1. 11.3 The Kidney and Osmoregulation

2. Essential idea: All animals excrete nitrogenous waste products and some animals also balance water and solute concentrations.

3. The type of nitrogenous waste in animals is correlated with evolutionary history and habitat.

4. Animals are either osmoregulators or osmoconformers.

5. Malpighian tubule system
In INSECTS
Carries out osmoregulation and removal of nitrogenous wastes.
Collects from hemolymph and empties into gut where it is disposed of at the end

6. Osmoregulation and Excretion: The Kidney

7. Purpose of the Kidney To filter the blood in order to accomplish…
Osmoregulation: management of the body’s water content and solute composition. (Maintain water balance)
Excretion= removal of waste products of metabolic pathways
Nitrogenous wastes: breakdown products of proteins and nucleic acids
Ex. ammonia-very toxic
is converted into urea
Urea: (less toxic) produced in liver, then excreted;
combo of NH3 and CO2.

8. Parts of the Kidney Renal artery/vein: kidney blood flow
Renal cortex (outer region)
Renal medulla (inner region)
Nephron: functional unit of kidney
Renal Pelvis
Ureter: urine excretory duct (leads to bladder)

9. Draw and Label: The kidney
Include:
-cortex
-medulla
-renal pelvis
-ureter
-renal blood vessels

10. How the Kidney Works: General
Production of urine by 3 processes:
•1)Ultrafiltration
•2) Reabsorption of water and valuable solutes
3) secretion of excess salts/ toxins into filtrate

11. Nephron Function: Step 1: Ultrafiltration
Afferent arteriole: supplies blood to nephron from renal artery
Glomerulus: ball of capillaries (blood pressure causes filtration by size here)
Bowman’s capsule: surrounds glomerulus (collects filtrate)
Efferent arteriole: blood from glomerulus flows into it (away from nephron)

12. Ultrafiltration (Structure and function)
The ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration.
difference in diameter of afferent and efferent arteriole: causes blood in glomerulus to be at high pressure;
capillary wall is fenestrated ( has small pores / holes)
basement membrane (that covers and supports the capillary wall) prevents large (protein) molecules from leaving blood plasma / only allows passage of small molecules
Podocytes (form inner wall of Bowman’s capsule and prevent molecules from being filtered out
passive process.

13. Nephron Function Step 2: Reabsorption
Proximal Convoluted Tubule
Selective Reabsorption of glucose, water, and salts.
Microvilli increase surface area
Active transport pumps useful substances out of tubule (to be reabsorbed by blood)
Osmosis- water follows reabsorbed solutes (to be reabsorbed by blood.)

14. Nephron Function, Step 3: Concentration of Solutes in Medulla
Loop of Henle: reabsorption of water and salt
Descending limb = permeable to water but not salt (water leaves Loop)
Ascending limb= permeable to Na+ but not water (Salt pumped into medulla.
Overall: this concentrates the fluid of the medulla (makes it hypertonic)
Purpose: to concentrate urine in collecting duct

15. Nephron Function Step 4:
Distal tubule: secretion and reabsorption.

16. Nephron Function: Step 5: Collection of Urine (and further concentration)
Collecting duct: Urine is concentrated as the filtrate moves down the collecting duct b/c medulla = hypertonic
Collecting duct carries filtrate to renal pelvis  ureter urinary bladder urethra toilet…

17. Thought Questions
Physicians used to diagnosis diabetes mellitus by tasting a patient’s urine. The urine of a diabetic patient would be sweet. Why?
IB standard addressed: Explain the presence of glucose in the urine of untreated diabetic patients.

18. Nephron Structure (annotate)

19. Hormonal Control of Osmoregulation
Antidiuretic hormone (ADH) ~ increases permeability of collecting ducts to water (reabsorption of H2O back to body)
Causes creation of aquaporins…
inhibited by alcohol and coffee

20. Think and write Journal question!
Explain the roles of the loop of Henle, medulla, collecting duct and ADH (vasopressin) in maintaining the water balance of the blood.
Discuss as a group
Each person should write down their answer
Students will be randomly chosen by number (in columns– to give their table’s answer)

21. Basic Nephron Function
VIDEO
C:\Documents and Settings\BBAUGHMAN\Desktop\bio powerpoints\Chapter 37 BDOL IC

22. The composition of blood in the renal artery is different from that in the renal vein.

23. Comparison of Fluids in the Kidney
Content (mg per 100 ml of fluid)
Substance
Blood in renal artery
Glomerular Filtrate
Urine
Blood in Renal Vein
Glucose 90
Urea 30
2000 24
Proteins
740
Explain the levels of each substance in each location.

24. The length of the loop of Henle is positively correlated with the need for water conservation in animals.

25. Application:
Consequences of dehydration and overhydration. (discuss)

26. Application: Treatment of kidney failure by hemodialysis or kidney transplant.

27. Application: Blood cells, glucose, proteins and drugs are detected in urinary tests.
Discuss:
What might be indicated by the presence of glucose?
What about proteins?

28. Utilization: • The removal of kidney stones by ultrasound treatment.

29. End of IB stuff in syllabus

30. Homeostasis
Homeostasis = Maintaining the internal environment between limits that are suitable for survival
Think: What internal parameters must be maintained?
Blood pH
CO2 concentration
Blood glucose
Body temp.
Water balance (osmoregulation)
Etc.

31. Negative Feedback The primary mechanism for maintaining homeostasis
Variables are monitored
Corrections are made to maintain homeostasis.

32. Thermoregulation: Regulating body Temperature
Vasodilation- of superficial blood vessels– allows heat transfer to environment
Vasoconstriction– reduces blood flow, conserves heat
Countercurrent heat exchange– arteries (carrying warm blood) and veins (carrying colder blood) are close together in extremities (i.e. legs)-- Artery warmth warms blood in veins.
Evaporative cooling (Sweat Glands)
Behavioral responses (ex.?)
Shivering
Changing metabolic rate (in which group?)
In mammals, the hypothalamus controls thermoregulation via feedback mechanisms. (like a thermostat)

33. Outline the structure and action of kidney dialysis machines.

34. Kidney regulation: hormones
Summary
ADH, JGA, RAAS (Renin, Angiotensin II and aldosterone) = increase blood volume, increased blood pressure, increased water reabsorption (sometimes by reabsorbing salt and water follows salt)
Atrial natriuretic factor– lowers blood volume and pressure, less reabsorption
Antidiuretic hormone (ADH) ~ secretion increases permeability of distal tubules and collecting ducts to water (H2O back to body); inhibited by alcohol and coffee
Juxtaglomerular apparatus (JGA) ~ responds to drop in blood pressure--->enzyme renin initiates conversion of angiotensinogen (plasma protein) to angiotension II (peptide); increase blood pressure and blood volume by constricting capillaries
Angiotensin II also stimulates adrenal glands to secrete aldosterone; acts on distal tubules to reabsorb more sodium, thereby increasing blood pressure (renin-angiotension-aldosterone system; RAAS)
Atrial natriuretic factor (ANF) ~ walls of atria; inhibits release of renin, salt reabsorption, and aldosterone release

35. Regulation during environmental extremes
Torpor~ low activity; decrease in metabolic rate during times of low food supply/ extreme temps.
1- Hibernation long term or winter torpor (winter cold and food scarcity); bears, squirrels
2- Estivation short term or summer torpor (high temperatures and water scarcity); fish, amphibians, reptiles
Both often triggered by length of daylight

36. Regulation of body temperature
Thermoregulation
4 physical processes:
Conduction~transfer of heat between molecules of body and environment
Convection~transfer of heat as water/air move across body surface
Radiation~ electromagnetic rays produced by sun and by organisms
Evaporation~loss of heat from liquid to gas
Sources of body heat:
Ectothermic: determined by environment (most invertebrates, fishes, amphibians, and reptiles)
Endothermic: metabolic rate generates body heat (mammals, birds, some fishes, and numerous insects)

37. Osmoregulators
Osmoconformer: no active adjustment of internal osmolarity (some marine animals like jellyfish); isoosmotic to environment
Osmoregulator: adjust internal osmolarity (freshwater, marine, terrestrial)
marine fishes (hypoosmotic/hypotonic)- loses water, gains salt; drinks large amount of saltwater
Freshwater fishes (hyperosmotic/hypertonic)- gains water, loses salts; excretes large amounts of urine salt