11.3 kidney

Essential idea: All animals excrete nitrogenous waste products and some animals also
balance water and solute concentrations.
11.3 The kidney and osmoregulation
The form in which nitrogenous
waste is excreted reflects
evolution and ecological niche
occupied, by the animal.

Understandings
Statement Guidance
11.3 U.1 Animals are either osmoregulators or
osmoconformers.
11.3 U.2 The Malpighian tubule system in insectsand
the kidney carry out osmoregulation and
removal of nitrogenous wastes.
11.3 U.3 The composition of blood in the renal arteryis
different from that in the renalvein.
11.3 U.4 The ultrastructure of the glomerulus and
Bowman’s capsule facilitate ultrafiltration.
11.3 U.5 The proximal convoluted tubule selectively
reabsorbs useful substances by active
transport.
11.3 U.6 The loop of Henle maintains hypertonic
conditions in the medulla.
11.3 U.7 ADH controls reabsorption of water in the ADH will be used in preference to vasopressin.
collecting duct.
11.3 U.8 The length of the loop of Henle is positively
correlated with the need for water
conservation in animals.
11.3 U.9 The type of nitrogenous waste in animals is
correlated with evolutionary history and
habitat.

Applications and Skills
Statement Guidance
11.3 A.1 Consequences of dehydration and
overhydration.
11.3 A.2 Treatment of kidney failure by hemodialysis or
kidney transplant.
11.3 A.3 Blood cells, glucose, proteins and drugsare
detected in urinary tests.
11.3 S.1 Drawing and labelling a diagram of the human
kidney.
11.3 S.2 Skill: Annotation of diagrams of the nephron. The diagram of the nephron shouldinclude
glomerulus, Bowman’s capsule, proximal
convoluted tubule, loop of Henle, distal
convoluted tubule; the relationship betweenthe
nephron and the collecting duct should be
included.

Types of metabolic waste
produced by living systems
1. Digestive waste
2. Respiratory waste
3. Excess water and salts
(through
osmoregulation)
4. Nitrogenous waste
(through excretion)

ANIMAL PHYSIOLOGY
OSMOREGULATORS:
• All terrestrial animals, freshwater
animals and some marine
organisms are osmoregulators
because they maintain constant
internal solute concentration,
even when living in marine
environments with very
different osmolarities
• Typically these organisms maintain
their solute concentration at about
one third of the concentration of
seawater and about 10 times that
of fresh water
• (Terrestrial Animals/ Freshwater
Animals/ Boney Fish)
OSMOCONFORMERS:
• Animals that have similar
internal solute concentration in
comparison to the solute
concentration to their
surrounding environment
• (Marine Invertebrates/
Cartilaginous Fish)
11.3 U.1 Animals are either osmoregulators or osmoconformers.

Osmoregulation Example
•Maintaining osmotic homeostasis
• Balancing water and solute concentrations (Salts/nitrogen)
• Maintains cell integrity
• Maintains enzyme function
• etc.
Osmoregulators When they live in fresh water, their bodies tend to
take up water because the environment is relatively hypotonic. In such hypotonic
environments, these fish do not drink much water. Instead, they pass a lot of very
dilute urine, and they achieve electrolyte balance by active transport of salts through
the gills.

Osmoconformers Example maintain an internal conditions that are
equal to osmolarity of their environment. Minimizing the osmotic gradient
minimizes the water movement in and out of cells. A disadvantage is that internal
conditions may be sub- optimal. When they move to a hypertonic marine
environment, these fish start drinking sea water; they excrete the excess salts
through their gills and their urine.
• Marine fish lose water by osmosis
 Actively excrete salt to maintain homeostasis
• Freshwater fish lose water by osmosis
 Excrete excess water

Two forms of excretory systems
Malpighian tubules – Insects, arthropods Kidneys - Vertebrates
1. Malpighian tubes: remove Nitrogen waste from hemolymph,
located near digestive tract. Secretes dry waste with feces.
2. Kidneys: compact organs containing tubules surrounded by
capillaries. Responsible for water and blood filtration, excretion of
Nitrogen waste and salt
11.3 U.9 The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.

Types of Nitrogenous Wastes:
1. Ammonia – water soluble, very
toxic; aquatic animals
2. Urea – produced by liver; less
toxic, conserves water; most
vertebrates
3. Uric acid – in birds & reptiles
ammonia is convert as uric acid.
Uric acid does not require water
and is highly concentrated. This is
beneficial to these organisms as
they do not have to carry the extra
water around excreted as paste or
crystals. Important in reducing
weight for flight
11.3 U.9 The type of nitrogenous waste in animals is correlated with evolutionary history
and habitat.
When animals breakdown amino and nucleic acids, nitrogenous waste is formed
in the form of ammonia. Ammonia is highly basic, toxic and can be very reactive.
What a Ammonia becomes after this step is determined by the organisms
evolutionary history and habitat. As an example: Marine and freshwater organisms
can release the ammonia directly into the surrounding water where it becomes dilute.

11.3 U.2 The Malpighian tubule system in insects and the kidney carry out osmoregulation
and removal of nitrogenous wastes.
The removal of nitrogenous waste and osmoregulation in insects by
the Malpighian tubule
• Nitrogenous wastes are broken down into URIC ACID in the insects.
• Malpighian tubules branch off from their intestinal tract.
• Uric acid, Na+, and K+ are actively transported from the hemolymph into the lumen of the
tubules.
• This draws water into the tubules by osmosis.
• The water, ions, and uric acid move into the hindgut.
• In the rectum, most of the water (osmosis) and salts (pumped) are selectively
REABSORBED while the dehydrated uric acid is eliminated as a semisolid paste with
the feces.

11.3 U.2 The Malpighian tubule system in insects and the kidney carry out osmoregulation
and removal of nitrogenous wastes.
Malpighian tubules are longer
and more convoluted than shown in
this simplified illustration, they extend
into the body cavity, where they are
surrounded by hemolymph.
Hemolymph is a fluid (analogous to the
blood) that circulates in the interior of the
insect’s body remaining in contact with the
tissues.
The removal of nitrogenous waste and osmoregulation in insects by
the Malpighian tubule

Osmoregulation: control solute
concentrations and balance water
gain/loss
Excretion: removal of nitrogenous
wastes from body
Diffusion is a form of passive transport, a net movement of
particles from an area of high concentration to an area of low
concentration. This is often through a partially permeable
membrane.
PASSIVE: DOES NOT REQUIRE ENERGY
Concentration gradient: the difference in concentration of
substances between two locations

Osmosis
Most cell are partially
permeable membrane, water
flows with the concentration
gradiant.
When a cell is submerged
in water, the water
molecules pass through the
cell membrane from an area
of low solute
concentration (outside
the cell) to one of high
solute concentration
(inside the cell)

Osmolarity is the measure of the concentration of solute inside of a fluid
or a cell. Cells can be in three types of Osmotic Environments:

How to make urine:
Water and solutes enter filtrate; blood
cells and proteins (nitrogen waste)
remain in body fluid.
Reclaim glucose, vitamins,
hormones
Add toxins and excess ions
Filtrate leaves body as urine

The urine
produced by
each kidney is
transported via
a URETER to
be stored in the
BLADDER.
The bladder
empties
through the
URETHRA.
11.3 S.1 Drawing and labelling a diagram of the human kidney

•The RENAL CORTEX
is the outer layer of
tissue under the
capsule where the
blood is filtered.
•The RENAL
MEDULLA is found
as a “middle” layer of
tissue. Water and salt
balance take place
here.
•Urine that has been
produced by the
filtration/reabsorption
processes of the
kidney is collected in
the RENAL PELVIS.
Structure of the Kidney

The kidney causes changes in the composition of blood
renal vein
(filtered blood)
renal artery
(unfiltered blood)
ureter
(urine)
blood in the renal vein compared and
contrasted with the renal artery has …
• no change in proteins – not filtered
• less urea and toxins#
• less oxygen*
• more carbon dioxide*
• less salts and ions$ (if in excess)
• less water$ (if in excess)
• less glucose*
*Oxygen and glucose are used for cell respiration in the kidney and carbon dioxide is produced.
urea
toxins
water
salts
ions
# Undesired waste is removed from the
blood.
$ The blood water and salt concentration
needs to be balanced (osmoregulation).
The kidney helps by removing these
molecules if in excess.
11.3 U.3 The composition of blood in the renal artery is different from that in the renal
vein.

• Each kidney is made up of
1.25 million filtering units
called nephrons.
• 1,100 to 2000 L of blood
flow through the kidneys
each day.
• The nephrons and
collecting ducts create 180
L of initial filtrate.
• Nearly all of the sugar,
vitamins, and organic
nutrients and 99% of water
are reabsorbed into the
blood.
• Only about 1.5 L of urine
are produced.
Nephron- the functional units of the kidney.
11.3 S.2 Annotation of diagrams of the nephron.

a and c. GLOMERULUS- Afferent
arteriole form branches of the renal
artery bed which filters the blood.
Efferent arteriole join together to
form the renal vein
b. BOWMAN’s CAPSULE-
surrounds the glomerulus and
collects the filtrate.
d. PROXIMAL CONVOLUTED-
selective reabsorption
e. LOOP OF HENLE- regulation
f. DISTAL CONVOLUTED –
secretion of wastes back into filtrate
g. COLLECTING DUCTS-
osmoregulation
11.3 S.2 Annotation of diagrams of the nephron.

Ultrafiltration: formation of kidney filtrate
11.3 U.4 The ultrastructure of the glomerulus and Bowman’s capsule facilitate
ultrafiltration.
•Hydrostatic pressure created as the afferent arterioles narrow in the
glomerulus capillaries forces a liquid against a semi-permeable membrane.
•Blood in capillaries is at high pressure in many of the tissues of the body, and
the pressure forces some of the plasma out through the capillary wall,
to form tissue fluid
•The pressure in the capillaries of the glomerulus are particularly high and the
capillary wall is particularly permeable, so the volume forced out is about
100 times greater than in other tissues.
Present moving in
Glucose
Proteins
Urea
Na+
Cl-
Present moving out
Urea
Filtered out of Blood
Glucose
Proteins
Na+
Cl-

1. In the Bowmen’s capsule a
cup-like sack where fluid is
collected by the high pressure
generate in the glomerulus
knot.
2. The capillary wall of the
glomerulus is fenestrated
(containing pores) allowing
fluid to move through it.
3. The basement membrane is
the effect filtration barrier only
allowing small molecules to
pass through it. Cells and large
macromolecules cannot pass
through this structure.
4. podocyte filtration slits acting
as another filter allowing only
smaller molecules to be filtered
*Note this means that the filtrate does not pass through the cells of either the
glomerulus or the Bowman's capsule
11.3 U.4 The ultrastructure of the glomerulus and Bowman’s capsule facilitate
ultrafiltration.

11.3 U.5 The proximal convoluted tubule selectively reabsorbs useful substances by active
transport.
Proximal Convoluted Tubule (PCT)
• This where most selective reabsorption occurs: All glucose, amino acids, vitamins and
hormones are reabsorbed here, along with approx 80% of the mineral ions and water
• Due to high concentrations of recovered substances in PCT cells the substances can passively
diffuse into the bloodstream (along the concentration gradient)
• microvilli cell lining to increase the surface area for the absorption
SELECTIVE REABSORPTION
(General Patterns)
• Amino acids, hormones
mineral ions & vitamins are
actively transported (a large
number of mitochondria
provide ATP for active
transport) into the PCT cells
• Glucose is actively transported
across the membrane (in
symport) with sodium
• Water follows the movement
of the ions passively (by
osmosis)

STRUCTURE
• The walls of the
PCT are one cell
thick.
• The filtrate
travels through
the lumen.
• The inner portion
of each tubule
has microvilli to
increase the
SURFACE AREA
for reabsorption
in the tubule.
11.3 U.5 The proximal convoluted tubule selectively reabsorbs useful substances by active
transport.
Selective reabsorption of useful substances from the proximal convoluted tubule (PCT)
The PCT extends from the Bowman’s capsule to the loop of Henle

LOOP of HENLE and the COLLECTING
DUCTS are responsible for the control of
the water balance.
Function:
1. The function of the loop of Henle is
to create a salt bath concentration in
the surrounding medullary fluid.
2. Later this results in water
reabsorption in the collecting duct
3. There is also a reduction in the
filtrate volume.
11.3 U.6 The loop of Henle maintains hypertonic conditions in the medulla. AND 11.3 U.7
ADH controls reabsorption of water in the collecting duct.
Osmoregulation is the control of water and solute concentrations in
the body fluids (e.g. the blood plasma).

11.3 U.6 The loop of Henle maintains hypertonic conditions in the medulla.

Distal Convolute Tubule (DTC)
Function:
It is partly responsible for the
regulation
of potassium, sodium, calcium, and pH
of urine by secreting protons and
absorbing bicarbonate
11.3 U.7 ADH controls reabsorption of water in the collecting duct.

• Filtrate enters the collecting duct from the
Distal Convoluted Tubule (DCT).
• Water moves from the Collecting Duct to the
capillaries by osmosis.
• They flow in opposite directions, maintaining a
Concentration gradient – a counter-current system
The Colleting Duct balances the water concentration
of the blood, through hormonal control

• Filtrate enters the collecting duct from the Distal
Convoluted Tubule (DCT).
• Water moves from the Collecting Duct to the
capillaries by osmosis
• They flow in opposite directions, maintaining a
concentration gradient – a counter-current system.
• If a person is dehydrated, ADH (a hormone) acts on
the walls of the collecting duct, producing
aquaporins (channels) making it more permeable
to water.
• More water is transferred into the blood.
Urine output is hypertonic (high solute
concentration)

Osmoregulation is an example of negative
Feedback control using hormones. Water content
of blood is monitored by the hypothalamus and
regulated by the pituitary gland.

11.3 U.8 The length of the loop of Henle is positively correlated with the need for water
Length of the loop of Henle and water
conservation: The kangaroo rat's kidneys are
especially efficient and produce only small
quantities of highly concentrated urine. They
have very long loops of Henle which builds a
higher ion concentration in the medulla (dark
orange below). The longer the loop the more
water will be reabsorbed in the collecting duct.
kangaroo rat

11.3 U.8 The length of the loop of Henle is positively correlated with the need for water
The ion concentration in the medulla builds as the loop of Henle descends. A longer loop of
Henle in implies a larger medulla (compared to the kidney size) than in animals with a
shorter loop of Henle..
Length of the loop of Henle and water conservation
* Values for the net ratios of
osmolarity for urine and
plasma (U/P ratios) are
provided to demonstrate the
concentration of urine
relative to that of the
blood. The ability of the
kangaroo rat and other
desert rodents to produce a
hyper-concentrated urine is
attributed to their
possession of extremely
long loops of Henle, which
is often quoted as an
extreme adaptation for life
in parched deserts.

Dehydration is due to loss of water
from the body so body fluids
become hypertonic.
• thirst, small quantities of dark colored
urine
• lethargy, (exposure to higher levels
of metabolic waste, reduced muscle
effeciency)
• low blood pressure (reduced blood
volume)
• raised heart rate (low blood
pressure)
• Inability to lower body temperature
(lack of sweat)
• in severe cases seizures, brain
damage and death
11.3 A.1 Consequences of dehydration and overhydration.

Overhydration is less common
and occurs when there is an
over- consumption of water.
• clear urine
• swelling of cells due to
osmosis (from hypotonic
body fluid)
• Headache, disruption of
nerve
function (Swelled cells)
• In more serious cases
delirium, blurred vision,
seizures, coma and
death
11.3 A.1 Consequences of dehydration and overhydration.

Urine Analysis
• A clinical procedure that examines urine for
deviation from the normal composition.
• Visual Examination: color determines
hydration.
• “Dipstick” Tests look for the presence
of:
• pH- normal (pH 4.6 to pH 8.0)-
extremes show improper
functioning of kidney
• Protein levels- possible kidney
damage
• Glucose- possible diabetes
• Monoclonal antibodies on strips look
for drug use and/or pregnancy.
• Blood cells infections, disease and
some cancers
• Drugs (or their breakdown products)
can often be detected in urine
samples
11.3 A.3 Blood cells, glucose, proteins and drugs are detected in urinary tests.
* As an example, excess sugar in the urine generally indicates diabetes

11.3 A.2 Treatment of kidney failure by hemodialysis or kidney transplant.
Treatment of kidney failure Kidney failure is a condition in which the kidneys fail to
adequately filter waste products from the blood. It can be
caused by injury or disease symptoms vary depending on
the seriousness and progression of the disease. If not
treated kidney failure leads to death.
Treatment of kidney failure focuses on
two main approaches:
• Hemodialysis
• Kidney transplants

http://www.kalingahospital.com/data/images/transplant1.jpg
Treatment of kidney failure
*If the match is not close enough the receipient’s immune system will react to
the new kidney as it would to a pathogen.
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*.
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.

Treatment of kidney failure
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.

Bibliography / Acknowledgments
Maura Pallilo

11.3 kidney

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