concentration

A

clearance

90
Q

used to measure the GFR

A

inulin and creatinine

91
Q

Amount of inulin excreted in urine =

A

amount that was filtered = filtered load

92
Q

clearance of inulin=

A

excretion rate/ plasma concentration = GFR

93
Q

excretion rate of inulin=

A

filtered load (filtration rate)= GFR x Pi

94
Q

what is inulin clearance equal to?

A

GFR

95
Q

what happens if filtration and excretion of inulin are the same?

A

then there is no net reabsorption or secretion, and the clearance of a substance equals the GFR

96
Q

what is used for clearance calculations?

A

Urine excretion rates and plasma concentrations for solutes

97
Q

how do you determine the fate of solute in renal tubules?

A
  • **If you know either inulin or creatinine clearance you can determine the renal handling of any compound
    • If Cx > GFR, then substance was secreted
    • If Cx < GFR, then substance was reabsorbed
98
Q
  • the process of urination

- urine does not change composition

A

micturition

99
Q

what is the path of urine?

A

ureter—-> bladder —–> urethra

100
Q

send signal to the spinal cord

A

Stretch receptors in bladder walls

101
Q

override basic reflexes under parasympathetic control (during micturition)

A

Centers in the brain stem and cerebral cortex

102
Q

found between the bladder and urethra

A

Internal sphincter (smooth muscle), external sphincter (skeletal muscle)

103
Q

what are the steps of micturition?

A
  1. stretch receptors fire
  2. parasympathetic neurons fire; motor neurons stop firing
  3. smooth muscle contracts; internal sphincter is passively pulled open; external sphincter relaxes

Human physiology (17 decks)

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