The document discusses homeostasis and the role of the kidneys in maintaining homeostasis. It begins by defining homeostasis as the maintenance of relatively stable internal conditions in the body despite changes in the external environment. It then describes the three main components of homeostasis - receptors that detect changes, control centers that regulate responses, and effectors that cause the responses. As an example, it explains how negative feedback loops work to regulate factors like body temperature and hormone levels. The document then focuses on the kidneys and urine formation. It describes the parts of the nephron, how ultrafiltration in the glomerulus produces an initial filtrate, and how subsequent reabsorption and secretion in the nephron tubules allow the kidneys to regulate

1. BIOLOGY FORM 5
CHAPTER 3
COORDINATION & RESPONSE PART 3

2. LEARNING OBJECTIVES
3.4 Synthesising the concept of homeostasis in humans
LEARNING OUTCOMES
 explain the necessity to maintain an optimal physical and chemical
condition in the internal environment
 state the meaning of homeostasis,
 design an experiment to study the effect of different quantities of
water intake on urine output,
 relate changes in blood osmotic pressure to urine output,
 describe the formation of urine,
 relate the formation of urine to excretion,
 describe briefly the mechanism of osmoregulation,
 predict the consequences of impaired kidney function,
 describe the regulation of blood sugar level,
 describe the regulation of body temperature,
 conceptualise homeostasis.

3. What is Homeostasis?
Body cells work best if they have the correct
 Temperature
 Water levels
 Glucose concentration
Your body has mechanisms to keep the cells in
a constant environment.

4. Homeostasis:
 Greek: ‘homoios’ = similar
‘stasis’ = standing still
Homeostasis is the
maintenance of a relatively
stable internal environment
The ‘internal’ environment is
the:
 tissue fluid [interstitial fluid]
 plasma

5. fluid
surrounding
cells
where
organism
lives

6. Are variables absolutely
constant?
STEADY
STATE
High
Variable
Low
NO

7. Examples of Physiological conditions
requiring homeostasis:
O2 and CO2 levels in the body
energy requirements
glucose level in blood
water / ion balance
pH
temperature

8. Living systems are seen to be open
systems. What does this mean?
Require a continuous exchange of matter
between the environment and themselves
Oxygen Carbon dioxide
Heat
Urea
Food
Water

9. We are a
complex system of chemical
processes
these processes are:
 self-regulating
 tend to maintain a steady state even though
the external environment changes

10. What is Homeostasis?
The maintenance of a
constant environment
in the body is called
Homeostasis

11. Why is homeostasis important?
We function more
efficiently if
conditions are
maintained within
optimum conditions
Fluctuations are caused by:
Changes in:
 external
 internal
Toprevent large
fluctuations from the
optimum
environments

12. Internal conditions may be maintained
constant within the body by:
developing a variety of mechanisms:
Structural
Physiological
Behavioural

13. Fat
Fur
Feathers
Structural

14. Sweat
Increase in
heart rate Cardiac arrest
in frozen frog
Physiological

15. HOT: Seek shade
HOT: Seek shade
COLD:
Bask in the sun
Behavioural

16. LEARNING OBJECTIVES
3.4 Synthesising the concept of homeostasis in humans
LEARNING OUTCOMES
 explain the necessity to maintain an optimal physical and chemical
condition in the internal environment
 state the meaning of homeostasis,
 design an experiment to study the effect of different quantities of
water intake on urine output,
 relate changes in blood osmotic pressure to urine output,
 describe the formation of urine,
 relate the formation of urine to excretion,
 describe briefly the mechanism of osmoregulation,
 predict the consequences of impaired kidney function,
 describe the regulation of blood sugar level,
 describe the regulation of body temperature,
 conceptualise homeostasis.

17. Principles of Homeostasis
Stimulus Receptors Self-corrective Mechanism Negative Feedback
Change in
internal
environment
Detect the
change
Regulation of
blood
glucose
concentration
Examples
To rectify
the change
Regulation
of blood
water
potential
Regulation of
body
temperature
The reverse
effect of the
change
HOMEOSTASIS
The maintenance of a constant internal
environment

18. Three basic components of a control
system:
1. Detector / Receptor / Sensor
2. Regulator / Control centre /
Co-ordinator / Integrating centre
3. Effector

19. Integrating Centre in mammals is:
An endocrine gland
Brain or
spinal cord

20. What is Feedback?
Feedback refers to responses made
after a change has been detected

21. Positive feedback
Two forms of feedback:
Equilibrium
Time
Divergence
Time
Negative feedback

22. Negative Feedback:
refers to the mechanism by which a system
responds to a fluctuation in the opposite
direction

23. Body
temperature:
RISES
Corrective mechanism:
DECREASES body
temperature
Body
temperature:
DECREASES
Corrective mechanism:
INCREASES body
temperature

24. Negative feedback also applies to the
regulation of a population size:
Death rate
increasesBirth rate
increases

25. Why is negative feedback very
common in the body?
increases the stability of
systems

26. Examples of Negative Feedback Control:
O2 and CO2 levels in the body
hormone levels, e.g. thyroxine
sex hormones
metabolic levels e.g. glucose
water balance
the regulation of pH
body temperature

27. Control of thyroxine release as an
example of negative feedback

29. Positive feedback:
 a disturbance leads to events which
increase the disturbance even further
 rare in biological systems
WHY rare?
lead to:
 an unstable situation
 extreme states
Time
Divergence

30. Examples of Positive Feedback Control:
1. Blood clotting
Activated platelet
releases chemicals
More platelets
are activated
A blood clot forms

31. Examples of Positive Feedback Control:
2. Child birth
Oxytocin stimulates
muscular contractions
of the uterus
More oxytocin is
released

32. Does the disturbance ever stop?
 once the purpose of the feedback loop is
completed
Oxytocin level
drops once baby
is born

33. LEARNING OBJECTIVES
3.4 Synthesising the concept of homeostasis in humans
LEARNING OUTCOMES
 explain the necessity to maintain an optimal physical and chemical
condition in the internal environment
 state the meaning of homeostasis,
 design an experiment to study the effect of different quantities of
water intake on urine output,
 relate changes in blood osmotic pressure to urine output,
 describe the formation of urine,
 relate the formation of urine to excretion,
 describe briefly the mechanism of osmoregulation,
 predict the consequences of impaired kidney function,
 describe the regulation of blood sugar level,
 describe the regulation of body temperature,
 conceptualise homeostasis.

36. LEARNING OBJECTIVES
3.4 Synthesising the concept of homeostasis in humans
LEARNING OUTCOMES
 explain the necessity to maintain an optimal physical and chemical
condition in the internal environment
 state the meaning of homeostasis,
 design an experiment to study the effect of different quantities of
water intake on urine output,
 relate changes in blood osmotic pressure to urine output,
 describe the formation of urine,
 relate the formation of urine to excretion,
 describe briefly the mechanism of osmoregulation,
 predict the consequences of impaired kidney function,
 describe the regulation of blood sugar level,
 describe the regulation of body temperature,
 conceptualise homeostasis.

37. Formation of Urine

38. The kidneys contribute to homeostasis
Let us see
how:

39. Urine Production
• Regulation of water
and salts in the body
- osmoregulation
• Rids body of waste –
excretion
• Maintaining blood pH
• Regulating blood
volume & pressure

40. Human Urinary System

41. The organs
of the
urinary system:
a)Kidneys
b)Ureters
c)Bladder
d)Urethra

42. Urinary system

44. The kidney
Organ of excretion & osmoregulation

45. The Job of the Kidneys
• cleans the blood
• by removing metabolic
wastes,
• excess solutes (eg. salts or
glucose)
• excess water
• and excreting them as urine
• maintain homeostasis in
blood solute concentration.

46. The Hard-working Kidneys
• The two kidneys in the body
receive between 1100 – 2000
liters (1160 – 2100 quarts or
500 gallons) of blood per day –
about the volume of a car!
• Because the body has only
about 5.6 liters of blood, your
blood runs through the kidneys
to be cleaned about once every
four minutes.

47. Position and structure of kidneys

48. External structure of a Pig Kidney

49. Kidneys are surrounded by a fibrous capsule:

50. Kidneys are surrounded by a fibrous capsule:

51. (b) Kidney structure
Ureter
Section of kidney from a rat
Renal
medulla
Renal
cortex
Renal
pelvis
Figure 44.13b
• Kidney has 2 internal layers
renal cortex - outer light red region
renal medulla – inner darker red-brown
region

52. LS through human kidney
medulla
cortex

53. LS through human kidney

54. The renal artery branches inside kidney
Renal
artery
Ureter
Renal
vein
Each capillary supplies blood to hundreds of thousands
of tiny filtration units called nephrons
Detail of a
nephron

57. Nephron
• functional unit of the kidney
• About a million in each kidney.
• Consists of 3 major parts : a) the glomerulus
• b) Bowman’s capsule
• c) Renal tubule

59. Bowman’s
Capsule
glomerulus
afferent
arteriole
efferent
arteriole
proximal
convoluted
tubule
capsular
space

60. Nephron Structure

61. The nephron
1.5 million per kidney
collecting
duct
Bowman’s
capsule
distal
tubule
loop of
Henle
proximal
tubule

62. The nephron
blood supply
peritubular
capillaries
Vasa
Recta
glomerulus
branch of renal
artery
afferent arterioles
efferent arterioles
branch of
renal
vein
The glomerular capillaries
drain into efferent arterioles
not venules.
‘Portal System’

63. CORTEXMEDULLA
The nephron

64. Nephron Structure (Draw)

66. vasa recta
Slow blood flow:
important to produce a
concentrated urine

70. Three key process in urine formation:
Ultrafiltration

71. Ultrafiltration
• takes place in the glomerulus & Bowman’s capsule
• is filtration under pressure
• pressure comes from blood pressure (hydrostatic
pressure)

72. Glomerulus & Bowman’s capsule

73. Hydrostatic pressure caused by:
Efferent
arteriole
Afferent
arteriole
Filtration
pressure
GFR maintained
• Diameter of the afferent
arterioles bigger than the
efferent arteriole
•  blood enters
glomerulus under high
hydrostatic presssure
• Pushes/filters small
particles from the blood
into the capsular space.

74. Glomerular Filtrate (GF): is the filtered fluid
 chemical composition is similar
to blood plasma, containing:-
Glucose
Amino acids
Vitamins
Ions
Nitrogenous waste
Some hormones
Water
Glomerular
filtrate

75. Explain why proteins & RBC are not found
in urine. Too large to be filtered.

76. But can blood ever be detected in urine?
YES. But, this
shows that
something is
wrong .

77. Ultrafiltration takes place through three layers:
1) Endothelium of the
blood capillary
2) Basement membrane of
the blood capillaries
3) Epithelium of the
Bowman' capsule

78. Filtrate passes through 3 layers

79. Cells lining the Bowman’s capsule:
Podocyte
Squamous
epithelium
Podocytes are
highly modified
for filtration

80. Basement
membrane
Fenestrated capillaries
(capillaries with windows)Permeable
to substances
< 100 nm
endothelial cell
fenestration
nucleus
Filtration Barrier

81. mesangial cells
podocyte
slit pore

83. glucoseamino acids
(basement membrane)
podocyte slit pore
Na+
--
-
-
-
---
-
-
-
-
-
-
-
-
-
-
-
-
- -
-
-
--
-
-
-
Limited permeability to
molecules between
7000 > mwt > 70000 Da
4 nm > diameter > 8 nm
Freely permeable to
small molecules
mwt < 7000 Da
diameter < 4 nm
Not permeable to
large molecules
mwt > 70000 Da
diameter > 8 nm
Water Permeablealbumin
60000 Da
completely
excluded…
because of –ve charge
endothelial cell
fenestration

85. Bowman’s Capsule
Bowman’s
Space
Proximal Tubule
petesmif@liv.ac.uk

86. Hydrostatic Pressure

87. GLOMERULAR FILTRATE

88. Glomerular Filtrate
Molecule or ion Approx. concentrations / g dm-3
Plasma Filtrate
water
protein
glucose
amino acids
urea
inorganic ions
900.0
80.0
1.0
0.5
0.3
7.2
900.0
0.0
1.0
0.5
0.3
7.2

89. Where does the glomerular filtrate go to after
being formed?

90. Recap: What is ultrafiltration?
Ultrafiltration begins in the Bowman's Capsule.
a) Blood arrives in the kidney in the Afferent arteriole
(with a wide blood vessel) at high pressure.
b) Blood passes through the Glomerulus and passes out
the Efferent arteriole (with a narrow blood vessel).
c) Blood pressure increases in the Glomerulus.
d) High hydrostatic pressure forces the plasma (liquid in
blood - water, salts, amino acids, glucose and urea) out
of the blood vessel into the inside of the Bowman's
Capsule - This is called "Glomerular Filtrate."

91. After ultrafiltration
2 more processes
2) Reabsorbtion
3)Secretion

92. Function of the nephron is to :
actively secrete
waste substances from
the blood capillaries to
the tubules
selectively
reabsorb
substances useful
to the body

93. The Proximal Convoluted Tubule
 longest (14 mm)
and widest (60 m)
part of the nephron
carries filtrate from
Bowman’s capsule to
loop of Henle
CORTEX
MEDULLA

94. b) Reabsorption
• Selective reabsorption
takes place when
substances move across
the walls of the renal
tubule into the capillary
network.
• It mostly occurs in the
proximal convoluted
tubule

95. Why Reabsorbtion?
Molecule or ion Approx. concentrations / g dm-3
Plasma Filtrate
water
protein
glucose
amino acids
urea
inorganic ions
900.0
80.0
1.0
0.5
0.3
7.2
900.0
0.0
1.0
0.5
0.3
7.2

96. Selective reabsorption in the proximal convoluted tubule
In humans:
Glomerular filtrate production: 125 cm3 min-1
Urine production: 1 cm3 min-1
24 cm3
100 cm3
Urine 1 cm3
125 cm3

97. Proximal convoluted tubule
• 65% water reabsorbed by
osmosis into blood
capillaries
• All glucose, AA, vitamins &
some salts reabsorbed by
active transport
• Urea not reabsorbed
• GF – now only water, some
salts & urea

99. Proximal Convoluted Tubule is composed of:
a single layer of cuboidal epithelial cells with
extensive microvilli forming a ‘brush border’ on the
inside surface of the tubule
Figure 44.9

100. Proximal Convoluted Tubule is adapted for
reabsorption in three ways:
1.large surface area for absorption due to:
Figure 44.9
Microvilli
Basal
channels
BLOOD FILTRATE
Tight
junction
Epithelial
cell

101. Proximal Convoluted Tubule is adapted for
reabsorption:
Figure 44.9
2. numerous mitochondria (M)
to provide
ATP for
active
transport.

102. Proximal Convoluted Tubule is adapted for
reabsorption:
Figure 44.9
3.closeness of blood capillaries
blood capillary
Glomerular
filtrate
Microvilli
Cuboidal
epithelium

103. Over 80% of filtrate is reabsorbed in the proximal tubule
REABSORBED
 all the glucose, amino acids,
vitamins, hormones
 about 80% water
 about 80% sodium
 about 80% chloride
 about 80% potassium
 about 40-50% urea
MECHANISM
 diffusion + active transport
 osmosis
 diffusion
+ active transport
 diffusion

104. Selective reabsorption of sodium and glucose
in the proximal convoluted tubule
Figure 44.9
Secondary
Active
Transport

105. Na+
glucoseNa+
ATP
ADP
Blood
Urine
Proximal tubule epithelial cell
petesmif@liv.ac.uk

106. Question:
Briefly describe the following processes in the context of urine
formation in humans.
a) Ultrafiltration. (2)
Filtration of blood occurs under high pressure. Small molecules
which can cross the glomerular lining, end up as glomerular
filtrate inside the Bowman’s capsule.
b) Selective reabsorption of glucose. (3)
Occurs in the proximal convoluted tubule. All glucose is
reabsorbed in a normal person but appears in urine in a
diabetic one. Active transport is involved in the reabsorption of
glucose.

107. THE LOOP OF HENLE
Function: to conserve water
the concentration of urine
produced is directly related to the:
length of the loop of Henle
 thickness of the medulla
relative to the cortex

108. The longer the loop of Henle, the more concentrated the
urine that can be produced
BEAVER
(abundant water)
RABBIT
(moderate water)
SAND RAT
(scarce water)

109. Birds & Mammals are the only vertebrates:
which can produce a urine which is more
concentrated than the blood
[hypertonic]
with loops of Henle
Loop of Henle

110. Three distinct regions in the loop of Henle
Thin
ascending
limb
Descending
limb
Thick
ascending
limb
Thin walls
Thick walls

111. Loop of Henle
• 20% of water &
some salts
reabsorbed

112. REABSORPTION IN LOOP OF HENLE

113. Permeability of the loop of Henle to water:
Highly
permeable
Descending
limb
Almost
totally
impermeable
to waterThin ascending
limb
Thick ascending
limb

114. Permeability of the loop of Henle to
Na+ & Cl-ions:
Not very
permeable
Descending
limb
Thin ascending
limb
Thick ascending
limb
Permeable
Active secretion

115. What happens to the concentration of the
fluid in the ascending limb as it reaches the
distal convoluted tubule?
The fluid becomes
very dilute
Distal convoluted tubule
Reason:
IONS are lost

116. WHY it is vital for ions to move out
of the tubule?
ions

117. To create an Osmotic Gradient From Cortex to
Medulla
PelvisMedulla
Cortex
The outer layer of the kidney is isotonic with the blood:
~300 milliosmoles/liter
The innermost layer (medulla) is very hypertonic:
~1200 milliosmoles/liter

118. The concentration gradient allows:
water to
move out by
osmosis
from the
descending
loop of Henle

119. Osmotic gradient is produced by a:
 countercurrent mechanism
located in the loop of Henle
What is a
‘countercurrent mechanism’?

120. Countercurrents exist when :
fluids flow in opposite directions in
parallel and adjacent tubes

121. Three Countercurrents:
1. the two limbs of the
Henle's loop

122. Three Countercurrents:
1. the two limbs of the
Henle's loop
2. the two limbs of
the vasa recta

123. Three Countercurrents:
1. the two limbs of the Henle's loop
2. the two limbs of the vasa recta
3. the descending limb of
Henle with the ascending
limb of the vasa recta;
the ascending limb of
Henle and the
descending vasa recta

125. Cortex
Water
leaves -
ion
concentra
tion in
filtrate
increases
Filtrate reaches maximum concentration
Chloride
ions out
(sodium
follows) -
ion
concentrat
ion in
filtrate
decreases
Medulla

126. To ureter
Collecting duct
•Several nephrons
empty into one
collecting duct.
•The collecting duct
passes through the
progressively more
concentrated
medulla, losing
water by osmosis.
This water is
reabsorbed by the
capillaries.
•This water is
conserved, and a
highly concentrated
urine is produced.
Water reabsorbed into vasa recta,
urine becomes more concentrated
Cortex
Medulla

127. Question: [SEP, 2009]
Briefly describe the role of each of the following in
osmoregulation in humans:
i) The descending limb of the Loop of Henle; (2)
Is permeable to water. Functions towards water
conservation.
ii) The ascending limb of the Loop of Henle; (2)
Is relatively impermeable to water but permeable to salts.
The tissue fluid inside the medulla becomes concentrated as
salts move out of the ascending limb. This causes water to be
drawn out of the descending limb.

128. Question:
The diagram below shows the
simplified structure of a human
nephron.the loop of Henle
Substance Quantity passing
through P
Quantity passing
through Q
%
reabsorbed
Water 180 dm3 1.5 dm3 99.17%
Glucose 180 g 0 g 100%
Urea 53 g 25 g 52.8%
The table below represents the quantities of water,
glucose and urea passing through P and Q over a
period of time, while the last column shows the
percentage reabsorption during the same period of
time.

129. Question:
a) Relate the role of structure R to the filtrate composition
as it passes through Q. (5)
Structure Q is permeable to water. Water is reabsorbed by
the vasa recta as fluid passes through Q. This is possible
because the ascending limb creates the ideal
concentration gradient within the medulla by losing ions.
The thin ascending limb of Structure R is permeable to ions
but impermeable to water. The thick ascending limb of
Structure R allows ions to move actively out of it and is
also impermeable to water. Loss of ions from the whole
ascending limb, creates an ever increasing salt
concentration on moving deeper into the medulla.

130. Question:
Substance Quantity passing
through P
Quantity passing
through Q
%
reabsorbed
Water 180 dm3 1.5 dm3 99.17%
Glucose 180 g 0 g 100%
Urea 53 g 25 g 52.8%
b) Explain the biological significance of the percentage
reabsorption of water and urea. (3)
Most of the water is reabsorbed to avoid dehydration.
Only half of the urea is reabsorbed so that it contributes to
the concentration of solutes in the medulla. A high solute
concentration is needed to ensure reabsorption of water from
the loop of Henle.

131. Distal convoluted tubule
Reabsorption & Secretion
occur
• More H2O reabsorbed 
osmosis
• Na+ and Cl- , HCO3
- ions
are reabsorbed  active
transport
• Secretion of NH4
-, H+,
some drugs & poisons 
active transport

132. COLLECTING DUCT
• More water leaves the
tube by osmosis, since the
tube is surrounded by salty
tissue.
• Some urea leaves by
diffusion, and may be
cycled through the system.
• More Na+ and Cl-
reabsorbed by active
transport

134. Summary: REABSORPTION
1. Proximal tubule
• Glucose, amino acid, Na+ and Cl- (active transport)
• Water, HCO3
- (passive transport)
2. Loop of Henle
• Na+ and Cl- (active transport)
• Water (passive transport)
3. Distal tubule
• Na+ and Cl- , HCO3- (active transport)
• Water (passive transport)
4. Collecting duct
• Na+ and Cl- (active transport)
• Water, urea (passive transport)

136. 3. Secretion
• By active transport
• Occurs only in the PROXIMAL TUBULE &
DISTAL TUBULE
• Proximal tubule – NH4-, H+, some drugs
& poisons
• Distal tubule – K+, H+
• Substances not filtered in the glomerulus
are secreted into the renal tubule to be
excreted.
• Reason: 1. To get rid of certain substances
2. To regulate blood pH

138. 1. Urine from collecting
duct drips into pelvis
2. passes via the ureter to
the bladder
3. Stored in bladder
4. Once ~200 cm3 urine
collected, stretch
receptor stimulated
desire to urinate

143. OSMOREGULATION, ADH &
URINE FORMATION

144. In this topic we mention TWO hormones that
affect the kidneys:
Urine
ADH
(antidiuretic
hormone)
Posterior
pituitary
Adrenal cortex
Aldosterone

145. ADH :
1. increases the permeability of the distal
convoluted tubule and collecting duct to
water
More ADH, more water is reabsorbed.

146. 2. increases the permeability of the collecting
duct to urea
1. Urea moves into
medulla
2. Medulla becomes
concentrated
RESULT:
3. Water moves out of
descending limb

147. ADH is released when osmoreceptors:
detect a low level
of water in blood
kidney

148. Water
Salts
Fig. 21 The effect of ADH on the permeability of the distal
convoluted tubule and collecting duct to water
Blood too concentrated
ADH level high
Blood too dilute
ADH level low
Dilute
urine
Urine
concentrated Water
Salts

150. Reabsorbing water
If you have too
little water in your
blood, you will
produce very
concentrated urine.
(very little water in
it)
If you have too
much water in your
blood, you will
produce very dilute
urine.
(lots of water in it)

152. Water level regulation by
negative feedback control

153. Water content
of the blood normal
Water content of
the blood HIGH
Water content of
the blood LOW
Too much water drunk
Too much salt
or sweating
Brain
produces
More ADH
Urine output
LOW
Brain
produces
Less ADH
Urine output
HIGH
High volume of water
reabsorbed by kidney
Low volume of water
reabsorbed by kidney
(small volume of
Concentrated urine)
(large volume of
dilute urine)

154. Release of ADH from the posterior
pituitary is inhibited by drinking
alcohol & caffeine.
How would this affect urination?
Increases
ADH

155. Failure to release sufficient ADH leads to a
condition: DIABETES INSIPIDUS
large quantities of dilute urine are produced
could lead to dehydration  death

156. ALDOSTERONE:
 is secreted by the adrenal cortex
 stimulates sodium reabsorption in the
nephron
 stimulates excretion of potassium
ions
Control of Blood Sodium Level:
Aldosterone is a:
Steroid hormone

157. Aldosterone causes:
2. K+ to move into
lumen & ends
in urine
1. Na+ ions to be pumped
from distal tubule into
the blood capillaries
TS distal
tubule
K+
Na+
RESULT OF more Na+ in
blood is….
More aldosterone secreted,
more Na+ ions reabsorbed
from distal tubule into the
blood capillaries

158. A decrease in blood Na leads to a
decrease in blood volume. WHY?
Because less water enters the
blood by osmosis.
Less water =
reduction in blood pressure

159. b) Complete the table below by filling in the empty
spaces with the appropriate answers: (3)
Hormone Site of
production
Effect
Antidiuretic
hormone
Hypothalamus
Stimulates distal
convoluted tubule and
collecting duct to
reabsorb water
Aldosterone
Adrenal
cortex
Stimulates excretion of
potassium ions and
reabsorption of sodium
ions in the nephron

160. Factors that affect kidney
function
• Antidiuretic hormone (ADH) – prevents excess
water loss from kidneys
• Alcohol – inhibits secretion of ADH = more
urine volume
• Aldosterone – prevents excess loss of sodium and
water from kidneys
• Caffeine – increases rate of salt and water loss
from kidneys
• Increased blood pressure – increase rate of water
loss from kidneys.

161. IIMPAIRED KIDNEY
FUNCTION

163. Kidney transplant

165. HAEMODIALYSIS

166. HAEMODIALYSIS

168. HAEMODIALYSIS VIDEO

169. KIDNEY STONES

170. KIDNEY STONES

171. Cause of kidney stones
• Exact cause of kidney stones
cannot always be found,
although they are usually
formed following a build-up
of a substance such as
calcium.
• The leading cause of kidney
stones is a lack of water.
• A kidney stone is formed
when a small speck of
mineral settles out of the
urine into the kidney or the
ureter, a tube that links the
kidney to the bladder.

173. Control of Blood pH

174. Longer-term adjustments in the ion balance of
the blood :
are made in the distal convoluted tubule
If the pH falls below 7.4:
distal tubule cells
secrete H+ into the urine
If the pH rises:
Distal tubule cells
secrete OH- & HCO3
-
into the urine
H+
HCO3
-
OH-

175. Manneken Piss [Brussels, Belgium]

176. THE END OF URINARY SYSTEM