Exercise 20: Excretory System

• Excretion - process of removal of nitrogenous metabolic wastes via organs of filtration.
• What is the excretory organ of lower metazoans such as flatworms?

  Protonephridia
• What is the excretory organ for mollusks and annelids?

  Metanephridia
• What is the excretory organ in crustaceans?

  Antennal gland
• What is the excretory organ in terrestrial arthropods?

  Malpighian tubules
• What is the main excretory organ in vertebrates?

  Kidneys
• Nitrogenous wastes can be excreted either as what?

  Ammonia, urea, or uric acid
• Malpighian tubules - very small and fine thread-like diverticula at the border of the midgut and hindgut
• The Malpighian tubules produce waste as crystalline uric acid which is excreted together with the feces via the anus
• What space do the mesonephric kidneys occupy?

  Cisterna magna
• Mesonephric duct - lies on the lateral surface of the kidney which descends posteriorly to the urinary bladder
• Urinary bladder - large delicate sac-like organ at the ventral side of the pelvis by which contents of the organ exit to the cloaca
• Adrenal glands - in fresh specimens where a yellow streak can be seen on the ventral surface of each kidney
• In male specimens, the kidneys are just dorsal to the ovoid and light-colored testes which are located dorsal to the large intestine
• Renal corpuscles - primary filtration sites of blood in the kidney
• Under HPO, what is the dark round mass of capillaries in the renal corpuscles?

  Glomerulus
• The immediate of the glomerulus is a very thin crest of squamous epithelia called what?

  Bowman's capsule
• Uriniferous tubules - located next to the renal corpuscles and have an elongated lumen and they are the sites of reabsorption of water and other substances
• Collecting tubules - located at the convex margin of the kidney section, have wider circular lumen and are lined with prominent cuboidal epithelia
• The uriniferous tubules and collecting tubules converge at what?

  Mesonephric duct
• At the more pointed side of the kidney section, near the base of the mesonephric duct, a section of the renal portal vein can be seen
• A section of the renal artery can be seen at the dorsal surface of the kidney while a section of the renal vein can be seen at the ventral surface
• What is the outer and inner region of the mammalian kidney respectively?

  Outer: Cortex Inner: Medulla
• What does the cortex contain?

  Renal corpuscles, distal and proximal tubules
• What does the medulla contain?

  Loop of Henle, collecting tubules
• The microscopic collecting tubules terminate at what?

  Renal papilla
• In the pig, the individual papillae converge to form the triangle renal pelvis
• The renal pelvis tapers to form what?

  Ureter
• Hilus - concavity of the kidney where the renal pelvis is located and where the ureter emerges and it is also where the renal artery and vein enters the kidney
• Label what is asked.

  A) Malpighian tubules.

  
• Label the following in the excretory system of the toad.

  A) Mesonephric kidney

  B) Mesonephric duct

  C) Urinary bladder

  D) Cloaca

  
• Label the following in the x.s. of a frog.

  A) Renal Corpuscles

  B) Glomerulus

  C) Bowman's capsules

  D) Uriniferous tubules

  E) Collecting tubules

  F) Mesonephric duct

  G) Renal portal vein

  H) Renal artery

  I) Renal vein

  J) Adrenal gland

  
• Label the following found in the mammalian kidney.

  A) Cortex

  B) Medulla

  C) Renal Papilla

  D) Renal pelvis

  E) Ureter

  
• What excretory structure is found specifically in arachnids where they secrete Na+ ions?

  Coxal gland
• What is the excretory structure for protonephridia in flatworms?

  Flame cells
• In mammals what has become of the mesonephric duct?

  Vas deferens