IB 11.3 Kidney and osmosregulation

1. 11.3 The Kidney and
Osmoregulation

2. Understandings
• Animals are either osmoregulators or osmoconformers.
• The Malpighian tubule system in insects and the kidney
carry out osmoregulation and removal of nitrogenous
waste.
• The composition of blood in the renal artery is different
from that in the renal vein.
• The ultrastructure of the glomerulus and Bowman’s
capsule facilitate ultrafiltration.
• The proximal convoluted tubule selectively reabsorbs
useful substances by active transport.
• The loop of Henle maintains hypertonic conditions in
the medulla.
• ADH controls reabsorption of water in the collecting
duct.
• The length of the loop of Henle is positively correlated
with the need for water conservation in animals.
• The type of nitrogenous waste in animals is correlated
with evolutionary history.
Applications/Skills
• A: Consequences of dehydration and overhydration
• A: Treatment of kidney failure by hemodialysis or kidney
transplant.
• A: Blood cells, glucose, proteins and drugs are detected in
urinary tests.
• S: Drawing and labeling a diagram of the human kidney.
• S: Annotation of diagrams of the nephron.
Guidance
- ADH will be used in preference to vasopressin
- The diagram of the nephron should include the
glomerulus, Bowman’s capsule, proximal convoluted
tubule, loop of Henle, distal convoluted tubule; the
relationship between the nephron and the collecting
ducts should be included.

3. Osmoregulation
There needs to be a balance between water ingested and
water eliminated
In order to maintain homeostatic levels of water, the body
must undergo osmoregulation
The amount of water eliminated depends on
- amount of water ingested recently
- perspiration rate
- ventilation rate
http://deepeestudios.com/wp-content/uploads/2012/08/drink-lots-of-water.jpg

4. Osmoregulators vs Osmoconformers
Osmoconformers have virtually the same solute
concentration as their environment
Water moves in and out freely due to osmotic balance
Restricted to living in environments which they are iso-
osmotically matched
Osmoregulators have different solute concentrations
than their environment
Have mechanisms to regulate water balance
https://s-media-cache-ak0.pinimg.com/736x/a0/4b/5b/a04b5b6cae29a90688186c565fc63ff0.jpg
http://upload.wikimedia.org/wikipedia/en/thumb/8/8d/Osmoseragulation_Carangoides_bartholomaei_bw_en2.png/290px-
Osmoseragulation_Carangoides_bartholomaei_bw_en2.png

5. Nitrogenous Waste Products
The bloodstream picks up molecular
waste products from tissues. As a
result, it needs to be continuously
filtered in order to remove these
products.
Nitrogenous wastes are waste
products that result from
deamination of amino acids.
Could be ammonia, urea, or uric acid.
Which type of nitrogenous waste is
produced depends on the species
evolutionary history and habitat.
http://images.slideplayer.us/1/257987/slides/slide_45.jpg

6. Waste Product Example Organism Advantages Disadvantages Evolutionary or
habitat relationship
Ammonia Fish Requires little energy
to produce
Very toxic; must be
diluted and removed
quickly by using a
great deal of water
Fish have an
unlimited water
supply to flush out
ammonia
Urea Mammals Requires less energy
to produce than uric
acid; toxic only at
high levels
Requires more
energy to produce;
requires some water
for dilution and
removal
Levels are kept under
control by kidneys;
requires less water
for dilution than
ammonia; can be
stored temporarily in
bladder
Uric Acid Birds Insoluble in aqueous
solutions
(blood/cytoplasm);
can be stored in
specialized structures
in eggs
Requires a great deal
of energy to produce
Since it’s not water
soluble, birds have
independence from
having to find water
frequently

7. Malpighian Tubules
http://bio1152.nicerweb.com/Locked/media/ch44/44_12MalpighianTubules_L.jpg
Small tubes that lie in pools of blood in an insects body
cavity
Closed at one end (distal end)
Opens into the insects gut (proximal end)
Components of the insects blood enter the tubules
Nitrogenous wastes, excess water, and salt ions remain in
the tubules and move to the proximal end that empties into
the gut; gets eliminated
Useful substances are transported back to the blood

8. Renal medulla- layer of tissue
surrounding the renal pelvis
Renal Artery- takes blood into the kidney
Renal vein- drains filtered blood away from
the kidney
Ureter- tube that takes urine to the bladder
Renal cortex- layer of tissue
to the outside of the renal
medulla
Renal pelvis- drains urine into
the ureter
The Kidney
https://classconnection.s3.amazonaws.com/895/flashcards/1528895/jpg/kidney1353974593999.jpg

9. Proximal convoluted tubule Distal convoluted tubule
Nephrons
Glomerulus- capillary bed that
filters substances from the
blood; walls of the capillaries
have fenestrations (small slits)
that open when blood
pressure is increased
Bowman’s capsule- surrounds
glomerulus
Afferent arteriole- brings
unfiltered blood to the
nephron
Efferent arteriole- drains
blood from the glomerulus;
has a smaller diameter than
the afferent arteriole
Afferent arteriole
Efferent arteriole
http://www.biologycorner.com/anatomy/urinary/urinary_images/nephron_labeled.jpg

10. Bowman’s Capsule
Afferent arterioleEfferent arteriole
Glomerulus
The afferent arteriole brings unfiltered blood to the nephron.
Branches into a capillary bed inside the Bowman’s capsule
(glomerulus)
An increase in blood pressure is caused by the decreased
diameter of the efferent arteriole
This causes the fenestrations in the capillaries to open
This leads to the ultrafiltration of the blood
Fluid filtered by the glomerulus passes through the basement
membrane into the proximal convoluted tubule; large molecules
(like proteins) cannot pass through
Blood carrying proteins and other substances not filtered leaves
through the efferent
Basement
membrane
Ultrafiltration
Adapted from:
http://www.mcatzone.com/uploads/gloss/bowmans_capsule.jpg

11. Reabsorption
The filtrate contains some substances that the body needs
(water, some ions, glucose, etc)
Most of these are recovered by reabsorption in the proximal
convoluted tubule
These substances leave the tubule filtrate and are taken back
into the bloodstream via the peritubular capillary bed
- Salt ions leave by active transport; this causes the
filtrate to become hypotonic
- Some water follows the salt ions due to osmotic
pressure
- Glucose is moved out by active transport

12. Loop of Henle
Much of the water remains after the filtrate
leaves the proximal convoluted tubule
It enters the descending portion of the loop
of Henle, which is permeable to water,
relatively impermeable to salt ions
Filtrate then enters the ascending portion of
the loop of Henle, which is permeable to salt
ions, relatively impermeable to water
This makes the interstitial fluid in the renal
medulla hypertonic in relation to the fluid in
the tubules and collecting ducts
*Despite the fact that water left in the descending portion,
the filtrate that moves up the ascending portion and into
the distal convoluted tubule is still relatively hypotonic

13. ADH
The collecting duct is differentially permeable to water
This depends on the presence or absence of antidiuretic
hormone (ADH)
If ADH is present, the collecting duct is permeable to
water and water moves by osmosis out of the duct into
the medulla, enters the capillary bed, and is returned to
the bloodstream
If ADH is absent, the collecting duct is impermeable to
water

14. http://www.patana.ac.th/secondary/science/IBtopics/IB%20Excretion(12)/12.1/variation.gif
Water Conservation
A longer loop of Henle = greater water conservation
Shorter loop= reduced ability to conserve water
- medulla is not made to be hypertonic
- water not reabsorbed from collecting duct
http://media-cache-ec0.pinimg.com/736x/02/8e/58/028e5878580b59f251800e32dcce0d64.jpg

15. Changes Made by the Kidney
Blood leaving the renal vein:
- Lowered amt of urea
- Lowered amt of salt ions
- Lowered amt of water
- Nearly identical amt of glucose
- Nearly identical amt of protein
- No change in blood cells
http://www.bbc.co.uk/bitesize/standard/biology/images/kidney_function.gif

16. http://3.bp.blogspot.com/-KoXDm8FtrKo/TrOEgXWmcaI/AAAAAAAAANY/jXoLArJoMxs/s1600/nephron_structure.jpghttp://img.docstoccdn.com/thumb/orig/152795543.png

17. Kidney Failure
https://commons.wikimedia.org/wiki/File:Hemodialy
Hemodialysis (commonly called kidney dialysis) is a
process of purifying the blood of a person whose
kidneys are not working normally.
Hemodialysis treatment lasts about four hours
and is done three times per week. A person can
be treated this way for years.
The Dialyser contains a
semi-permeable
membrane that allows
small particles (e.g. urea)
to diffuse through, but
larger molecules and
cells remain in the blood
Used dialysate collects
filtered out small
molecules such urea
Fresh dialysate contains:
• No urea – to encourage
diffusion from the blood
• Glucose and other useful
molecules at optimal
concentrations – to
minimize loss from the
blood.
• High solute concentration
removes excess water.
Saline solution prevents
excessive water loss
which could lead to
dehydration.

18. http://www.kalingahospital.com/data/images/transplant1.jpg
A transplant is the best long-term treatment.
Donors can be either:
• Someone who has recently died
• A person who has chosen to give up one of
their two kidneys
Donors and the recipient have to be a close
match in both blood and tissues to minimize
the chance of rejection*.
*If the match is not close enough the recipient's immune system will react to
the new kidney as it would to a pathogen.
The transplanted kidney is grafted in
to the lower abdomen with the renal
artery, renal vein and ureter
connected to the recipient’s blood
vessels and bladder.
Kidney Transplant

19. http://learn.parallax.com/sites/default/files/content/Reference/Urinalysis/Multistix-Urinalysis-Color-Key.png
http://detoxlabs.com/wp-content/uploads/2014/08/pee-cup.jpg
Urinalysis
• Presence of blood cells infections, disease
and some cancers.
• Glucose is a strong indication of diabetes.
• Trace amounts of protein are normal
(some proteins are very small), but larger
amounts indicate kidney disease.
• Drugs (or their breakdown products) can
often be detected in urine samples
Diagnostic tests of urine samples provide an
easy effective way to detect illness and drug
abuse.
Processes that affect the metabolism
affect the metabolic waste that is
produced and then excreted in urine.

20. Dehydration and Overhydration
Dehydration Overhydration
Sleepiness Change in behavior, confusion
Constipation Blurred vision
Dry mouth/skin Muscle cramps
Dizziness, headache Nausea, vomiting

21. Homework
VOCAB
Urea, deamination, excretion, nitrogenous
waste, Malpighian tubules, renal artery, renal
vein, urine, renal pelvis, ureter, renal medulla,
renal cortex, nephron, glomerulus, bowman’s
capsule, ultrafiltration, osmoregulation, ADH,
osmoregulators, osmoconformers, kidney
dialysis, dehydration, overhydration
OTHER
Exercises 9-15, pg 478