1. Chapter 44 Osmoregulation and excretion

2.  Osmoregulation is the regulation of solute particles and balancing water loss and gain  Excretion is the removal of nitrogen containing waste from metabolism  Osmoregulation and excretion are both homeostatic processes

3. Osmolarity  Osmoregulation functions based on the movement of solute particles between internal fluids and external environment

4. Osmolarity continued  Osmolarity the concentration of solute in a solution (same as osmotic pressure o When the two solutions have the same osmolarity, the solutions are Isoosmotic o If the two concentrations are unequal the greater concentration of solutes is hyperosmotic o The more dilute concentration is hypoosmotic

5. Osmoregulation Animals that do not regulate their internal osmolarity are osmoconformers Animals that do not regulate their internal osmolarity are osmoconformers Occurs in animals that live in stable aquatic environments Occurs in animals that live in stable aquatic environments Osmoregulators adjust their osmolarity to create a difference between membranes Osmoregulators adjust their osmolarity to create a difference between membranes Allows organism to live in diverse environment but costs energy to transport solutes Allows organism to live in diverse environment but costs energy to transport solutes Amount of energy expended depends on the solution the organism is immersed Amount of energy expended depends on the solution the organism is immersed

6. Osmoregulation  Animals vary in the in change in external molarity they can survive animals that can not handle a large change in osmolarity are stenohaline animals that can not handle a large change in osmolarity are stenohaline animals that are euryhaline can handle a large change in osmolarity animals that are euryhaline can handle a large change in osmolarity a common euryhaline example is salmon a common euryhaline example is salmon

7. Adaptations of marine and freshwater animals Most marine animals are osmoregulators Most marine animals are osmoregulators Vertebrate Fish drink large amounts of water and uses gills to remove sodium chloride Vertebrate Fish drink large amounts of water and uses gills to remove sodium chloride Other minerals are moved through the kidneys Other minerals are moved through the kidneys Cartilaginous fish, such as sharks, retain their waste and are hyperosmotic Cartilaginous fish, such as sharks, retain their waste and are hyperosmotic Freshwater fish are immersed in a hypoosmotic environment and they excrete dilute urine to prevent salt loss Freshwater fish are immersed in a hypoosmotic environment and they excrete dilute urine to prevent salt loss

9. Anhydrobiosis A dormant state that allows organisms to “hibernate” in extreme environments A dormant state that allows organisms to “hibernate” in extreme environments Sugars such as trehalose allow for organisms to survive with only 2% of water as their body mass Sugars such as trehalose allow for organisms to survive with only 2% of water as their body mass

10. Land organism adaptations Plants and animals utilize waxes to reduce dehydration Plants and animals utilize waxes to reduce dehydration Camel’s fur helps insulate the body from heat Camel’s fur helps insulate the body from heat Desert dwellers are nocturnal Desert dwellers are nocturnal Animals rely on drinking water and using water generated from cellular respiration to maintain homeostasis Animals rely on drinking water and using water generated from cellular respiration to maintain homeostasis

11. Transport epithelia Epithelial cells help regulate the movement of solute particles Epithelial cells help regulate the movement of solute particles They may connect to the outside environment or form channels for regulation (albatross’s salt glands). They may connect to the outside environment or form channels for regulation (albatross’s salt glands).

13. Waste management The digestion of macromolecules produces ammonia; a very toxic compound The digestion of macromolecules produces ammonia; a very toxic compound Some animals excrete ammonia but most expend energy to convert it to less toxic compounds. Some animals excrete ammonia but most expend energy to convert it to less toxic compounds.

14. Ammonia Requires the accompaniment of plenty of water when secreted Requires the accompaniment of plenty of water when secreted Aquatic species secrete ammonia through their entire body surface Aquatic species secrete ammonia through their entire body surface

15. Urea Is 100,000 times less toxic than ammonia and requires less water when it is excreted Is 100,000 times less toxic than ammonia and requires less water when it is excreted However, energy must be used to convert it to urea However, energy must be used to convert it to urea Mammals, most amphibians, sharks, some marine bony fishes and turtles secrete urea Mammals, most amphibians, sharks, some marine bony fishes and turtles secrete urea

16. Uric acid Is insoluble in water and can be excreted as a semisolid Is insoluble in water and can be excreted as a semisolid Requires even more energy than urea to produce Requires even more energy than urea to produce Insects, land snails, reptiles, and birds excrete this waste Insects, land snails, reptiles, and birds excrete this waste

18. Evolutionary trends of waste removal Urea can diffuse out of shell-less eggs while the eggs of birds and reptiles use uric acid. Urea can diffuse out of shell-less eggs while the eggs of birds and reptiles use uric acid. The type of waste produced also depends on habitat The type of waste produced also depends on habitat Finally, the amount of waste excreted depends on diet. Finally, the amount of waste excreted depends on diet.

19. Excretory Process Filtration - movement of water and solutes known as the filtrate across a selective permeable membrane. Selective Reabsorption - reabsorption of valuable solutes from the filtrate. Secretion – toxins and excess ions are extracted from body fluids and added to the excretory tube. Excretion – filtrate is excreted from the body as urine.

21. Protonephridia: Flame-Bulb Systems Flatworms have an excretory system called Protonephridia, consisting of a branching network of dead-end tubules. Flatworms have an excretory system called Protonephridia, consisting of a branching network of dead-end tubules. These are capped by a flame bulb that draws water and solutes from the interstitial fluid, through the flame bulb, and into the tubule system. These are capped by a flame bulb that draws water and solutes from the interstitial fluid, through the flame bulb, and into the tubule system. The urine in the tubules exits through openings called nephridiopores. The urine in the tubules exits through openings called nephridiopores.

23. Metanephridia Consists of internal openings that collect body fluids from the coelom through a ciliated funnel, the nephrostome, and release the fluid to the outside through the nephridiopore. Consists of internal openings that collect body fluids from the coelom through a ciliated funnel, the nephrostome, and release the fluid to the outside through the nephridiopore.

24. Malpighian Tubes Insects and other terrestrial arthropods have organs called Malpighian tubules. Insects and other terrestrial arthropods have organs called Malpighian tubules. These open into the digestive system and dead-end at tips that are immersed in the hemolymph. These open into the digestive system and dead-end at tips that are immersed in the hemolymph. This system is highly effective in conserving water and is one of several key adaptations contributing to the tremendous success of insects on land. This system is highly effective in conserving water and is one of several key adaptations contributing to the tremendous success of insects on land.

25. Vertebrate Kidneys The kidneys of vertebrates usually function in both osmoregulation and excretion. The kidneys of vertebrates usually function in both osmoregulation and excretion. the kidneys of most vertebrates are compact, nonsegmented organs containing numerous tubules arranged in a highly organized manner. the kidneys of most vertebrates are compact, nonsegmented organs containing numerous tubules arranged in a highly organized manner. The vertebrate excretory system includes a dense network of capillaries intimately associated with the tubules, along with ducts and other structures that carry urine out of the tubules and kidney and eventually out of the body. The vertebrate excretory system includes a dense network of capillaries intimately associated with the tubules, along with ducts and other structures that carry urine out of the tubules and kidney and eventually out of the body.

26. Function of the Mammalian Kidney renal artery – supplies kidney with blood renal artery – supplies kidney with blood renal vein – drains blood supply from kidney renal vein – drains blood supply from kidney urine exits kidney through duct called ureter, drains into the urinary bladder, and exits the body through the urethra. urine exits kidney through duct called ureter, drains into the urinary bladder, and exits the body through the urethra.

27. Regions of the Nephron There are two regions, the renal cortex and the renal medulla. There are two regions, the renal cortex and the renal medulla. The nephron consists of a single long tubule and ball of capillaries called the glomerous. The nephron consists of a single long tubule and ball of capillaries called the glomerous. Bowmans capsule surrounds the glomerous. Bowmans capsule surrounds the glomerous.

29. Path of the Filtrate From Bowmans capsule goes through three regions From Bowmans capsule goes through three regions Proximal tube- reabsorption of bicarbonate ions helps regulate the bloods pH. Solutes actively transport out of the filtrate leaving it more dilute causing water to follow by osmosis. This water and filtrate reenter the blood. Proximal tube- reabsorption of bicarbonate ions helps regulate the bloods pH. Solutes actively transport out of the filtrate leaving it more dilute causing water to follow by osmosis. This water and filtrate reenter the blood.

30. Path of the Filtrate Cont. Loop of Henle – concentration of solutes increases, water reabsorbed into blood. In the ascending loop the surrounding fluid becomes more dilute. Water can not pass through but sodium chloride can. Sodium chloride diffuses out, further diluting filtrate. Loop of Henle – concentration of solutes increases, water reabsorbed into blood. In the ascending loop the surrounding fluid becomes more dilute. Water can not pass through but sodium chloride can. Sodium chloride diffuses out, further diluting filtrate.

31. Path of the Filtrate Cont. Distal tube – Substances are reabsorbed including bicarbonate ions from the distal tube to regulate body pH. Hydrogen ions and other toxins are secreted into the filtrate to further adjust the body’s pH. Distal tube – Substances are reabsorbed including bicarbonate ions from the distal tube to regulate body pH. Hydrogen ions and other toxins are secreted into the filtrate to further adjust the body’s pH. The distal tube empties into collecting duct which is drained into renal pelvis where it is drained by the ureter. The distal tube empties into collecting duct which is drained into renal pelvis where it is drained by the ureter.

33. Path of the Filtrate Cont. Cortical nephrons make up 80% of the nephrons in the human kidney. They have reduced loops and are confined to the renal cortex. Cortical nephrons make up 80% of the nephrons in the human kidney. They have reduced loops and are confined to the renal cortex.

34. Path of the Filtrate Cont. Juxtamedullary nephrons have well developed loops that extent deep into the renal medulla. Only mammals and vertebrates have these. The nephrons of other vertebrates lack loops of Henle. These nephrons allow mammals to produce urine that is hyperosmotic to body fluids, an adaptation that is important for water conservation. Juxtamedullary nephrons have well developed loops that extent deep into the renal medulla. Only mammals and vertebrates have these. The nephrons of other vertebrates lack loops of Henle. These nephrons allow mammals to produce urine that is hyperosmotic to body fluids, an adaptation that is important for water conservation.

35. Blood Vessels Associated with the Nephron Afferent arterioles supply each nephron with blood. Afferent arterioles supply each nephron with blood. Capillaries converge forming efferent arteriole. Capillaries converge forming efferent arteriole. Vessel subdivides again, forming the peritubular capillaries, which surround the proximal and distal tubules. Vessel subdivides again, forming the peritubular capillaries, which surround the proximal and distal tubules. Vasa recta are the capillaries that serve the loop of Henle. Vasa recta are the capillaries that serve the loop of Henle.

36. Water Conservation by Kidney The osmolarity of the urine excreted by the kidney is up to 4 times as concentrated as the osmolarity of human blood. The osmolarity of the urine excreted by the kidney is up to 4 times as concentrated as the osmolarity of human blood. How is this possible? How is this possible? The loops of henle is greatly responsible for the osmotic gradient that concentrates urine. The loops of henle is greatly responsible for the osmotic gradient that concentrates urine.

37. Loops of Henle produce regions of high osmolarity in the kidney, allowing water to be extracted by the filtrate. Loops of Henle produce regions of high osmolarity in the kidney, allowing water to be extracted by the filtrate. Figure 44.15 Figure 44.15 Descending limb: Produces a saltier filtrate Descending limb: Produces a saltier filtrate Ascending limb: Allows for diffusion of NaCl to maintain high osmolarity of kidney. Ascending limb: Allows for diffusion of NaCl to maintain high osmolarity of kidney. Descending and Ascending limbs work together to maintain gradient of osmolarity. Descending and Ascending limbs work together to maintain gradient of osmolarity. Water Conservation by Kidney (cont’d)

39. Loop of Henle as Countercurrent Multiplier System Since energy must be used to transport the NaCl from the filtrate in the upper part of the ascending limb of the loop, the loop of Henle is known as a countercurrent multiplier system. Since energy must be used to transport the NaCl from the filtrate in the upper part of the ascending limb of the loop, the loop of Henle is known as a countercurrent multiplier system. Helps maintain osmotic gradient between the medulla and cortex. Helps maintain osmotic gradient between the medulla and cortex.

40. Regulation of Kidney Function Antidiueretic hormone (ADH) Antidiueretic hormone (ADH) Renin-angiotensin-aldosterone system (RAAS) Renin-angiotensin-aldosterone system (RAAS) Atrial natriuretic factor (ANF) Atrial natriuretic factor (ANF)

41. Antidiueretic hormone (ADH) Produced in hypothalamus of the brain, stored and released from posterior pituitary gland. Produced in hypothalamus of the brain, stored and released from posterior pituitary gland. When osmolarity of blood rises above 300 mosm/L, more ADH is released into the bloodstream, amplifying water absorption by increasing the permeability of the epithelium. When osmolarity of blood rises above 300 mosm/L, more ADH is released into the bloodstream, amplifying water absorption by increasing the permeability of the epithelium. Uptake of additional water is still needed to improve osmolarity. Uptake of additional water is still needed to improve osmolarity.

43. Juxtaglomerular apparatus (JGA) A type of tissue that supplies blood to the glomerulus. A type of tissue that supplies blood to the glomerulus. Used when blood pressure or blood volume in the arteriole drops. Used when blood pressure or blood volume in the arteriole drops. The peptide angiotensin II (formed by renin) functions as a hormone and raises blood pressure by constricting the arterioles. The peptide angiotensin II (formed by renin) functions as a hormone and raises blood pressure by constricting the arterioles. Leads to the release of aldesterone which makes the nephons’ distal tubules reabsorb more water and sodium, increasing blood volume and pressure. Leads to the release of aldesterone which makes the nephons’ distal tubules reabsorb more water and sodium, increasing blood volume and pressure. All together known as renin-angiotensin-aldosterone system (RAAS). All together known as renin-angiotensin-aldosterone system (RAAS).

45. Atrial natriuretic factor (ANF) A peptide that opposes the RAAS and decreases blood pressure by inhibiting release of renin. A peptide that opposes the RAAS and decreases blood pressure by inhibiting release of renin.

46. Examples of Environmental Adaptations of the Vertebrate Kidney Mammals excrete very hyperosmotic urine so they have longer loops of henle. Mammals excrete very hyperosmotic urine so they have longer loops of henle. Birds and other reptiles have uric acid as the nitrogen waste molecule, which can be excreted as a paste, reducing urine volume. Birds and other reptiles have uric acid as the nitrogen waste molecule, which can be excreted as a paste, reducing urine volume. Amphibians can reabsorb water across the epithelium of the urinary bladder. Amphibians can reabsorb water across the epithelium of the urinary bladder. Marine bony fishes excrete little urine, so they must get rid of double charged ions by excreting them with urine. Marine bony fishes excrete little urine, so they must get rid of double charged ions by excreting them with urine.