Download Homeostasis 2 - 9.4 9.5

Water Balance & Excretion
9.4 & 9.5
Osmoregulation
• process of actively regulating the
osmotic pressure of bodily fluids and
cells
• hyperosmotic (hypertonic)
• hypoosmotic (hypotonic)
• isoosmotic (isotonic)
Homework: p.445
#11. Explain the difference between the
terms “hypertonic” and “hyperosmotic”.
Unicellular Organisms
• water balance is often maintained by
contractile vacuoles
• video of Paramecium:
http://www.youtube.com/watch?v=mTXRc
bjuYGU
Excretion
• eliminating waste is important for all living
organisms
Types of Waste
• Our bodies eliminate wastes through
various organs:
•
•
•
•
lungs (CO2)
large intestine (solid wastes)
liver (transforms toxins for removal)
kidneys (soluble wastes)
Nitrogenous Wastes
• mostly from deamination
• animals that live in water can remove
ammonia with lots of water
• mammals, some reptiles, most
amphibians form urea
• birds and some invertebrates produce
uric acid
Homework: p.445
#4. Explain the advantages &
disadvantages for terrestrial animals of
creating urea rather than other forms of
nitrogenous waste.
#5. Why is it an advantage for birds to
create uric acid as their nitrogenous
waste compound? (Think of flight.)
Human Excretory System
Renal Blood Flow
• blood is brought to
the kidneys by the
renal arteries
• filtered blood leaves
the kidneys through
the renal veins
)
The Urinary System
• kidneys can hold up to 25% of the
body’s blood at a time
• kidneys filter the blood
• urine (with wastes and toxins) is
conducted to the bladder through the
ureters
Kidney Structure
Basic structure:
• cortex
• medulla
• renal pelvis
Kidney Kiwi
Kidney Kiwi Dissection
Nephron
• the functional unit of the kidney is the
nephron
• there are about 1 million nephrons in
each kidney
Other links…
• Khan academy…this video starts off
with the structure of the kidney &
nephron, then goes into detail about the
formation of urine (covered in 9.5)
• http://www.khanacademy.org/video/thekidney-and-nephron?playlist=Biology
How is urine formed?
Urine Formation
• filtration
• reabsorption
• secretion
• Simple overview of urine formation:
• http://www.pennmedicine.org/encyclopedia/em_DisplayAnimatio
n.aspx?gcid=000136&ptid=17
Filtration
• higher blood pressure in glomerulus
• water, ions, smaller dissolved molecules
(glucose, amino acids, urea) can move
through the walls of the glomerulus
• your kidneys filter your entire blood
plasma 65 times a day
Reabsorption
• ion pumps reabsorb Na+, K+, Cl- (active)
• active transport proteins reabsorb
amino acids, glucose
• filtrate becomes hypoosmotic to
interstitial fluid, so water is reabsorbed
by osmosis and through aquaporins
Where?
• a lot of reabsorption occurs in the
proximal convoluted tubule
• filtrate with high concentration of urea
and other wastes enters loop of Henle
and then distal convoluted tubule:
– more water and ions (Na+& Cl-)are
reabsorbed
Where (cont’d)?
• collecting ducts are permeable to water
but not salt ions, so more water is
reabsorbed
• at bottom of medulla, urea is
reabsorbed through passive urea
transporters
Secretion
• H+ ions (active) to adjust blood pH
(HCO3- is also reabsorbed to balance)
• products of detoxified poisons (passive)
• water-soluble drugs (passive)
• nitrogen-containing wastes (such as
small amounts of NH3)
• in the proximal and distal convoluted
tubules
Animations
• Narrated animation on urine formation; good
amount of detail:
•
http://davisplus.fadavis.com/scanlon6e/Animations/animations.cfm?exercise=Ne
phronFiltration&title=Nephron%20Filtration
• Narrated animation of structure & function; quite
detailed:
•
http://bcs.whfreeman.com/thelifewire/content/chp51/51020.html
Kidney Disorders
Urinalysis
• can be used to detect many metabolic
and kidney disorders as well as urinary
tract infections
• urine can be assessed using a dipstick
or at a laboratory
Multiple Test Dipstick
Diabetes Mellitus
• Type 1 - body cannot produce insulin
• Type 2 - cells fail to use insulin properly
• gestational - hormones of pregnancy
interfere with action of insulin
• urinalysis would show high levels of
glucose (and greater volumes of urine)
Kidney Stones
• caused by
precipitation of
minerals, can be
alkaline or acidic
• VERY painful
Kidney Stones - Treatment
• time…
• lithotripsy (shockwave therapy)
• ureteroscopy (and
placement of stent
or surgical removal
of stone)
Dialysis
• for low-functioning
kidneys, dialysis
machine can filter
blood
Homework: p.454
#2. What may be the reasons that the body
normally uses two kidneys?
#3. Describe the flow of blood into and out of
the kidneys. Compare the contents of the
blood when entering and exiting the kidneys.
#9. What would be the result on the body if
Na+, K+, and Cl- were not reabsorbed in the
kidneys?