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Biology IB HL > 11.3 The Kidney > Flashcards

11.3 The Kidney Flashcards

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1
Q

What is excretion?

A

Excretion is the removal from the body of the waste products of metabolic activity

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2
Q

Is defecation considered part of excretion?

A

Defecation is not considered part of excretion as faeces are undigested food remnants and not metabolic waste products

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3
Q

What are the two key functions of an excretory system?

A

Removes nitrogenous wastes that may be toxic to the body in large concentrations

Removes excess water to maintain a suitable osmolarity within the tissues and cells

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4
Q

What produces nitrogenous wastes?

A

Nitrogenous wastes are produced from the breakdown of nitrogen-containing compounds like amino acids and nucleotides

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5
Q

Why must nitrogenous wastes be excreted?

A

Nitrogenous wastes are toxic to the organism and hence excess levels must be eliminated from the body

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6
Q

What is the type of nitrogenous waste correlated with?

A

The type of nitrogenous waste in animals is correlated with the evolutionary history of the animal and the habitat

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7
Q

In what form do most aquatic organisms excrete nitrogenous waste?

A

Most aquatic animals eliminate their nitrogenous wastes as ammonia (NH3)

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8
Q

Why is ammonia the most common form of nitrogenous waste in aquatic environments?

A

Ammonia is highly toxic but also very water soluble and hence can be effectively flushed by animals in aquatic habitats

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9
Q

Why does nitrogenous waste differ for terrestrial animals?

A

Terrestrial animals have less access to water and hence must package nitrogenous waste in less toxic forms

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10
Q

In what ways do mammals excrete nitrogenous wastes and why?

A

Mammals eliminate their nitrogenous wastes as urea, which is less toxic and hence can be stored at higher concentrations

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11
Q

In what ways do reptiles and birds excrete nitrogenous wastes and why?

A

Reptiles and birds eliminate wastes as uric acid, which requires more energy to make but is relatively non-toxic and requires even less water to flush (it is eliminated as a semi-solid paste)

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12
Q

Why do water levels within an organism change?

A

Water levels within an organism are constantly changing as a result of metabolic activity

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13
Q

In general, what reactions produce and consume water?

A

Water is produced via condensation reactions (anabolism) and is consumed during hydrolysis reactions (catabolism)

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14
Q

What impacts tissue viability?

A

The concentration of water within cells (osmolarity) will impact tissue viability (i.e. governs osmotic pressure within cells)

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15
Q

What are the two terms for animals depending on how they manage their internal osmotic conditions?

A

Animals may be either osmoconformers or osmoregulators according to how they manage their internal osmotic conditions:

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16
Q

What are osmoconformers?

A

Osmoconformers maintain internal conditions that are equal to the osmolarity of their environment

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17
Q

What are osmoregulators?

A

Osmoregulators keep their body’s osmolarity constant, regardless of environmental conditions

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18
Q

How do osmoconformers minimise water movement?

A

By matching internal osmotic conditions to the environment, osmoconformers minimise water movement in and out of cells

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19
Q

What is the advantage of osmoconformers?

A

Less energy is used to maintain internal osmotic conditions within an osmoconformer

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20
Q

What is an advantage of osmoregulators?

A

While osmoregulation is a more energy-intensive process, it ensures internal osmotic conditions are always tightly controlled

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21
Q

What is the key difference between osmoconformers and regulators?

A

Osmoregulators can maintain optimal internal conditions whereas osmoconformers are affected by environmental conditions

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22
Q

What specialised systems do animals have in terms of excretion?

A

All animals possess a specialised excretory system for osmoregulation and the removal of nitrogenous wastes

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23
Q

What is the difference between the excretory system in mammals and insects?

A

In mammals, the excretory system (kidneys) is separate from the digestive system of the animal

In insects, the excretory system (Malpighian tubules) connects to the digestive system of the animal

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24
Q
  1. What circulatory system do insects have
    Malpighian Tubules
A

Insects have a circulating fluid system called hemolymph that is analogous to the blood system in mammals

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25
Q
  1. What is the role of these tubules?
    Malpighian Tubules
A

Malpighian tubules branch off from the intestinal tract and actively uptake nitrogenous wastes and water from the hemolymph

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26
Q
  1. Where are these materials passed from the tubules?
    Malpighian Tubules
A

The tubules pass these materials into the gut to combine with the digested food products

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27
Q
  1. What is the ultimate product of the excretory system?
    Malpighian Tubules
A

Solutes, water and salts are reabsorbed into the hemolymph at the hindgut,

whereas nitrogenous wastes (as uric acid) and undigested food materials are excreted via the anus

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28
Q

What is the role of the kidneys?

A

The kidney functions as the blood’s filtration and water balancing system – it removes metabolic wastes for excretion

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29
Q

Describe the blood flow through the kidney?

A

Blood enters the kidneys via the renal artery and exits the kidneys via the renal vein

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30
Q

What filters blood in the kidney?

A

Blood is filtered by specialised structures called nephrons which produce urine

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31
Q

Where is urine transported to from the kidneys? What is it transported through?

A

The urine is transported from the kidneys via the ureter, where it is stored by the bladder prior to excretion

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32
Q

What is the role of the nephrons?

A

The kidney contains specialised structures called nephrons which function to filter the blood and eliminate wastes

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33
Q

What does the filtering function of the kidney say about the composition of the blood entering and leaving the kidney?

A

Consequently, the composition of blood entering the kidney (via renal artery) differs to that exiting the kidney (via renal vein)

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34
Q

How will the urea content of blood in the renal vein differ from the blood in the renal artery?

A

Less urea (large amounts of urea is removed via the nephrons to form urine)

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35
Q

How will the water and solute/ion content of blood in the renal vein differ from the blood in the renal artery?

A

Less water and solutes / ions (amount removed will depend on the hydration status of the individual)

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36
Q

How will the glucose and oxygen content of blood in the renal vein differ from the blood in the renal artery?

A

Less glucose and oxygen (not eliminated, but used by the kidney to generate energy and fuel metabolic reactions)

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37
Q

How will the carbon dioxide content of blood in the renal vein differ from the blood in the renal artery?

A

More carbon dioxide (produced by the kidneys as a by-product of metabolic reactions)

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38
Q

What is a nephron?

A

The nephron is the functional unit of the kidney

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39
Q

What are the 4 components of a nephron?

A

Bowman’s capsule
Proximal convoluted tubule
Loop of Henle
Distal Convoluted Tubule

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40
Q

What is the Bowman’s Capsule?

A

first part of the nephron where blood is initially filtered (to form filtrate)

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41
Q

What is the Loop of Henle?

A

a selectively permeable loop that descends into the medulla and establishes a salt gradient

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42
Q

What is the proximal convoluted tubule?

A

folded structure connected to the Bowman’s capsule where selective reabsorption occurs

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43
Q

What is the distal convoluted tubule?

A

a folded structure connected to the loop of Henle where further selective reabsorption occurs

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44
Q

How does blood enter and leave the Bowman’s capsule?

A

The blood to be filtered enters the Bowman’s capsule via an afferent arteriole and leaves the capsule via an efferent arteriole

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45
Q

Where is blood filtered within the glomerulus?

A

Within the Bowman’s capsule, the blood is filtered at a capillary tuft called the glomerulus

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46
Q

What does the efferent arteriole form in the Bowman’s Capsule and what is its purpose?

A

The efferent arteriole forms a blood network called the vasa recta that reabsorbs components of the filtrate from the nephron

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47
Q

What does each nephron connect to?

A

Each nephron connects to a collecting duct (via the distal convoluted tubule), which feed into the renal pelvis

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48
Q

Why are collecting ducts not considered to be a part of the nephron?

A

The collecting ducts are shared by nephrons and hence are not technically considered to be part of a single nephron

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49
Q

What is the role of nephrons?

A

Nephrons filter blood and then reabsorb useful materials from the filtrate before eliminating the remainder as urine

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50
Q

What are the 3 processes that occur in a nephron?

A

ultrafiltration
selective reansorption
osmoregulation

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51
Q

What is ultrafiltration?

A

Blood is filtered out of the glomerulus at the Bowman’s capsule to form filtrate

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52
Q

What is selective reabsorption?

A

Usable materials are reabsorbed in convoluted tubules (both proximal and distal)

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53
Q

What is osmoregulation?

A

The loop of Henle establishes a salt gradient, which draws water out of the collecting duct

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54
Q

Where does ultrafiltration occur and give a definition?

A

It is the non-specific filtration of the blood under high pressure and occurs in the Bowman’s capsule of the nephron

55
Q

What is the glomerulus encapsulated by?

A

This glomerulus is encapsulated by the Bowman’s capsule
, which is comprised of an inner surface of cells called podocytes

56
Q

What do podocytes have?

A

Podocytes have cellular extensions called pedicels that wrap around the blood vessels of the glomerulus

57
Q

What is between the podocytes and glomerulus?

A

Between the podocytes and the glomerulus is a glycoprotein matrix called the basement membrane that filters the blood

58
Q

What is the role of the basement membrane?

A

Blood is filtered by a mesh called the basement membrane, which lies between the glomerulus and Bowman’s capsule

59
Q

Why can blood freely leave the glomerulus?

A

Glomerular blood vessels are fenestrated (have pores) which means blood can freely exit the glomerulus

60
Q

How do podocytes allow for fluid to move freely?

A

The podocytes of the Bowman’s capsule have gaps between their pedicels, allowing for fluid to move freely into the nephron

61
Q

What is the sole filtration barrier in the nephron?

A

Consequently, the basement membrane functions as the sole filtration barrier within the nephron

62
Q

What does the basement membrane restrict?

A

The basement membrane is size-selective and restricts the passage of blood cells and large proteins

63
Q

Due to the basement membrane being size-selective, what is not in the filtrate?

A

Hence when the blood is filtered, the filtrate formed does not contain any blood cells, platelets or plasma proteins

64
Q

What is the role of ultrafiltration?

A

Ultrafiltration involves blood being forced at high pressure against the basement membrane, optimising filtration

65
Q
  1. What creates the high hydrostatic pressure?
    Ultrafiltration
A

This high hydrostatic pressure is created in the glomerulus by having a wide afferent arteriole and a narrow efferent arteriole

66
Q
  1. what is the role of the high hydrostatic pressure?
    Ultrafiltration
A

This means it is easy for blood to enter the glomerulus, but difficult for it to exit – increasing pressure within the glomerulus

67
Q
  1. What other adaption does the glomerulus have?
    Ultrafiltration
A

Additionally, the glomerulus forms extensive narrow branches, which increases the surface area available for filtration

68
Q
  1. What is the overall movement of blood in the glomerulus?
    Ultrafiltration
A

The net pressure gradient within the glomerulus forces blood to move into the capsule space (forming filtrate

69
Q

What is the second process in the nephron?

A

Selective reabsorption is the second of the three processes by which blood is filtered and urine is formed

70
Q

What is the role of selective reabsorption?

A

It involves the reuptake of useful substances from the filtrate and occurs in the convoluted tubules (proximal and distal)

71
Q

Where does the majority of selective reabsorption occur?

A

The majority of selective reabsorption occurs in the proximal convoluted tubule, which extends from the Bowman’s capsule

72
Q

How is the proximal convoluted tubule adapted for selective reabsorption?

A

The proximal convoluted tubule has a microvilli cell lining to increase the surface area for material absorption from the filtrate

The tubule is a single cell thick and connected by tight junctions, which function to create a thin tubular surface with no gaps

73
Q

What organelle does the proximal convoluted tubule have a large number of?

A

There are also a large number of mitochondria within these tubule cells, as reabsorption involves active transport

74
Q

Where are substances actively transported in the proximal convoluted tubule?

A

Substances are actively transported across the apical membrane (membrane of tubule cells facing the tubular lumen)

75
Q

Where do substances passively diffuse in the proximal convoluted tubule?

A

Substances then passively diffuse across the basolateral membrane (membrane of tubule cells facing the blood)

76
Q

What do the tubules reabsorb?

A

The tubules reabsorb all glucose, amino acids, vitamins and hormones, along with most of the mineral ions (~80%) and water

77
Q

How are mineral ions and vitamins transported in the PCT - (proximal convoluted tubule) ?

A

Mineral ions and vitamins are actively transported by protein pumps and carrier proteins respectively

78
Q

How is glucose transported in the PCT?

A

Glucose and amino acids are co-transported across the apical membrane with sodium (symport)

79
Q

How is water transported in the PCT?

A

Water follows the movement of the mineral ions passively via osmosis

80
Q

What is the third process in the nephron?

A

Osmoregulation is the third of three processes by which blood is filtered and urine is formed

81
Q

What is osmoregulation? (definition)

A

Osmoregulation is the control of the water balance of the blood, tissue or cytoplasm of a living organism

82
Q

Where does osmoregulation occur?

A

Osmoregulation occurs in the medulla of the kidney

83
Q

What is the role of the loop of Henle in osmoregulation?

A

The loop of Henle establishes a salt gradient (hypertonicity) in the medulla

84
Q

What is the role of ADH in osmoregulation?

A

Anti-diuretic hormone (ADH) regulates the level of water reabsorption in the collecting duct

85
Q

What is the function of the loop of Henle?

A

The function of the loop of Henle is to create a high solute (hypertonic) concentration in the tissue fluid of the medulla

86
Q

What is the descending limb permeable to?

A

The descending limb of the loop of Henle is permeable to water but not salts

87
Q

What is the ascending limb permeable to?

A

The ascending limb of the loop of Henle is permeable to salts but not water

88
Q

What is the solute like in the loop of Henle descending limb?

A

This means that as the loop descends into the medulla, the interstitial fluid becomes more salty and hypertonic

89
Q

What surrounds the loop of Henle?

A

Additionally, the vasa recta blood network that surrounds the loop of Henle flows in the opposite direction (counter-current)

90
Q

What is the role of the vasa recta?

A

This means that salts released from the ascending limb are drawn down into the medulla, further establishing a salt gradient

91
Q

WATER REABSORPTION
1. What draws out water in the collecting duct?

A

As the collecting duct passes through the medulla, the hypertonic conditions of the medulla will draw water out by osmosis

92
Q

WATER REABSORPTION
2. What controls water reabsorption?

A

The amount of water released from the collecting ducts to be retained by the body is controlled by anti-diuretic hormone (ADH)

93
Q

WATER REABSORPTION
3. When is ADH released and from where?

A

ADH is released from the posterior pituitary in response to dehydration (detected by osmoreceptors in the hypothalamus)

94
Q

WATER REABSORPTION
4. What is the role of ADH?

A

ADH increases the permeability of the collecting duct to water, by upregulating production of aquaporins (water channels)

95
Q

WATER REABSORPTION
5. What do high levels of ADH do to urine?

A

This means less water remains in the filtrate, urine becomes concentrated and the individual urinates less (i.e. anti-diuresis)

96
Q

WATER REABSORPTION
6. What happens when an individual is suitably hydrated?

A

When an individual is suitably hydrated, ADH levels decrease and less water is reabsorbed (resulting in more dilute urine)

Remember: ADH is produced when you Are DeHydrated

97
Q

What is critical for the survival of an organism?

A

Maintaining an appropriate water balance within the body’s tissues and cells is critical to the survival of an organism

98
Q

What cannot be maintained if water levels are not regulated?

A

Homeostasis cannot be maintained if water levels drop (dehydration) or are raised (overhydration) without regulation

99
Q

What is dehydration?

A

Dehydration is a loss of water from the body such that body fluids become hypertonic

100
Q

What will individuals experience when dehydrated?

A

Individuals will experience thirst and excrete small quantities of heavily concentrated urine (to minimise water loss)

101
Q

What happens to blood pressure when an individual is dehydrated?

A

Blood pressure will drop (less water in plasma) and the heart rate will increase to compensate for this

102
Q

What will happen to an individual temperature-wise when dehydrated?

A

The individual will become lethargic and experience an inability to lower body temperature (due to lack of sweat)

103
Q

What may severe cases of dehydration cause?

A

Severe cases of dehydration may cause seizures, brain damage and eventual death

104
Q

What is overhydration?

A

Overhydration is a less common occurrence that results when an over-consumption of water makes body fluids hypotonic

105
Q

How will overhydration affect urine production?

A

Individuals will produce excessive quantities of clear urine in an effort to remove water from the body

106
Q

What can overhydration do to body cells?

A

The hypotonic body fluids will cause cells to swell (due to osmotic movement), which can lead to cell lysis and tissue damage

107
Q

What can overhydration lead to in mild cases?

A

Overhydration can lead to headaches and disrupted nerve functions in mild cases (due to swelling of cells)

108
Q

What can overhydration lead to in severe cases?

A

In severe cases, overhydration may lead to blurred vision, delirium, seizures, coma and eventual death

109
Q

What will the need for water conservation depend on?

A

All animals need to maintain an appropriate water balance, however the need for water conservation will depend on habitat

110
Q

What habitats will require more efficient water conservation?

A

Animals in arid, desert environments will need more efficient water conservation than animals in moist, mesic environments

111
Q

How can water conservation be improved?

A

Water conservation can be improved by having a longer loop of Henle, which increase the salt gradient in the medulla

112
Q

How does an increased salt gradient help water reabsorption?

A

A greater the salt gradient in the medulla means more water is reabsorbed by the collecting ducts and urine is concentrated

113
Q

What is the length of the loop of Henle positively correlated with?

A

Hence, the length of the loop of Henle is positively correlated with the degree of water conservation in animals

114
Q

What type of nephrons do animals have that live in moist environments?

A

Animals living in moist environments have short loops of Henle that don’t descend deeply into the medulla (cortical nephrons)

115
Q

What type of nephrons do animals have that live in arid environments?

A

Animals living in arid environments have long loops of Henle that descend deeply into the medulla (juxtamedullary nephrons)

116
Q

What are kidney diseases?

A

Kidney diseases are conditions which incapacitate the kidney’s ability to filter waste products from the blood

117
Q

What will individuals with kidney diseases demonstrate?

A

Individuals with kidney diseases will demonstrate a reduced glomerular filtration rate (GFR)

118
Q

What can untreated kidney diseases lead to?

A

If untreated, kidney diseases can lead to kidney failure – which is life threatening

119
Q

What do kidneys prevent?

A

Kidneys prevent the excretion of blood cells and proteins (during ultrafiltration), as well as glucose (selective reabsorption)

120
Q

What substances in urine can be an indicator of kidney diseases? (4)

A

glucose
proteins
blood cells
drugs/toxina

121
Q

How is the presence of glucose in urine an indicator of kidney diseases?

A

The presence of glucose in urine is a common indicator of diabetes (high blood glucose = incomplete reabsorption)

122
Q

How is the presence of proteins in urine an indicator of kidney diseases?

A

High quantities of protein in urine may indicate disease (e.g. PKU) or hormonal conditions (e.g. hCG = pregnancy)

123
Q

How is the presence of blood cells in urine an indicator of kidney diseases?

A

The presence of blood in urine can indicate a variety of diseases, including certain infections and cancer

124
Q

How is the presence of drugs/toxins in urine an indicator of kidney diseases?

A

Many drugs pass through the body into urine and can be detected (e.g. performance enhancing drugs)

125
Q

What does kidney dialysis involve?

A

Kidney dialysis involves the external filtering of blood in order to remove metabolic wastes in patients with kidney failure

126
Q

What is the dialyzer similar to?

A

Blood is removed and pumped through a dialyzer, which has two key functions that are common to BIOLOGICAL MEMBRANES:

127
Q

What are the two similarities between a dialyzer and a biological membrane?

A

It contains a porous membrane that is semi-permeable (restricts passage of certain materials)

It introduces fresh dialysis fluid and removes wastes to maintain an appropriate concentration gradient

128
Q

How often is kidney dialysis needed?

A

Kidney dialysis treatments typically last about 4 hours and occur 3 times a week – these treatments can be effective for years

129
Q

What is a problem of hemodialysis?

A

Hemodialysis ensures continued blood filtering, but does not address the underlying issue affecting kidney function

130
Q

What is the best long-term treatment for kidney diseases?

A

The best long-term treatment for kidney failure is a kidney transplant

131
Q

Where is the transplanted kidney grafted into?

A

The transplanted kidney is grafted into the abdomen, with arteries, veins and ureter connected to the recipient’s vessels

132
Q

What must the transplanted kidney be similar to?

A

Donors must typically be a close genetic match in order to minimise the potential for graft rejection

133
Q

How many kidneys are needed to survive?

A

Donors can survive with one kidney and so may commonly donate the second to relative suffering kidney failure

Biology IB HL (56 decks)

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