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SK299 > Kidneys & Homeostasis > Flashcards

Kidneys & Homeostasis Flashcards

1
Q

Roughly how much of our body’s weight is water?

A

60%

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2
Q

What are the constituents of the fluid component of our blood (plasma)?

A
  • Ions

* Proteins

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3
Q

On average, what is the pH of human blood?

A

7.35-7.45

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4
Q

Is a solution more acidic or more alkali if it has an excess of OH- (hydroxide) ions?

A

Acidic

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5
Q

What are the organs which comprise the urinary system?

A
  • Kidneys
  • Ureters
  • Bladder
  • Urethra
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6
Q

How much urine does an average healthy adult produce per day?

A

Between 600 and 2300ml

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7
Q

What are the three regions of a kidney?

A
  • The renal capsule
  • The renal cortex
  • The renal medulla
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8
Q

How much of the cardiac output do the kidneys receive?

A

Around a litre a minute / 20%

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9
Q

What is the renal corpuscle?

A

The structure in a nephron which filters the blood

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10
Q

What is the renal tubule?

A

The structure which processes the filtered urine

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11
Q

What are the 4 main regions of the renal tubule?

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

What is the name for the network of tubules which surrounds the renal tubule?

A

The peritubular capillaries

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13
Q

What are the three main functions of nephrons?

A
  • Filtration
  • Reabsorption
  • Secretion
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14
Q

What is the renal capsule?

A

The thin outer membrane

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15
Q

Roughly how many nephrons does each kidney have?

A

One million

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16
Q

What is the name of the network of blood vessels which surround the renal tubule?

A

Peritubular capillaries

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17
Q

What are the main components of the nephron?

A
  • The renal corpuscle (glomerulus and Bowman’s capsule)
  • Proximal convoluted tubule
  • Loop of Henle
  • Distal convoluted tubule
  • Collecting duct
  • Peritubular capillaries
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18
Q

What does “afferent” mean?

A

“Carrying blood to”

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19
Q

What does “efferent” mean?

A

Carrying blood away from

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20
Q

In which part of the kidney does filtration occur?

A

The glomerulus

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21
Q

What is the ‘formula’ for urinary excretion?

A

Excretion =

filtration - reabsorption + secretion

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22
Q

What is the renal corpuscle and what does it do?

A
  • The part of the nephron that consists of the glomerulus and surrounding Bowman’s capsule
  • It is where filtration occurs
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23
Q

What are the main features of epithelial cells?

A
  • They line the surface of skin, glands and cavities of the body
  • Epithelium can be formed be one or many layers of epithelial cells
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24
Q

What is the endothelium composed of?

A

One layer of cells

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25
Q

What is the most abundant protein in the blood?

A

Albumin

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26
Q

What are the two main structures which comprise the renal corpuscle?

A
  • Glomerular capillaries

* Bowman’s capsule

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27
Q

Where is glomerular filtrate formed?

A

The Bowman’s capsule

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28
Q

Where does the unfiltered blood from the glomerular capillaries flow to?

A

The efferent arteriole

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29
Q

What often causes renal dysfunction?

A

Inappropriate or insufficient filtration

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30
Q

What is the average capillary pressure in the nephron?

A

55 mmHg

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31
Q

What is the hydrostatic pressure in the Bowman’s space?

A

Approximately 15 mmHg

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32
Q

What is the oncotic pressure?

A

Approximately 30 mmHg

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33
Q

What is the effect of hyper albuminaemia?

A

Capillary oncotic pressure increases, which reduces glomerular filtration rates

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34
Q

Does glomerular blood pressure accelerate or oppose filtration?

A

Accelerate

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35
Q

Does hydrostatic pressure in the Bowman’s capsule accelerate or oppose filtration?

A

Oppose

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36
Q

Does oncotic pressure accelerate or oppose filtration?

A

Oppose

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37
Q

What does the renal corpuscle filter?

A

Water and small solutes

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38
Q

What is endothelial fenestration?

A

Pores in endothelial cells

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39
Q

How is the glomerular filtration rate calculated?

A

GFR = filtered plasma volume / time

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40
Q

What is the glomerular filtration rate in an average, healthy person?

A

Around 125ml per minute

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41
Q

What is meant by the term ‘filtered load’?

A

The total amount of any substance filtered through the glomerulus per unit time

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42
Q

Which is the part of the kidney involved in filtration?

A

The glomerulus

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43
Q

What is proteinuria?

A

High levels of protein in the urine

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44
Q

What is haematuria?

A

The presence of red blood cells in urine

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45
Q

What are the characteristics of nephrotic syndrome?

A
  • Severe proteinuria
  • Hypoalbuminaemia
  • Oedema
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46
Q

What are the characteristics of nephritic syndrome?

A
  • Haematuria

* Reduced urine production (oliguria)

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47
Q

What is oliguria?

A

Reduced excretion of urine

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48
Q

Where are most of the substances filtered by the glomerulus reabsorbed to?

A

The peritubular capillaries

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49
Q

What are the substances found in glomerular filtrate?

A
  • Water
  • Nutrients
  • Ions
  • Waste substances
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50
Q

What are the peritubular capillaries?

A

A network of small blood vessels which surround the renal tubule

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51
Q

What are ‘active processes’?

A

Body processes which require the use of cellular energy (ATP) due to substances being moved against their concentration gradient

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52
Q

What are ‘passive processes’?

A

Processes which do not require the use of energy as the substances are moved with the concentration gradient (ie from areas of high concentration to areas of low concentration)

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53
Q

Name three passive transport processes

A
  • Osmosis
  • Simple diffusion
  • Facilitated diffusion
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54
Q

Name two active transport processes

A
  • Active transport

* Facilitated diffusion

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55
Q

What is osmosis?

A

The diffusion of water molecules down their concentration gradient, across a semi-permeable membrane

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56
Q

What does the glomerulus do?

A

Filters your blood

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57
Q

What does a renal corpuscle consist of?

A
  • A Bowman’s Capsule

* A glomerulus

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58
Q

What are the two routes through which water and solutes can be absorbed?

A
  • Paracellular

* Transcellular

59
Q

In the kidneys, where does sodium begin and end reabsorption?

A
  • Begin - proximal convoluted tubule

* End - distal convoluted tubule

60
Q

What type/s of transport are involved in the reabsorption of sodium in the kidneys?

A
  • Facilitated diffusion
  • Primary active transport
  • Secondary active transport
61
Q

What is glycosuria and when does it commonly happen?

A

The pathological presence of glucose in the urine

Frequently found in people with severe diabetes

62
Q

What is the main waste product in plasma?

A

Urea

63
Q

What is creatinine a waste product of?

A

Skeletal muscle metabolism

64
Q

What is urea?

A

A nitrogen-containing molecule formed during the catabolism of amino acids

65
Q

What is the Loop of Henle?

A

A u-shaped structure within the nephrons which controls water reabsorption

66
Q

In the Loop of Henle, which direction does urine flow?

A

Opposite to the direction of blood flow

67
Q

The relationship between which two things enables the nephrons to regulate water reabsorption from the Loop of Henle?

A
  • Osmotic pressure

* Selective permeability

68
Q

What are the main ions secreted in urine?

A
  • Hydrogen

* Potassium

69
Q

What is the process which enables potassium and hydrogen ions to be secreted in urine?

A

Active cotransport coupled to sodium reabsorption

70
Q

What is the main similarity and the main difference between active transport and facilitated diffusion?

A
  • Both are mediated by protein channels
  • Facilitated diffusion is passive
  • Active transport requires the use of cellular energy
71
Q

Name at least three of the components of urine

A
  • Water
  • Urea
  • Uric acid
  • Creatinine
  • Ammonia
  • Sodium
  • Potassium
  • Chlorides
  • Phosphates
  • Sulfates
  • Oxalates
  • Some drugs
  • Toxins
72
Q

What type of muscle is involved in control of the internal urethral sphincter?

A

Smooth muscle

73
Q

What type of muscle is involved in control of the external urethral sphincter?

A

Skeletal muscle

74
Q

How is renal function measured?

A

By calculating the glomerular filtration rate

75
Q

What is the formula for calculating the glomerular filtration rate?

A

GFR = filtered plasma volume / time

76
Q

What does the term ‘renal clearance’ mean?

A

The volume of plasma from which a substance is completely removed by the kidneys per unit of time

77
Q

Which substance in the body is not reabsorbed by the kidneys, and secreted in only very small amounts, and can therefore be used to measure glomerular filtration rates?

A

Creatinine

78
Q

What is creatinine the breakdown product of?

A

Creatine

79
Q

What is phosphocreatine?

A

One way muscle cells store ATP reserves

80
Q

What is phosphocreatine converted to?

A

Creatinine (plus ATP)

81
Q

What two factors affect creatinine concentration in the blood?

A
  • Production by muscles

* Elimination by kidneys

82
Q

What factors can affect blood creatinine levels?

A
  • Gender
  • Age
  • Ethnicity
  • Level of muscle mass
83
Q

What is the formula used to calculate creatinine clearance, in order to then estimate GFR?

A

clearance of creatinine / ml min-1 =

          amount of creatinine excreted / mg min-1 
					                  ——————————————
							plasma concentration of creatinine / mg ml-1
84
Q

Name at least three essential functions of water in the body.

A

Metabolic reactions
Transport of nutrients
Controlling the body’s temperature
Eliminating metabolic wastes

85
Q

On average, how much water would a 70kg person have in their body?

A

42 litres

86
Q

Where in the body is most of the water contained?

A

In the cells

87
Q

On average, over 24hrs, how much water is lost via the skin and lungs?

A

About 900ml

88
Q

Through which mechanisms or body parts do we lost most of our water each day?

A 
Skin 
Lungs
Sweat
In faeces
Urine
89
Q

In total, roughly how much water do we lose per day?

A

About 2550ml

90
Q

Does dehydration affect just intracellular fluids, just extracellular fluids, or both?

A

Both

91
Q

What is meant by the term ‘osmolarity’?

A

The concentration of a solution expressed as the total number of solute particles per litre

92
Q

Over what percentage of body water loss will be fatal?

A

15-20%

93
Q

How is osmolarity measured?

A

Either osmoles per litre or osmoles per kilogram

94
Q

What is one-thousandth of an osmole called?

A

A milli-osmole

95
Q

What are the two receptors the body has for detecting changes in water content?

A
  • Osmoreceptors

* Vascular stretch receptors

96
Q

What are the two types of vascular stretch receptor?

Bonus: where are they found / under what conditions do they activate?

A
  • Volume receptors - found in walls of large veins and atria. Activate when there are small changes in blood volume.
  • Arterial pressure receptors - Activate when there is severe blood volume loss
97
Q

What is antidiuretic hormone also known as?

When is it released, and from which part of the brain?

A
  • Vasopressin

* If osmoreceptors detect low water levels. From the hypothalamus.

98
Q

What is the purpose of ADH/vasopressin?

A

To increase reabsorption of water

99
Q

What are aquaporins? What do they do?

A
  • A class of membrane protein

* They activate water-permeable channels in the cell membrane

100
Q

Dehydration triggers what responses?

A
  • Behavioural - thirst

* Renal - reduced water excretion

101
Q

What is meant by oncotic pressure?

A

The pressure exerted by plasma proteins on the capillary wall

102
Q

What are some of the mechanisms for ensuring adequate water balance in the body?

A
  • Thirst, stimulating an increased intake of water
    ADH
  • Increasing oncotic pressure reduces GFR, which reduces water excretion
103
Q

What are the nephron’s functions?

A
  • Filtration
  • Secretion
  • Reabsorption
104
Q

How does blood pressure in the capillaries affect the GFR?

A

Higher pressure = higher GFR

105
Q

What is meant by the term ‘myogenic’?

A

Originating in muscle tissue (as opposed to originating in nerve impulses)

106
Q

What is the most abundant ion dissolved in plasma?

A

Sodium

107
Q

What happens if we ingest too much sodium?

A

There will be an increase in plasma osmolarity which in turn will cause water retention. The increase of blood volume will ultimately increase systemic blood pressure.

108
Q

What is the juxtaglomerular apparatus?

A

A structure in the kidney which regulates the function of each nephron

109
Q

What is the macula densa?

A

An area of closely-packed cells which can either change resistance to blood flow in the afferent arterioles or increase renin release from the juxtaglomerular cells

110
Q

What are juxtaglomerular cells?

A

Cells which synthesise, store and release renin

111
Q

What is renin?

A

An enzyme which causes vasoconstriction and increases the GFR

112
Q

What are extraglomerular mesangial cells?

A

Multi-funcitonal cells which contribute to the regulation of systemic blood pressure through the renin-angiotensin system

113
Q

What is the renin-angiotensin system?

A

A hormone system which regulates blood pressure and fluid and electrolyte balance

114
Q

What are paracrine factors?

A

Hormone-like signalling substances that act locally on cells within the tissue they are released into

115
Q

What is the polypeptide precursor molecule which angiotensin I is cleaved from? Where is that precursor produced?

A
  • Angiotensinogen

* The liver

116
Q

Where is Angiotensin-Converting Enzyme (ACE) located?

A

In the inner (luminal) surface of capillary endothelial cells, especially those in the lungs

117
Q

What are the two homeostatic roles of the renin-angiotensin system (RAS)?

A
  • Counteracting a drop in blood pressure

* Counteracting an excessive reduction of the GFR

118
Q

How do ACE inhibitors work?

A
  • By blocking the conversion of angiotensin I to angiotensin II, which reduces levels of angiotensin II in the blood.
  • This causes less vasoconstriction, which reduces blood pressure
119
Q

What are the two macula-independent ways renin production can be stimulated?

A
  • Nervous stimulation (noradrenalin stimulates beta-1 adrenergic receptors in juxtaglomerular cells, which increases renin production and so activates the RAS system)
  • Juxtaglomerular cells are able to detect changes in blood pressure and secrete more renin
120
Q

What is aldosterone?

A

A steroid hormone which increases sodium reabsorption from the collecting ducts

121
Q

What happens if plasma sodium levels are too high?

A

Atrial natriuretic factor inhibits sodium reabsorption and increases GFR

122
Q

What are the two mechanisms by which kidneys are able to regulate blood pH?

A

Hydrogen ion secretion and bicarbonate reabsorption

Production of bicarbonate via tubular metabolism

123
Q

What effect does vomiting have on blood pH and why?

A

Increases it due to the loss of hydrogen ions from the stomach

124
Q

What is the pH range within which the kidneys produce urine?

A

6.5 - 8

125
Q

Which part of the kidney filters bicarbonate?

About what percentage of filtered bicarbonate is reabsorbed?

A
  • The glomerulus

* About 80%

126
Q

What happens to the pH of blood when bicarbonate is reabsorbed?

A

It increases

127
Q

What is tubular metabolism?

A

The metabolic reactions which occur in renal tubule cells

128
Q

Roughly how much fixed acid do the kidneys eliminate per day?

A

About 70-100 mol

129
Q

What are “fixed acids”?

Give an example of one

A

Acids produced in the body as a result of digestion, metabolism or other physiological processes.

Lactic acid (from anaerobic glucose metabolism)
Acetoacetic acid (from fat metabolism)
130
Q

Can fixed acids be excreted via the respiratory system?

A

No

131
Q

What is alkalosis?

Name some of the symptoms

A
  • A condition which occurs if blood pH rises above 7.45

* Confusion, nausea, muscle twitching

132
Q

What is acidosis?

Name some of the symptoms

A
  • When arterial blood pH is lower than 7.35

* Confusion, headaches, fatigue, increased heart rate

133
Q

What are the three hormones which modify the function of specific renal cells but which are not produced by the kidneys?

A
  • ADH
  • Angiotensin II
  • Aldosterone
134
Q

What type of renal cell does the hormone ADH target, and what homeostatic system does it affect?

A
  • Tubular cells

* Water balance

135
Q

What type of renal cell does the hormone Angiotensin II target, and what homeostatic system does it affect?

A
  • Efferent arteriolar

* Blood pressure

136
Q

What type of renal cell does the hormone Aldosterone target, and what homeostatic system does it affect?

A
  • Tubular cells

* Sodium balance

137
Q

What is erythropoietin?

A

A peptide hormone, produced by the kidneys, which stimulates red blood cell production in the bone marrow

138
Q

Give two sets of circumstances in which erythropoietin (produced by the kidneys to facilitate red blood cell production) may be used.

A
  • To treat certain types of anaemia

* By athletes, trying to enhance their performance capabilities

139
Q

As well as blood detoxification, what other purposes are kidneys necessary for?

A
  • Maintenance of water and salt pH homeostasis
  • Control of blood pressure
  • Regulation of hormones which control the functions of other body systems
140
Q

What are the two hormones the kidneys are involved in the production and secretion of?

A
  • ADH (antidiuretic hormone, a peptide hormone secreted in the hypothalamus)
  • Vitamin D
141
Q

Where is renin secreted?

A

The Juxtaglomerular Apparatus

142
Q

Which part of the kidney is responsible for the reabsorption of amino acids?

A

The proximal convoluted tubule

143
Q

What is the Loop of Henle’s function?

A

The reabsorption of water by osmosis

144
Q

What occurs in the collecting ducts in the kidney?

A

Aldosterone-dependent sodium reabsorption

SK299 (15 decks)

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