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Osmoregulation

Osmoregulation. Chapter 44. Osmotic Balance. 2/3’s body is water Intracellular & extracellular Ions (solutes) Na +1 , Cl -1 Mg 2+, Ca 2+. Osmolarity. Hypertonic Hypotonic Isotonic Normal saline (0.9%) 5% dextrose. Osmoregulation. Osmocomfomers

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Osmoregulation

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  1. Osmoregulation Chapter 44

  2. Osmotic Balance • 2/3’s body is water • Intracellular & extracellular • Ions (solutes) • Na+1, Cl-1 • Mg2+, Ca2+

  3. Osmolarity • Hypertonic • Hypotonic • Isotonic • Normal saline (0.9%) • 5% dextrose

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

  5. Osmoregulation

  6. Nitrogenous wastes • Amino acids & nucleic acids contain nitrogen • Break downs-waste • NH3 • Urea • Mammals, amphibians • Uric acid • Birds, reptiles, insects

  7. Nitrogenous wastes

  8. Urea • Uric acid

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

  10. Excretion • Filters • Reabsorbs • Secretes • Excretion • Blood is filtered • Ions & nutrients are recovered • Wastes & water form urine

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

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

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

  14. Kidney

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

  16. Nephron

  17. Kidney

  18. Kidney

  19. Pathway

  20. 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

  21. 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

  22. Pathway through kidney

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

  24. Nephron E:\Chapter_44\A_PowerPoint_Lectures\44_Lecture_Presentation\44_14NephronIntroduction_A.html

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

  26. Glomerulus Afferent arteriole from renal artery Bowman’s capsule 10 µm SEM Proximal tubule Peritubular capillaries Nephron 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

  27. Pathway through kidney • 1000-2000L 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)

  28. Regulation diagram

  29. 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

  30. Closer look E:\Chapter_44\A_PowerPoint_Lectures\44_Lecture_Presentation\44_15BowmansCapsule_A.html

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

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

  33. Closer look E:\Chapter_44\A_PowerPoint_Lectures\44_Lecture_Presentation\44_15LoopOfHenle_A.html

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

  35. Closer look E:\Chapter_44\A_PowerPoint_Lectures\44_Lecture_Presentation\44_15CollectingDuct_A.html

  36. Regulation diagram

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

  38. 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

  39. Osmoreceptors in hypothalamus trigger release of ADH. Thirst Hypothalamus Drinking reduces blood osmolarity to set point. ADH 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)

  40. ADH E:\Chapter_44\A_PowerPoint_Lectures\44_Lecture_Presentation\44_19EffectOfADH_A.html

  41. 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

  42. 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

  43. 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

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

  45. 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

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

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