The Urinogenital System

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The Urinogenital System
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Function of the Urinary System

• Rid the body of metabolic waste, particularly
  those from proteins, ie urea and uric acid which
  contain nitrogen.
• Maintain osmotic balance within the body.

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Basic Terminology

• Osmosis
• the process in which water migrates through a
  semipermeable membrane from an area containing a
  lesser concentration of dissolved particles to an
  area containing a greater concentration of
  dissolved particles.

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Basic Terminology

• Hyperosmotic
• Refers to a solution whose osmotic pressure is
  greater than that ofanother solution with which
  it is compared. Contains a greater concentration
  of dissolved particles, and gains water through a
  semipermeable membrane from a solution containing
  fewer particles.

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Basic Terminology

• Hyposmotic
• (hypotonic) refers to a solution whose osmotic
  pressure is less than that of another solution
  with which it is compared.
• Isosmotic
• (isotonic) having an osmotic concentration equal
  to that of a solution with which it is compared.

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Basic Terminology

• Nephron The basic functional and structural unit
  of the kidney.
• Renal corpuscle.
• Glomerulus
• Bowmans capsule
• Proximal and Distal convoluted tubules.

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Evolution of the internal glomerulus

• In the hypothetical ancestral protochordate stage
  there is one pair of uriniferous tubules per body
  segment (metameric organization again). These
  uriniferous tubules are connected by a
  holonephric duct (archinephric duct) which runs
  the entire length of the body on both sides.
  These uriniferous tubules simple drain the
  ceolomic cavity of filtrates produced by
  capillary beds in the mesoderm.

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Evolution of the Internal Glomerulus

• Aglomerular stage
• Each uriniferous tubule drains a special pocket
  in the ceolom, the nephrocele.
• The opening of the nephrocele into the
  splanchnocele is the peritoneal funnel.
• Extraction of metabolic wastes is again simply
  via drainage of the ceolomic fluids.

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Evolution of the Internal Glomerulus

• External glomerular stage
• Found in hypothetical holonephric animals. It is
  found in no extant adults, only in embryos.
• The circulatory system now empties filtrate via a
  glomerulus, directly into the nephrocele.

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Evolution of the Internal Glomerulus

• Primitive internal glomerular stage.
• Found in some anamniotes.
• Very little excretory material is picked up from
  the ceolom, virtually all the material is from
  the glomerulus.
• The peritoneal funnel becomes constricted.

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Evolution of the Internal Glomerulus

• Advanced internal glomerular stage
• Found in amniotes.
• Complete separation of the renal corpuscle from
  the ceolom.

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Evolution of Kidney Types

• Unlike most other organs, kidneys must function
  at a very early stage in life.
• For this reason, embryonic kidneys often differ
  from those found in adults.
• The sex glands lie close to the urinary system,
  and tend to invade the system.

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Evolution of Kidney Types

• Holonephros
• The idealized embryonic kidney.
• Found in the larvae of hagfishes
• Each metamere is drained by one pair of nephrons.
• Opisthonephros
• Found in adult hagfishes.
• Pronephric portin of the holonephros is lost, it
  is functional only in the embryo, results in the
  opisthonephros.

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Evolution of Kidney Types

• Mesonephros
• found in adult fishes and amphibians.
• Metanephros
• Found in adult amniotes
• Amniote embryo still utilizes a mesonephric
  kidney.
• Testis have invaded the holonephric duct (now
  called the wolfian duct). The kidney is not
  drained by a new duct, the ureter.

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Evolution of the Tubular Capillary Network

• Cyclostome condition
• No capillary network surrounds the uriniferous
  tubule
• The glomerulus is fed via a renal artery from the
  dorsal aorta and drained via a renal vein leading
  to some systemic vein. Each individual glomerulus
  is not fed and drained by a renal artery and
  vein, rather, all of them together are fed and
  drained by a renal artery and vein leading to and
  from each kidney.

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Evolution of the Tubular Capillary Network

• Gnathostome fishes, amphibians, and reptiles
• A tubular capillary network now surrounds the
  convoluted tubule.
• The capillary network (vasa recta) is supplied
  with blood from the venous renal protal vein.
• An efferent renal vein drains the vasa recta.
• The posterior cardinal vein drains both the
  glomeruli and the vasa recta of each urinifeous
  tubule.

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Evolution of the Tubular Capillary Network

• Changes in endotherms
• Anastomosis of the tubular capillary network with
  the base of the efferent renal vein.
• Transformation of the anastomosis and part of the
  efferent renal vein between the glomerulus and
  the anastomosis into a single efferent glomerular
  artery.
• Loss of the part of the efferent renal vein
  between the anastomosis and the branch draining
  the tubular capillary network.

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Evolution of the Tubular Capillary Network

• Los of the afferent renal vein.
• Loss of the renal protal vein (mammals only)

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