3931631
The Kidneys (Nephron)
- Bowman's capsule -- proximal convoluted tubule -- loop of Henle -- distule convoluted tubule -- collecting duct
- ultrafiltration
- 1. The
endothelium
of the
capillaries in
the
glomerulus is
thin. it
creates a
barrier to
only cells.
- 2. A Basement membrane
of collagen fibres lies in
the Bowman's capsule. it
allows water and small
molecules to pass
through. proteins are
filtered out as they are
too large and are repelled
by the negative charge on
the fibres
- small molecules = glucose, amine acids, vitamins and drugs.
- small molecules = glucose, amine acids, vitamins and drugs.
- 3. The epithelium of the
Bowman's capsule is made of
Podocytes specialised for
filtration.
- filtrate moves into the
bowman's capsule due
to hydrostatic
pressure.
- The afferent
arteriole is wider
than the efferent
arteriole
- The kidneys are close to the heart.
- The afferent
arteriole is wider
than the efferent
arteriole
- 1. The
endothelium
of the
capillaries in
the
glomerulus is
thin. it
creates a
barrier to
only cells.
- Selective Reabsorption
- the inner walls of the proximal
convoluted tubule are covered
with microvilli to increase
surface area for absorption
- 1. Outer
membrane of
the cells of
the tubule
actively pump
NA+ into the
tissue fluid.
- 2. The
concentration
of NA+ is
lowered inside
the cells.
- 3. NA+ ions in
the filtrate
diffuse into the
cells of the
tubule down
their
concentration
gradient.
- 4. The NA+ ions carry
another molecule
with them into the
surrounding cells Eg)
amino acids
- Co- transport
- Co- transport
- 5. The amino acids diffuse
down their concentration
gradient into the blood.
- 6. The water potential in the
blood is lowered so water moves
back into the blood by Osmosis
- the inner walls of the proximal
convoluted tubule are covered
with microvilli to increase
surface area for absorption
- Water Reabsorption
- 1. Na and Cl are actively pumped out of the ascending limb.
- 2. This decreases the water
potential in the surrounding tissue.
- 3. As a result, Na and Cl
diffuse into the descending
limb down their
concentration gradient.
- 5. As the fluid
moves down the
descending limb,
the
concentration of
Na and Cl
increases. Na
and Cl diffuse
into the tissue
fluid in the
cortex, at the
bottom of the
loop of Henle
- 4. Some water moves into the tissue fluid by osmosis.
- 6. The collecting duct lies in the medulla.
Therefore, water in the collecting duct moves
into the surrounding tissue by osmosis. this
reduces the amount of water lost in
urination.
- The longer the Loop of Henle, the more
concentrated the salt in the tissue fluid gets, so in
organisms with longer loops, more water is absorbed
and less is lost in urination.
- 1. Na and Cl are actively pumped out of the ascending limb.
- Osmoregulation
- 1. Osmoreceptors in the
hypothalamus detect a low
water potential in the blood.
- 2. Neurosecretory cells in the
hypothalamus produce and
release ADH.
- 3. ADH passes
down the
axons of the
osmoreceptors
to the
posterior
pituitary
glands.
- 4. ADH binds to complementary
receptors on the cells of the
collecting duct. Enzymes are activated.
- 5. This stimulates aquaporins to to move from
the cytoplasm into the cell membranes, forming channels for water.
- 6. Therefore, the permeability to water is
increased, so more water moves into the tissue
fluid and subsequently into the capillaries by
osmosis.
- 7. The water potential in the
blood rises, so the
hypothalamus stops producing
ADH.
- 1. Osmoreceptors in the
hypothalamus detect a low
water potential in the blood.
- Kidney failure
- causes
- diabetes
- hypertension
- kidney infection
- diabetes
- treatment
- Dialysis: Partially permiable
membrane allows the
exchange of salt, urea and
water between blood and
dialysis fluid.
- Haemodialysis
- Blood from a vein is
passed into a machine
where it is passed over
an artificial dialysis
membrane
- Heparin is added to avoid clotting.
- Blood from a vein is
passed into a machine
where it is passed over
an artificial dialysis
membrane
- Peritoneal dialysis
- Dialysis solution is
poored through a
surgically implanted
tube, filling the space
between the abdominal
wall and the organs
- After a few hours, the
solution is drained and
the correct balance in
the body should have
been restored.
- Dialysis solution is
poored through a
surgically implanted
tube, filling the space
between the abdominal
wall and the organs
- Haemodialysis
- Transplant
- positives
- freedom and less limited diet
- able to travel
- freedom and less limited diet
- negatives
- must take immunosepressants
- risk of the causation of fluid retention, high
blood pressue and infection
- Risks of being put under general anaesthetic
- must take immunosepressants
- positives
- Dialysis: Partially permiable
membrane allows the
exchange of salt, urea and
water between blood and
dialysis fluid.
- causes
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