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People with kidney failure (腎衰竭 ) must be treated immediately.
3
Otherwise, they may die quickly.
4
They can eitherundergo a kidney transplant (移植 ).
transplanted kidney
5
They can eitheruse a kidney machine (洗腎機 ).
6
They can eitherundergo peritoneal dialysis (腹膜透析 ).
dialysis fluid in
dialysis fluid out
4 hours later
7
They also have to make some changes in their diet.
8
e.g. avoid taking too much fluid and high-protein food.
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Why may a person die quickly if thekidneys fail to function1
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How does a kidney machine treatkidney failure2
11
Why can’t people with kidney failuretake in too much fluid and high-protein food
3
12
1.1 Importance of regulating water content
water intake
water loss
balanced
13
•Figure 20-2
Water Balance in the BodyWater Balance in the Body
14
• Land animals manage water budgets by drinking and eating moist foods and using metabolic water
•Water
•balance in a
•kangaroo rat
•(2 mL/day)
•Water
•balance in
•a human
•(2,500 mL/day)
•Water
•gain
•Water
•loss
•Derived from
•metabolism (1.8 mL)
•Ingested
•in food (0.2 mL)
•Derived from
•metabolism (250 mL)
•Ingested
•in food
•(750 mL)
•Ingested
•in liquid
•(1,500 mL)
•Evaporation (900 mL)
•Feces (100 mL)•Urine
•(1,500 mL)
•Evaporation (1.46 mL)
•Feces (0.09 mL)•Urine
•(0.45 mL)
15
• if water intake water loss affects water content in blood affects water potential of tissue fluid water enters or leaves cells by osmosis cells do not function properly or
even die
1.1 Importance of regulating water content
16
control of the water content in the body
control of the water content in the body
osmoregulation (滲透調節 )
osmoregulation (滲透調節 )
done by kidneys of urinary system (泌尿系統 )
done by kidneys of urinary system (泌尿系統 )
1.1 Importance of regulating water content
17
1 keeps the water potential of the tissue fluid and hence the water potential of the cells stable, so that cells can function properly to sustain life.
Osmoregulation
1.1 Importance of regulating water content
18
2 The of thesystem are the major organs for osmoregulation.
kidneys
1.1 Importance of regulating water content
urinary
19
1.2 The human urinary system
(dorsal aorta)
female
(posterior vena cava)
(renal artery)
(renal vein)
20
1.2 The human urinary system
female
kidneys
ureters
urinary bladder
21
1.2 The human urinary system
female
sphincter muscles
control urinationcontrol
urination
22
1.2 The human urinary system
female urethramale
23
1.2 The human urinary system
male
ureters
urinary bladder
(vas deferens)
urethra
(penis)
24
1.1
Examination of the mammalian urinary system
Video
1.2 The human urinary system
1 Examine the urinary system of a dissected rat.
2 Identify the structures.
25
1.2 The human urinary system
Structure of the kidney3D model
cortex (皮質 )medulla ( 髓 )pelvis (腎盂 )
renal vein
renal artery
ureter
26
1.2 The human urinary system
Structure of the kidney
27
1.2 The human urinary system
Structure of the kidney
cortex
medulla
28
1.2 The human urinary system
Structure of the kidney
branch from renal artery
branch from renal vein
29
1.2 The human urinary system
Structure of the kidneynephron (腎元 )
30
•Filtration
•Reabsorption
•Secretion
•Excretion
•Excretory
•tubule
•Capillary
•Filtrate
•Urin
e
Key functions of most excretory systems:
•Filtration: pressure-filtering of body fluids
•Reabsorption: reclaiming valuable solutes
•Secretion: adding toxins and other solutes from the body fluids to the filtrate
31
1.2 The human urinary system
Structure of the kidney
Bowman’s capsule
proximal convoluted tubule
collecting duct
distal convoluted tubule
loope of Henle
kidney tubulekidney tubule
32
1.2 The human urinary system
Structure of the kidney
Bowman’s capsule
proximal convoluted tubule
collecting duct
distal convoluted tubule
flow of urine
from another nephron
loop of Henle
33
1.2 The human urinary system
Structure of the kidney
glomerulus
Bowman’s capsule
kidney tubule
34
Capillary Beds of the Nephron
• Every nephron has has twotwo capillary beds capillary beds– Glomerulus – Peritubular capillaries
• Each glomerulus is: – Fed by an afferent arteriole – Drained by an efferent arteriole
35
1.2 The human urinary system
Blood supply of a nephron
branch from renal artery
afferent arteriole
glomerulus
efferent arteriole
Peritubular
capillary
branch from renal vein
36
1.2
Examination of the mammalian kidney
1.2 The human urinary system
1 Put a fresh pig’s kidney on a dissection tray.
2 Examine whether there are tubes coming from the kidney. Remove any fatty tissues and identify the tubes.
37
1.2
1.2 The human urinary system
3 Cut the kidney longitudinally.
38
1.2
1.2 The human urinary system
4 Identify various structures of the kidney.
5 Draw a labelled diagram of the longitudinal section of the kidney.
39
1.2 The human urinary system
1 Parts of urinary system
Function
Purify blood and form urine
Carry urine from kidneys to urinary bladder
Kidneys
Ureters
40
1.2 The human urinary system
1 Parts of urinary system
Function
Stores urine temporarily
Carries urine from urinary bladder to the outside
Urinary bladder
Urethra
41
a A nephron consists of the
2 Structure of a nephron:
Bowman’s capsule
1.2 The human urinary system
, theproximal convoluted tubulethe
, distal convoluted tubule
and the .
collecting duct
42
b The Bowman’s capsule encloses a network of capillaries called the
2 Structure of a nephron:
glomerulus
1.2 The human urinary system
. The kidney tubule
is surrounded by another network of capillaries which is continuous with the glomerulus.
43
ultrafiltration(超濾 )
reabsorption(重吸收 )
1.3 Functioning of a nephron• urine is formed by mainly two
processes:
44
Active secretionActive secretion
1.3 Functioning of a nephron• and:
ultrafiltration reabsorption
45
Mechanism of Urine Formation• Urine formation
and adjustment of blood composition involve three major processes – Glomerular
filtration– Tubular
reabsorption– Active
Secretion
•Figure 24.9
46
1 Ultrafiltration• blood is under high
hydrostatic pressure
1.3 Functioning of a nephron
glomerulus
forces small molecules through the thin walls
Bowman’s capsule
• capillary wall is differentially permeable
47
1 Ultrafiltration1.3 Functioning of a nephron
glucose
amino acids
water
salts
urea
48
1 Ultrafiltration• fluid filtered into the
Bowman’s capsule: glomerular filtrate
1.3 Functioning of a nephron
to proximal convoluted tubule
49
1 Ultrafiltration1.3 Functioning of a nephron
to proximal convoluted tubule
water
glucose
amino acids
salts
urea
plasma proteins
• composition similar to plasma
50
Net Filtration Pressure (NFP)• The pressure responsible for filtrate formation• NFP equals the glomerular hydrostatic pressure
(HPg) minus the osmotic pressure of glomerular blood (OPg) combined with the capsular hydrostatic pressure (HPc)
NFP = HPg – (OPg + HPc)
51
Glomerular Filtration Rate (GFR)
•Figure 24.10
52
2 Reabsorption• absorption of useful substances and most
of the water from the filtrate to the blood
1.3 Functioning of a nephron
•Your kidneys filter approximately 180L of plasma/day
•99% of the filtrate gets reabsorbed, leaving 1.5-2 L of urine per day
•Your kidneys filter approximately 180L of plasma/day
•99% of the filtrate gets reabsorbed, leaving 1.5-2 L of urine per day
53
2 Reabsorption1.3 Functioning of a nephron
from renal artery
flow of urine
to renal vein
54
Sodium Reabsorption: Sodium Reabsorption: PrimaryPrimary Active TransportActive Transport
Tubule lumen with renal fluid
55
Glucose Reabsorption: Glucose Reabsorption: SecondarySecondary Active TransportActive Transport
56
Reabsorption: Both Primary and Reabsorption: Both Primary and secondary Active Transportsecondary Active Transport
• Sodium reabsorption is almost always by active transport– Na+ enters the tubule cells
from the lumen / filtrate– Na+ is actively transported
out of the tubules by a Na+-K+ ATPase pump
• From there it moves to peritubular capillaries
• Na+ reabsorption provides the energy and the means for reabsorbing most other solutes
57
Reabsorption by PCT CellsReabsorption by PCT Cells
•Figure 24.12
58
Reabsorption by PCT CellsReabsorption by PCT Cells
• Active pumping of Na+ drives reabsorption of: – Water by osmosis– Anions by diffusion– Organic nutrients and selected ions by
secondary active transport
59
Reabsorption by PCT CellsReabsorption by PCT Cells
•Figure 24.12
60
2 Reabsorption1.3 Functioning of a nephron
proximal convoluted tubule blood
glucose
amino acids
water
salts
amino acids
61
2 Reabsorption1.3 Functioning of a nephron
Substance Substance reabsorbed reabsorbed
Process Process Region where Region where reabsorption occurs reabsorption occurs
Glucose (100%)
Amino acids (100%)
Water (99%)
Salts (80%)
Urea (50%)
Diffusion, active transport
Osmosis
Diffusion, active transport
Diffusion, active transport
Diffusion
At proximal convoluted tubule, loop of Henle, distal convoluted tubule & collecting duct
At proximal convoluted tubule only
62
•Figure 19-5
Filtration FractionFiltration Fraction
63
2 Reabsorption1.3 Functioning of a nephron
• kidney tubule is highly coiled to increase the surface area and the time for reabsorption
64
2 Reabsorption1.3 Functioning of a nephron
• remaining glomerular filtrate in collecting duct is called urine
mostly water with salts, urea and other
metabolic waste
65
Essentially reabsorption in reverse, where substances move from peritubular capillaries or tubule cells into filtrate
• Tubular secretion is important for:– Eliminating undesirable substances such as
urea and uric acid– Controlling blood pH
3. Secretion
66
1.3 Functioning of a nephron
Proteins pass through the walls of the glomerulus and the Bowman’s capsule.
67
1.3 Functioning of a nephron
It is the amino acids that are filtered into the Bowman’s capsule and reabsorbed later.
68
1 In ultrafiltration, the highhydrostatic pressure
1.3 Functioning of a nephron
glomerulus forces small molecules out of the blood into the Bowman’s capsule.
inside the
69
The capillary wall of the glomerulus is1
differentially permeable
1.3 Functioning of a nephron
only allows small molecules to pass through.
and
70
2 The composition of the glomerular filtrate is similar to that of plasma but it contains no .
plasma proteins
1.3 Functioning of a nephron
71
1.3 Functioning of a nephron
a All and
3 Reabsorption along the kidney tubule:
glucose amino acidsin the glomerular filtrate are reabsorbed into the blood by diffusion and active transport.
72
1.3 Functioning of a nephron
b Most is reabsorbed by osmosis.
3 Reabsorption along the kidney tubule:
water
73
1.3 Functioning of a nephron
c Some are reabsorbed by diffusion and active transport.
3 Reabsorption along the kidney tubule:
salts
74
1.3 Functioning of a nephron
d Some is reabsorbed by diffusion and the rest is removed in the urine.
3 Reabsorption along the kidney tubule:
urea
75
1.4 The role of the kidneys
• kidneys carry out osmoregulation by controlling the amount of water reabsorbed from the glomerular filtrate
Osmoregulation
76
• the amount of water reabsorbed is controlled by antidiuretic hormone (ADH) (抗利尿激素 )
1.4 The role of the kidneys
• secretion of ADH is controlled by the hypothalamus (下丘腦 )
77
Diuresis• Diuretics are a group of drugs given to
help the body eliminate excess fluid through the kidneys. e.g. to treat hypertension, glaucoma, et
• Natural diuretic foods and drinks• Melon• Watercress• Coffee• Tea• Coke (caffeinated soda)
78
1.4 The role of the kidneys
hypothalamus• has receptors to
detect water content in blood
• controls secretion of ADH
79
1.4 The role of the kidneys
pituitary gland• secretes ADH
• ADH is transported by blood
80
• under the action of ADH
1.4 The role of the kidneys
permeability of the wall of the collecting duct to water increases
a greater proportion of water is reabsorbed from the filtrate
• urine in different volumes and concentrations can be formed
81
•Figure 20-4
Urine ConcentrationUrine ConcentrationOsmolarity changes as filtrate flows through the
nephron
82
Formation of Dilute Urine / Formation of Dilute Urine / hypotonic urinehypotonic urine
• Filtrate is hypotonic after passing through the loop of Henle
• Dilute urine is created by allowing this filtrate to continue into the renal pelvis
• This will happen as long as antidiuretic hormone (ADH) is not being secreted
• Collecting ducts remain impermeable to water; no further water reabsorption occurs
• Diuresis – hypotonic urine (large volume of)
83
•Figure 20-5b
Water ReabsorptionWater Reabsorption
84
•Figure 20-5a
Water ReabsorptionWater ReabsorptionWater movement in the collecting duct in the
presence of vasopressin (ADH)
85
Formation of Concentrated / Formation of Concentrated / hypertonic Urine hypertonic Urine
• Antidiuretic hormone (ADH) inhibits diuresis
• In the presence of ADH, 99% of the water in filtrate is reabsorbed
• ADH is the signal to produce concentrated urine
• The kidneys’ ability to respond depends upon the high medullary osmotic gradient
86
The kidneys’ ability to make hypertonic urine depends upon the high medullary osmotic gradient
•Click the diagram to
see an animation
87
1.4 The role of the kidneys
receptors in hypothalamus
water content increases
normal water content in blood
wall of collecting duct
pituitary glandless ADH
detected by
less permeablesmaller proportion
of water reabsorbed
larger volume of dilute urine
88
receptors in hypothalamus
water content decreases
normal water content in blood
wall of collecting duct
pituitary glandmore ADH
detected by
more permeable
smaller volume of concentrated urine
greater proportion of water
reabsorbed
1.4 The role of the kidneys
89
•Filtrate
•H2O
•Salts (NaCl and others)
•HCO3– ; H+ (control pH)
•Urea
•Glucose; amino acids
•Some drugs
•Key
•Active transport
•Passive transport •INNER
•MEDULLA
•OUTER
•MEDULLA
•NaCl
•H2O
•CORTEX
•Descending limb
•of loop of
•Henle
•Proximal tubule
•NaCl •Nutrients•HCO3
–
•H+
•K+
•NH3
•H2O
•Distal tubule
•NaCl •HCO3–
•H+•K+
•H2O
•Thick segment
•of ascending
•limb•NaCl
•NaCl
•Thin segment
•of ascending
•limb
•Collecting
•duct
•Urea
•H2O
90
•Figure 20-6
Water Reabsorption Water Reabsorption (reference)(reference)
The mechanism of vasopressin action
Collecting
duct
lumen
Filtrate
300 mOsmH2O
Exocytosis
of vesicles
Cross-section of
kidney tubule
Collecting duct cell
Second
messenger
signal
H2O
cAMP
Storage vesicles
Aquaporin-2
water pores
600 mOsM
H2O
Medullary
interstitial
fluid
Vasopressin
receptor
600 mOsM
Vasa
recta
H2O
700 mOsM
Vasopressin
Vasopressin
binds to mem-
brane receptor.
Receptor activates
cAMP second
messenger system.
Cell inserts AQP2
water pores into
apical membrane.
Water is absorbed
by osmosis into
the blood.
1 2 3 4
1
2
3
4
91
•Figure 20-6, step 1
Water Reabsorption Water Reabsorption (reference)(reference)
Collecting
duct
lumen
Filtrate
300 mOsm
Cross-section of
kidney tubule
Collecting duct cellMedullary
interstitial
fluid
Vasopressin
receptor
Vasa
recta
Vasopressin
Vasopressin
binds to mem-
brane receptor.
1
1
600 mOsM
600 mOsM
700 mOsM
92
•Figure 20-6, steps 1–2
Collecting
duct
lumen
Filtrate
300 mOsm
Cross-section of
kidney tubule
Collecting duct cell
Second
messenger
signal
cAMP
Medullary
interstitial
fluid
Vasopressin
receptor
Vasa
recta
Vasopressin
Vasopressin
binds to mem-
brane receptor.
Receptor activates
cAMP second
messenger system.
1 2
1
2
600 mOsM
600 mOsM
700 mOsM
Water Reabsorption Water Reabsorption (reference)(reference)
93
•Figure 20-6, steps 1–3
Collecting
duct
lumen
Filtrate
300 mOsm
Exocytosis
of vesicles
Cross-section of
kidney tubule
Collecting duct cell
Second
messenger
signal
cAMP
Storage vesicles
Aquaporin-2
water pores
Medullary
interstitial
fluid
Vasopressin
receptor
Vasa
recta
Vasopressin
Vasopressin
binds to mem-
brane receptor.
Receptor activates
cAMP second
messenger system.
Cell inserts AQP2
water pores into
apical membrane.
1 2 3
1
2
3
600 mOsM
600 mOsM
700 mOsM
Water Reabsorption Water Reabsorption (reference)(reference)
94
•Figure 20-6, steps 1–4
Collecting
duct
lumen
Filtrate
300 mOsmH2O
Exocytosis
of vesicles
Cross-section of
kidney tubule
Collecting duct cell
Second
messenger
signal
H2O
cAMP
Storage vesicles
Aquaporin-2
water pores
600 mOsM
H2O
Medullary
interstitial
fluid
Vasopressin
receptor
600 mOsM
Vasa
recta
H2O
700 mOsM
Vasopressin
Vasopressin
binds to mem-
brane receptor.
Receptor activates
cAMP second
messenger system.
Cell inserts AQP2
water pores into
apical membrane.
Water is absorbed
by osmosis into
the blood.
1 2 3 4
1
2
3
4
Water Reabsorption Water Reabsorption (reference)(reference)
95
•Figure 20-7
Factors Affecting Vasopressin ReleaseFactors Affecting Vasopressin Release
96
•Figure 20-8
Water BalanceWater Balance
The effect of plasma osmolarity on vasopressin secretion by the posterior pituitary
97
smaller amount of salts and greater proportion of water reabsorbed
higher concentration of salts in blood
smaller volume of urine with a high salt concentration formed
(hypertonic urine)
taking in excess salts
1.4 The role of the kidneys
98
Regulation of Kidney FunctionRegulation of Kidney Function
• The osmolarity of the urine is regulated by nervous and hormonal control of water and salt reabsorption in the kidneys
• Antidiuretic hormone (ADH) increases water reabsorption in the distal tubules and collecting ducts of the kidney
99
Osmoreceptors
in hypothalamus
Hypothalamus
ADH
Pituitary
•gland
Increased
permeability
Distal
tubule
Thirst
Drinking reduces
blood osmolarity
to set point
•Collecting duct H2O reab-
sorption helps
prevent further
osmolarity
increase
Homeostasis:
Blood osmolarity
STIMULUS
The release of ADH is
triggered when osmo-
receptor cells in the
hypothalamus detect an
increase in the osmolarity of the blood
100
What’s the effect of the following on urine output :
• 1. a lot of water
• 2. a lot of salty foods
• 3. a large volume of salty solution. E.g seawater
AssignmentAssignment: 1.Explain why we cannot survive on seawater as drinking water. 2. Write an essay on how one can survive without drinking water while drifting on a raft in the open ocean (>300 words)
101
• by forming urine
Excretion1.4 The role of the kidneys
to remove metabolic waste (e.g. urea)
102
• by forming urine
Excretion1.4 The role of the kidneys
to remove metabolic waste (e.g. urea)
• constantly produced• high concentration is toxic
103
Diuretics Diuretics (reference)(reference)
• Chemicals that enhance the urinary output include:– Any substance not reabsorbed– Substances that exceed the ability of the renal
tubules to reabsorb it• Osmotic diuretics include:
– High glucose levels – carries water out with the glucose
– Alcohol – inhibits the release of ADH– Caffeine and most diuretic drugs – inhibit sodium ion
reabsorption– Lasix – inhibits Na+-K+-2Cl symporters
104
Physical Characteristics of Physical Characteristics of Urine (reference)Urine (reference)
• Color and transparency
– Clear, pale to deep yellow (due to urobilin) -from the breakdown of heme
– Concentrated urine has a deeper yellow color
– Drugs, vitamin supplements, and diet can change the color of urine
– Cloudy urine may indicate infection of the urinary tract
105
Concentrated urine has a deeper yellow color
106
Physical Characteristics of Physical Characteristics of UrineUrine
• Odor / smell– Fresh urine is slightly
aromatic– Standing urine develops an
ammonia odor– Some drugs and vegetables
(asparagus) alter the usual odor
107
Physical Characteristics of Physical Characteristics of UrineUrine
• pH – Slightly acidic (pH 6) with a
range of 4.5 to 8.0– Diet can alter pH
• Specific gravity– Ranges from 1.001 to 1.035 – Dependent on solute
concentration
108
Chemical Characteristics of Chemical Characteristics of UrineUrine
• Urine is 95% water and 5% solutes• Nitrogenous wastes include urea, uric acid, and
creatinine• Other normal solutes include:
– Sodium, potassium, phosphate, and sulfate ions– Calcium, magnesium, and bicarbonate ions
• Abnormally high concentrations of any urinary constituents may indicate pathology
• Disease states alter urine composition dramatically
109
Functions of the KidneysFunctions of the Kidneys
• Regulation of extracellular fluid volume and blood pressure
• Regulation of osmotic potential in blood
• Maintenance of ion balance
• Homeostatic regulation of pH
• Excretion of wastes
110
secretes less ADHpituitary gland
1.4 The role of the kidneys
1 Regulation of water content by negative feedback mechanism:
normal water content in blood
high water content in blood
hypothalamus kidneys
111
1.4 The role of the kidneys
In the kidneys:
a wall of collecting duct becomespermeable to water
less
b a proportion of water reabsorbed
smaller
c a volume of urine is formed
larger
dilute
112
secretes less ADHpituitary gland
1.4 The role of the kidneys
1 Regulation of water content by negative feedback mechanism:
normal water content in blood
high water content in blood
hypothalamus kidneys
water content in blood falls
113
secretes more ADHpituitary
gland
1.4 The role of the kidneys
1 Regulation of water content by negative feedback mechanism:
normal water content in blood
low water content in blood
hypothalamus kidneys
114
1.4 The role of the kidneys
In the kidneys:
a wall of collecting duct becomespermeable to water
more
b a proportion of water reabsorbed
greater
c a volume of urine is formed
smaller
concentrated
115
secretes more ADHpituitary
gland
1.4 The role of the kidneys
1 Regulation of water content by negative feedback mechanism:
normal water content in blood
low water content in blood
hypothalamus kidneys
water content in blood rises
116
2 After excess salts are taken into the body, the excess salts have to be excreted. A amount of salts and a proportion of water are reabsorbed. As a result, a
smaller
1.4 The role of the kidneys
greater
small
volume of urine with a high salt concentration is formed.
117
3 Excretion is necessary because metabolic waste is constantly produced and a high concentration of this waste is to the body. The kidneys form to remove metabolic waste (e.g. urea) from the blood.
1.4 The role of the kidneys
toxic urine
118
1.5 The dialysis machine
• kidney machineAnimation
• helps remove metabolic waste by haemodialysis (血液透析 )
119
1.5 The dialysis machine
1 blood with metabolic waste
pump dialysis tubing
fresh dialysis fluid
120
1.5 The dialysis machine
dialysis tubing
fresh dialysis fluid
same concentration of solutes as normal plasma but has no metabolic waste
same concentration of solutes as normal plasma but has no metabolic waste
121
1.5 The dialysis machine
dialysis tubing
fresh dialysis fluid
constant temperature bath
dialysis fluid
122
1.5 The dialysis machine
differentially permeable membrane of dialysis tubing
123
1.5 The dialysis machine
2 urea diffuses through the pores to the dialysis fluid
124
1.5 The dialysis machine
3 glucose is retained in blood (no net movement from blood to dialysis fluid
125
1.5 The dialysis machine
4 plasma proteins and blood cells are too large to pass through the pores
126
1.5 The dialysis machine
5 ‘cleaned’ blood
used dialysis fluid (with urea)
127
1.5 The dialysis machine
• each treatment lasts for 4-6 hours• three times a week• costly
128
Peritoneal dialysis
Peritoneal dialysis (PD) is a treatment for patients with severe chronic kidney disease. The process uses the patient's peritoneum in the abdomen as a membrane across which fluids and dissolved substances are exchanged from the blood.
129
Kidney transplant
130
1 A dialysis machine removesmetabolic waste
patient’s blood.
from the
1.5 The dialysis machine
131
2 The dialysis fluid has the same concentration of solutes as normalplasma
1.5 The dialysis machine
This allows metabolic waste to diffuse from the patient’s blood to the dialysis fluid while
but no metabolic waste.
glucoseand other useful substances are retained in the blood.
132
Why may a person die quickly if thekidneys fail to function?1When the kidneys fail to function, the body cannot keep the water content in blood stable for cells to function properly.
133
Why may a person die quickly if thekidneys fail to function?1Besides, metabolic waste builds up in blood which can cause death.
134
How does a kidney machine treatkidney failure?2A kidney machine removes metabolic waste from the patient’s blood by haemodialysis.
135
Why can’t people with kidneyfailure take in too much fluid and high-protein food?
3
Excess proteins in the body are converted to urea by the liver.
136
3
The failed kidney cannot remove excess fluid and urea from the body.
Why can’t people with kidneyfailure take in too much fluid and high-protein food?
137
3
Therefore, excessive intake of fluid and high-protein food must be avoided.
Why can’t people with kidneyfailure take in too much fluid and high-protein food?
138
detected by
is the maintenance of a stable
Osmoregulation
water content in blood
hypothalamus
urinary system
done by
kidneys
main parts include
139
hypothalamus kidneyscontrols secretion of
antidiuretic hormone
functional units
nephrons
controls concentration and volume of
form
urine
140
by
ultrafiltration
kidneysurine
reabsorption helps body remove
fail to function can be treated by
metabolic waste
contains
dialysis machine