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BIOL 2005 > (Lectures 16-17, Chapter 19) Urinary System > Flashcards

(Lectures 16-17, Chapter 19) Urinary System Flashcards

1
Q

Functions of the urinary system (6)

A

1) Detoxification: removal of metabolic and foreign waste
2) Regulation of Plasma Ion Consumption: regulates secretion of ions
3) Regulation of Plasma Osmolarity: adjusts rate of water excretion relative to plasma solutes
4) Regulation of Plasma Volume + Blood Pressure: controls rate of water excreted in urine, which directly affects BV/BP
5) Regulation of Plasma pH: controls [HCO3-] and [H+] in plasma
6) Endocrine Functions: secretion of erythropoietin and renin, activation of vitamin D3

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2
Q

What is the functional unit of the kidney? What is its main purpose?

A

Nephron; gets rid of unwanted substances in the blood plasma as blood passes through the kidneys

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3
Q

What is the outer tissue of the kidney called?

A

Cortex

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4
Q

What is the middle/inner layer of tissue in the kidney called?

A

Medulla

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5
Q

These channels collect urine and direct it out of the kidney.

A

Minor/major calyces

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6
Q

What happens once urine reaches the end of the major calyx?

A
  • Enters renal pelvis

- Travels into the ureter, which leads into the bladder

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7
Q

Where is most plasma filtered in the nephron?

A

Glomerulus

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8
Q

What substance is generated when plasma is filtered in the glomerulus?

A

Filtrate

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9
Q

T/F: all of the material in the filterate ends up being part of the urine

A

False: some substances are reabsorbed into the bloodstream as tubular fluid (i.e. filterate) passes through the renal tubules

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10
Q

Renal Corpuscle

A

Part of the nephron; receives blood supply and generates filterate

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11
Q

The glomerulus is enclosed in the _____ ______

A

Bowman’s capsule

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12
Q

What is the first region to emerge from the renal corpuscle?

A

Proximal convoluted tubule (PCT)

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13
Q

What is the purpose of the loop of Henle/nephron loop?

A

Concentration of filterate

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14
Q

What part of the nephron follows after the loop of Henle?

A

Distal convoluted tubule (DCT)

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15
Q

Multiple DCTs join at the ______ ___, which sends the remaining filterate to the ____ ______, and the filterate enters the minor/major calyces in the kidney.

A

Collecting duct, renal papulla

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16
Q

Where are the most adjustments made to tubular fluid in the nephron?

A

PCT

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17
Q

T/F: once the tubular fluid enters the collecting duct, no more adjustments can be made to it (re: solute/water content)

A

True

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18
Q

Cortical Nephrons

A
  • Account for ~80% of all nephrons
  • located mostly in the cortex
  • Regulate substances: water/nutrient retention, electrolyte balance, drug/waste elimination
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19
Q

Juxtamedullary Nephrons

A
  • Account for ~20% of all nephrons
  • Renal corpuscle is located in the cortex, very long loop of Henle is located in the medulla
  • Same roles as cortical nephrons
  • Long loop of Henle makes them important for water retention
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20
Q

Glomerular Capillaries

A
  • Let fluid + solutes flow out of capillaries and into Bowman’s capsule
  • high pressure
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21
Q

Peritubular Capillaries

A
  • Let fluid + solutes flow from nephron tubes to capillaries (i.e. they join the venous return)
  • low pressure
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22
Q

Vasa Recta

A
  • Capillaries of JM nephrons in the medulla

- Blood flow is v. slow

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23
Q

What blood vessels enter and exit the glomerulus? What is their purpose?

A

Enter - Afferent Arterioles
Exit - Efferent Arterioles
Purpose is to regulate kidney function

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24
Q

Between afferent and efferent arterioles, which ones are larger? What does this size difference/structure create?

A

Afferent arterioles

Structure generates backflow, pressure

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25
Q

A group of crowded-together epithelial cells near the afferent/efferent arterioles form a _____ _____

A

macula densa

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26
Q

What are the smooth muscle cells of the afferent arteriole (located near the macula densa) called?

A

Juxtaglomerular cells

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27
Q

Juxtaglomerular cells + macula densa = ?

A

Juxtaglomerular Apparatus

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28
Q

Renal Functions (3)

A

1) Filtration of blood in the glomerulus; blood pressure forces water/solutes into the capsular space (across membranes of glomerular capillaries)
2) Reabsorption; water/solutes move from tubular fluid to peritubular fluid, across the tubular epithelium
3) Secretion; solutes move from peritubular fluid to tubular fluid

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29
Q

Once filtered, most substances are reabsorbed in the ___

A

PCT

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30
Q

Permeability of the loop of Henle

A

Desc. loop: permeable to/allows reabsorption of water

Asc. loop: permeable to/allows reabsorption of ions

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31
Q

Based on the ____ _____ ____, more adjustments are made to the tubular fluid in the DCT.

A

body’s specific needs

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32
Q

Do kidneys always work at 100% capacity?

A

No; it’s possible to live with only one kidney

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33
Q

Where is the filtration membrane located? How many layers does it have that plasma solutes must pass through? What are they called?

A
  • Located in the renal corpuscle
  • Has 3 layers

1) Glomerular Endothelium (fenestrated layer)
2) Basement Membrane of glomerular capillary
3) Filtration Slits, formed from the extensions of podocytes that cover the glomerular capillaries

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34
Q

Sufficient ____ is needed for glomerular filtration

A

pressure

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35
Q

What creates the main pressure into the glomerulus?

A

Afferent/efferent arterioles (i.e. regulation by arteriole size

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36
Q

What causes hydrostatic backpressure in the glomerulus?

A

Fluid in the renal tubules and Bowman’s capsule, including fluid that has already been filtered

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37
Q

What causes resistance pressure (aka colloid osmotic pressure) in the glomerulus? Is it good to for this to be elevated?

A
  • Caused by proteins in the Bowman’s capsule

- No, it should be 0; there should be no proteins in the filterate in a healthy kidney

38
Q

What causes pulling pressure (aka plasma colloid osmotic pressure) in the glomerulus? What does this pressure do?

A
  • Caused by differences in solute concentration; it’s higher in blood plasma than in filterate
  • pulls water out of filterate and into capillaries/bloodstream
39
Q

The sum of all pressures acting on fluids in the glomerulus is:

A

Net filtration pressure

40
Q

What substances are reabsorbed at the PCT? How is this accomplished?

A

> 99% of the glucose filtered at the glomerulus, amino acids, ions, organic nutrients; moved via transport proteins (active transport)

41
Q

Water is reabsorbed via ______, which can also regulate the permeability of parts of the nephron to water.

A

aquaporins

42
Q

How much of the initial fliterate reaches the DCT?

A

15-20%

43
Q

Examples of reabsorption/secretion at the DCT (3)

A
  • Na+ reabsorbed in exchange for K+
  • H+ secreted in exchange for Na+; makes body fluid less acidic (i.e. increases pH)
  • Secretion of toxins/drugs via carrier proteins
44
Q

The permeability of these parts of the nephron to water can be regulated/changed.

A

DCT, collecting duct

45
Q

What is the measure of the concentration of solutes in a solution (specifically in tubular fluid)?

A

Osmolarity (mOsm/L)

46
Q

What happens if the kidneys don’t filter out enough water?

A

Blood volume + blood pressure increase

47
Q

In which part of the loop of Henle does tubular fluid become more concentrated?

A

Desc. loop, as the reabsorption of water occurs here

48
Q

How does tubular fluid become less concentrated in the asc. loop of Henle?

A

Ions pumps allow for reabsorption of ions

49
Q

T/F: urine is concentrated (i.e. has a lot of solutes)

A

False; it’s dilute, with a typical osmolarity of 65 mOsm/L

50
Q

Anti-Diuretic Hormone (ADH); examples of effects

A

Causes water retention by stimulating aquaporins to allow water to exit the DCT and collecting duct

More ADH = more water reabsorbed
High blood volume = low ADH = less water reabsorbed

51
Q

Urine is concentrated by this process, which allows for the exchange of fluid and solutes:

A

Countercurrent Multiplication - exchange of solutes/water between vasa recta and interstitial fluid of renal medulla

Countercurrent = exchange between fluids moving in opposite directions
Multiplication = effect increases as fluid moves through
52
Q

Effects of Countercurrent Multiplication

A
  • Creates concentration gradient in interstitial fluid of renal medulla
  • Allows for production of highly-concentrated urine (removal of water required)
  • Transport of ions from asc. loop to peritubular fluid drives osmosis of water out of the desc. loop (multiplication effect)
53
Q

How does the vasa recta act as an ‘exchanger?’

A

Exchanges solutes and water between the interstitial fluid in the renal medulla and the blood; it surrounds the nephron loop in the renal medulla

54
Q

What effects do blood volume and blood pressure have on urine concentration?

A

Low BV/BP = more water drawn out from tubular fluid = concentrated urine

High BV/BP = less water drawn out = dilute urine

55
Q

Obligatory Water Reabsorption

A

Presence of aquaporins means that the rate of water reabsorption cannot be regulated; occurs in PCT, desc. loop of Henle

56
Q

Facultative Water Reabsorption

A
  • ADH-dependent, tightly-controlled water reabsorption; ADH must stimulate aquaporins
  • Occurs in DCT, collecting duct
57
Q

How does ADH stimulate aquaporins for facultative water reabsorption?

A
  • Aquaporins are contained in vesicles; their release forms channels
  • ADH controls aquaporin activity; stimulates the movement/integration of aquaporins to the membrane
58
Q

Why is ADH ineffective in stimulating water reabsorption in the asc. loop of Henle?

A

There are no aquaporins

59
Q

Glomerular Filtration Rate

A
  • Amount of filterate formed per minute; measure of kidney function
  • Determined with blood/urine tests
60
Q

High levels of this breakdown product from muscles in the blood indicates a low GFR:

A

Creatinine

61
Q

What could the presence of proteins in urine indicate?

A

Breakdown of filtration membranes, because proteins shouldn’t be in there!

62
Q

What are some possible effects of a low GFR? (2)

A
  • Low tubular fluid flow in nephron

- Reabsorption of unneeded materials

63
Q

GFR regulation moderates these two things:

A
  • Blood flow into the kidney

- Size of capillaries in the glomerulus (dilated capillaries = more surface area to filter things)

64
Q

The juxtaglomerular apparatus has specialized cells. What are some of their functions? What does this allow for?

A
  • sense Na+/NaCl levels
  • release renin (hormone)
  • contract
  • allows for autoregulation of GFR
65
Q

Why are the macula densa important for glomerular filtration?

A

They contain chemoreceptors that sense the NaCl content of the filterate

66
Q

Granular/Juxtaglomerular Cells

A
  • Enlarged smooth muscle cells in arteriole
  • Act as mechanoreceptors; they sense BP in the afferent arteriole
  • Contain secretory granules that contain renin
67
Q

Mesangial Cells

A
  • Pass signals between macula densa and granular cells
  • Found between arteriole and tubular cells
  • Interconnected by gap junctions
  • Ensures unification of entire JGA in regulating GFR
68
Q

Autoregulation of GFR

A
  • Stimulus disrupts homeostasis, which decreases blood flow to the kidneys, which then decreases filtration pressure and results in decreased filtrate/urine production
  • Contraction of mesangial cells + dilation of aff. arteriole + constriction of eff. arteriole = increased glomerular BP + restoration of homeostasis
69
Q

Central Regulation of GFR - Endocrine Response

A
  • Release of renin into the bloodstream increases systemic BP by working w/enzymes (e.g. increase in glomerular BP)
  • Can cause hypertension, which would lead to overfiltration
70
Q

What is aldosterone? What effects does it have?

A
  • Release in central GFR regulation increases Na+ retention, which causes increased BP/BV and glomerular BP
71
Q

Central Regulation of GFR - Neural Response

A

Activation of nervous effectors leads to increased BP/BV and increased glomerular BP

  • Stimulation of thirst = more fluid consumption
  • ADH production = fluid retention
  • Sympathetic motor tone = constriction of systemic veins, increased cardiac output
72
Q

T/F: urine must contain exact amounts of different substances

A

False; each component of normal urine falls within a range (e.g. pH, solute/water content, volume, osmolarity)

73
Q

What are some abnormal (i.e. shouldn’t be there) components of urine?

A
  • Proteins (e.g. albumin)
  • Glucose
  • Ketones
  • Red blood cells
  • Pus
74
Q

What is renal failure?

A

Occurs when kidneys are no longer able to maintain homeostasis

75
Q

What are some ways in which renal failure can affect the body (excluding the urinary system)?

A
  • Toxin buildup due to reduced urine production (i.e. can’t get rid of waste)
  • Ionic/fluid imbalances
  • Increased BV/BP = issues with cardiovascular system
  • Issues with CNS
76
Q

How does chronic renal failure differ from acute renal failure?

A 
Chronic = gradual deterioration of kidney function
Acute = sudden deterioration of kidney function
77
Q

Can chronic renal failure be reversed?

A

No; issues will accumulate over time, but the deterioration can be slowed down

78
Q

How is chronic renal failure managed? How is this effective?

A
  • Reduced water/salt/protein intake

- Less work for kidney, reduced chance of protein in urine due to faulty filtration membrane

79
Q

Acidosis can occur due to chronic renal failure. What does this mean? What effects does this have? (Hint: doesn’t have to do w/urinary system!)

A
  • Reduced blood pH (i.e. acidic blood)

- Linked to elevated respiratory function - faster breathing rate taxes respiratory muscles

80
Q

Chronic renal failure is precipitated by….

A

Elevated (too much filterate) or decreased (not enough filterate) BP in the kidneys

81
Q

What are some possible causes of acute renal failure?

A
  • Exposure to toxic drugs
  • Renal ischemia (inadequate blood supply)
  • Urinary obstruction
  • Trauma
  • Allergic response to antibiotics or anaesthetics
82
Q

T/F: at least some function can be recovered in cases of acute renal failure

A

True, if patients survive the initial incident that caused the renal failure. With proper treatment, the survival rate is ~50%

83
Q

The first approach to treating renal failure is usually medication. What would be the goal of doing this?

A

Treating BP, water/Na+ retention

84
Q

What is the basic premise of dialysis?

A

Passive diffusion across a selective-permeable membrane

85
Q

What is hemodialysis?

A
  • Regulation of blood composition using a machine and an artificial membrane that “replaces” the membrane around the glomerulus
  • Pores in the artificial membrane allow for the diffusion of ions, nutrients, and organic waste out of the blood (i.e. takes over the kidney’s filtration function
86
Q

T/F: for hemodialysis, the composition of the dialysis fluid is the same for every patient

A

False; solute concentrations are tailored for each patient

87
Q

T/F: hemodialysis is an invasive process that must be done often

A

True; involves direct exchange of blood (drawn out of patient and into machine), usually done 3x per week, in 2-4hr sessions

88
Q

How does peritoneal dialysis work?

A
  • Peritoneal lining of lower abdomen is used as a membrane, and dialysis fluid enters the belly via a catheter
  • Solution sits for several hours and exchange w/blood occurs across peritoneal membrane; solution is then drained out
89
Q

How often does peritoneal dialysis occur for a patient? Is it an invasive procedure?

A

Occurs several times a day, or overnight

Noninvasive procedure

90
Q

What is the time where dialysis solution sits in the abdomen called?

A

Dwell time

BIOL 2005 (8 decks)

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