1. Unit 4
Excretion & Waste
Management
(Chapter 16: Page
303 – 317)

2. EXCRETION
VIDEO

4. Excretion
• Every metabolic process in the human
body uses energy and generates wastes.
• The process of getting rid of metabolic
wastes is called excretion.
• There are many organs and systems
responsible for excretion:
– the skin
– the lungs
– the liver
– the kidneys

5. Excretion

6. Excretion and Homeostasis
• Cells produce water and carbon dioxide as
by-products of metabolic breakdown of
sugars, fats, and proteins.
• Chemical groups such as nitrogen, sulfur,
and phosphorous must be stripped, from
the large molecules to which they were
formerly attached, as part of preparing
them for energy conversion.
• Excretion aids homeostasis by removing
metabolic wastes and regulating the salt
and water balance.

7. Excretion and Homeostasis
• The blood picks up carbon dioxide,
excess salts, nitrogen compounds, and
any excess water that may be present in
the interstitial fluid and carries them to
the excretory organs, which channel the
wastes out of the body.
• Therefore, the excretory system
regulates volume of internal body fluids
as well as eliminates metabolic wastes
from the internal environment.

8. Excretion and Homeostasis
• Several organs take part in human
excretion. The skin, lungs, liver, and the
kidneys.
• The metabolic wastes produced and
the organs that excrete them are
summarized in the chart on the next
slide.

9. Organ of
Wastes Formed From
Excretion
1. Carbon Cellular Respiration lungs
Dioxide
2. Water Cellular Respiration & kidneys,
Dehydration Synthesis skin, lungs
3. Nitrogenous Metabolism of Proteins (Amino kidneys,
Wastes Acids) liver, skin
a) Ammonia deamination of amino acids by liver
(extremely toxic) the liver
b) Urea ammonia combined with carbon kidneys,
dioxide skin
product of the breakdown of
c) Uric Acid liver
nucleic acids, such as DNA
4. Mineral Salts Metabolism of Various Food kidneys,
(NaCl, KSO4) Substances skin

10. Skin and Homeostasis
• The skin has many functions in the body
with excretion being one of them.
• Your skin has approximately 2 million
sweat glands.

11. Skin and Homeostasis
• These glands secrete sweat continuously, even
when you are not exercising.
• Sweat consists primarily of water, along with
salts, and some urea (nitrogen-based waste).
These materials pass from the blood vessels in
the skin into the sweat glands. The wastes
travel up the tubules and onto the surface of
the skin through tiny openings called pores.
• The wastes form perspiration on the skin,
which eventually evaporates. The solid wastes
in the perspiration remain on the surface of
the skin or on clothing.

12. Skin and Homeostasis

13. Excretion in the Lungs
• Carbon dioxide and water are produced by
all cells during cellular respiration.
• The blood carries these to the lungs.
• Carbon dioxide diffuses into the alveoli
and is removed from the body when we
exhale.
• Some water also leaves the lungs as water
vapour.

14. Excretion in the Lungs

15. The Role of the Liver in
Excretion
• Some proteins and other nitrogenous
compounds are broken down in the liver by a
process called deamination.
• The extraction of energy from proteins
produces ammonia (NH3), a highly toxic
substance. The liver converts ammonia to a
non-toxic substance called urea by combining
it with carbon dioxide.
• The blood then delivers urea to the kidneys,
where it is excreted.

16. The Role of the Liver in Excretion
• The liver also breaks down red blood cells.
• The liver is also responsible for removing
potentially hazardous chemicals from the
blood. It "detoxifies" the blood.
• The liver breaks down harmful and
foreign substances, such as many
ingested poisons and drugs after they are
absorbed by the digestive system and
before they reach the rest of the body.

17. The Role of the Liver in
Excretion

18. The Urinary System

19. The Urinary System
• The human urinary system consists of
two kidneys, two ureters, the urinary
bladder, and the urethra. Normally,
there are two of kidneys, one on either
side of the spine under the lower ribs.
The ureters lead from the kidneys to
the urinary bladder, which lies low in
the abdominal cavity. The urethra
extends from the bladder to the
exterior of the body, carrying urine
through the urogenital organs, either
the penis or vagina.

21. Importance of Kidneys
 Your kidneys are important because
they do these essential things.
1. Regulate water
2. Remove wastes
3. Produce hormones

22. Importance of Kidneys

23. Structure of Kidneys
• Kidneys are reddish brown in colour and
shaped like kidney beans. Each kidney is
about the size of your clenched fist. If you
were to cut a kidney in half, you would see
the following parts:
– renal capsule - a thin, outer membrane
that helps protect the kidney
– cortex - a lightly colored outer region
– medulla - a darker, reddish-brown,
inner region
– renal pelvis - a flat, funnel shaped
cavity that collects the urine into the
ureters

25. The Nephron

26. The Nephron
• The working units of the kidney are
microscopic structures called nephrons. Each
kidney contains about one million nephrons.
• A nephron contains a network of capillaries
called the glomerulus, which filters blood into
a cup-shaped structure known as the
Bowman's capsule. The filtrate then passes
into a series of tubules. Water and waste
products are separated from the blood by the
filtering process and the flow into and out of
the tubules. Much of the water is reabsorbed
by the tubules and the wastes are
concentrated into urine.

27. The Nephron

28. The Nephron
The nephron is a tube; closed at one end,
open at the other. It consists of a:
– Glomerulus - coiled capillaries inside the
Bowman's capsule.
– Bowman's (Glomerular) capsule -
closed end at the beginning of the
nephron. It is located in the cortex.
– Proximal convoluted tubule - first
twisted region after the Bowman's
capsule. It is also in the cortex.

29. • Loop of Henle - long, loop after the
proximal tubule. It extends from the
cortex down into the medulla and
back.
• Distal convoluted tubule - second
twisted portion of the nephron after
the loop of Henle. It is also in the
cortex.
• Collecting duct - long straight
portion after the distal tubule that is
the open end of the nephron. It
extends from the cortex down
through the medulla.

31. The nephron also has a unique and rich blood
supply compared to other organs. They are
listed below.
– Renal artery - supplies blood to the kidney
from the circulatory system
– Renal vein - returns blood from the kidney
to the circulatory system
– Afferent arteriole - connects the renal
artery with the glomerular capillaries.
– Efferent arteriole - connects the
glomerular capillaries with the peritubular
capillaries.
– Peritubular capillaries - located after the
glomerular capillaries and surrounding the
proximal tubule, loop of Henle, and distal
tubule.

32. Kidney Function
• Many of the substances in the blood and
body fluids must be kept at the correct level
for the body to function properly. Regulating
the composition of these fluids involves the
following:
– Keeping the concentrations of various
ions and other important substances
constant.
– Keeping the volume of water in your body
constant.
– Removing wastes from your body.
– Keeping the acid/base concentration of
your blood constant.

33. Kidney Function
The kidney performs these functions by a
combination of:
• Filtration - the passage of substances
through the capillaries of the
glomerulus into Bowman's capsule.
• Reabsorption - the transfer of essential
solutes and water from the nephron
back into the blood
• Secretion - the movement of materials
from the blood back into the nephron.

35. The Kidney & the Nephron

36. Formation of Urine
• The nephron makes urine by:
– filtering the blood of its small
molecules and ions and then
– reclaiming the needed
amounts of useful materials.
– Surplus or waste molecules
and ions are left to flow out as
urine.

37. Formation of Urine
The steps include:
• Blood enters the glomerulus under pressure.
• This causes water, small molecules (but not
macromolecules like proteins) and ions to filter
through the capillary walls into the Bowman's
capsule. This fluid is called the filtrate.
• The filtrate collects within the Bowman's capsule and
then flows into the proximal tubule.
• Here large amounts of glucose, amino acids, and salts
are reabsorbed by active transport.
• As these solutes are removed from the filtrate, a
large volume of the water follows them by osmosis.

38. Formation of Urine
The steps include:
• As the fluid flows into the loop of Henle, it is
approximately isotonic to the blood. Here
more sodium ions are pumped out, but water
does not follow them. So, the interstitial fluid
becomes very hypertonic and the fluid within
the loop of Henle becomes hypotonic.
• In the distal tubules, more sodium is reclaimed
by active transport. The amount is closely
regulated, chiefly by the action of the
hormone aldosterone. Water may follow by
osmosis.

39. Formation of Urine
The steps include:
• The final adjustment of the water content of
the body occurs in the collecting ducts.
• The permeability of this tubule can vary
depending upon the bodies need.

40. Formation of Urine
Reabsportion of Water:
– Hormonal control of collecting duct
permeability
• Blood too concentrated in solutes
–Posterior pituitary releases ADH
(antidiuretic hormone)
»Increases permeability of
collecting duct to water
»More water is reabsorbed
from filtrate (urine)
»Small volume of hypertonic
urine produced

41. Formation of Urine
Reabsorption of Water:
– Blood too diluted
–ADH shut off
–Collecting duct decreases
permeability to water
–More water lost in urine
–High volume of dilute urine
produced

42. Formation of Urine
• Diuretics
– Increase flow of urine
– Alcohol
• Shuts off ADH
• Dehydration causes hangover
– Caffeine
• Increases glomerular filtration rate
• Decreases tubular reabsorption of
sodium

44. Kidney Failure
• In the event of kidney failure due to infection
or disease, the kidney can no longer remove
metabolic waste products from the body.
Excretion of metabolic waste is a vital function
and their accumulation will result in eventual
death.
• There are a number of known causes of kidney
failure but in quite a few people, the cause is
never found. The most common causes are
diabetes, high blood pressure and a painless
inflammation of the kidneys called
glomerulonephritis. There is a progressive loss
of the filtering units (nephrons) in the kidney.

45. Kidney Failure
• If the kidneys are damaged, they may carry on
producing urine but become less efficient at
removing waste products from the blood.
Instead, the waste products continue to circulate
and build up in the bloodstream.
• At the same time, without the hormones that a
healthy kidney would produce, the bone marrow
becomes less efficient at producing red cells, so
anaemia develops.

46. Kidney Failure
• For some patients, this may be a very gradual
process. Over time, however, it can cause quite
a wide range of symptoms. Not everyone will
experience all the symptoms. Also, because it
can be such a gradual process, some people
don’t even realize the effect the symptoms are
having until - with treatment - they begin to feel
better.
• There are two solutions to the problem of
kidney malfunction or failure:
– Kidney transplant (the best solution)
– Kidney dialysis

47. Dialysis
• Dialysis is a way to clean the blood by removing
wastes and excess water. There are two types:
hemodialysis and peritoneal dialysis.
• Hemodialysis
– During hemodialysis, the blood is passed
through an artificial kidney. The artificial
kidney cleans the blood in almost the same
way that healthy kidneys do. The treatment is
performed usually three times a week. It can
take between three and five hours each time
and is called a run.

48. Dialysis – Hemodialysis continued
• Hemodialysis
– Hemodialysis can be done in a hospital dialysis unit, in a self-
care centre (with some assistance from the staff), or at home
with the aid of a partner. Special training is required for self-
care or home dialysis.

49. Dialysis
• Peritoneal Dialysis
– Peritoneal dialysis works on the same
principle as hemodialysis, but the blood
is cleaned inside the body rather than
through an artificial kidney. Your
abdomen or "belly" has a peritoneal
cavity lined by a thin membrane called
the peritoneum that surrounds the
intestines and other internal organs.

50. Dialysis – Peritoneal Dialysis continued
• Peritoneal Dialysis
– In peritoneal dialysis, your peritoneal cavity is
filled with a special dialysis fluid. Excess water
and wastes pass through the peritoneum into
the dialysis fluid. This fluid is then drained from
the body and discarded. The process is
repeated between four to five times a day or a
machine called an automatic cycler can
perform exchanges while you sleep. In most
cases, this treatment can be performed
without assistance, at home or at work.
Peritoneal dialysis is sometimes done in a
hospital, but more often, you are trained to do
this independently at home.

51. Kidney Transplant
• A kidney transplant is a surgical
procedure in which a healthy donated
kidney is transplanted into another
body. A successful kidney transplant
will allow the person to return to a
more normal lifestyle and will free
them from dialysis treatments.
• There are two types of kidney
transplants: a living donor transplant
and a cadaveric transplant.

52. Kidney Transplant
• A Living Donor Transplant
– In a living donor transplant, a kidney from a
donor, usually a blood relative is transplanted.
The most suitable donors are usually members
of the immediate family.
– The donor's blood group and tissue type must
be compatible, and extensive medical tests will
be done to determine the health of the donor.
People who donate a kidney can live a normal
life with one kidney and there are few risks to
healthy donors.
– Living donor transplants have a 90 to 95%
success rate. That means that after one year,
90 to 95 of every 100 transplanted kidneys are
still working.

53. Kidney Transplant
• A Cadaveric Transplant
– A transplant from a non-living donor is
called a cadaveric transplant. In this type
of transplant, a healthy kidney from
someone who has died suddenly is
transplanted. Before a cadaveric donor's
organs can be transplanted, a series of
medical tests is done to determine if they
are healthy. In addition, the family of the
donor must consent to organ donation.
– After a series of tests, the person will be put
on a transplant waiting list until a kidney is
found that is compatible.
– Cadaveric transplants have an 80 to 85%
success rate.

54. Kidney Transplant

55. You are a doctor
Imagine you are a new doctor who has received
test results for a patient showing signs of renal
failure. Your task is to prepare an explanation
for the patient on what the problem is, within the
context of what normal kidney function looks
like, and what the treatment options are
(dialysis and transplant). You must describe the
options in detail, including pros and cons. Your
preparation will take the form of a written report,
which will be shared with fellow doctors to
confirm your
information. This patient is in dire need of help,
therefore you must have this report completed
ASAP.

56. You are a doctor
Assessment:
Students must prepare a written submission, which
will be evaluated by the teacher. Criteria for the
written piece includes:
• Explanation of kidney function is clear and complete
• Appropriate terminology is used
• Diagrams are included
• Accurate explanation of the consequences or renal
failure are included
• Description of treatment option is clear, concise,
accurate, understandable by patient and includes
pros and cons

57. Diabetes

58. Testing for Healthy
Kidney Function
• Healthy kidneys remove wastes and
excess fluid from the blood.
• Blood tests show whether the kidneys are
failing to remove wastes.
• Urine tests (urinalysis) can show how
quickly body wastes are being removed
and whether the kidneys are leaking
abnormal amounts of protein.

59. Making the Strange
Sound Familiar
• Make the following comparison:
– The excretory system is like an automobile
because . . .
– The excretory system is not like an automobile
because . . .
– The excretory system is like an house
because . . .
– The excretory system is not like an house
because . . .

60. Print Master
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