Excretory system

• excretory system

  • includes organs facilitating removal of waste from body
  • Organs include kidney, ureter, urinary bladder + urethra
• Kidneys

  • two located in cranial abdominal cavity
  • Characteristics include bean shape - indented area called hilus
  • Blood vessels, nerves + ureters enter and leave
• Components of the kidney

  • renal column
  • Medulliary pyramid
  • Calyx
  • renal artery
  • renal vein
  • pelvis
  • ureter
  • renal capsule
  • cortex
• Whole excretory system components

  • dorsal aorta
  • Renal artery and vein
  • Vena cava
  • Kidney
  • Ureter
  • Urethra
  • Bladder
  • Sphincter (controls urine exit)
• What does the kindey do?

  • filters
  • Deals with by-products from blood where proteins have been broken down into amino acids then converted into urea
  • two Key filtration processes called ultrafiltration + selective reabsorption
  • Waste in form of ammonia (NH3)
  • Terrestrial animals convert ammonia into urea to conserve water
• how is urea excreted?


  transported in the blood then extracted and excreted through the bladder
• Nephron (ultrafiltration and reabsorption)

  • each unit of kidney is a nephron
  • Millions of nephrons tightly packed in kidneys
  • Responsible for filtration of blood + urine production
• • Bowmans capsule - ultrafiltration
  • Proximal tubule - selective reabsorption
  • Loop of Henle - osmoregulation (salt)
  • distal tubule - selective reabsorption
  • Collecting duct - osmoregulation (water)
• Glormerular capsule

  • network of capillaries called glormerulus
  • High pressure forcing small particles to filter though pores to be drained in next section
• Proximal convoluted tubule

  • lined with microvilli increasing SA
  • Allows reabsorption of water + electrolytes
• Loop of henle

  • u-shaped decending loop to reabsorb water particles
  • Ascending loop reabsorbs sodium
• distal convoluted tubule

  • reabsorbs sodium + secretes potassium and hydrogen
  • extretuon of H to balance pH levels
• Collecting duct

  • recieves urine from multiple nephrons to drain from ureter
• Ureters

  • two
  • Narrow muscular tube running towards bladder
  • Urine formed in nephrons pushed along ureters to bladder
• bladder (voluntary and unvoluntart control)

  • each ureter enters single bladder close to neck
  • pear shaped hollow organ
  • Collects + stored urine
  • Bladder sphincter controls flow of urine to urethra
  • Two parts of sphincter: internal sphincter (smooth muscle, involuntary) external sphincter (stirated muscle, voluntary)
• Urethra

  • tube running from bladder to outside
  • Varies between animal and gender
• How do endocrine, excretory and digestive system link?


  • excretory works with endocrine to maintain homeostasis (Hormones signal kidneys to filter water/salt depending on levels in body)
• Loop of henle in desert and non-desert animals

  • desert have elongated loops for steep osmotic gradient
  • Non-desert animals have shorter loops and Less steep gradient
• Urine concentration in desert animals dn non-desert animals

  • desert animals have highly concentrated using to minimise water loss
  • Non-desert animals have moderately concentrated urine
• Water source in desert and non-desert animals

  • desert animals have metabolic water, water from food and use minimal drinking
  • Non-desert animals have drinking as their primary source
• Water loss in desert and non-desert animals

  • desert animals have minimal water loss via respiration and excretion
  • Non-desert animals have high water loss in urine and swear eg
• behavioural adaptations in desert and non-desert animals

  • desert animals have nocturnal, reduced activity in the heat
  • Non-desert animals have no significant need for these adaptations
• Osmoregulation in marine and freshwater animals

  • marine animals lose water to environmen and gain excess salts
  • Freshwater animals gain water from environment and lose salts
• Kidney function in marine and saltwater animals

  • marine animals have small glomeruli, converse water and excrete salts
  • Freshwater animals have large glomeruli and excrete less water
• Gills in marine and saltwater animals

  • marine animals actively pump out salts
  • Freshwater animals actively absorb salts
• Urine concenration in marine and saltwater animals

  • marine animals have highly concentrated using to conserve water
  • Freshwater animals have dilure urine to expel excess water
• Water quality sensitivity in Marine and saltwater animals

  • marine animals are sensitive to changed in salinity pillution
  • Saltwater animals are sensitive to pollutants and acidification