Transcript Excretion - kyoussef-mci

http://www.youtube.com/watch?v=hXysuAt_U9s
Excretion
 removal of metabolic waste
 Protein and nucleic acid metabolism  nitrogen
containing compounds
 does not include feces
 Excretion is an example of
homeostasis
 Prevent build up of toxic
wastes within our body
 Contribute to water
balance in our body
Organs Responsible for Excretion
Composition of Urine
 solution of metabolic waste
 Water (mostly)
 urea and uric acid
 salts
 organic compounds
 Compounds within
asparagus are
metabolized
 Produce a byproducts
that contain sulfur
 fluid for urine
comes from
 filtered blood
 extracellular
fluid (ECF)
Forms of Nitrogenous Waste
 Urea
 Ammonia
 Uric Acid
 deamination – removal
of amine group
 Occurs in the liver
 Byproducts are sent to
the kidneys for further
processing
Urea
 product of two other waste molecules
 ammonia, NH3 (very toxic)
 carbon dioxide, CO2
Ammonia
 ammonia released when liver breaks down proteins
 0.005 mg NH3 is lethal
 reacts with CO2 to produce less toxic urea
 100 000x less toxic than NH3
Uric Acid
 product of nucleic acid breakdown
 specifically of purine bases
Role of Kidneys
1. Removal of wastes
 Urea, uric acid and
other materials are
filtered through the
kidney and excreted
2. Water balance
 average person loses
2L of liquids a day
 suggested to consume
2L H2O / day
Excretion: Ameoba
Ameoba remove
waste and excess
water through a
contractile vacuole.
Excretion: Fish
Fish can excrete
ammonia directly
through their gills.
Excretion: Birds
Birds excrete uric acid
directly with feces.
Excretion: Earthworms
capillary
network
bladder
collection
tubule
nephrostome
nephridiopore
AKA The Kidney
Role of Kidney
1.
2.
3.
4.
5.
blood filtration
waste excretion
acid / base balance
blood pressure regulation
hormone secretion
Kidney Structure
renal cortex – outside of
kidney; location of
Bowman’s capsule
renal medulla (lobes) –
middle of kidney; location of
loop of Henle
renal pelvis – location of the
ends of collecting ducts
Kidney Blood Flow
Blood enters the kidney
through the renal artery.
 renal arteries stem from the
aorta
 Carry oxygenated blood
Filtered blood exits the kidney
through the renal vein.
 renal veins flow into the
inferior vena cava
 Carry de-oxygenated blood
Nephron
 Functional unit
of the kidney
 Responsible
for the
formation of
urine
 A million
nephrons
make up the
kidney
Blood and the Nephron
Blood from renal artery is
filtered through nephrons.
Nephrons collect liquid to
be excreted
Filtered blood is returned to
renal vein
Renal artery
The renal artery is split into afferent arterioles.
 blood brought to glomerulus; a capillary bed.
 blood leaves through the efferent arterioles
 no veins involved
Efferent arterioles are the beginning of a network of
peritubular capillaries, that wrap around the
nephron.
Glomerulus and Bowman’s Capsule
Efferent
Arteriole
Afferent
Arteriole
Filtrate
From the bowman’s capsule:
 fluids to become urine flow to narrow proximal tubule
 urine flows through loop of Henle
 urine flows through distal tubule
 Urine from multiple nephrons flow into the
collecting duct.
Urine Flow
Urine leaves the renal pelvis
through the ureters and travels
to the bladder. Fluid leaves
the body through the urethra.
When ~200 mL of urine has
collected in the bladder, the
walls stretch and signals are
sent to the brain.
At ~600 mL, urine will
involuntarily be released.
ureters
Nephron Structure
efferent arteriole
proximal
tubule
glomerulus
Bowman’s
capsule
distal
tubule
collucting
duct
afferent arteriole
Loop of
Henle
Urinary System
aorta
inferior vena
cava
renal
cortex
renal
medulla
renal artery
renal vein
kidney
ureter
bladder
renal
pelvis
nephrons
urethra
ureter
Question
Athletes now undergo random
urine testing for drugs.
Describe the pathway of drugs
through the urinary system,
from the time they enter the
glomerulus until they are
excreted in the urine.
Homework Quiz Question 1
Homework Quiz Question 2
 You are sick and take an antibiotic.
 Describe the pathway of the drug through the urinary
system, starting from the aorta to the toilet!
Passive transport.
Substances move spontaneously
down their concentration gradients, crossing a
membrane with no expenditure of energy by the cell.
The rate of diffusion can be greatly increased by transport
proteins in the membrane.
Active transport.
Some transport proteins act as pumps,
moving substances across a membrane
against their concentration gradients.
Energy for this work is usually supplied
by ATP.
ATP
Diffusion. Hydrophobic
molecules and (at a slow
rate) very small uncharged
polar molecules can diffuse through the
lipid bilayer.
Facilitated diffusion. Many hydrophilic
substances diffuse through membranes with the
assistance of transport proteins,
either channel or carrier proteins.
Three Functions of Urine Formation
1.
3.
Capillary
1
Excretory
tubule
Filtration.
Filtrate
2.
Filtration – movement of
fluids from the blood in the
glomerulus to the
Bowman’s capsule
Reabsorption – transfer of
fluids from nephron into
peritubular capillaries
Reabsorption.
3
Secretion.
interstitial
fluid
Urine
Secretion – transfer of
fluids from peritubular
capillaries into nephron
2
4 Excretion.
Filtration
 Water and solutes flow from
1
Excretory
tubule
Filtration.
Filtrate
the glomerulus into Bowman’s
capsule due to high blood
pressure flow
Capillary
 65 mmHg vs. normall ~ 25
2
Reabsorption.
mmHg
3
Secretion.
Urine
 Semi-permeable membrane
 Red blood cells, platelettes and
some blood proteins are too
large to fit through the filtration
slits and pores.
4 Excretion.
Nutrient Flow
Solute
Glomerulus  Bowman’s
Capsule?
water
NaCl
H+ ions
yes
yes
yes
amino acids
glucose
yes
yes
plasma proteins
no
red blood cells
(erythrocytes)
no
platelets
no
Reabsorption
Capillary
1
 Reabsorption reclaims
Filtration.
Filtrate
Excretory
tubule
valuable substances from
the filtrate and returns
them to the body fluids.
 Water, salt and nutrients
 saves us from having to
Reabsorption
3
Secretion.
20% of fluid flowing into kidney
is filtered into nephrons;
however less than 1% of the
fluid in the nephron is used
to
4 Excretion.
make urine.
Urine
continuously replenish
our body with fluid.
2
A LOT OF REABSORPTION!
Secretion
Capillary
1
Filtration.
Filtrate
 Other substances are
Excretory
tubule
extracted from body fluids and
added to the contents of the
nephron
2
Reabsorption.
 toxins and excess ions
3
Secretion.
Urine
4 Excretion.
Capillary
1
Reabsorption
Filtration.
Filtrate
Excretory
tubule
 protein transporters
Secretion.
4 Excretion.
Secretion
 protein transporters
move
Diffusion. Hydrophobic
wastes from blood to
interstitial fluid to nephron
molecules and (at a slow
rate) very small uncharged
polar molecules can diffuse
through the
lipid bilayer.
Reabsorption.
3
Urine
move nutrients into
interstitial fluid and
blood
 kidney tissue will only
reabsorb a certain
level of nutrients –
threshold level
2
Facilitated diffusion. Many
hydrophilic substances diffuse
through membranes with the
assistance of transport proteins,
either channel or carrier proteins.
ATP
The Details…
1. Bowman’s Capsule
 High pressure filter
 water and dissolved solutes leave
glomerulus; enter Bowman’s
capsule
water
Na+
H+
Clglucose
amino acids
vitamins
minerals
urea
uric acid
2. Proximal Tubule
HCO3-, K+
Na+, ClH2O
amino acids
glucose
vitamins
 Selective reabsorption of
nutrients (need transporters)
 Secretion of H+ and ammonia
 pH determined by HCO3-
reabsorption and H+ secretion
H+
NH3
3. Loop of Henle – Descending Limb
 Nephron membrane only
permeable to H2O (osmosis)
and impermeable to salt
 Reabsorption of water
 As fluids travel down the loop
of henle, the fluids within the
tube become more
concentrated.
H2O
4. Loop of Henle – Ascending Limb
 only permeable to salt (need
ionic transporters) and not
permeable to water
 Reabsorption of salt
 As fluids travel up the loop of
henle the fluid is becoming less
concentrated
NaCl
5. Distal Tubule
HCO3Na+, ClH2O
 Selective reabsorption of
nutrients (need transporters)
 Secretion of H+, ammonia and K+
 pH determined by HCO3-
reabsorption and H+ secretion
H+
NH3
K+
6. Collecting Duct
 Urine formation by concentration
of nephron fluid
 Any urea and urine that is
reabsorbed is less than that was
filtered into nephron
 Why is some urea reabsorbed?
 Contributes to the formation of a
hypertonic interstitial fluid
 causes water to be reabsorbed
 CONCENTRATING THE URINE
NaCl
urea
water
1
Proximal tubule
NaCl
HCO3
Nutrients
H2O
K+
H+
NH3
4
Distal tubule
H2O
NaCl
HCO3
K+
H+
CORTEX
2 Descending limb
of loop of
Henle
Filtrate
H2O
Salts (NaCl and others)
HCO3–
H+
Urea
Glucose; amino acids
Some drugs
3 Thick segment
of ascending
limb
NaCl
H2O
OUTER
MEDULLA
NaCl
3 Thin segment
of ascending
limb
Key
Urea
NaCl
Active transport
Passive transport
5 Collecting
duct
INNER
MEDULLA
H2O
Osmolarity of
interstitial
fluid
(mosm/L)
300
300
100
300
100
CORTEX
NaCl
H2O
Active
transport
200
400
300
300
400
400
600
600
H2O
H2O
NaCl
H2O
H2O
NaCl
H2O
Passive
transport
OUTER
MEDULLA
NaCl
H2O
400
600
H2O
NaCl
H2O
NaCl
H2O
H2O
Urea
700
900
INNER
MEDULLA
H2O
NaCl
900
H2O
Urea
H2O
1200
Urea
1200
1200
Osmolarity – concentration of solutes in a solution, the higher the Osmolarity,
the more concentrated the solution, the better it is able to pull water towards it.
http://www.biologymad.com/resources/kidney.swf
Diabetes (Type II)

Not enough insulin released from pancrease
 High levels of glucose in the blood
Why do you think that individuals with Type II Diabetes
(untreated)
(a) Excrete a large amount of gluose in the urine?
(b) Excrete large amounts of urine?
Kidney Stones
 crystallization of some
urine solutes
 a 2 – 3 mm stone can
obstruct flow to the ureter
Treatment:
 increased water
consumption
 surgery
Homework/Classwork
7.3 – Pg. 345 #1-4,6
7.4 – Pg. 348 #1-3
7.5 – Pg. 352 #2-8
Homework Quiz next class!