The Urinary system

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The Urinary system
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Waste Products

• Liver removes amine groups from proteins
• Called deamination
• Ammonia is a highly toxic by-product... 0.005mg
  can kill a human!!
• Liver combines Ammonia and CO2 to form Urea.
• Uric Acid is formed by the breakdown of nucleic
  acids.
• See page 342

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Anatomy of the Urinary System Kidneys (urine
formation) Lower Urinary Tract Ureters
(2) Bladder (1) Urethra (1) (urine collection,
storage, excretion)
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The Kidney

• Filters blood and removes cellular waste
  products.
• Also a major homeostatic organ.
• They control water balance, pH and levels of
  sodium, potassium, bicarbonate and calcium ions
  in the blood.
• Secrete erythropoietin...a hormone that
  stimulates red blood cell production and they
  activate vitamin D production in the skin

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Kidney Structure

• 3 sections Cortex, Medulla and Pelvis
• Within the Cortex and Medulla are 1million
  Nephrons.
• Nephrons -
• -Bowmans capsule, proximal tubule, loop of
  Henle, distal tubule collecting duct.
• Each nephron is surrounded by cells and a network
  of blood vessels
• By controlling what stays leaves in the
  nephrons, the kidneys keep levels of water, ions
  and other materials constant within the limits
  necessary to maintain homeostatis.

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Cortex Glomeruli Medulla Renal
tubules Ureter Takes urine to bladder Blood
carried to the kidney by the renal artery and
taken away by the renal vein.
Cortex
Medulla
Renal hilum
Renal artery
Renal vein
Renal pelvis
Ureter
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Each KIDNEY consists of 1 million NEPHRONS

• Each nephron consists of a
• GLOMERULUS (found in cortex)
• forms a protein-free filtrate from blood
• TUBULE (found in medulla)
• processes the filtrate to form urine
• Each TUBULE consists of several segments
• Proximal tubule
• Loop of Henle
• Distal Tubule
• Collecting Ducts.

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Functional Unit of the Kidney is the NEPHRON
Glomerulus (inside Bowmans capsule) Proximal
Tubule Loop of Henle Distal Tubule Collecting
Duct
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• http//www.youtube.com/watch?vaQZaNXNroVYfeature
  related
• P 345 1-3
• P348 1-4

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Urine Formation - Filtration

• Is accomplished by movement of fluids from blood
  into Bowmans capsule.
• Each nephron of kidney has its own blood supply
• Materials move from high to low generally

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Reabsorption

• Involves the transfer of essential solutes and
  water from the nephron back to the blood
• About 600mL fluid flows through kidneys every
  minute
• About 20 filtered into nephrons
• 1mL of urine formed for every 120mL of fluid
  filtered into nephron (remainder reabsorbed)
• selective Reabsorption both active and passive
• carrier molecules move Na ions over across cell
  membranes of cells which line the nephron
• Negative ions (Cl-, HCO3-) follow Na by charge
  attraction
• Excess NaCl remains in nephron and excreted in
  urine when reabsorption reaches the threshold
  level (max amount of material that can be moved
  across the nephron.
• Proteins in the bloodstream draw water from the
  interstitial fluid (fluid that surrounds the body
  cells) into the blood

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Secretion

• Involves movement of materials from blood back to
  nephron
• N-containing wastes, excess H ions, and minerals
  such as K are examples of substances secreted
• Even drugs (e.g. penicillin) can be secreted
• Molecules are shuttled (active tran) from blood
  to nephron

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• Page 352 1-6

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Water Balance

• Involves the interaction of the bodys two
  communication systems
• Nervous system
• Endocrine system

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Regulating ADH

• Antidiuretic hormone (ADH)
• helps regulate osmotic pressure of body fluids by
  causing kidneys to increase water reabsorption
• when ADH released, more concentrated urine is
  produced (therefore conserving water)
• ADH produced by hypothalamus and moves to
  pituitary gland (via specialized fibres) which
  stores and releases ADH into blood

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• Osmoreceptors located in hypothalamus detect
  changes in osmotic pressure
• Decrease of water causes blood solutes to
  increase in , thereby increasing bloods
  osmotic pressure
• Water then moves into bloodstream causing
  hypothalamus cells to shrink and sensation of
  thirst
• Causes signalling the release of ADH from
  pituitary, carried by bloodstream to kidneys
• Kidneys reabsorb more water, thereby creating
  more concentrated urine, preventing increase of
  osmotic pressure of body fluids.

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• If sensation of thirst causes intake of water, if
  more water is taken in, it is absorbed by blood
  and of solutes in blood decreases.
• Greater amount of H2O taken in, lower osmotic
  pressure of blood.
• Blood becomes more dilute, fluids move to
  hypothalamus cells and they swell.
• Nerve messages to pituitary stop.
• Less ADH released, less H2O reabsorbed from
  nephrons.
•  

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Kidneys and Blood Pressure

• Dec. Blood pressure or blood volume (from
  dehydration, blood loss) can cause a reduction in
  the delivery of oxygen nutrients to tissues.
• Blood pressure receptors in the Juxtaglomerular
  Apparatus (found near the glomerulus) detect this
  low BP
• Specialized cells in the J.A. then release Renin
• Renin is an enyme that converts Angiotensinogen
  (a plasma Protein produced by the liver) into
  Angiotensin (active form)

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Kidneys and Blood Pressure

• Angiotensin causes constriction of blood vessels
  this increases Blood Pressure.
• It also stimulates the release of Aldosterone
  (from the Adrenal Glands above each kidney)
• It acts on the Nephrons to increase Na
  reabsorption
• This increases the osmotic gradient, so water
  moves out of the Nephron by osmosis back into the
  bloodstream.
• This increase Blood Volume

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pH Balance

• Kidneys maintain pH balance
• pH of human body remains relatively constant
  (7.3-7.5)
• pH may lower during Cell Resp Acids produced
• Acid-base balance maintained by buffer systems
  that absorb excess H ions.
• Buffer systems maintain Acid-Base balance

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pH Balance

• Bicarbonate ions buffer excess H ions, producing
  carbonic acid
• Carbonic acid is a weak acid that breaks down
  into CO2 and goes to the lungs and is exhaled.
• This rxn is reversed in the kidneys
• CO2 is actively transported from capillaries into
  the cells that line the nephron.
• Here CO2 combines with water to initiate the
  reverse rxn generating HCO3- H ions
• The ions diffuse back into the blood, restoring
  the buffer
• The H ions left recombine with the phosphate
  ions or ammonia and are excreted with the nephric
  filtrate

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Kidney Diseases

• Make short note on...
• Diabetes Mellitus
• Diabetes Insipitus
• Brights Disease
• Kidney Stones
• Dialysis Technology
• Kidney Transplants and Xenotransplants (p360)
• HW Page 356 1-8

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Urine Analysis Lab