Frog Anatomy and Physiology Notes

Circulatory System of Frog

  • The vascular system in frogs is a well-developed, closed type.

  • Frogs also possess a lymphatic system.

  • The blood vascular system consists of:

    • Heart
    • Blood vessels
    • Blood

  • The heart is a muscular structure located in the upper part of the body cavity.

  • It has three chambers:

    • Two atria
    • One ventricle

  • The heart is covered by a membrane called the pericardium.

  • Special venous connections:

    • Hepatic portal system: connects the liver and intestine.
    • Renal portal system: connects the kidney and lower parts of the body.

  • Blood composition:

    • Plasma
    • Cells
      • Red blood cells (RBCs) or erythrocytes
      • White blood cells (WBCs) or leucocytes
      • Platelets

  • Frog RBCs:

    • Oval shaped
    • Nucleated
    • Contain red colored pigment called haemoglobin.

  • Lymph:

    • Differs from blood.
    • Lacks few proteins.
    • Lacks RBCs.

  • Blood function:

    • Carries nutrients, gases, and water to respective sites during circulation.

  • Circulation:

    • Achieved by the pumping action of the muscular heart.

  • Lymphatic system components:

    • Lymph
    • Lymph channels
    • Lymph nodes

Excretory System

  • The elimination of nitrogenous wastes is carried out by a well-developed excretory system.

  • Components of the excretory system:

    • A pair of kidneys
    • Ureters
    • Cloaca
    • Urinary bladder

  • Kidneys:

    • Compact, dark red, and bean-like structures.
    • Located a little posteriorly in the body cavity on both sides of the vertebral column.

  • Each kidney is composed of several structural and functional units called uriniferous tubules or nephrons.

  • Urethra is absent.

  • In male frogs, the ureters act as the urinogenital duct, which opens into the cloaca.

  • In females, the ureters and oviduct open separately into the cloaca.

  • A thin-walled urinary bladder is present ventral to the rectum, which also opens into the cloaca.

  • The frog excretes urea and thus is a ureotelic animal.

  • Excretory process:

    • Excretory wastes are carried by blood into the kidney where it is separated and excreted

  • Nitrogenous Waste Urea

    • KidneyKidney
    • UretersUreters
    • UrinarybladderUrinary bladder
    • CloacaCloaca

Nervous System of Frog

  • The brain is enclosed in a bony structure called the brain box (cranium).
  • The brain is divided into:
    • Forebrain
    • Midbrain
    • Hindbrain
  • Forebrain includes:
    • Olfactory lobes
    • Paired cerebral hemispheres
    • Unpaired diencephalon
  • Midbrain:
    • Characterized by a pair of optic lobes.
  • Hindbrain consists of:
    • Cerebellum
    • Medulla oblongata
  • The medulla oblongata passes out through the foramen magnum and continues into the spinal cord, which is enclosed in the vertebral column.

Male Reproductive System of Frog

  • Male reproductive organs consist of a pair of yellowish ovoid testes.
  • Testes are adhered to the upper part of kidneys by a double fold of peritoneum called mesorchium.
  • Vasa efferentia:
    • 10-12 in number.
    • Arise from the testes.