Biology II FBI102 Lecture Notes PDF

7 Assoc. Prof. Dr. Melis SÜMENGEN ÖZDENEFE. 1 2  Physiological systems of animals operate in a fluid environment That mean a lot of things to do  Relative concentrations of water and solutes must be maint...

7 Assoc. Prof. Dr. Melis SÜMENGEN ÖZDENEFE. 1 2  Physiological systems of animals operate in a fluid environment That mean a lot of things to do  Relative concentrations of water and solutes must be maintained within fairly narrow limits _.‫عضالت امللساء ← وتعني العضالت من دون نواة‬.  Osmoregulation controls solute concentrations and balances water gain and loss 3  Desert and marine animals face desiccating environments that can quickly deplete body water  Freshwater animals survive by conserving solutes and absorbing salts from their surroundings  Excretion rids the body of nitrogenous metabolites and other waste products 4  Osmoregulation is based largely on balancing the uptake and loss of water and solutes  The driving force for movement of solutes and water is a concentration gradient of one or more solutes across the plasma membrane 5  Water enters and leaves cells by osmosis  Osmolarity, the solute concentration of a solution, determines the movement of water across a selectively permeable membrane  If two solutions are isoosmotic, water molecules will cross the membrane at equal rates in both directions 6  If two solutions differ in osmolarity, the net flow of water is from the hypoosmotic (less concentrated) to the hyperosmotic (more concentrated) solution 7  Selectively permeable membrane Solutes Water Hyperosmotic side: Hypoosmotic side: Higher solute Lower solute concentration concentration Lower free H O Higher free H O 2 2 concentration concentration Net water flow 8  The type and quantity of an animal’s waste products may greatly affect its water balance  Among the most significant wastes are nitrogenous breakdown products of proteins and nucleic acids  Some animals convert toxic ammonia (NH3) to less toxic compounds prior to excretion 9  Animals excrete nitrogenous wastes in different forms: ammonia, urea, or uric acid  These differ in toxicity and the energy costs of producing them 10  Animals (most aquatic animals, including most bony fishes) that excrete nitrogenous wastes as ammonia need access to lots of water  They release ammonia across the whole body surface 11  Most terrestrial mammals and many marine species excrete urea, which is less toxic than ammonia  In vertebrates urea is produced in the liver  The circulatory system carries urea to the kidneys, where it is excreted  Conversion of ammonia to urea is energetically expensive; excretion of urea requires less water than ammonia 12  Insects, land snails, and many reptiles, including birds, mainly excrete uric acid  Uric acid is relatively nontoxic and does not dissolve readily in water  It can be secreted as a paste with little water loss  Uric acid is more energetically expensive to produce than urea 13  Proteins Nucleic acids Amino Nitrogenous acids bases Amino groups Most aquatic Mammals, most Many reptiles animals, including amphibians, (including birds), most bony fishes sharks, some insects, land bony fishes snails Ammonia Urea Uric acid 14  Excretory systems regulate solute movement between internal fluids and the external environment  These systems are central to homeostasis 15  Most excretory systems produce urine by refining a filtrate derived from body fluids  Key functions of most excretory systems ◦ Filtration: Filtering of body fluids ◦ Reabsorption: Reclaiming valuable solutes ◦ Secretion: Adding nonessential solutes and wastes to the filtrate ◦ Excretion: Processed filtrate containing nitrogenous wastes is released from the body 16  1 Filtration Capillary Filtrate Excretory tubule 2 Reabsorption 3 Secretion Urine 4 Excretion 17  Systems that perform basic excretory functions vary widely among animal groups  They usually involve a complex network of tubules 18  A protonephridium (planarian) is a network of dead-end tubules connected to external openings  The smallest branches of the network are capped by a cellular unit called a flame bulb  These tubules excrete a dilute fluid and function in osmoregulation 19 Tubules of protonephridia INTERSTITIAL FLUID Cap Cilia cell Tubule cell Flame bulb Tubule Opening in body wall 20  Each segment of an earthworm has a pair of open-ended metanephridia  Metanephridia consist of tubules that collect coelomic fluid and produce dilute urine for excretion  Metanephridia of earthworms function in excretion and osmoregulation 21  Coelom Capillary network Components of a metanephridium: Collecting tubule Internal opening Bladder External opening 22  In insects and other terrestrial arthropods, Malpighian tubules remove nitrogenous wastes from hemolymph and function in osmoregulation  Insects produce a relatively dry waste matter, mainly uric acid, an important adaptation to terrestrial life  Some terrestrial insects can also take up water from the air 23  Digestive tract Rectum Intestine Hindgut Midgut Malpighian (stomach) tubules Salt, water, and Feces and urine To anus nitrogenous wastes Malpighian tubule Rectum Reabsorption HEMOLYMPH 24  Kidneys, the excretory organs of vertebrates, function in both excretion and osmoregulation  The numerous tubules of kidneys are highly organized  The vertebrate excretory system also includes ducts and other structures that carry urine from the tubules out of the kidney and out of the body 25 26 27 Excretory Organs Kidney Structure Nephron Types Renal Cortical Juxtamedullary cortex nephron nephron Renal Posterior medulla vena cava Renal Renal artery artery and vein Kidney Renal Aorta vein Renal cortex Ureter Urinary Ureter Renal bladder medulla Urethra Renal pelvis 28 Nephron Organization Afferent arteriole from renal artery Glomerulus Bowman’s capsule Proximal tubule Peritubular Distal capillaries tubule Efferent arteriole from glomerulus Branch of renal vein Descending limb Vasa recta Loop of Collecting Henle duct 200 µm Ascending limb Blood vessels from a human kidney. Arterioles and peritubular capillaries appear pink; glomeruli appear yellow. 29  The filtrate produced in Bowman’s capsule contains salts, glucose, amino acids, vitamins, nitrogenous wastes, and other small molecules 30 Proximal Tubule  Reabsorption of ions, water, and nutrients takes place in the proximal tubule  Molecules are transported actively and passively from the filtrate into the interstitial fluid and then capillaries 31  As the filtrate passes through the proximal tubule, materials to be excreted become concentrated  Some toxic materials are actively secreted into the filtrate 32 Descending Limb of the Loop of Henle  Reabsorption of water continues through channels formed by aquaporin proteins  Movement is driven by the high osmolarity of the interstitial fluid, which is hyperosmotic to the filtrate  The filtrate becomes increasingly concentrated 33 Ascending Limb of the Loop of Henle  In the 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 34 Distal Tubule  The distal tubule regulates the K+ and NaCl concentrations of body fluids  The controlled movement of ions (H+ and HCO3-) contributes to pH regulation 35 Collecting Duct  The collecting duct carries filtrate through the medulla to the renal pelvis  One of the most important tasks is reabsorption of solutes and water  Urine is hyperosmotic to body fluids 36  1 Proximal tubule 4 Distal tubule NaCl Nutrients H2O HCO3- H2O K+ NaCl HCO3- H+ NH3 K+ H+ Interstitial CORTEX fluid 3 Thick segment Filtrate 2 Descending limb of ascending of loop of limb H2O Henle Salts (NaCl and others) NaCl H2O HCO3- OUTER NaCl H+ MEDULLA Urea 3 Thin segment 5 Collecting Glucose, amino acids duct of ascending Some drugs limb Urea Active transport NaCl H2O Passive transport INNER MEDULLA 37  The mammalian kidney’s ability to conserve water is a key terrestrial adaptation  Hyperosmotic urine can be produced only because considerable energy is expended to transport solutes against concentration gradients  The two primary solutes affecting osmolarity are NaCl and urea 38  In the proximal tubule, filtrate volume decreases as water and salt are reabsorbed, but osmolarity remains the same  As the filtrate flows to the descending limb of the loop of Henle, solutes become more concentrated due to water leaving the tubule by osmosis  NaCl diffusing from the ascending limb maintains a high osmolarity in the interstitial fluid of the renal medulla 39  Energy is expended to actively transport NaCl from the filtrate in the upper part of the ascending limb  The countercurrent multiplier system involving the loop of Henle maintains a high salt concentration in the kidney  This system allows the vasa recta to supply the kidney with nutrients, without interfering with the osmolarity gradient 40  In the collecting duct, osmosis extracts water from the filtrate as it passes from cortex to medulla and encounters interstitial fluid of increasing osmolarity  Urine produced is isoosmotic to the interstitial fluid of the inner medulla, but hyperosmotic to blood and interstitial fluids elsewhere in the body 41  300 mOsm/L 300 300 300 H2O CORTEX 400 400 Active H2O transport Passive transport H2O H2O OUTER 600 600 MEDULLA H2O H2O 900 900 H2O INNER MEDULLA 1,200 1,200 42  300 mOsm/L 300 100 300 100 300 H2O NaCl CORTEX 400 200 400 Active H2O NaCl transport Passive transport H2O NaCl H2O NaCl OUTER 600 400 600 MEDULLA H2O NaCl H2O NaCl 900 700 900 H2O NaCl INNER MEDULLA 1,200 1,200 43  300 mOsm/L 300 100 300 100 300 300 H2O NaCl H2O CORTEX 400 200 400 400 Active H2O NaCl H2O transport NaCl Passive transport H2O NaCl H2O NaCl H2O NaCl H2O OUTER 600 400 600 600 MEDULLA H2O NaCl H2O Urea H2O NaCl H2O 900 700 900 Urea H2O NaCl H2O INNER Urea MEDULLA 1,200 1,200 1,200 44