Transcript waste removal & water balance

WASTE REMOVAL & WATER
BALANCE
What is waste and why?
• Human body is not 100% efficient in converting raw material into
useable substances, creates some waste product.
• Protein contains nitrogen, which is not used by the body, when the
protein is broken down it becomes a waste product and must be
removed.
• Humans release Nitrogen in the form of urea (ammonia is converted
into urea in the liver so it can me carried in the blood)
• Other animals can also release nitrogen in the form of ammonia and
uric acid
H
H
N
NH2
O
NH2
H
Ammonia
C
Urea
Uric Acid
THE URINARY SYSTEM
• The kidneys are 2 bean shaped
organs located in the back of the
upper abdomen at either side of
the spinal cord (fist sized)
• The RENAL ARTERY brings
blood containing nitrogenous
waste to the kidneys. (As it is a
filter, the kidneys may hold as
much as 25% of the bodies
blood at any given time)
• The artery branches into
capillaries, each capillary enters
a nephron where filtration occurs
THE NEPHRON
• Each kidney contains approx 1 million slender tubes called
nephrons.
Flow of blood through the kidneys
GLOMERULUS
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•
•
Blood enters via the renal
artery and into the
Glomerulus which is a ball
of capillaries that sits inside
the BOWMANS CAPSULE.
The blood is effectively
squeezed through the
Glomerulus under high
pressure, filtering out RBC,
WBC and the platelets
through pores in the
Bowmans capsule
Only the clear Plasma and
over dissolved materials
continue through the
Bowmans capsule and into
the proximal tubule
PROXIMAL TUBULE
• Hollow winding tube (large diameter)
• SOLUTE REABSORPTION of glucose, sodium, calcium, phosphate
and amino acids occurs via Active transport back into the blood
stream
• Most urea remains in the tubule
LOOP OF HENLE (DESCENDING)
• WATER REABSORPTION occurs
• Concentration of water inside the tubule is higher than the
surrounding blood vessels, thus water is removed from the urea
back into the capillaries by osmosis
LOOP OF HENLE (ASCENDING)
• REABSORPTION of sodium back into the capillaries occurs
(actively pumped)
• (Ascending part of the tubule is impermeable to water, this stops
osmosis occurring despite the urea now having a low solute
concentration)
DISTAL TUBULE
• WATER BALANCE
• Final adjustment of water and dissolved materials occurs
(dependant on level of body hydration.
• dehydrated: distal tubule increases permeability and allows water to
leave urea and return to the capillaries
• hydrated: permeability decreases to water remains in the urea,
diluting the urine that will be removed
COLLECTING DUCT
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•
•
•
SECRETION
Other wastes are transferred from the capillary network into the duct
Some final re-absorption of water back into blood stream may occur
Now contains urine which will be excreted from the body
URINE
• Urine is approx 95% water, 5% dissolved
salts, urea and a few other minerals
• If the urine is overly concentrated its pH
can become too high, and cause damage
to cells
• If all fluid that entered the kidneys were
excreted, you would have to drink 1L of
fluid every 10 minutes to maintain water
balance