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Frog Morphology and Anatomy Overview

May 9, 2025

Frogs – Morphology and Anatomy

General Characteristics

  • Frogs are carnivorous, tailless amphibians, commonly found in India.
  • Species in India are known as Rana tigrina.
  • Belong to the class Amphibia, phylum Chordata.
  • They are cold-blooded animals (poikilotherms):
    • Body temperature changes with the environment.
    • Undergo aestivation in summer and hibernation in winter.
  • Capable of camouflage by changing skin color according to surroundings.

Morphology

  • Adult frogs have a stout body divided into head and trunk.
  • Features include:
    • Nostrils, protruding eyes, tympanum (ear).
    • Moist, slippery/warty skin.
    • Webbed limbs.
  • Skin:
    • Highly permeable and acts as a respiratory organ.
    • Produces mucus and toxins to deter predators.
  • Locomotion via forelimbs and hind limbs.
  • Unisexual with sexual dimorphism:
    • Males: Vocal sacs and copulatory pads on forelimbs.
    • Females: Lack these features.

Anatomy

Digestive System

  • Composed of alimentary canal and accessory organs.
  • Frogs are carnivorous with a short intestine.
  • Alimentary canal sequence: Mouth → Pharynx → Oesophagus → Stomach → Small intestines → Large intestines → Rectum → Cloaca.

Respiratory System

  • Two modes: Cutaneous and pulmonary respiration.
  • In water: Cutaneous respiration via skin.
  • On land: Combination of skin and lungs.
  • During aestivation/hibernation: Only skin is used.

Circulatory System

  • Muscular heart with three chambers: Two atria, one ventricle.
  • Blood and lymph transport substances through vessels.

Excretory System

  • Ureotelic animals excreting urea.
  • Composed of kidneys, ureters, cloaca, and urinary bladder.
  • Nephrons filter blood and excrete waste.

Coordination System

  • Composed of nervous and endocrine systems.
  • Endocrine glands: Pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals, and gonads.
  • Nervous System:
    • Divided into CNS and PNS.
    • Brain has forebrain, midbrain, and hindbrain.

Reproductive System

  • Male frogs have testes for sperm production, ejected via cloaca.
  • Female frogs have ovaries producing ova, passed to oviduct and then cloaca.
  • External fertilization of 2500 to 3000 eggs.