URINOGENITAL SYSTEM

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Urinogenital System
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I. Basic Structure of Kidney Units

• A. The nephron - early dependence on filtering
  the coelomic fluid
• 1. Aglomerular stage - peritoneal funnel
  filtering directly from the coelomic fluid

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• 2. External glomerular stage - glomerulus - A
  ball of capillaries receiving blood from renal
  arteries
• Glomerulus suspended into coelom and closely
  associated with nephrogenic duct - filters coelom
  and blood

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3. Primitive internal glomerular stage -
glomerulus imbedded in body wall and filtering
blood and coelomic fluid
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4. Advanced internal glomerular stage -

• Glomerulus divorced from coelom and imbedded in
  kidney.

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Water Balance
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II. Maintenance of osmotic and water balance

• A. Hypotonic fresh water H2O - kidney for H2O
  only
• 1. Kidney serves only to regulate water
• 2. Reduction of integumentary blood supply to
  prevent water absorbtion
• 3. Increase in size of glomerulus to filter more
  water
• 4. Don't swallow water
• 5. Ions absorbed through the gills
• 6. Excrete nitrogenous waste across gills in the
  form of ammonia

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• B. Hypertonic marine kidneys
• 1. Impervious skin to prevent water loss
• 2. Reduction in integumentary blood supply to
  prevent diffusion of water
• 3. Small glomerlus to decrease filtration of
  water
• 4. Exchange excess ions across gill epithelia
• 5. Excrete nitrogenous waste across gills in form
  of ammonia
• 6. Some sharks increase tissue osmotic pressure
  with dissolved materials such as urea

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• C. Terrestrial kidneys
• 1. Impervious skin "coated" with keratin
• 2. Reduction in vascularization of the integument
• 3. Decrease in size of the glomerulus
• 4. Excreted water is absorbed by cloacal walls in
  reptiles and birds
• 5. Loop of Henle present in mammals to reabsorb
  water
• 6. Uric acid excreted by many to conserve water
• 7. Produce metabolic water

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III. Kinds of Kidneys Among Vertebrates

• A. Basis for classification of kidney types
• 1. Extent of association with the circulatory
  system
• 2. Extent of association with the coelom
• 3. Number of tubules
• 4. Position in the body and in the nephrotomal
  plate (anterior, middle, posterior)
• 5. Form - compact or diffuse
• 6. Occurrence - embryonic or adult
• 7. Duct which drains kidney

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B. Kidney types

• 1. Holonephros
• a. Holonephros archinephros lack
  glomerulib. Kidney extends full length of the
  bodyc. Kidney drained by the holonephric
  ductd. Kidney is diffusee. Present in
  embryonic hagfish (agnatha) presumably in
  ostracoderms and protochordates

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2. Pronephros

• a. This kidney is the earliest embryonic kidney
  of all vertebratesb. External
  glomerulic. Open peritoneal funnelsd. Kidney
  located in extreme anterior end of the
  nephrogenic mesoderm

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• e. Retains the old holonephric duct, now termed
  the pronephric duct
• f. Pronephric kidney is diffuse
• g. Functional kidney in embryonic fish and
  amphibians, but not in most amniotes where the
  tissue develops but remains nonfunctional

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3. Opisthonephros functional mesonephros

• a. Internal glomeruli
• b. Peritoneal funnel vestigial narrow
• c. Numerous tubules
• d. Kidney extends full length of the abdomen

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• e. Duct is the opisthonephric duct also called
  the Wollfian duct
• the duct is derived from the holonephric duct
  and includes all but the anterior end.
• f. Opisthonephric kidney occurs as the adult
  kidney in fishes and amphibians (anamniotes)
• g. Embryos of fish and amphibians have a
  pronephric kidney which is nonfunctional in the
  adult

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Opisthonephric Kidneys
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4. Metanephros -

• a. Kidney type of all adult amniotes
• b. Internal glomeruli lacking funnels
• c. Millions of tubules

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• d. Metanephric duct or ureter forms from a split
  of the old mesonephric or Wollfian duct
• e. Kidney is compact
• f. Kidney is preceded by the pronephros and
  mesonephros
• g. In mammals, tubules have
• U-shaped loop of Henle

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Progression from Amphibians to Amniotes
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• 5. Mesonephros
• Precursor to the metanephros in embryonic
  amniotes
• Some authors equate this type with the functional
  opisthonephros of fish and amphibians
• a. directly evolved from opisthonephros
• b. internal glomeruli lacking funnels
• c. millions of tubules

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• d. metanephric duct or ureter formed from a
  portion of the mesonephric (Wolffian duct)
• e. kidney compact
• f. occurs in amniotes
• g. mesonephros degenerates leaving the
  metanephros as the adult kidney

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Summary of Kidney Types
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II. Urinogenital Ducts

• A. Holonephros -
• 1. Reproductive organs have no duct and gametes
  pass via abdominal pores
• 2. Kidney duct holonephric duct
• B. Opisthonephros - fish and amphibians
• 1. Early forms- no reproductive ducts, i.e.,
  genital pores
• 2. Reproductive duct in later forms arises de
  novo in female as the Mullerian duct
• 3. Opisthonephric duct Wolffian duct and
  gives rise to ureter in both sexes and later to
  vas deferens in male tetrapods

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Origin of Mullerian Duct (oviduct) - forms as
evagination of dorsal body wall
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Pronephros
Gut
Body Wall
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• C. Metanephros
• 1. Urinary ducts - ureter from remnants of old
  Wolffian duct
• 2. Reproductive ducts
• a. Female - Mullerian duct develops de novo and
  becomes oviduct
• b. Male - vas deferens develops from split of
  Wolffian duct

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Urogenital Ducts
Salamander
Frog
Bird
Lizard
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The male mammal
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Uteri of Mammals
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III. Summary of origin of ducts

• 1. Female Ureter Wolffian duct Oviduct
  Mullerian duct Ostia anterior pronephric
  (opisthonephric) tubule
• 2. Male Ureter Wolffian duct Vas deferens
  Wolffian duct

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• IV. Urinary Bladders
• A. Tubal - teleosts - enlargement of Wolffian
  duct
• B. Cloacal - amphibians - evagination of cloaca
• C. Allantoic - bladders arises from enlargement
  of base of allantois

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• B. Derivatives of indifferent state of external
  genitalia Female Male Genital
  Tubercle clitoris penis
• Genital Fold labia minora penisGenital
  Swelling labia majora scrotum Urogenital
  Sinus vagina/urethra urethra

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V. Urinogenital Sinus and External Genitalia

• Mammals - and external genitalia
• A. Indifferent state

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Differentiation In female
Genital Tubercle clitoris Urogenital
Sinus Urethra Vagina Genital fold labia
minora Genital Swelling labia majora
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Genital Tubercle penis Urogenital
Sinus Urethra Genital fold penis Genital
Swelling scrotum
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Developmental Progression of Genitalia
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Internal Fertilization Intromittent Organs

• Internal Fertilization - no intromittent organ
• Amphibians - spermatophores

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A Parade of Intromittent Organs
But what is Austin Powers MoJo??
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The Cloaca
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VI. Gonads

• A. Indifferent Gonad - develops along nephrogenic
  mesoderm of dorsal body wall.
• cortex - ovarymedulla - testisone ovary left
  in birds