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AN SCI 373 > Week 9 an phys > Flashcards

Week 9 an phys Flashcards

1
Q

Percentage of body weight is total body fluid

A

60%

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2
Q

Percentage of body weight is intracellular fluid

A

40%

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3
Q

Percentage of body weight is extracellular fluid

A

20%

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4
Q

Percent of body weight is plasma

A

4%

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5
Q

Percent of body weight is interstitial fluid

A

16%

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6
Q

Hypertonic

A
  • Water moves out of blood cell
  • 1000 mOsm, seawater
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7
Q

Isotonic

A
  • Conditions are normal
  • 300 mOsm, 0.9% NaCl
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8
Q

Hypotonic

A
  • Water moves into cell
  • 100 mOsm
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9
Q

Calculation of Osmolarity

A
  • mM multiplied by number of particles
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10
Q

Intracellular percent of body water

A

67%

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11
Q

Interstitial percent of body water

A

27%

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12
Q

Circulating plasma percent of body water

A

6%

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13
Q

How many times do the nephrons filter the plasma per day

A

60x

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14
Q

Water filtered per day/excreted per day/% reabsorbed

A

180 L/day filtered per day
1.8 L/day excreted per day
99% reabsorped

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15
Q

Intake of water per day

A
  • Drink
  • In food
  • Metabolically produced
  • Total: 2550 mL/d
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16
Q

Output of water per day

A
  • Sweat
  • Feces
  • Urine
  • Total: 2550 mL/d
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17
Q

Key regulator of water output

A

Urine

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18
Q

If water intake doubles

A
  • Water excreted per day doubles (3.6 L/day) and only 98% is reabsorbed
  • Osmolarity decreases
  • Detected by chemoreceptors in hypothalamus
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19
Q

Sodium filtered per day/excreted per day/% reabsorbed

A
  • 630 g/day filtered
  • 3.2 g/day excreted
  • 99.5% reabsorbed
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20
Q

If sodium intake is increased

A
  • Osmolarity increases
  • Detected in Kidney
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21
Q

Glucose filtered per day/excreted per day/% reabsorbed

A
  • 162 g/day filtered
  • 0 g/day excreted
  • 100% reabsorbed
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22
Q

If glucose intake is increased

A
  • Blood glucose increases
  • Detected by Beta Cells of pancreas- insulin
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23
Q

Percent of blood flow going to kidney

A

22%

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24
Q

Osmolarity of Renal Cortex

A

300 mOsm

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25
Q

Osmolarity of Renal medulla

A

1200 mOsm

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26
Q

Regions of the kidney

A
  • Renal cortex (outer)
  • Renal medulla (inner): medulla is divided into renal pyramids in larger mammals
  • Renal pelvis: drainage area in center of kidney
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27
Q

Nephron

A
  • smallest functional unit of the kidney
  • 1 million nephrons in human kidney
  • Consists of a tubule and associated vascular component
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28
Q

Juxtamedullary nephron

A

long looped nephron important in establishing the medullary vertical osmotic gradient

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29
Q

Juxtamedullary nephron components

A
  1. Bowmans capsule
  2. Glomerulus
  3. Proximal convoluted tubule
  4. Thin descending limb
  5. Thin ascending limb
  6. Thick ascending limb
  7. Distal convoluted tubule
  8. Collecting duct
  9. afferent and efferent arteriole
  10. Peritubular capillaries
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30
Q

Loop of Henle

A

Descending and ascending limbs used to establish a concentration gradient

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31
Q

Cortical vs juxtamedullary nephrons

A

Cortical nephrons:
- Glomeruli in outer cortex
- Short loops of Henle dip only into outer medulla
Juxtaglomerular nephrons:
- Glomeruli in inner cortex near medulla
- Long loops of henli plunge into inner medulla
- Peritubular capillaries from hairpin vascular loops

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32
Q

Four basic renal processes

A
  1. Filtration
  2. Secretion
  3. Reabsorption
  4. Osmoconcentration
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33
Q

Function of Glomerulus-Bowmans Capsule

A

Filtration of blood

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34
Q

Function of proximal tubule

A

Reabsorption

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35
Q

Function of loop of henle

A

Establishment of osmotic gradient

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36
Q

Function of distal tubule

A

Regulated reabsorption and secretion

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37
Q

Function of collecting ducts

A

Regulated removal of water

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38
Q

Bladder

A

Excretion of waste

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39
Q

How many liters of plasma enter kidney per day

A

900 L

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40
Q

Liters of plasma filtered into bowmans capsule per day

A

180 L

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41
Q

Molecular sieve layers

A
  • Glomerular capillary wall
  • Basement membrane
  • Inner layer of Bowman’s capsule
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42
Q

Glomerular capillary wall

A

-Single layer of flattened endothelial cells
- Perforated with pores
- Pores are too small for proteins to pass

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43
Q

Basement membrane

A
  • Gelatinous layer composed of collagen and glycoproteins
  • Glycoproteins further limit protein movement
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44
Q

Inner layer of Bowman’s capsule

A

consists of podocytes with filtration slits

45
Q

Is filtration in nephron intercellular or extracellular

A

Extracellular

46
Q

Driving forces of glomerular filtration

A
  • Glomerular capillary blood pressure (higher than capillary blood pressure elsewhere) (55 mmHg)
  • Plasma colloid osmotic pressure (30 mmHg)
  • Bowman’s capsule hydrostatic pressure (15 mmHg)
47
Q

Net filtration pressure

A

55 - ( 30 + 15) = 10 mmHg

48
Q

Glomerular filtration rate (GFR)

A
  • Depends on net filtration pressure, surface area and permeability of glomerular membrane
  • Filtration coefficient x net filtration pressure
  • 20% of plasma that enters the glomerulus is filtered
  • GFR is an adult human is 115-125 mL/min or ~180 L/day
49
Q

Glomerular Capillary Blood Pressure

A

Favors filtration - 55 mmHg

50
Q

Plasma-Colloid Osmotic Pressure

A

Opposes filtration - 30 mmHg

51
Q

Bowman’s Capsule Hydrostatic Pressure

A

Opposes filtration- 15 mmHg

52
Q

Net Glomerular filtration pressure

A

Favors filtration - 10 mmHg

53
Q

Contents of Plasma

A
  • Water and salts (300 mOsm)
  • Nutrients (Glucose and amino acids)
  • Small proteins and large proteins
  • Blood cells
54
Q

Contents of Glomerular Filtrate

A
  • Water and salts (300 mOsm)
  • Nutrients (Glucose and amino acids)
  • Some small proteins
55
Q

Blood pressure in Glomerulus

A

55 mmHg

56
Q

Osmotic pressure in plasma due to proteins

A

30 mm Hg

57
Q

Hydrostatic pressure in Glomerular Filtrate

A

15 mmHg

58
Q

Osmotic pressure due to proteins in Glomerular Filtrate

A

0 mmHg

59
Q

Production of filtrate at the glomerulus occurs primarily by what

A

Bulk flow

60
Q

Molecule exchange by location in nephron

A
  • Proximal tubule: Mostly reabsorption of HCO3, NaCl, H2O, Nutrients, K+
  • Descending loop: Reabsorption of H2O
  • Ascending loop: Reabsorption of NaCl
  • Distal Tubule: Reabsorption of NaCl and H2O
61
Q

Percent of salt, water and glucose reabsorbed by mammalian tubules

A
  • 99% salt and water
  • 100% glucose and amino acids
62
Q

Where does most reabsorption occur

A

Proximal tubule

63
Q

Is reabsorption passive or active

A

Can be either

64
Q

What two things must a substance pass through to be reabsorbed

A

Renal tubular epithelial cell and capillary wall

65
Q

Path of reabsorption

A
  1. Luminal membrane of tubular epithelial cell
  2. Cytosol of tubular epithelial cell
  3. Basolateral membrane of epithelial cell
  4. Interstitial fluid
  5. Capillary wall
66
Q

Where does regulation of water occur mostly

A

Collecting duct due to actions of ADH (Anti-diuretic hormone)

67
Q

Is reabsorption of water passive or active

A
  • Passive
  • H2O passively follows osmotic gradient across both membranes
68
Q

Thick Ascending limp of loop of Henle and Water

A

Thick Ascending limp of loop of Henle is impermeable to water

69
Q

How is reabsorption of water from collecting duct regulated

A

Subject to hormonal control

70
Q

Aquaporins (AQPs)

A
  • AQP-1 channels in proximal tubule are always open (common)
  • AQP-2 channels in collecting duct are regulated by ADH (vasopressin) (unique to cells of collecting duct and are hormonally regulated)
71
Q

Where are AQP-1 channels found

A

Luminal membrane of tubular epithelial cell and basolateral membrane of tubular epithelial cell in proximal tubule

72
Q

Purpose of Aquaporins

A

Allows water to cross membranes using osmosis

73
Q

How much of the kidney’s total energy requirement is used for Na+ transport

A

80%

74
Q

Is Na+ reabsorption active or passive

A
  • Active in most sections of the tubule but passive in some (basolateral vs luminal membrane)
  • Active steps involve Na+/K+ ATPase pump in basolateral membrane
  • Transport of Na+ across luminal membrane is passive (Na+/glucose cotransporter is located in luminal membrane)
75
Q

Where is Na+ reabsorbed

A
  • Proximal tubule (67%)
  • Loop of Henle in Ascending limb (25%) (Na+ is not reabsorbed from the descending limb)
  • Distal tubule (8%)
76
Q

Reabsorption of glucose and amino acids

A
  • 100% reabsorbed, reflecting their nutritional value
  • Secondary active transport
  • Symporter in apical membrane transports Na+ down its concentration gradient and a specific organic molecule up its gradient from the lumen into the tubular cell
  • Basolateral Na+/K+ pump indirectly drives this cotransport system
  • Once inside the cell, the organic molecule is transported into ECF by facilitated diffusion
77
Q

Renal threshold

A
  • Max Plasma concentration of glucose in which the about of glucose reabsorbed is able to match the amount that is filtered
  • After renal threshold is reached, the amount of glucose excreted starts to increase from 0
  • The amount reabsorbed falls below what is being filtered and slowly increases until it reaches the tubular maximum
78
Q

Tubular maximum (Tm)

A
  • Max amount of glucose that can be reabsorbed
  • Once this maximum has been reached, the amount reabsorbed remains constant and the excretion rate skyrockets
79
Q

What causes Tubular maximum

A
  • Plasma membrane carriers exhibit saturation
80
Q

Glucose reabsorption in diabetes mellitus

A
  • Plasma glucose is high in diabetes mellitus (hyperglycemia)
  • Glucose is filtered into Bowman’s capsule at the same concentration as in plasma
  • When filtered glucose exceeds Tm for glucose reabsorption, the excess spills over into urine (first occurs at renal threshold)
  • Glucose in urine is diagnostic of diabetes mellitus
81
Q

Where does passive transport of Na+ occur

A

Thin Ascending limb

82
Q

Where does active transport of Na+ occur

A
  • Thick Ascending limb
  • Collecting duct
83
Q

Osmolarity of Proximal Tubule

A

300 mOsm

84
Q

Osmolarity of Descending and Ascending Loop of Henle

A

600 mOsm

85
Q

Osmolarity of bottom of loop of Henle

A

1200 mOsm

86
Q

Osmolarity of Thick Ascending Loop of Henle

A

200 mOsm

87
Q

Osmolarity of Distal Tubule

A

100 mOsm

88
Q

Where is Urea reabsorbed

A

Collecting duct towards the bottom

89
Q

Why can urine be more concentrated than plasma

A
  • The inner medulla of the kidney has a very high osmolarity due to:
  • Active NaCl in thick ascending limb of loop of henle
  • Thick ascending limb being relatively impermeable to water
    so NaCl is left behind in the medulla
  • Urine can have variable osmolarity due to selective permeability of collecting duct to water (ADH)
90
Q

Antidiuretic Hormone (ADH) Vasopressin

A
  • Increases osmolarity of urine and decreases urine volume
  • Is secreted when there is an increase in blood osmolarity
  • Increases water channels in collecting duct
  • Water will be removed from collecting duct resulting in concentrated urine
91
Q

What triggers release of ADH

A
  • Osmoreceptors in hypothalamus trigger release of ADH from the hypothalamus when blood osmolarity is high and also increases thirst
92
Q

Feedback loop of ADH

A
  • Hypothalamus triggers release of ADH and thirst
  • Drinking reduces blood osmolarity and ADH increases collecting duct permeability resulting in H2O reabsorption which helps prevent further osmolarity increase
  • Decrease of blood osmolarity results in decrease of ADH and thirst
93
Q

Collecting duct when no ADH is present

A

Collecting duct is not permeable to water

94
Q

Collecting duct when ADH is present

A

Collecting duct is highly permeable to water

95
Q

AQP-2

A
  • Water channel regulated by ADH
  • Premade and packaged in vesicles
  • ADH stimulates exocytosis and AQP-2 insertion in Luminal membrane
96
Q

AQP-3 and AQP-4

A

in Basolateral membrane

97
Q

Process of how ADH works

A
  • ADH from blood binds to ADH receptor located in basolateral membrane of tubular epithelial cell
  • ATP is used and cAMP is created in cytosol
  • cAMP increases permeability of luminal membrane to H2O by inserting new AQP-2 water channels
98
Q

Decrease in Arterial Blood pressure will do what to Urine

A
  • A decrease in glomerular capillary blood pressure (due to general arteriolar vasoconstriction) will lead to decreased urine volume and and increase in conservation of fluid and salt
  • This is a long-term adjustment to increase arterial blood pressure
99
Q

Pathway of Angiotensinogen

A
  • Liver releases angiotensinogen
  • Kidney releases renin
  • Renin converts angiotensinogen to angiotensin I
  • Lungs release Angiotensin converting enzyme
  • Angiotensin converting enzyme converts angiotensin I into angiotensin II
100
Q

Role of Angiotensin II

A
  • Increases vasopressin (which increases H2O reabsorption by kidney tubules)
  • Increases thirst (which increases fluid intake)
  • Causes arteriolar vasoconstriction
  • These three things help correct low arterial blood pressure and low ECF volume
101
Q

Aldosterone

A
  • Secreted by adrenal cortex
  • Acts on kidney to increase Na+ reabsorption by kidney tubules which increases the amount of H2O conserved when blood volume is low
  • Decreases K+ concentrations when K+ is high**
  • Acts in distal tubule and early collecting duct
  • Helps correct low NaCl and low arterial blood pressure
102
Q

Two Clinical Examples of Excessive Urine Flow

A

-Diabetes Insipidus (rare)
- Diabetes Mellitus

103
Q

Diabetes insipidus

A
  • High urine flow rate - not sweet
  • Lack/Deficiency of ADH
104
Q

Diabetes Mellitus

A
  • High glucose in blood
  • Sweet urine - high urine flow rates
  • High filtered glucose is not all reabsorbed in PT
  • Glucose reaches collecting ducts and provides osmolarity to reduce H2O reabsorption
105
Q

Weak osmoconcentrators

A
  • Water dwelling mammals
  • Have primarily cortical nephrons
  • Don’t need to reabsorb as much water since their environment has abundant water
106
Q

Strong osmoconcentrators

A

-Desert-dwelling mammals
- Juxtamedullary nephrons with long loops of Henle
- Elongated medulla has an exaggerated vertical osmotic gradient
- Countercurrent multiplier is more active in small mammals with higher metabolic rates

107
Q

Regulated variable of ECF volume

A
  • Long term control of arterial pressure
  • Regulated via maintenance of salt balance by aldosterone and Na+ excretion
108
Q

Regulated variable of EDF osmolarity

A
  • Prevent detrimental osmotic movement of water from ECF into or out of cells
  • Regulated by maintenance of free H2O balance by ADH

AN SCI 373 (9 decks)

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