1. Water Balance & Excretion
9.4 & 9.5

2. Osmoregulation
process of actively regulating the osmotic pressure of bodily fluids and cells
hyperosmotic (hypertonic)
hypoosmotic (hypotonic)
isoosmotic (isotonic)

3. Homework: p.445
#11. Explain the difference between the terms “hypertonic” and “hyperosmotic”.

4. Unicellular Organisms
water balance is often maintained by contractile vacuoles
video of Paramecium:

5. Excretion eliminating waste is important for all living organisms
(Image from:

6. Types of Waste Our bodies eliminate wastes through various organs:
lungs (CO2)
large intestine (solid wastes)
liver (transforms toxins for removal)
kidneys (soluble wastes)
Lungs - CO2
Large intestine - solid wastes
Liver - transforms toxins
Kidneys - soluble wastes

7. 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

8. 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.)

9. Human Excretory System
Image from:

10. Renal Blood Flow)
blood is brought to the kidneys by the renal arteries
filtered blood leaves the kidneys through the renal veins
(Image from:

11. 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

13. Kidney Structure Basic structure: cortex medulla renal pelvis
(Image from:

14. Kidney Kiwi
Found this website of a medical illustrator on December 6, 2011
(Images from:

15. Kidney Kiwi Dissection

16. Nephron the functional unit of the kidney is the nephron
there are about 1 million nephrons in each kidney

18. Image from :http://kcfac. kilgore. cc. tx

19. (Image from: http://www. medical-illustrations
Afferent Arrives…Efferent Exits

20. 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)

21. How is urine formed?

22. Urine Formation filtration reabsorption secretion
Simple overview of urine formation:
(Image on previous slide from: ,-Sterile.html

23. 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
glucose, NaCl, H+ ions, amino acids,

24. 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
If you produced 120 mL of urine a minute…
(your bladder’s stretch receptors signal to your brain when there is 200mL of urine; can hold up to )
Osmotic gradient created by glucose, amino acids moves water back to blood.

25. 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

26. 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

27. 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

28. Animations
Narrated animation on urine formation; good amount of detail:
Narrated animation of structure & function; quite detailed:

29. Kidney Disorders

30. 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

31. Multiple Test Dipstick
(Image on next slide from:

32. 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)

33. Kidney Stones
caused by precipitation of minerals, can be alkaline or acidic
VERY painful
(Image from:

34. Kidney Stones - Treatment
time…
lithotripsy (shock-wave therapy)
ureteroscopy (and placement of stent or surgical removal of stone)
(Images from:

35. Dialysis
for low-functioning kidneys, dialysis machine can filter blood
(Image from:

36. (Image from: http://www.metrohealth.org/body.cfm?id=1452)

37. 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?