1. Osmoregulation
Chapter 44

2. Osmoregulation Balance of water & solute concentration
Intracellular & extracellular
Ions (solutes)
Na+1, Cl-1

3. Osmolarity Hyperosmotic Hypoosmotic Isoosmotic Normal saline (0.9%)
5% dextrose

4. Selectively permeable membrane
Solutes
Water
Hyperosmotic side:
• Higher solute concentration • Lower free H2O concentration
Hypoosmotic side:
• Lower solute concentration • Higher free H2O concentration
Figure 44.2 Solute concentration and osmosis
Net water flow

5. Osmoregulation Osmocomfomers
Body fluids have same concentration as environment
Ocean invertebrates
Osmoregulators
Constant blood osmolarity
Vertebrates

6. Osmoregulation

7. (a) Hydrated tardigrade (b) Dehydrated tardigrade
50 µm
Figure 44.5 Anhydrobiosis
(a) Hydrated tardigrade
(b) Dehydrated tardigrade

8. Nitrogenous wastes Proteins, DNA & RNA contain nitrogen
Break downs-waste (NH2)
Aquatic animals
NH3
Mammals, amphibians
Urea
Birds, reptiles, insects
Uric acid

9. Nitrogenous wastes

10. Urea
Uric acid

11. Most aquatic animals, including most bony fishes Mammals, most
Nitrogen wastes
Most aquatic
animals, including
most bony fishes
Mammals, most
amphibians, sharks,
some bony fishes
Many reptiles
(including birds),
insects, land snails
Ammonia
Urea
Uric acid

12. Excretory process Excretory systems Regulate solute concentrations
Produce urine
Refine filtrate from body fluids

13. Excretory process Filtration Blood (body fluids) is filtered
Forms filtrate (urine)
Reabsorption
Ions & nutrients are recovered
Returned to body from filtrate

14. Excretory process Secretion
Wastes/water from capillaries to filtrate (urine)
Excretion
Release filtrate (urine) from body
Release nitrogenous metabolites

15. Filtration Capillary Excretory tubule Reabsorption Secretion Excretion
Filtrate
Excretory
tubule
Reabsorption
Secretion
Urine
Excretion

16. Excretory Organs Nephron Types Kidney Structure Figure 44.12a
Renal cortex
Cortical nephron
Juxtamedullary nephron
Renal medulla
Posterior vena cava
Renal artery
Renal artery and vein
Kidney
Renal vein
Aorta
Renal cortex
Ureter
Figure 44.12a Exploring the mammalian excretory system (part 1)
Ureter
Urinary bladder
Renal medulla
Urethra
Renal pelvis

17. Anatomy Kidney Ureter Bladder Urethra Renal artery/vein
Blood supply of kidney

18. Anatomy Renal cortex Outside of kidney Renal medulla
Inside of kidney (hypertonic)
Renal pelvis
Funnel shaped
Ureter meets kidney

19. Kidney

20. Anatomy Nephron: Functioning unit of kidney 1 million in each kidney
Glomerulus
Bowman’s capsule
Proximal (convoluted) tubule
Loop of henle
Distal (convoluted) tubule

21. Nephron

22. Kidney

23. Kidney

24. Pathway

25. Pathway through kidney
Blood forced into glomerulus
Bed of capillaries
Blood cells & proteins are too large
Plasma goes through with minerals & water
Filtrate
Enters Bowman’s capsule
Proximal tubule
Located in renal cortex

26. Pathway through kidney
Enters loop of Henle
In the loop goes deep in the renal medulla
Fluid returns
Distal tubule
Drains into collecting duct
Goes into renal pelvis (urine)
Ureter

27. Pathway through kidney

28. Juxtamedullary Cortical nephron nephron Renal cortex Collecting ductTo
renal
pelvis
(c) Nephron types

29. Nephron

30. Pathway through kidney
Capillaries surround the loop
Reabsorb water & ions

31. 10 µm Afferent arteriole from renal artery Glomerulus Bowman’s capsule
Nephron
Afferent arteriole
from renal artery
Glomerulus
10 µm
Bowman’s capsule
SEM
Proximal tubule
Peritubular capillaries
Efferent
arteriole from
glomerulus
Distal
tubule
Branch of
renal vein
Collecting
duct
Descending
limb
Loop of
Henle
Ascending
limb
Vasa
recta
(d) Filtrate and blood flow

32. Pathway through kidney
L of blood flow through a day
180 L of water a day
Urinate only 1.5 L per day
Reabsorb glucose, aa, vitamins & water
Excrete wastes, harmful substances, H+ & water
Maintain homeostasis (blood volume, pH electrolytes & BP)

33. Regulation diagram

34. Closer look Proximal tubule Most nutrients reabsorbed to blood
NaCl, H2O, HCO3-1 reabsorbed to blood
NH3, H+1 secreted into the tubule from blood

35. Bowman’s Capsule and Proximal Tubule

36. Closer look Loop of Henle Descending loop water is reabsorbed
Ascending loop NaCl is reabsorbed
Longer loop-more NaCl is absorbed

37. Closer look Distal tubule Regulation of K+1 & NaCl here
Depends on body’s needs
K+ is secreted into tubule
NaCl reabsorbed into tubule

38. Loop of Henle and Distal Tubule

39. Closer look Collecting duct NaCl can be reabsorbed here
Some urea diffuses out of tube
Remaining filtrate passes as urine

40. Collecting Duct

41. Regulation diagram

42. Transport Proximal tubule Distal tubule Filtrate CORTEX Loop of Henle
NaCl
Nutrients
H2O
HCO3–
H2O K+
NaCl
HCO3– H+
NH3 K+ H+
Filtrate
CORTEX
Loop of
Henle
NaCl
H2O
OUTER
MEDULLA
NaCl
NaCl
Collecting
duct
Key
Urea
Active
transport
NaCl
H2O
Passive
transport
INNER
MEDULLA

43. Regulation of kidney ADH (antidiurectic hormone) Vasopressin
Released by posterior pituitary gland
Released in response to increased solute concentration in plasma
Dehydrated or eating salty foods
Distal tubule/collecting duct become more permeable to water
Decreases the amount of water in urine
Reabsorbs more water

44. ADH Thirst Hypothalamus ADH Pituitary gland Distal tubule H2O reab-
Osmoreceptors in
hypothalamus trigger
release of ADH.
Thirst
Hypothalamus
Drinking reduces
blood osmolarity
to set point.
ADH
Pituitary
gland
Increased
permeability
Distal
tubule
H2O reab-
sorption helps
prevent further
osmolarity
increase.
STIMULUS:
Increase in blood
osmolarity
Collecting duct
Homeostasis:
Blood osmolarity
(300 mOsm/L)
(a)

45. Aquaporin water channel
ADH
ADH receptor
LUMEN
Collecting duct
COLLECTING DUCT CELL
ADH
Second messenger
cAMP
Protein kinase A
Storage vesicle
Exocytosis
Figure ADH response pathway in the collecting duct
Aquaporin water channel
H2O
H2O

46. Effect of ADH

47. Regulation of kidney Low blood volume Juxtaglomerular apparatus
Tissue located near artery supplies blood to glomerulus
Secretes renin (enzyme)
Angiotensinogen to angiotensin I
Angiotensin I to angiotension II
Causes blood vessels to constrict
Causes release of aldosterone

48. Regulation of kidney Aldosterone Released by the adrenal cortex
Due to low sodium levels
Due to low blood volume
Stimulates distal tubules/collecting ducts to reabsorb sodium
Chlorine & water follow
Stimulates potassium to be excreted

49. Regulation of kidney Aldosterone Increases serum sodium levels
Increases water (blood volume)
Decreases serum potassium levels
ACE inhibitor
Blood pressure medication
Blocks the affects of aldosterone

50. Aldosterone Liver Distal tubule Renin Angiotensin I Juxtaglomerular
Angiotensinogen
Renin
Angiotensin I
Juxtaglomerular
apparatus (JGA)
ACE
Angiotensin II
STIMULUS:
Low blood volume
or blood pressure
Adrenal gland
Aldosterone
Increased Na+
and H2O reab-
sorption in
distal tubules
Arteriole
constriction
Homeostasis:
Blood pressure,
volume

51. Regulation of kidney ANH (atrial natriuretic homone)
Secreted by right atrium
Due to increased blood volume
Causes sodium/water to be released
Lowers blood volume
Opposes aldosterone

52. Problems Diabetes insipidus Lacks ADH Pituitary problem
Increased urination
Leads to dehydration & low BP
Alcohol consumption
Blocks ADH