Osmoregulation and Excretion: Sections 44.2,44.3, and 44.5 w/ some IB Topics

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Osmoregulation and ExcretionSections 44.2,44.3,
and 44.5 w/ some IB Topics

• Deanna, Stephanie, Christen

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Nitrogenous Wastes

• Breakdown products of proteins and nucleic acids
• Ammonia very soluble, highly toxic, tolerable
  only at low concentrations excreted b/c animal
  needs access to lots of water aquatic species
  readily lost by diffusion across body surface /
  thru gills to surrounding H2O
• Urea terrestrial animals (b/c less access to
  water for ammonia release) produced in the
  vertebrate liver by a metabolic cycle that
  combines ammonia w/ CO2 100,000x less toxic than
  NH3 disadvantage must expend energy to produce
  urea from NH3
• Uric Acid relatively nontoxic in insects, land
  snails, reptiles, birds largely insoluble in
  water excreted as semi-sold paste w/ lil water
  loss adv for animals w/ lil water access but
  lots of energy to produce (so lots of ATP needed)

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Pg. 927
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Influence of Evolution and Environment on
Nitrogenous Wastes

• Depends upon an animals evolutionary history and
  habitat esp availability of water
• Mode of reproduction affected which kind
• Shelled egg vs. shell-less egg or mammalian
  embryo
• Adjusting to environment
• Ex certain tortoise changes from urea to uric
  acid when temp increases and water less available
• Amount produced depends on energy budget type
  of food
• Ex endotherms eat more food so more wastes

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IB Syllabus!
Arrows pointing to the IB slides in this
presentation.
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11.3.9 Explain the presence of glucose in urine
of untreated diabetic patients

• Glucose is often present in the urine of
  untreated diabetic patients. This is because the
  glucose concentration of blood rises much higher
  than 90 mg per 100 ml, so the pumps in the
  proximal convoluted tubule cant reabsorb all the
  glucose that is filtered out into the glomerulus.

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11.3.8 Explain the differences in concentration
of proteins, glucose and urea between blood
plasma, glomerular filtrate and urine.
Comparison of Fluid in the Kidney
Content (mg per 100mg of blood)
Blood in renal artery Urine Glomerular filtrate Blood in renal veins
Glucose 90 0 90 90
Urea 30 2000 30 24
Proteins 740 0 0 740
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• Remember drawing this from yesterday? The next
  slide helps explain in more detail.

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11.3.4 Explain the process of ultrafiltration,
including blood pressure, fenestrated blood
capillaries, and basement membrane.

• Function of glomerulus is production of filtrate
  from blood by ultrafiltration
• Blood plasma escape through walls of capillaries
  remember video?, but in glomerulus 20 escapes
  (more than usual)
• Why this happens
• Blood pressure very high b/c efferent arteriole
  is narrower than afferent arteriole
• Capillaries in the glomerulus are fenestrated
  (porous)
• These pores are large enough to let any molecules
  through, but on the outside of the capillary wall
  is a basement membrane composed of a gel of
  glycoprotein. It lets all substances in the blood
  plasma through except plasma proteins.
• The fluid produced by ultrafiltration is
  collected by the Bowmans capsule and flows on
  into the proximal convoluted tubule.

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11.3.7 Explain the roles of the loop of Henle,
medulla, collecting duct and ADH (vasopressin) in
maintaining the water balance of the blood.
(pg102)
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Survey of Excretory Systems - Intro

• Various excretory mechanisms have evolved in
  animals for the purpose of osmoregulation and for
  the removal of toxins.
• Toxins include by-products of cellular
  metabolism, such as the nitrogen wastes.

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Contractile Vacuoles

• Found in the cytoplasm of various protists, such
  as paramecia and amoebas.
• These vacuoles accumulate water, merge with the
  plasma membrane, and release the water to the
  environment.

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Flame Cells

• Aka protonephridium
• Flatworms.
• Network of dead-end tubules lacking internal
  openings. The cells are distributed along a
  branched tube system that permeates the flatworm.
  
• Body fluids are filtered across the flame cells
  whose internal cilia move the fluids through the
  tube system.
• Wastes (water and salts) are excreted from the
  tubule system through pores that exit the body.
• Tubules reabsorb most solutes before the urine
  exits the body so the urine is dilute.

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Nephridia

• Aka Metanephridia
• Unlike previous, has internal openings
• Earthworms.
• Occur in pairs within each segment of the
  earthworm. Interstitial fluids enter through a
  cilated opening called a nephrostome.
• Fluids concentrated as they pass through the
  collecting tubule which includes a storage
  bladder that opens to the outside through a
  pores.
• As urine moves along the tubule, most solutes are
  reabsorbed and returned to the blood in the
  capillaries. Nitrogenous wastes remain and are
  excreted outside.
• Live in damp soil and absorb water through
  osmosis. They balance water influx by making
  diluted urine.

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Malpighian Tubules

• Insects and other terrestrial arthropods.
• Tubes attached to the midsection of the digestive
  tract collect body fluids from the hemolymph that
  bathe the cells.
• Fluids which include both nitrogen wastes and
  materials to be retained (salts and water), are
  deposited to the midsection.

• As fluids pass near the rectum, most solutes are
  pumped back into the hemolymph.
• The nitrogenous wastes are eliminated as nearly
  dry matter along with the feces.

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Kidney

• The last one..
• Kidneys.
• But you all should be experts on that now.
  Teehee.

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Regulation of Kidney Functions Hormones

• These hormones influence osmoregulation by
  regulating the concentration of salts in the
  urine
• ADH
• JGA
• Angiotensin II
• Aldosterone
• ANF

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Antidiuretic Hormone (ADH)

• Increases the reabsorption of water by the body
  and increases the concentration of salts in the
  urine.
• It does this by increasing the permeability of
  the collecting duct to water.
• Urine becomes more concentrated as water diffuses
  out of the collecting duct as the filtrate
  descends into the renal pelvis.
• Recall its position Posterior Pituitary
• Recall process of Feedback Inhibition

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Juxtaglomerular Apparatus (JGA) to Angiotensin II

• Location near afferent arteriole that supplies
  blood to the glomerulus
• When blood pressure/volume drops, an enzyme
  (renin) aids in producing a peptide called
  angiotensin II.
• This hormone raises blood pressure by
  constricting arterioles, decreasing blood flow to
  many capillaries, like in the kidney.
• Also stimulates the proximal tubules of the
  nephrons to reabosorb more NaCL and water which
  reduces the amount of both in the urine.

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Aldosterone

• This hormone acts on the nephrons distal tubules
  making them reaborb more sodium (Na) and water
  allowing for further increase of blood
  volume/pressure
• It does this by increasing the permeability of
  the distal tubule and collecting duct to Na
• As a result, more Na diffuses out of this tubule
  and duct allowing for water to passive flow.

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In summary so far, RAAS

• Starting basically from the JGA to Aldosterone,
  that whole process is called RAAS
• When blood pressure drops, JGA is released and
  aids in rising it again with angiotensin II and
  aldosterone.
• So, the first hormone ADH and the RAAS process
  raise blood pressure. Isnt this a bit redundant?

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ADH vs RAAS

• Both increase water reabsorption, but counter
  different osmoregulatory proglems.
• ADH is a response to body dehydration.
• A loss of both salt and body fluids such as an
  injury or severe diarrhea will reduce blood
  volume without increasing osmolarity.
• This will not induce a change in ADH release but
  RAAS will respond by increasing water and Na
  reabsorption.

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Atrial Natriuretic Factor (ANF)

• This hormone opposes the former RAAS
• Recall renin, the enzyme that helped make JGA
• ANG inhibits the release of renin, inhibits NaCl
  reabsorption by the collecting ducts, and reduces
  aldosterone release.
• This basically lowers blood volume/pressure.
• Thus, ADH, RAAS, and ANF is basically a
  biological check and balance system

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Guess what?!

• No more new info! Review if time.
• Enjoy your 3 day weekend!
• Study away for those exams./