6 - FROG MAJOR EXTERNAL ORGANS

• What modifications does the frog's body show for locomotion?

  Enlarged hind limbs and a compact body
• How are the hind limbs of a frog adapted for movement?

  They are enlarged and strengthened for jumping
• What is the position of the frog's neck?

  It is reduced, restricting head movement
• What effect does the shortened vertebral column have on frogs?

  It limits body movement
• How is the head of a frog shaped?

  It is flattened dorsoventrally
• Why does the rounded outline of a frog's head reduce resistance in water?

  It allows smoother movement through water
• What features do each of a frog's eyes have?

  Upper and lower eyelids
• What is the function of the nictitating membrane in frogs?

  It protects the eye underwater while allowing vision
• How can you observe a frog's nictitating membrane?

  Pull the lower eyelid and lift the membrane
• Where is the tympanum located on a frog?

  Posteroventral to the eye
• How does the size of the tympanum compare to the eye?

  It is slightly larger than the eye
• Where are the external nares located on a frog?

  Anterior to the eyes and slightly medial
• What is the function of the external nares?

  They serve as openings for nostrils
• What adaptations do the hind limbs of frogs have for movement?

  They are large and muscular for jumping
• How does webbing between a frog's toes assist in swimming?

  It provides resistance during swimming strokes
• How do the forelimbs and hind limbs of frogs differ in terms of digits?

  The thumb is reduced in size compared to toes
• What is the function of the thumb (pollex) in male frogs?

  It acts as a nuptial pad for mating
• Where is the anus located on a frog?

  Between the hind limbs, dorsally positioned
• What is the cloaca's function in frogs?

  It serves as a common exit for multiple systems
• What is a common laboratory preparation detail for frogs?

  A large gash in the thigh exposes the sciatic vein
• What is injected into posterior veins during frog preparation?

  Blue latex through the sciatic vein
• What is the purpose of injecting red latex into arteries?

  To distinguish arteries and veins more easily
• Why must the frog's skin remain moist?

  It lacks horny epidermal scales like reptiles
• How does the skin of frogs contribute to respiration?

  It is rich in blood vessels for gas exchange
• What type of glands are present in frog skin?

  Numerous mucous glands and larger poison glands
• What is the role of mucous glands in frog skin?

  They keep the skin moist
• How do larger poison glands in frog skin compare to mucous glands?

  They are present but less abundant