Osmoregulation and Excretion Chapter 44 Osmoregulation and Excretion

How does an albatross drink salt water without ill effect? Figure 44.1 How does an albatross drink salt water without ill effect?

Osmoconformers vs. Osmoregulators What is the difference?

Osmotic Challenges Osmoconformers, consisting only of some marine animals, are isoosmotic with their surroundings and do not regulate their osmolarity Osmoregulators expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment (stenohaline and euryhaline) © 2011 Pearson Education, Inc.

Do I drink water? Describe my pee. Do I drink water? Describe my pee.

(a) Osmoregulation in a marine fish Figure 44.3 (a) Osmoregulation in a marine fish (b) Osmoregulation in a freshwater fish Gain of water and salt ions from food Excretion of salt ions from gills Osmotic water loss through gills and other parts of body surface Gain of water and some ions in food Uptake of salt ions by gills Osmotic water gain through gills and other parts of body surface Figure 44.3 Osmoregulation in marine and freshwater bony fishes: a comparison. Gain of water and salt ions from drinking seawater Excretion of salt ions and small amounts of water in scanty urine from kidneys Key Excretion of salt ions and large amounts of water in dilute urine from kidneys Water Salt

Figure 44.4 Sockeye salmon (Oncorhynchus nerka), euryhaline osmoregulators

Water balance in a kangaroo rat (2 mL/day) Figure 44.6 Water balance in a kangaroo rat (2 mL/day) Water balance in a human (2,500 mL/day) Ingested in food (0.2) Ingested in food (750) Ingested in liquid (1,500) Water gain (mL) Derived from metabolism (1.8) Derived from metabolism (250) Figure 44.6 Water balance in two terrestrial mammals. Feces (0.09) Feces (100) Water loss (mL) Urine (0.45) Urine (1,500) Evaporation (1.46) Evaporation (900)

Figure 44.UN01 Animal Inflow/Outflow Urine Freshwater fish. Lives in water less concentrated than body fluids; fish tends to gain water, lose salt Does not drink water Large volume of urine Salt in (active trans- port by gills) H2O in Urine is less concentrated than body fluids Salt out Marine bony fish. Lives in water more concentrated than body fluids; fish tends to lose water, gain salt Drinks water Small volume of urine Salt in H2O out Urine is slightly less concentrated than body fluids Salt out (active transport by gills) Figure 44.UN01 Summary figure, Concept 44.1 Terrestrial vertebrate. Terrestrial environment; tends to lose body water to air Drinks water Moderate volume of urine Salt in (by mouth) Urine is more concentrated than body fluids H2O and salt out 13

Counter-current exchange in salt-excreting nasal glands Counter-current exchange in salt-excreting nasal glands What else exhibits c-c e? Secretory cell of transport epithelium Lumen of secretory tubule Vein Artery Nasal salt gland Ducts Nasal gland Salt ions Capillary Secretory tubule Transport epithelium Nostril with salt secretions (a) Location of nasal glands in a marine bird (b) Secretory tubules Blood flow Salt secretion Figure 44.7 Countercurrent exchange in salt-excreting nasal glands. Key (c) Countercurrent exchange Salt movement Blood flow Central duct

Most aquatic animals, including most bony fishes Figure 44.8 Proteins Nucleic acids Amino acids Nitrogenous bases —NH2 Amino groups Most aquatic animals, including most bony fishes Mammals, most amphibians, sharks, some bony fishes Many reptiles (including birds), insects, land snails Figure 44.8 Forms of nitrogenous waste. Ammonia Urea Uric acid

Figure 44.9 Figure 44.9 Recycling nitrogenous waste.

Key steps of excretory system function: an overview. 1 Filtration Capillary Filtrate Excretory tubule 2 Reabsorption Figure 44.10 Key steps of excretory system function: an overview. 3 Secretion Urine 4 Excretion

Components of a metanephridium: Figure 44.12 Coelom Capillary network Components of a metanephridium: Collecting tubule Figure 44.12 Metanephridia of an earthworm. Internal opening Bladder External opening

Salt, water, and nitrogenous wastes Figure 44.13 Digestive tract Rectum Hindgut Intestine Midgut (stomach) Malpighian tubules Salt, water, and nitrogenous wastes Feces and urine To anus Malpighian tubule Figure 44.13 Malpighian tubules of insects. Rectum Reabsorption HEMOLYMPH

Excretory Organs Kidney Structure Nephron Types Cortical nephron Figure 44.14-a Excretory Organs Kidney Structure Nephron Types Cortical nephron Juxtamedullary nephron Renal cortex Posterior vena cava Renal medulla Renal artery Renal artery and vein Kidney Renal vein Renal cortex Aorta Ureter Figure 44.14 Exploring: the Mammalian Excretory System Ureter Renal medulla Urinary bladder Urethra Renal pelvis

Nephron Organization Afferent arteriole from renal artery Glomerulus Figure 44.14-b Nephron Organization Afferent arteriole from renal artery Glomerulus Bowman’s capsule Proximal tubule Peritubular capillaries Distal tubule Efferent arteriole from glomerulus Branch of renal vein Figure 44.14 Exploring: the Mammalian Excretory System Descending limb Loop of Henle Vasa recta Collecting duct 200 m Ascending limb Blood vessels from a human kidney. Arterioles and peritubular capillaries appear pink; glomeruli appear yellow.

Animation: Bowman’s Capsule and Proximal Tubule Right-click slide / select “Play” © 2011 Pearson Education, Inc.

Proximal tubule Distal tubule Filtrate CORTEX Loop of Henle Figure 44.15 Proximal tubule Distal tubule NaCl Nutrients H2O HCO3 H2O K NaCl HCO3 H NH3 K H Filtrate CORTEX Loop of Henle NaCl H2O OUTER MEDULLA NaCl Collecting duct Figure 44.15 The nephron and collecting duct: regional functions of the transport epithelium. Key Urea Active transport NaCl H2O Passive transport INNER MEDULLA

Animation: Loop of Henle and Distal Tubule Right-click slide / select “Play” © 2011 Pearson Education, Inc.

Animation: Collecting Duct Right-click slide / select “Play” © 2011 Pearson Education, Inc.

Osmolarity of interstitial fluid (mOsm/L) Figure 44.16-1 Osmolarity of interstitial fluid (mOsm/L) 300 300 300 300 H2O CORTEX 400 400 H2O H2O OUTER MEDULLA H2O 600 600 Figure 44.16 How the human kidney concentrates urine: the two-solute model. H2O H2O 900 900 Key H2O INNER MEDULLA Active transport 1,200 1,200 Passive transport

Osmolarity of interstitial fluid (mOsm/L) Figure 44.16-2 Osmolarity of interstitial fluid (mOsm/L) 300 300 300 100 100 300 H2O NaCl CORTEX 400 200 400 H2O NaCl H2O NaCl OUTER MEDULLA H2O NaCl 600 400 600 Figure 44.16 How the human kidney concentrates urine: the two-solute model. H2O NaCl H2O NaCl 900 700 900 Key H2O NaCl INNER MEDULLA Active transport 1,200 1,200 Passive transport

Osmolarity of interstitial fluid (mOsm/L) Figure 44.16-3 Osmolarity of interstitial fluid (mOsm/L) 300 300 300 100 100 300 300 H2O NaCl H2O CORTEX 400 200 400 400 H2O NaCl H2O NaCl H2O NaCl H2O NaCl OUTER MEDULLA H2O NaCl H2O 600 400 600 600 Figure 44.16 How the human kidney concentrates urine: the two-solute model. H2O NaCl H2O Urea H2O NaCl H2O 900 700 900 Urea Key H2O NaCl H2O INNER MEDULLA Urea Active transport 1,200 1,200 1,200 Passive transport

Loops of Henle quiz… Who would have longer loops of Henle, a beaver or a desert hare?

Loops of Henle quiz… Who would have longer loops of Henle, a beaver or a desert hare? WHY?

Figure 44.18 A vampire bat (Desmodus rotundas), a mammal with a unique excretory situation.

How do we hold our pee (Micturition reflex video)

Antidiuretic Hormone The osmolarity of the urine is regulated by nervous and hormonal control Antidiuretic hormone (ADH) makes the collecting duct epithelium more permeable to water An increase in osmolarity triggers the release of ADH, which helps to conserve water © 2011 Pearson Education, Inc.

Animation: Effect of ADH Right-click slide / select “Play” © 2011 Pearson Education, Inc.

Osmoreceptors in hypothalamus trigger release of ADH. Figure 44.19-1 Osmoreceptors in hypothalamus trigger release of ADH. Thirst Hypothalamus ADH Pituitary gland STIMULUS: Increase in blood osmolarity (for instance, after sweating profusely) Figure 44.19 Regulation of fluid retention in the kidney by antidiuretic hormone (ADH). Homeostasis: Blood osmolarity (300 mOsm/L)

Osmoreceptors in hypothalamus trigger release of ADH. Figure 44.19-2 Osmoreceptors in hypothalamus trigger release of ADH. Thirst Hypothalamus Drinking reduces blood osmolarity to set point. ADH Increased permeability Pituitary gland Distal tubule STIMULUS: Increase in blood osmolarity (for instance, after sweating profusely) Figure 44.19 Regulation of fluid retention in the kidney by antidiuretic hormone (ADH). H2O reab- sorption helps prevent further osmolarity increase. Collecting duct Homeostasis: Blood osmolarity (300 mOsm/L)

Second-messenger signaling molecule Figure 44.20 ADH receptor LUMEN Collecting duct COLLECTING DUCT CELL ADH cAMP Second-messenger signaling molecule Storage vesicle Exocytosis Figure 44.20 ADH response pathway in the collecting duct. Aquaporin water channel H2O H2O

How might alcohol affect your water balance? © 2011 Pearson Education, Inc.

The Renin-Angiotensin-Aldosterone System The renin-angiotensin-aldosterone system (RAAS) is part of a complex feedback circuit that functions in homeostasis A drop in blood pressure near the glomerulus causes the juxtaglomerular apparatus (JGA) to release the enzyme renin Renin triggers the formation of the peptide angiotensin II © 2011 Pearson Education, Inc.

Angiotensin II Raises blood pressure and decreases blood flow to the kidneys Stimulates the release of the hormone aldosterone, which increases blood volume and pressure © 2011 Pearson Education, Inc.

Homeostasis: Blood pressure, volume Figure 44.22-1 JGA releases renin. Distal tubule Renin Juxtaglomerular apparatus (JGA) STIMULUS: Low blood volume or blood pressure (for example, due to dehydration or blood loss) Figure 44.22 Regulation of blood volume and blood pressure by the renin-angiotensin-aldosterone system (RAAS). Homeostasis: Blood pressure, volume

Homeostasis: Blood pressure, volume Figure 44.22-2 Liver Angiotensinogen JGA releases renin. Distal tubule Renin Angiotensin I ACE Angiotensin II Juxtaglomerular apparatus (JGA) STIMULUS: Low blood volume or blood pressure (for example, due to dehydration or blood loss) Figure 44.22 Regulation of blood volume and blood pressure by the renin-angiotensin-aldosterone system (RAAS). Homeostasis: Blood pressure, volume

Juxtaglomerular apparatus (JGA) Figure 44.22-3 Liver Angiotensinogen JGA releases renin. Distal tubule Renin Angiotensin I ACE Angiotensin II Juxtaglomerular apparatus (JGA) STIMULUS: Low blood volume or blood pressure (for example, due to dehydration or blood loss) Adrenal gland Figure 44.22 Regulation of blood volume and blood pressure by the renin-angiotensin-aldosterone system (RAAS). Aldosterone Arterioles constrict, increasing blood pressure. More Na and H2O are reabsorbed in distal tubules, increasing blood volume. Homeostasis: Blood pressure, volume

Homeostatic Regulation of the Kidney ADH and RAAS both increase water reabsorption, but only RAAS will respond to a decrease in blood volume Another hormone, atrial natriuretic peptide (ANP), opposes the RAAS ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin © 2011 Pearson Education, Inc.

Check out Bioflix, and Bozeman “Osmoregulation”

Test Your Understanding question 7 Figure 44.UN02 Appendix A: answer to Test Your Understanding, question 7