THE EXCRETORY SYSTEM

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THE EXCRETORY SYSTEM
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Urinary System Equal Time
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Kidney
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The Kidney
Cortex
Medulla
Calyx
Pelvis
Ureter
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Gross Anatomy
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The Kidney
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Renal Functions

• Regulate water concentration, ion composition,
  volume of internal environ.
• Excrete metabolic waste products.
• Urea (protein)
• Uric acid (nucleic acids)
• Creatinine (muscle creatine)
• Excrete exogenous substances (drugs).
• Gluconeogenesis.

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FUNCTIONS OF URINARY SYSTEM

•      Monitor and filter blood
•         Remove metabolic wastes
•           Remove excess materials
•           Eliminate above from body as urine
  contents
• Contribute to homeostasis
•            pH
•            water content
•            electrolyte concentration
•            blood gas transport (produce
  erythropoietin)
•            blood pressure

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Specific Functions of Kidneys

• Filtering Wastes From Blood Plasma
• The kidneys filter about 180L of blood/day.
• About 99 of this blood plasma (minus most of the
  wastes) is reabsorbed by the kidneys to reduce
  urine production to about 1- 2 L/day.
• Without functioning kidneys, wastes accumulate in
  the blood causing a serious condition called
  "uremic poisoning" or "uremia."
• Kidneys are also responsible for regulating the
  acidity of the blood.

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Nephron of Kidney
PCT
Bowmans capsule
DCT
Vasa recti
Glomerulus
Ascending tubule
Descending Tubule
Collecting duct
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Cortex of Kidney
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Renal Vasculature(red dye)
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Collecting Ducts and Glomeruli
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Bowmans Capsule
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Glomerulus with Podocytes
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Filtration Slits
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Blood Supply to Kidney
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Renal Circulation

• High resistance in afferent arteriole
• Then in efferent arteriole
• BP declines from 95mm in renal art to 8mm in
  renal veins
• Resistance of aff art protects glomeruli from
  high systemic pressure
• Resistance of eff art maintains high pressure in
  glomeruli and reduces pressure in peritubular cap
• Capillaries of Bowmans capsule
• Peritubular capillaries

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Nephron
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Tubules
Proximal Tubule
Distal Tubule
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Collecting Ducts
Cuboidal Epithelium lining ducts
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Urine Formation

• Glomerular filtration
• Tubular reabsorption
• Tubular secretion
• Urinary excretion
• glomerular filtration
• tubular secretion
• - tubular reabsorption

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Calculating Amount Excreted into Urine

• Amount Excreted Amount filtered Amount
  Secreted Amount Reabsorbed

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Filtration Pressure

• Net pressure that forces substances out of
  glomerulus
• Factors affecting filtration pressure
• Hydrostatic pressure (60mm Hg)
• Altered by change in diameter of arterioles
• Osmotic pressure of plasma (30mm Hg)

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