Finals 1 - Osmoregulation PDF

(1st Semester) By Dr. Asif Ahmad Kamgar Assistant Professor Department of Zoology  Freshwater animals show adaptations that reduce water uptake and conserve solutes  Desert and marine animals face desiccating environments that can quickly deplete body water  Osmoregulation reg...

(1st Semester) By Dr. Asif Ahmad Kamgar Assistant Professor Department of Zoology  Freshwater animals show adaptations that reduce water uptake and conserve solutes  Desert and marine animals face desiccating environments that can quickly deplete body water  Osmoregulation regulates solute concentrations and balances the gain and loss of water  Excretion gets rid of metabolic wastes Osmoregulation balances the uptake and loss of water  Osmoregulation and on is based largely controlled movement of solutes between solutes internal fluids and the external environment  Osmoregulators expend energy to control water uptake and loss in a hyperosmotic or hypoosmotic environment  Gain of water and Osmotic water loss salt ions from food through gills and other parts and by drinking of body surface seawater Excretion of salt ions Excretion of and small amounts salt ions of water in scanty from gills urine from kidneys Osmoregulation in a saltwater fish  Osmotic water gain through gills and other parts of body surface Uptake of water and some ions in food Uptake of Excretion of salt ions large amounts of by gills water in dilute urine from kidneys Osmoregulation in a freshwater fish Effects of osmoregulation  Affects internal pH, metabolite concentration, waste management.  Affects composition of internal body fluid (e.g. hemolymph, interstitial fluid).  Maintain cytoplasmic composition in cells Salt Excreting Glands  Birds, although they have loops of Henle, cannot make a very concentrated urine - their loops are fairly short.  Marine birds and reptiles (which cannot make a concentrated urine) have evolved extrarenal routes of salt excretion.  Birds use nasal glands that release salt excretions into the nasal passages.  Sea turtles have modified tear ducts that secrete salt into the orbit of the eye. Osmoconformers: some marine animals animals whose body fluids are isotonic to their environment. They do not actively adjust the internal osmolarity. Osmoregulators: Animals whose body fluids are hypotonic. They will gain water from the environment and must continuously eliminate excess water. Animals whose body fluids are hypertonic. They will lose water to the environment and must continuously take in excess water. Osmoregulators must expend energy to maintain osmotic balance (5% to 30% of metabolic rate).  Proteins Nucleic acids Amino acids Nitrogenous bases —NH2 Amino groups Most aquatic Mammals, most Many reptiles animals, amphibians, (including including most sharks, some bony birds), insects, bony fishes fishes land snails Ammonia Urea Uric acid Ammonia  Animals that excrete nitrogenous wastes as ammonia need lots of water  They release ammonia across the whole body surface or through gills Urea  The liver of mammals and most adult amphibians converts ammonia to less toxic urea  The circulatory system carries urea to the kidneys, where it is excreted Uric Acid  Insects, land snails, and many reptiles, including birds, mainly excrete uric acid  Uric acid is largely insoluble in water and can be secreted as a paste with little water loss Excretory Processes  Most excretory systems produce urine by refining a filtrate derived from body fluids  Key functions of most excretory systems:  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 Nephrons and associated blood vessels are the functional unit of the mammalian kidney  Kidneys, the excretory organs of vertebrates, function in both excretion and osmoregulation  The mammalian excretory system centers on paired kidneys, which are also the principal site of water balance and salt regulation  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 common urinary bladder Posterior vena cava Renal artery and vein Kidney Renal Aorta medulla Renal Ureter cortex Renal Urinary bladder pelvis Urethra Excretory organs and Ureter major associated blood vessels Kidney structure Section of kidney from a rat Juxta- Cortical medullary nephron Afferent nephron arteriole Glomerulus from renal artery Bowman’s capsule Proximal tubule Renal Peritubular capillaries cortex Collecting duct SEM 20 µm Efferent Renal arteriole from Distal medulla glomerulus tubule To Collecting renal Branch of renal vein duct pelvis Descending Loop limb Nephron of Henle Ascending limb Vasa recta Filtrate and blood flow Structure and Function of the Nephron and Associated Structures The mammalian kidney has two distinct regions: an outer renal cortex and an inner renal medulla The nephron consists of a single long tubule and a ball of capillaries called the glomerulus Filtration of the Blood  Filtration occurs as blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman’s capsule  The filtrate in Bowman’s capsule mirrors the concentration of solutes in blood plasma 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 several nephrons flows into a collecting duct From Blood Filtrate to Urine: A Closer Look  Filtrate becomes urine as it flows through the mammalian nephron and collecting duct  Secretion and reabsorption in the proximal tubule change the filtrate’s volume and composition  Reabsorption of water occurs as filtrate moves into the descending limb of the loop of Henle  In the ascending limb of the loop of Henle, salt diffuses from the permeable tubule into the interstitial fluid.  The distal tubule regulates the K+ and NaCl concentrations of body fluids.  The collecting duct carries filtrate through the medulla to the renal pelvis and reabsorbs NaCl.  The mammalian kidney conserves water by producing urine that is much more concentrated than body fluids.  Proximal tubule Distal tubule NaCl Nutrients H2O HCO3– H2O K+ NaCl HCO3– H+ NH3 K+ H+ CORTEX Descending limb Thick segment Filtrate of loop of of ascending Henle limb H2O Salts (NaCl and others) NaCl HCO3– H2O H+ OUTER NaCl MEDULLA Urea Glucose; amino acids Thin segment Collecting Some drugs of ascending duct limb Key Urea Active transport NaCl H2O Passive transport INNER MEDULLA Solute Gradients and Water Conservation  The action and precise arrangement of the loops of Henle and collecting ducts are largely responsible for the osmotic gradient that concentrates the urine.  NaCl and urea contribute to the osmolarity of the interstitial fluid, which causes reabsorption of water in the kidney and concentrates the urine.  Osmolarity of interstitial fluid 300 (mosm/L) 300 100 300 100 300 300 H2O NaCl H2O CORTEX Active transport 400 200 400 400 H2O NaCl H2O Passive transport H2O NaCl H2O OUTER H2O NaCl H2O MEDULLA 600 400 600 600 H2O NaCl H2O Urea H2O NaCl H2O 900 700 900 Urea H2O NaCl H2O INNER Urea MEDULLA 1200 1200 1200  The collecting duct conducts filtrate through the osmolarity gradient, and more water exits the filtrate by osmosis  Urea diffuses out of the collecting duct as it traverses the inner medulla  Urea and NaCl form the osmotic gradient that enables the kidney to produce urine that is hyperosmotic to the blood Regulation of Kidney Function  The osmolarity of the urine is regulated by nervous and hormonal control of water and salt reabsorption in the kidneys  Antidiuretic hormone (ADH) increases water reabsorption in the distal tubules and collecting ducts of the kidney.  Aldosterone is a hormone that regulates salt reabsorption in the kidney.