Topic 11 Excretion

1. Observe the solutions A & B!
Compare the colour!
Compare the volume!
Compare the smell!
Compare the temperature!
(optional) Compare the
texture!
(optional) Compare the taste!

2. Subject X
Urine collect from
this boy an hour
after he drank 1
litre of water.

3. Subject Y
Urine collected
from this energetic
boy who did not
drink any water for
the past 5 hours.

4. Which sample belongs to
subject X?
 Which sample belongs to
subject Y?
Why???

5. Chapter 11
Part 1Excretion in
Humans

6. define excretion and explain the
importance of removing wastes
from the body.
to identify and state the functions
of different parts of the urinary
system.

7. • Removal of metabolic wastes &
toxic materials
• Metabolism = all the chemical
activities in living cells
Metabolism = Catabolism + Anabolism

8.  Chemical processes that cause the
breakdown of complex substances
into simpler ones
 Examples:
1) Aerobic or anaerobic respiration
2) Deamination of proteins and
excess amino acids in the liver to
form urea.
3) Digestion of food substances

9.  Chemical processes that form
complex substances from simpler
ones
 Examples:
1) Photosynthesis
2) Conversion of glucose into
glycogen or starch
3) Synthesis of new cells

10.  Excreted substances are:
 Carbon dioxide?
 Can change the pH level of blood plasma
 Water?
 Can change the water potential in the
blood plasma
 Urea?
 Can be toxic if accumulated to high
amounts
 Not useful to the body, excrete!

11. Excretory product Excretory organ
Carbon dioxide
Lungs  excreted
during exhalation
Urea Kidneys 
excreted in the
form of urineExcess water

13. CENSORED

14.  A pair of dark red, bean-
shaped organs
 They are attached to the
dorsal body wall, one on
each side of the spinal
cord
 The left kidney is slightly
higher than the right one
(Why ley?)

16. a) Ureter:
– A narrow tube
carrying urine
from the kidneys
to the bladder
– By peristalsis
b) Renal Pelvis:
– The enlarged
portion of the
ureter inside the
kidney

17. c) Urinary Bladder:
A hollow muscular bag
used to store urine
temporarily
d) Sphincter muscles:
Relaxes to allow urine
to flow from the bladder
to the urethra
e) Urethra:
A tube which carries
urine out of body

18.  Each kidney is covered by
an outer layer of
protective cells called the
capsule
 It has 2 main regions:
 Medulla
 Cortex

19.  Medulla
 the inner region
 In man, it is split into
12 -16 conical
structures, called the
pyramids
 Cortex
 the outer region

20.  The functional unit of the
kidney
 Part of it is located in the
medulla, part of it is located
in the cortex
 Urine is formed in the
nephron
 About 1 million in each kidney
 Each is about 3 cm in length
 Total length: about 60 km

22. • The renal artery brings
blood from the body into
the kidneys.
• It branches into
numerous afferent
arterioles.
• Each arteriole branches
into a mass of blood
capillaries in the renal
capsule
Blood from the body

23. • This mass of
blood capillaries
is called the
glomerulus.
Glomerulus
+
Renal Capsule
Malpighian (Renal)
Corpuscle

24. • Blood leaves the
glomerulus through
the efferent arteriole
and enters blood
capillaries
surrounding the
tubule.
• These blood
capillaries then unite
to form the renal vein
Blood leaves the kidneys

25.  Small
substances are
forced under
high pressure
from the
glomerulus into
the renal capsule
Ultrafiltration
occurs here

26.  The renal capsule
leads into the
Proximal
Convoluted
Tubule
Selective reabsorption
occurs here

27.  The proximal
convoluted tubule
straightens out as
it passes into the
medulla, makes a
U-turn & passes
back into the
cortex
Selective reabsorption
continues here

28.  Distal Convoluted
Tubule: The tubule
then becomes coiled
again
Selective reabsorption
continues here

29.  It then leads into a
Collecting Duct and
eventually leads into
the renal pelvis
Selective reabsorption
continues here

30. Time for activity!

31. Different in diameter
Afferent has a bigger
diameter than efferent
So what???

32. Topic 8: Chapter 11
Part 2
Excretion

33. Excretion
Waste Products removed by the Kidneys
Excess
Mineral Salts
Nitrogenous waste
• Mainly urea
• Creatinine
• Uric acid
Excess H2O

34. Right Kidney Left
Kidney
Sphincter
Muscle
Inferior Vena
Cava
Dorsal Aorta
Renal Artery
Renal Vein
Ureter
Ureter
Urinary Bladder
Urethra

35. Role of the Kidney
Carry out High Pressure Filtration of the blood to
achieve 2 functions
Removal of Urea
and toxins from
the blood
Osmoregulation
Maintain a
constant blood
plasma
concentration

36. Renal Cortex
Medulla
The Right Kidney

37. The Nephron
Proximal
Convoluted Tubule
Descending Limb of
Loop of Henle
Ascending Limb of
Loop of Henle
Distal Convoluted
Tubule
Bowman’s
Capsule
Glomerulus
Collecting
Duct
Blood
Capillaries

38. Ultrafiltration
Forced out of blood into kidney tubules Remains in the blood
Water RBC
Platelets
Blood Proteins (e.g Fibrinogen)
Small Solute Molecules
• Glucose
• Amino Acids
• Nitrogenous waste products
(especially Urea)
• Mineral Salts
2 conditions required:
1) High Blood Pressure – Afferent
arteriole has a larger diameter
than the efferent arteriole
2) Partially permeable membrane
– Basement membrane of
glomerulus has small pores that
allows only water and small
molecules to pass through

39. Diffusion and
Active transport of
•Ions (Na+, Cl-)
•Amino Acids
•Glucose
Back into the
bloodstream
1
Water potential
gradient created
H2O flows out of
tubule into the
blood capillaries by
Osmosis
2
* Descending Limb is
impermeable to Na+ and Cl- ions
As the filtrate moves
through the Distal
tubule and down the
Collecting Duct, more
H2O is reabsorbed
from the filtrate by
Osmosis
* Ascending Limb is
impermeable H2O
4
Na+ and Cl- ions
leaves the Ascending
Limb into the
interstitial fluid and is
reabsorbed into the
bloodstream by
Diffusion & Active
Transport
Proximal Convoluted Tubule
Proximal Convoluted
Tubule + Descending Loop
of Henle
Distal convoluted Tubule +
Collecting Duct
Ascending Limb + Distal
Convoluted Tubule
Selective
Reabsorption
3
Interstitial
Fluid
2
1
H2O
H2O
H2O
H2O
Na+
Cl-
3
H2O
H2O
H2O
H2O
H2O
H2O
4
Urine to Ureter
H2O
Na+
Cl-

40. Flows through
Ureter
Urinary Bladder
Bladder wall is stretched
Bladder muscle will contract
Urine from the urinary bladder flows into the urethra
To the
Urine flows out of the body
Urine
Urea + Other nitrogenous waste (Creatinine, uric acid) +
Excess Salts and ions + Excess water

41. Topic 8: Chapter 11
Part 3
Excretion

42. • Maintenance of a constant water potential
in the body
• by regulating the water and solute levels
in the blood
• This is an example of homeostasis (the
maintenance of a constant internal
environment)

43. Absence of osmoregulation - Effects
• Blood plasma water potential will be higher than the surrounding
cells and tissues
• Water will enter the blood cells and surrounding tissue cells by
osmosis
• Cells will swell and burst
Blood plasma too dilute
Blood plasma too concentrated
• Blood plasma water potential will be lower than the
surrounding cells and tissues
• Water will leave the blood cells and surrounding tissue cells by
osmosis
• Cells will shrink and crenate and be unable to perform its
metabolic functions

44. Kidneys as osmoregulators
1) Hypothalamus
• Control centre in the brain which controls body activities (e.g
temperature regulation, blood plasma regulation and other
involuntary responses in the body)
2) Pituitary gland
• Releases hormones (e.g Antidiuretic Hormone) which are
transported in the bloodstream to target organs to carry out its
effect
3) Antidiuretic Hormones (ADH)
• Increases water reabsorption by the kidney tubules back to the
bloodstream
• Causes vasoconstriction of arterioles
Organs/Glands/Hormones involved in osmoregulation

45. The pituitary gland

46. Negative
feedback
mechanis
m
1) Blood Plasma •volume drops
• water potential decreases
• volume increases
• water potential increases
Stimulus
2) Receptors in the
Hypothalamus
Are triggered Are triggered Receptor
3) Pituitary Gland Releases more ADH Releases less ADH Corrective
mechanisms
which brings
about a response
4) Distal Convoluted
Tubule and
Collecting Duct
More permeable to water Less permeable to water
5) Effect: More water reabsorbed
back to the bloodstream
Less water reabsorbed back
to the bloodstream
6) Urine •Becomes more
concentrated
• Volume decreases
• Becomes more dilute
• Volume increases
Effect
7) Blood Plasma • Volume increases
• Water potential increases
• Volume decreases
• Water potential decreases
Water potential returns to normal
• Hypothalamus detects the
normal blood plasma
water potential and
decreases the release of
ADH by the pituitary
gland.
• Hypothalamus detects the
normal blood plasma
water potential and
increases the release of
ADH by the pituitary
gland back to the normal
level.
Negative
feedback to
resume normal
activity of
pituitary gland
Water lost
through
sweat
Water
gained
through
drinking

47. • Sodium chloride concentration in the blood
plasma also has an effect on the water potential
of the blood plasma.
• If sodium chloride content in the blood plasma
is high,
• Sodium and chloride ion re-absorption from the
glomerular filtrate back to the bloodstream will
be reduced.

48. Kidneys controlling blood
pressure
Blood Volume Diameter of blood vessels
High blood pressure High Narrow
Low blood pressure Low Wide
How are the kidneys involved in
the treatment of high blood
pressure?
• By the prescription of “Diuretics”
• Reduces the reabsorption of water from the distal
convoluted tubule and collecting duct back to the
blood capillaries
• Blood volume decreases, Urine volume increases
• Blood pressure decreases

49. Topic 8: Chapter 11
Part 4Excretion

50. - Partially -Permeable
- Allows small molecules
to pass:
• Water
• Sugars
• Salts
• Amino acids
• Urea
- Long and coiled to
increase SA to VR for
exchange of substances
Consists of: Purpose:
• H2O at a preset
temperature
To maintain an environment as close
to the body as possible
•Normal
concentrations of
essential substances
as blood: (1)Glucose,
(2)Mineral Ions,
(3)Amino Acids
- To ensure similar osmotic
concentrations on both sides of
tubing. (Minimize loss of water and
essential substances from blood)
•Blood and Dialysis
Fluid flow in opposite
directions
- To create and maintain a diffusion
gradient
•Anti Coagulant Prevent blood from clotting
The Dialysis
Machine
Pump
Dialysis Tube Dialysis Fluid
Pum
p
• Smoothen the blood flow
• Maintain blood pressure
• Maintain speed of blood
flow

51. Difference in the concentration between the blood and dialysis fluid
Results in
Blood is purified
Therefore
Blood is drawn from an artery in the patient’s arm
• Diffusion of urea and waste products down a concentration
gradient
• Diffusion of excess mineral down a concentration gradient
• Movement of excess water out of blood by osmosis
• Diffusion of essential mineral salts if lacking in blood
Blood to Dialysate
Dialysate to Blood
Blood is returned to a vein in the patient’s arm

52. Difference between the Dialysis Machine and the Nephron
Dialysis Machine Nephron
Filtration does not take place Ultrafiltration occurs at the
Bowman’s Capsule
The pump keeps the blood
pressure constant throughout
the tubing
Blood is under great pressure
No active transport of solutes Active transport of solutes at
the proximal and distal
convoluted tubule, and loop of
Henle.
Depends largely on diffusion Depends largely on active
transport and osmosis. Minimal
diffusion

53. Name: …………………………… ( ) Class: ……… Date: ……….………
Diagram of a Kidney

54. Diagram of a Kidney Tubule (Nephron)

55. Renal Cortex
Medulla
The Right Kidney