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Welcome
Kidney
Yo there all you students. Kid
Rock here to make everything
clear. I’ve got a lot of important
information for you today. Lets
get you learning with the power
of music! Also try to stay COOL
like me.
Now those kidneys are important organs, but how ‘bout tellin’ me why?
Those kidneys filter my blood and that’s no lie
They tell me it’s ‘bout excretion
Hey I don’t listen to all their preachin’
If you gotta get rid of nitrogen waste
You gotta put the urine in the usual place
If you eat the meat and protein for lunch
Metabolism breaks it into an ammonia crunch
That ‘mmonia got to go so you make urine
That sure be right, that’s the song your hearin’
Now they want me to get technical and discuss
comparative excretory systems. I’m a musician
not a biologist so I hired an assistant to help with
the difficult stuff. You might know him; he’s on
CNN. Say hello to Dr. Sanjay Gupta.
Hello students. I will be going though the details of excretory
systems with a concentration on the human kidneys..
Excretory systems are important to eliminate wastes from
organisms
Excretory systems also are involved in water balance
(osmoregulation) of organisms.
The most common and very toxic waste that builds up in the
body is a chemical called ammonia. It is produced as a
product whenever proteins are broken up into amino acids
and the amino acid in turn is broken down for energy. The
removal of the amine group (called deamination) results in
ammonia being produced.
Most aquatic animals get rid of ammonia by
excreting it in very dilute solutions. Most terrestrial
animals convert the ammonia to urea or uric acid
which conserves water because the less toxic urea
can be transported and stored in the body.
Ammonia
Hey I’m in
freshwater. I
can even
excrete this
stuff through
my gills
Urea
Just use carbon
dioxide and 2
ammonia
molecules to
make this in the
liver.
Urea conserves water as it allows us to
concentrate the urine without it being
too toxic. Salt water fish ,like us sharks
need to conserve too. We use urea in our
blood circulation to balance our ions.
Our environment is hyperosmotic.
Uric Acid
Forms a paste that
minimizes water loss.
Used by birds, insects
and land snails (some
reptiles)
DID YOU KNOW?
In areas that birds frequent and
deposit their uric acid it is called
guano and can be used for
fertilizer or even the manufacture
of gunpowder explosives because
of its high nitrogen and
phosphorus content!
Uric acid deposits
are called Guano
This big hill is solid
guano being mined.
Gunpowder
explosion
Hey, that bird
excrement really
added up! Wait a
minute. Is that my
car? Lousy birds!
So tell me. Which organisms don’t
have kidneys
Unicellular organisms like
the amoeba, paramecium,
and primitive multicellulars
like the sponge
Diffusion of waste out of the cells into
the water. Osmoregulation by
contractile vacuoles.
The planarian is also called the flatworm. It has
protonephridia also called flame cells that allow excretion
of urine and regulate water balance (osmoregulation)
Earthworm has the nephrostome or
metanephridia. These have cilia that filter
the blood in the worm segments. Urine
leaves through pores in the skin called
nephridiopores
The insects use Malpighian tubules which
excrete the uric acid into the gut for
elimination
So then what are the organisms with kidneys?
Mammals
Amphibians
Fish
Reptiles
Birds
Now let’s go into a little detail about the kidney main functions
1.WATER BALANCE the amount of water in the body must be
balanced with the amount of water intake through drinking and
eating the amount of water lost in sweat, urine breathing etc.
2.Excretion of metabolic wastes--urea, creatinine, drugs
and chemicals we ingest.
3. Blood pressure regulation using the reninangiotensin-aldosterone system
4. Blood electrolyte balance - Na+, Ca 2+, K+ ....
5. Body’s acid base (pH) balance regulation
6.Erythropoietin hormone regulation which
controls rbc production
7.Vitamin D production assisted
The basic components of the human
urinary system are shown in this diagram
Notice that the
renal artery actually
brings blood to be
cleaned into the
kidney. Only some
of the blood is
diverted from the
dorsal aorta
The renal vein
carries cleaned
blood back to the
inferior vena cava
to return to the
heart
In this diagram the two
kidneys can clearly be seen.
Normally, they would not be
visible, as they are located at
the back of the abdominal
cavity behind the intestines
and stomach.
Blood is delivered to each
kidney by the renal artery, a
branch off the Inferior vena
cava which runs alongside
the backbone.
The kidney filters and
returns clean blood to the
renal vein which leads to
the Inferior vena cava
Waste from the kidneys
constantly drips down the
ureters.
Urine collects in the
urinary bladder
Urine leaves the body
through the urethra
Urinary system
How much urine can you store
in the bladder Doc?
Even under severe water
shortage, the kidneys will
still excrete about 500mL
of urine a day
The prostate
gland shown is a
common site for
cancer in males.
Females do not
have a prostate
You can hold about 1.5 litres
of fluid in the bladder.
Stretch receptors on the
bladder send signals to the
brain when the bladder is
full. The external urethral
sphincter allows for control of
the bladder. The urinary
mucous coat protects the
inner membrane from the
toxic substances in the urine
until elimination.
PROSTATE
You may hear
the micturion
reflex-it just
means
urination
Take a look
at this
dissection
specimen
to put it in
perspective
. Notice
the arch of
the aorta
and how it
curves
down along
the spine
as the
dorsal
aorta.
Take a look at the three layers of the
kidney.
CORTEX is the outer
layer
MEDULLA is the
Middle layer –
Remember, both
medulla and middle
are “M” words.
PELVIS is the
innermost collecting
area.
Nephrons regulate the composition of blood by a
combination of the following three processes that
involve a transfer of material between the renal
tubules and the capillaries that surround them.
FILTRATION- nephron podocytes in the Bowman’s capsule
regulate what enters the tubular filtrate.
SECRETION –selective transport from the
surrounding interstitial fluid of the tubule. This is
used by the kidney to control blood pH as hydrogen
ions can be secreted into the nephron if needed.
REABSORPTION-small molecules essential to the
body are returned to the blood plasma from the
tubule. This is regulated by the tubule
epithelium.Nearly all the sugar, vitamins and organic
nutrients are reabsorbed.
The adrenal
glands are
located here at
the top of the
kidneys. They
make
adrenaline and
corticosteroids
The important
one for this
discussion is
ALDOSTERONE
Inside the kidney is the
functional unit of filtration
called the nephron. When
the blood is filtered, the
fluids, both bad and good
enter into the Bowman’s
capsule from the
glomerulus capillary bed.
That includes glucose
ureaamino acids, creatinine
and ions.
Large proteins
and blood
cells remain in
the capillaries.
Fluids leave the
glomerulus and
enter the
Bowman’s
capsule
The glomerulus
is located in the
cortex region of
the kidney
Efferent arteriole
Afferent arteriole
“A “ comes before “E” and starts. Therefore
blood originates at the afferent end
Shown here is the functional unit of the
kidney called the nephron. Much of it is
a series of tubules used in the process of
reabsorbing good substances back into
the bloodsteam
RENIN-ANGIOTENSIN-ALDOSTERONE SYSTEM
Active Na+
reabsorption
uses energy
Loop of Henle
Retaining salt instead of excreting it into
urine increases the osmolarity of the
blood and so the blood volume
Aldosterone stimulates the
active reabsorption of sodium
across the distal tubule. This
causes increased reabsorption
of water as the water follows
the solute by osmosis. BODY
CONSERVES WATER-connected
to blood pressure maintenance
The loop of Henle is located in
the medulla portion of the
kidney. Collecting tubules are
also in this region.
Osmotic balance of the blood requires
more Na+ if more water is reabsorbed.
ADH brings in more water but not sodium
Shown here are the secretion and
reabsorption processes
H2O
Secretion of
some
hormones
and
potassium
from
capillaries
into tubules
occurs here
Reabsorption
Water is
normally
passively
reabsorbed
in the
descending
tubule
NaCl
Reabsorption
Sodium chloride is
normally actively
reabsorbed in the
ascending tubule
The kidneys respond to changes in
blood pH by altering the excretion of
acidic or basic ions in the urine. If the
body becomes more acidic, the
kidneys excrete acidic hydrogen ions
(H+) and conserve basic bicarbonate
ions (HCO3-). If the body becomes
more basic, the kidneys excrete basic
bicarbonate ions and conserve acidic
hydrogen ions.
Definitions apply here. Proximal means close and the proximal
tubule is immediately after the Bowman’s capsule. Distal means far
and the distal tubule is located far away on this tubule line after the
filtrate has passed through the loop of Henle.
Collecting tubule
More ADH
Less urine
produced
ADH is a hormone
responsible for
increasing water
conservation. It acts
on the distal and
collecting tubules
making them more
permeable to water.
This returns more
water to the blood
and less water out
through
the urine.
ADH
counters
the effects
of dehydration of the
blood together with
aldosterone.
Notice how the blood capillaries (peritubular) wind around
the nephron tubules. Many good chemicals and water must
be reabsorbed back into the bloodstream and permeability
of the nephron walls regulates this.
The length of the loop
of Henle is essential in
water reabsorption. The
longer the loop of
Henle the greater the
change in osmotic
gradient.
RESULT=concentrated
urine. Ex Kangaroo rats
DID YOU KNOW?
Birds have kidneys with short loops of Henle. That means they are
not as good as mammalian kidney at water reabsorption. Yet birds
need to make a more concentrated form of urine to restrict water
loss in their light weight bodies. This is accomplished with the
excretion of the paste like uric acid rather than the urea of
mammals.(exceptions like hummingbirds excrete ammonia and are
described as facultative ammonotelic rather than the typical
unicotelic bird.
Water? I
don’t need
no stinking
water!
Kangaroo rats live in the
American SW desert. They
survive by not drinking any
water. 90% of its water comes
from metabolism the other
10% from food
I’m different. I can be
“ammonotelic”
Water, water, everywhere but
not a drop to drink
Humans cannot drink sea
water. Our kidneys cannot
process out the salt and
reabsorb the water when
you ingest salt water. The
result is dehydration. The
effects are serious and the
brain begins to hallucinate
and send the body into a
premature death.
Rats, on the other hand,
have kidneys capable of
processing the salt water.
Rats thus can drink the salt
water as they float on the
ship until they get to land.
You’re not doin’ no urine test
on me are ya Doc?
No, but in the next
presentation that will be
examined.
KIDNEY
ENDS