1. Osmoregulation and Excretion
Chapter 44
Osmoregulation and Excretion

2. Osmoregulation and Excretion Overview
Regulate water and solutes (like salts)
Excretion
Getting rid of waste (like nitrogen from proteins and nucleic acids)

3. Review

4. Osmoregulatory Mechanisms
Osmoconformer
Isotonic to environment
Ex. Hagfish
Osmoregulator
Have to regulate environment
Costs energy to regulate
Amoeba- contractile vacuoles
Platyhelminthes- flame cells
Annelida- metanephridium
Insecta- Malpighian tubules (extensions of digestive track)
Dark waste- fecal material; light waste- nitrogenous waste
Tardigrada- anhydrobiosis (“life without water”), can go from 85% to 2% water
Review Isotonic, hyper/hypotonic

5. Transport Epithelium

6. Osmoregulation in Marine/Freshwater Fish
Marine Fish- bony fish
Freshwater Fish
Marine Fish- cartilaginous fish
Transport epithelium
Bony- don’t want to lose water
Sharks- keep high urea levels
Freshwater- don’t want to lose salts
FIGURE AT THE END OF THE CHAPTER

7. Another way to look at it…

8. Moving to Land Must protect from water loss How we get water
Drinking water
Food
Cellular respiration
How to get rid of nitrogenous waste
Ammonia
Easiest to make out of the three
Urea
Mammals make this
Uric Acid
Hardest to make out of the three
Helps save water

9. Excretory system

10. Organs
Cloaca
Common opening for urinary, reproductive, and digestive system in birds, reptiles, and sharks
Humans:
Males have open opening for excretory and reproductive system
Females have one opening for each ^

11. Kidneys and Nephrons
85% of nephrons are cortical nephrons, which reach only a short distance into the medulla. The rest, the juxtamedullary nephrons, extend deep into the medulla. Juxtamedullary nephrons are essential for production of urine that is hyperosmotic to body fluids, a key adaptation for water conservation in mammals.

12. Process of Filtration/Excretion
Filter stuff out of blood and put it into the nephron as filtrate
Reabsorption
Send nutrients back into the blood/body
Secretion
Interstitial fluid around nephron has stuff we want to get rid of so it goes back into the nephron/filtrate
Excretion
Filtrate leaves through renal pelvis and starts getting ready to leave the body

14. Parts of a Nephron Bowman’s capsule Glomerulus Proximal Tubule
Loop of Henle
Distal Tubule
Collecting duct

15. Filtration Secretion Reabsorption
Afferent arterioles bring blood into the glomerulus
The high blood pressure in the glomerulus pushes out water, salts, urea, glucose, amino acid, etc. into Bowman’s capsule
Specialized cells called podocytes in Bowman’s capsule act like filters
Reabsorption
Now we are in the proximal tubule.
We are reabsorbing the “good stuff” we want in our blood: bicarbonate, nutrients (glucose), water, sodium chloride, potassium, etc.
We see some secretion here, too, into the tubule: hydrogen ions, ammonia, toxins, etc.
Secretion
Some in proximal tubule, but more in distal tubule
Distal tubule is the “final check” (with ACTIVE transport)
Sees what the body needs – NaCl? Bicarbonate? Potassium? Hydrogen ions?
Reabsorbs and secretes

16. Loop of Henle Descending loop Only permeable to water Ascending loop
Only permeable to sodium chloride
Closer to bottom = passive transport, closer to top = active transport

17. Excretion
Collecting duct
Urea and NaCl control how much water is taken back
Urea is reabsorbed, but then goes back into the loop of Henle
REVIEW OF NEPHRON AND URINE PRODUCTION: ons/content/kidney.html
And this cool thingy >>

18. Regulation Antidiuretic Hormone (ADH)
Made by hypothalamus, stored by posterior pituitary
Hypothalamus has osmoreceptors which control the release of ADH

19. ADH
Aquaporins

20. Regulation of Blood Volume and Blood Pressure
When blood pressure drops (like during dehydration), the JGA senses it and releases renin.
Renin activates angiotensinogen into angiotensin I which is converted into angiotensin II by ACE (angiotensin converting enzyme)
Angiotensin II raises blood pressure by constricting arterioles, which decreases blood flow to capillaries in the kidney (and elsewhere).
Angiotensin II also stimulates the adrenal glands to release a hormone called aldosterone. Aldosterone causes the nephrons’ distal tubules and collecting duct to reabsorb more Na+ and water, increasing blood volume and pressure.
Atrial natriuretic protein (ANP) does the opposite of the whole process (negative feedback)
Bonus question – JGA (must spell it out)
FINISH THIS SLIDE
Practice:

21. Chemistry of a Hangover
Alcohol inhibits ADH
Symptoms of “hangover”
Dehydration

22. Thresholds
When something enters the kidneys and you have enough of it (or don’t need it), you send it out of the body.
Ex. Glucose- normal concentration is sent back into the body, abnormal concentration makes glucose apparent in the urine (urine test for diabetes)
Ex. Drugs- no threshold for certain drugs so it comes out in the urine (urine test for drugs)

23. Comparing Kidneys Deserts animals Freshwater animals
Longer loops of Henle
Freshwater animals
Shorter loops of Henle
Creatures that drink saltwater have salt glands/ducts to get rid of salts
Not on test!