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Chapter 44

Chapter 44. Regulating the Internal Environment. Osmoregulation balances the uptake and loss of water and solutes. Osmoconformers - isoosmotic with their surroundings do not regulate their osmolarity Osmoregulators - control water gain/loss in hyperosmotic or hypoosmotic environment.

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Chapter 44

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  1. Chapter 44 Regulating the Internal Environment

  2. Osmoregulationbalances the uptake and loss of water and solutes • Osmoconformers- isoosmotic with their surroundings do not regulate their osmolarity • Osmoregulators- control water gain/loss in hyperosmotic or hypoosmotic environment

  3. Selectively permeable membrane Solutes Net water flow Water Hypoosmotic side Hyperosmotic side

  4. Marine Animals • Bony fishes in sea water lose water by osmosis and gain salt by diffusion and from food • They balance water loss by drinking seawater and excreting salts

  5. Excretion of salt ions from gills Osmotic water loss through gills and other parts of body surface Gain of water and salt ions from food Gain of water and salt ions from drinking seawater Excretion of salt ions and small amounts of water in scanty urine from kidneys (a) Osmoregulation in a saltwater fish

  6. Freshwater Animals • Constantly take in water by osmosis and lose salts by diffusion • Maintain water balance by excreting large amounts of dilute urine • Salts lost by diffusion are replaced in foods and by uptake across the gills

  7. Osmotic water gain through gills and other parts of body surface Uptake of water and some ions in food Uptake of salt ions by gills Excretion of large amounts of water in dilute urine from kidneys (b) Osmoregulation in a freshwater fish

  8. Animals That Live in Temporary Waters • Anhydrobiosis- Some aquatic invertebrates that lose almost all their body water and survive in a dormant state (b) Dehydrated tardigrade (a) Hydrated tardigrade

  9. Land Animals • Manage water budgets by drinking and eating moist foods and using metabolic water

  10. 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 (250) Derived from metabolism (1.8)

  11. Water balance in a kangaroo rat (2 mL/day) Water balance in a human (2,500 mL/day) Feces (0.09) Feces (100) Water loss (mL) Urine (1,500) Urine (0.45) Evaporation (900) Evaporation (1.46)

  12. Transport Epithelia in Osmoregulation • Animals regulate the composition of body fluid that bathes their cells • Transport epithelia are specialized epithelial cells that regulate solute movement • They are essential components of osmotic regulation and metabolic waste disposal • They are arranged in complex tubular networks • An example is in salt glands of marine birds, which remove excess sodium chloride from the blood

  13. EXPERIMENT Nasal salt gland Ducts Nostril with salt secretions

  14. Vein Artery Secretory tubule Secretory cell Salt gland Capillary Secretory tubule Transport epithelium NaCl NaCl Direction of salt movement Central duct Blood flow Salt secretion (b) (a)

  15. An animal’s nitrogenous wastes reflect its phylogeny and habitat • Nitrogenous wastes result from the breakdown of proteins and nucleic acids • Some animals convert toxic ammonia (NH3) to less toxic compounds prior to excretion

  16. Proteins Nucleic acids Amino acids Nitrogenous bases Amino groups Most aquatic animals, including most bony fishes Mammals, most amphibians, sharks, some bony fishes Many reptiles (including birds), insects, land snails Ammonia Uric acid Urea

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

  18. Forms of Nitrogenous Wastes • Ammonia- Needs lots of water to excrete. No energy needed. • Urea- The liver converts ammonia to less toxic urea. Excreted from the kidneys. Energy required. • Uric Acid- Insects, land snails, and reptiles, including birds, excrete uric acid. Lots of energy needed. Uric acid is insoluble in water and is secreted as a paste with little water loss.

  19. Excretory Processes Filtration Capillary • Filtration: pressure-filtering of body fluids • Reabsorption: reclaiming valuable solutes • Secretion: adding toxins and other solutes from the body fluids to the filtrate • Excretion: removing the filtrate from the system Filtrate Excretory tubule Reabsorption Secretion Urine Excretion

  20. Protonephridia- a network of dead-end tubules connected to external openings (planarian) Nucleus of cap cell Cilia Flame bulb Interstitial fluid flow Opening in body wall Tubule Tubules of protonephridia Tubule cell

  21. Metanephridia- tubules that collect coelomic fluid and produce dilute urine (earthworm) Coelom Capillary network Components of a metanephridium: Internal opening Collecting tubule Bladder External opening

  22. Malpighian Tubules- remove nitrogenous wastes from hemolymph (insects and arthropods) Digestive tract Rectum Hindgut Intestine Midgut (stomach) Malpighian tubules Salt, water, and nitrogenous wastes Feces and urine Rectum Reabsorption HEMOLYMPH

  23. Kidneys • Kidneys, the excretory organs of vertebrates, function in both excretion and osmoregulation Renal medulla Posterior vena cava Renal cortex Renal artery and vein Kidney Renal pelvis Aorta Ureter Urinary bladder Ureter Urethra Section of kidney from a rat (a) Excretory organs and major associated blood vessels (b) Kidney structure 4 mm

  24. Structure of the Mammalian Excretory System • Each kidney is supplied with blood by a renal artery and drained by a renal vein • Urine exits each kidney through a duct called the ureter • Both ureters drain into a urinary bladder, and urine is expelled through a urethra • The kidney has two distinct regions: an outer renal cortex and an inner renal medulla • The nephron, the functional unit of the kidney, consists of a single long tubule and a ball of capillaries called the glomerulus • Bowman’s capsule surrounds and receives filtrate from the glomerulus Animation: Nephron Introduction

  25. Posterior vena cava Renal artery and vein Kidney Aorta Ureter Urinary bladder Urethra (a) Excretory organs and major associated blood vessels

  26. Renal medulla Renal cortex Renal pelvis Ureter Section of kidney from a rat (b) Kidney structure 4 mm

  27. Filtration of the Blood • Blood pressure forces fluid from the blood in the glomerulus into the Bowman’s capsule • The filtrate contains salts, glucose, amino acids, vitamins, and nitrogenous wastes

  28. Afferent arteriole from renal artery Glomerulus Juxtamedullary nephron Cortical nephron Bowman’s capsule 10 µm SEM Proximal tubule Peritubular capillaries Renal cortex Efferent arteriole from glomerulus Collecting duct Distal tubule Branch of renal vein Renal medulla Collecting duct Descending limb To renal pelvis Loop of Henle Ascending limb Vasa recta (c) Nephron types (d) Filtrate and blood flow

  29. Pathway of the Filtrate • From Bowman’s capsule, the filtrate passes through three regions of the nephron: the proximal tubule, the loop of Henle, and the distal tubule • Fluid from nephrons flows into a collecting duct, which lead to the renal pelvis

  30. Juxtamedullary nephron Cortical nephron Renal cortex Collecting duct Renal medulla To renal pelvis (c) Nephron types

  31. Glomerulus Afferent arteriole from renal artery Bowman’s capsule 10 µm 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. From Blood Filtrate to Urine • Proximal Tubule- Reabsorption of ions, water, and nutrients takes place • Descending Limb of the Loop of Henle- Reabsorption of water continues through channels formed by aquaporinproteins. The filtrate becomes increasingly concentrated • Ascending Limb of the Loop of Henle. Salt but not water is able to diffuse from the tubule into the interstitial fluid. The filtrate becomes increasingly dilute • Distal Tubule- Regulates the K+ and NaCl concentrations of body fluids • Collecting Duct- Carries filtrate through the medulla to the renal pelvis

  33. Animation: Bowman’s Capsule and Proximal Tubule Animation: Loop of Henle and Distal Tubule Animation: Collecting Duct Animation: Collecting Duct

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

  35. Adaptations of the Vertebrate Kidney to Diverse Environments • Mammals- Mammals that inhabit dry environments have long loops of Henle, while those in fresh water have relatively short loops • Birds and Other Reptiles- Birds have shorter loops of Henle but conserve water by excreting uric acid instead of urea

  36. Adaptations of the Vertebrate Kidney to Diverse Environments • Freshwater Fishes and Amphibians- Freshwater fishes conserve salt in their distal tubules and excrete large volumes of dilute urine. Amphibians conserve water on land by reabsorbing water from the urinary bladder • Marine Bony Fishes- are hypoosmotic compared to their environment and excrete very little urine

  37. Antidiuretic Hormone • Increases water reabsorption in the distal tubules and collecting ducts of the kidney. Helps to conserve water. • Alcohol is a diuretic as it inhibits the release of ADH Animation: Effect of ADH

  38. The Renin-Angiotensin-Aldosterone System • A drop in blood pressure near the glomerulus causes the juxtaglomerular apparatus (JGA) to release the enzyme rennin. • Renintriggers the formation of the peptide angiotensin II. • AngiotensinII Raises blood pressure and decreases blood flow to the kidneys. • Stimulates the release of the hormone aldosterone, which increases blood volume and pressure

  39. Homeostatic Regulation of the Kidney • ADH and RAAS both increase water reabsorption, but only RAAS will respond to a decrease in blood volume • Atrialnatriuretic factor (ANF), opposes the RAAS. ANP is released in response to an increase in blood volume and pressure and inhibits the release of renin

  40. Animal Inflow/Outflow Urine Large volume of urine Freshwater fish Does not drink water Salt in H2O in (active trans- port by gills) Urine is less concentrated than body fluids Salt out

  41. Animal Inflow/Outflow Urine Bony marine fish Drinks water Small volume of urine H2O out Salt in Urine is slightly less concentrated than body fluids Salt out (active transport by gills)

  42. Urine Inflow/Outflow Animal Terrestrial vertebrate Moderate volume of urine Drinks water Salt in (by mouth) Urine is more concentrated than body fluids H2O and salt out

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