1. THE KIDNEY & OSMOREGULATION
All animals excrete nitrogenous waste products and some animals also balance water and solute concentrations.
AHL Topic 11.3
IB Biology
Miss Werba

2. TOPIC 11 – ANIMAL PHYSIOLOGY
11.1
ANTIBODY PRODUCTION & VACCINATION
11.2
MOVEMENT
11.3
THE KIDNEY & OSMO-REGULATION
11.4
SEXUAL REPRODUCTION
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3. THINGS TO COVER Statement Guidance U.1 U.2 U.3 U.4 U.5 U.6 U.7 U.8 U.9
Animals are either osmoregulators or osmoconformers.
U.2
The Malpighian tubule system in insects and the kidney carry out osmoregulation and removal of nitrogenous wastes.
U.3
The composition of blood in the renal artery is different from that in the renal vein.
U.4
The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration.
U.5
The proximal convoluted tubule selectively reabsorbs useful substances by active transport.
U.6
The loop of Henle maintains hypertonic conditions in the medulla.
ADH will be used in preference to vasopressin.
U.7
ADH controls reabsorption of water in the collecting duct.
U.8
The length of the loop of Henle is positively correlated with the need for water conservation in animals.
U.9
The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.
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4. THINGS TO COVER Statement Guidance A.1 A.2 A.3 S.1 S.2 NOS 1.5
Consequences of dehydration and overhydration.
A.2
Treatment of kidney failure by hemodialysis or kidney transplant.
A.3
Blood cells, glucose, proteins and drugs are detected in urinary tests.
S.1
Drawing and labelling a diagram of the human kidney.
S.2
Annotation of diagrams of the nephron.
The diagram of the nephron should include glomerulus, Bowman’s capsule, proximal convoluted tubule, loop of Henle, distal convoluted tubule; the relationship between the nephron and the collecting duct should be included.
NOS 1.5
Curiosity about particular phenomena— investigations were carried out to determine how desert animals prevent water loss in their wastes.
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5. EXCRETION The removal of waste products of metabolism from the body.
If these waste products are allow to accumulate, they could become toxic.
This can occur in a number of ways but is mainly through the lungs, skin and renal system.
Examples of animals waste products:
carbon dioxide (excreted from the lungs)
nitrogenous compounds like urea from the breakdown of proteins
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6. EXCRETION
U.9
The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.
Most of metabolic waste is in the form of nitrogen
This is from the breakdown of amino acids and nitrogen bases.
Fish and amphibians produce ammonia (NH3).
Mammals produce urea (because its less toxic than NH3).
Reptiles and birds produce uric acid.
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7. EXCRETION
U.9
The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.
Selection pressures would have included access to or a lack of constant water to flush out toxins.
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8. OSMOCONFORMERS
U.1
Maintain internal conditions that are equal to the osmolarity of their environment.
The osmotic gradient (resulting in water movement in/out of cells) would need to be minimised.
Internal conditions could end up being sub-optimal.
eg. marine invertebrates like starfish
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9. OSMOREGULATORS
U.1
Internal conditions are maintained within narrow limits, irrespective of their environment.
The kidney carries out osmoregulation and removal of nitrogenous wastes.
Involves the reabsorption of water
Requires ATP
eg. more common in the animal kingdom
- eg. bony fish, humans
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10. OSMOREGULATORS
U.2
The Malpighian tubule system in insects carries out osmoregulation and removal of nitrogenous wastes.
Malpighian tubules extend into the body cavity and are surrounded by hemolymph.
Hemolymph is a fluid that circulates in the insect’s body around the tissues.
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11. OSMOREGULATORS
U.2
Salts and uric acid are actively transported from the hemolymph into the tubules to mix with the undigested food.
Water moves in by osmosis.
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12. OSMOREGULATORS
U.2
The salts and water are reabsorbed once the material moves through to the hindgut.
Wastes are excreted with faeces.
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13. THE HUMAN KIDNEY
S.1
You need to be able to draw and label a diagram of the human kidney.
The renal (excretory) system filters blood and produces urine
Humans have 2 kidneys
Each kidney has:
a renal artery leading to it  brings blood to be cleaned
a renal vein leading away from it  removes clean blood
a ureter leading to the bladder  removes urine
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14. THE HUMAN KIDNEY
S.1
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15. THE HUMAN KIDNEY carries filtered blood away from kidney
reabsorption of water
carries unfiltered blood to kidney
urine is delivered here from the collecting ducts and passed to the ureter
ultrafiltration and reabsorption of blood contents
carries urine to the bladder
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16. BLOOD COMPOSITION
U.3
The composition of blood in the renal artery is different from that in the renal vein.
Blood in the renal vein has…
more CO2
less O2, salts, ions water, glucose
same proteins
…than the renal artery.
The wastes are removed from the blood and end up in the urine.
Excess water and salts are also removed this way.
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17. BLOOD BALANCE ULTRAFILTRATION REABSORPTION of glucose, salt & H2O
OSMOREGULATION
EXCRETION
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18. THE NEPHRON You need to be able to annotate diagrams of the nephron.
The nephron is the functional unit of the kidney.
There are ~1 million in each kidney!
The nephrons are made up of different structures, each with its own function:
Bowman’s capsule and the glomerulus are located in the renal cortex
the loops of Henlé, the collecting ducts & the vasa rectae are located in the renal medulla
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19. THE NEPHRON
S.2
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20. THE NEPHRON
S.2
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21. THE NEPHRON selective reabsorption (glucose, salt & water)
secretion of toxins into urine
ultrafiltration
AFFERENT ARTERIOLE
EFFERENT ARTERIOLE
delivers urine to renal pelvis -
regulated by anti-diuretic hormone (ADH)
delivers blood to nephron for filtering
DESCENDING LIMB
ASCENDING LIMB
osmoregulation
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22. ULTRAFILTRATION
U.4
Process is facilitated by the ultrastructure of the glomerulus and Bowman’s capsule.
Ultrafiltration takes place within Bowman’s capsule
The afferent arteriole brings unfiltered (oxygenated) blood into the glomerulus and the efferent arteriole takes filtered blood away.
Because the efferent arteriole is smaller than the afferent, it increases blood pressure within the glomerulus.
The high blood pressure pushes blood against the capillary wall.
AFFERENT ARTERIOLE
EFFERENT ARTERIOLE
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23. ULTRAFILTRATION
U.4
Process is facilitated by the ultrastructure of the glomerulus and Bowman’s capsule.
The capillary wall and basement membrane are fenestrated. This means that they have tiny pores.
The inner wall of the Bowman’s capsule is lined with podocyte cells. These cells also have gaps between them.
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24. ULTRAFILTRATION
U.4
The high blood pressure in the glomerulus forces the blood contents across the capillary wall and basement membrane.
Water, glucose, amino acids, vitamins, hormones and salt are able to move through the filter established by the capillary wall, basement membrane, fenestrations and podocytes.
Large proteins, platelets and blood cells cannot cross inter the nephron.
The glomerular filtrate continues through to the proximal convoluted tubule (PCT) of the nephron.
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25. ULTRAFILTRATION
U.4
Ref: IB Biology OSC
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26. ULTRAFILTRATION
U.4
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27. SELECTIVE REABSORPTION
U.5
Selective reabsorption occurs in the proximal convoluted tubule (PCT).
the PCT extends from the Bowman’s capsule to the loop of Henle
Glucose, water and salts are reabsorbed as needed.
Reabsorption occurs by means of:
active transport
osmosis and
facilitated diffusion
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28. SELECTIVE REABSORPTION
U.5
Active transport:
mitochondria in PCT cells provide ATP
used to reabsorb salt (Na+ ions)
LUMEN
MICROVILLI
CHANNEL PROTEIN
PCT CELL
MITOCHONDRIA
RBC
CAPILLARY
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29. SELECTIVE REABSORPTION
U.5
Osmosis (passive transport):
microvilli in PCT cells to increase the surface area for reabsorption
used to reabsorb water, using the concentration gradient established by the active transport of salt
LUMEN
MICROVILLI
CHANNEL PROTEIN
PCT CELL
MITOCHONDRIA
RBC
CAPILLARY
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30. SELECTIVE REABSORPTION
U.5
Facilitated diffusion (co-transport):
channel proteins in PCT cell membrane help larger substances across the membrane
used to reabsorb glucose and amino acids
LUMEN
MICROVILLI
CHANNEL PROTEIN
PCT CELL
MITOCHONDRIA
RBC
CAPILLARY
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31. SELECTIVE REABSORPTION
U.5
This takes substances from the filtrate in the nephron back into the blood capillaries surrounding the PCT.
Normally:
65-80% of water is reabsorbed
100% of glucose and amino acids are recovered
(cf. Diabetes)
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32. SELECTIVE REABSORPTION
U.5
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33. OSMOREGULATION
U.6
U.7
Osmoregulation: the control of water balance of the blood, tissue or cytoplasm
In the nephron, osmoregulation involves the:
loop of Henlé
distal convoluted tubule (DCT)
and collecting duct
Osmoregulation is under endocrine control by anti-diuretic hormone (ADH)
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34. OSMOREGULATION Loop of Henlé: In the medulla
Generates a high concentration of solutes in the cells and fluid of the medulla
The loops of Henlé have 2 limbs:
Descending limb (connected to PCT)
Ascending limb (connected to DCT)
The loop of Henlé is surrounded by a capillary network called the vasa rectae.
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35. OSMOREGULATION Loop of Henlé: Descending limb (connected to PCT)
Permeable to water
Impermeable to salt
Ascending limb (connected to DCT)
Impermeable to water
Permeable to salt
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36. OSMOREGULATION Loop of Henlé: Descending limb (connected to PCT)
osmotic gradient is established because solute concentration in medulla is high
water leaves by osmosis
solute concentration in filtrate increases
Ascending limb (connected to DCT)
no water leaves
osmotic balance maintained by active transport
Na+ ions pumped into medulla
solute concentration in filtrate decreases
solute concentration in medulla increases
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37. OSMOREGULATION Loop of Henlé:
This is called the counter-current effect.
Overall effect:
Filtrate volume decreases
Filtrate leaving the loop of Henlé is slightly more dilute
Large quantity of salt has been removed
The vasa rectae (the blood vessels of the loops of Henlé) help maintain the concentration gradient in the medulla.
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38. OSMOREGULATION
U.6
U.7
Ref: IB Biology OSC
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39. OSMOREGULATION Distal convoluted tubule (DCT):
Walls of the DCT are permeable
Allows more water to leave the filtrate and re-enter the bloodstream.
Anti-diuretic hormone (ADH) regulates the permeability of both the DCT and the collecting duct.
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40. OSMOREGULATION Collecting duct:
Balances the water concentration of the blood through hormonal control.
The filtrate enters the collecting duct from the DCT.
Water can leave the collecting duct by osmosis.
The collecting duct also contains water-pores called aquaporins that are opened by ADH.
Opening the aquaporins makes the collecting duct more permeable to water.
This allows more water to leave the collecting duct.
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41. OSMOREGULATION Collecting duct: ADH secretion is triggered by:
a drop in osmotic concentration of the blood
an increase in solute concentration of the blood
The osmotic concentration of the blood is monitored by the hypothalamus.
ADH is released by the pituitary
Osmoregulation is controlled by negative feedback.
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42. OSMOREGULATION Increase in body osmotic concentration
Normal blood osmotic concentration (60-80% body weight)
Increase in body osmotic concentration
Decrease in body osmotic concentration
 ADH secretion by pituitary
 H2O reabsorption by nephron
 salt reabsorption by nephron
Kidney makes small amount of concentrated urine
Detected by hypothalamus,
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43. OSMOREGULATION Decrease in body osmotic concentration
 ADH secretion by pituitary
 H2O reabsorption by tubules
 salt reabsorption by tubules
Kidney makes large amount of dilute urine
Detected by hypothalamus,
Decrease in body osmotic concentration
Increase in body osmotic concentration
Normal blood osmotic concentration (60-80% body weight)
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44. WATER CONSERVATION IN ANIMALS
NOS 1.5
Curiosity about particular phenomena
Investigations were carried out to determine how desert animals prevent water loss in their wastes.
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45. WATER CONSERVATION IN ANIMALS
U.8
The length of the loop of Henle is positively correlated with the need for water conservation in animals.
Example: kangaroo rats (D. Nitratoides)
Has a longer LoH than other rodents
Can survive in deserts
Have very efficient kidneys
Produce small volumes of highly concentrated urine (3,500mmol/L compared to humans (400mmol/L))
Longer LoH helps build up a higher salt concentration therefore allowing more water to be reabsorbed in the collecting duct.
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46. WATER CONSERVATION IN ANIMALS
U.8
What conclusions could you draw from the data shown?
Withers, P.C. (1992) Comparative Animal Physiology. Saunders College Publishing, Fort Worth ©
The relationship between relatively medullary area in the mammalian kidney and the max. urine concentration that can be produced.
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47. WATER CONSERVATION IN ANIMALS
U.8
Rodents generally have kidneys with a larger medullary area and produce more concentrated urine than bats and other mammals.
Interested?
Read this article
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48. U.8
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49. DEHYDRATION & OVERHYDRATION
Due to loss of water
Body fluids become hypotonic
Results in:
Thirst
Small volumes of dark, coloured urine
Lethargy
Raised heart rate
Inability to lower body T˚
Severe cases: seizures, brain damage, death
Overhydration
Due to overconsumption of water
Body fluids become hypertonic
Results in:
Large volumes of clear urine
Swelling of cells due to osmosis
Headache, disrupted nerve function
Severe cases: delirium, blurred vision, seizures, coma, death
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50. TREATMENT OF KIDNEY FAILURE
Kidney failure: when the kidneys fail to adequately filter waste products from the blood
Treatment of kidney failure focuses on 2 approaches:
Haemodialysis and
Kidney transplant
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51. TREATMENT OF KIDNEY FAILURE
Haemodialysis:
process of purifying the blood outside of the body
treatments last ~4hrs, three times a week, for years
Fresh dialysate is pumped into the dialyzer, and the used dialysate is collected.
Fresh dialysate contains no urea, glucose and other necessary molecules/ions, with a high solute concentration
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52. TREATMENT OF KIDNEY FAILURE
Kidney transplant:
a good long-term treatment
a donor is needed that is a close blood/tissue match to minimise the chance of rejection
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53. URINARY TESTS Able to detect blood cells, glucose, proteins and drugs
Things that affect metabolism will affect the metabolic waste that is produced.
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54. URINARY TESTS
A.3
Presence of blood cells  infections, disease, some cancers
Presence of glucose  diabetes
Proteins (in large amounts)  kidney disease
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55. EXCRETION
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56. THE KIDNEY & OSMOREGULATION
Q1. The diagram below shows a longitudinal section through a kidney. What is the structure labelled Z and what is its function?
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57. THE KIDNEY & OSMOREGULATION
Q2.
Define the term excretion. (1)
Explain the process of ultrafiltration. (2)
The diagram to the right shows part of the human kidney. The arrow shows the direction of blood flow.
Compare the composition of the fluids found in the regions labelled I and II by giving one difference and one similarity. (2)
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58. THE KIDNEY & OSMOREGULATION
Q3. Explain the process of ultrafiltration.
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59. THE KIDNEY & OSMOREGULATION
Q4. Explain osmoregulation in the kidney.
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