Frog: Circulatory System

  • Frogs have a well-developed and closed type circulatory system (including a blood vascular system and a lymphatic system).
  • The lymphatic system consists of – lymph, lymph channels and lymph nodes.
  • Blood vascular system: It involves heart, blood vessels and blood

Blood Vessels

    • The arteries carry blood from the heart to all parts of the body (arterial system).
    • The veins collect blood from different parts of body to the heart and form the venous system.
    • Special venous connections are present between liver and intestine. It is called hepatic-portal system.
    • The venous connections between kidney and lower parts of the body are called renal portal system.

Heart

    • Amphibian heart is a tripartite (3 chambers) muscular structure situated in the upper part of the body cavity.

    • It contains two atria and a single ventricle.
    • The heart is covered by a membrane called pericardium.
    • A triangular structure called sinus venosus is present near the right atrium.
    • The flow of venous blood into atrium takes place by the contraction of sinus venosus.
    • It receives blood through the major veins called vena cava.
    • The ventricle opens into a sac-like conus arteriosus on the ventral side of the heart.

Blood

    • The blood is composed of plasma and cells.
    • The blood cells are RBC (red blood cells) or erythrocytes, WBC (white blood cells) or leucocytes and platelets.
    • RBC’s are nucleated and contain red colored pigment namely hemoglobin.
    • The lymph is different from blood.
    • It lacks few proteins and RBCs.
    • The blood carries nutrients, gases and water to the respective sites during the circulation.
    • The circulation of blood is achieved by the pumping action of the muscular heart.

Frog: Excretory System

  • The excretory product of an adult frog is urea and that of a tadpole is ammonia.
  • Excretory wastes are carried by blood into the kidney where it is separated and excreted.
  • The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder.

Kidney

  • Kidneys are bean – shaped structures present on either sides of the vertebral column.
  • Each kidney is composed of several structural and functional units called uriniferous tubules or nephrons.

Ureters

  • A pair of ureter arises from the kidney (one from each kidney).
  • In males, the ureters act as a common duct for the passage of wastes and sperm. It is hence known as the urinogenital duct which opens into the cloaca.
  • In females the ureters and oviduct open seperately in the cloaca.

Urinary bladder

  • It is a thin-walled bulb – like structure present near the rectum. Both rectum and urinary bladder opens into the cloaca.
  • The frog excretes urea and thus is a ureotelic animal.
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