Respiratory system :
- In water frog respire through skin (cutaneous respiration)
- Exchange of respiratory gases takes place through diffusion.
- In land it respires through buccal cavity, skin and lungs.
- Respiration by lungs is called pulmonary respiration.
- During aestivation and hibernation it respires through skin.
Circulatory system :
- The blood vascular system includes heart, blood vessel and blood.
- The lymphatic system includes lymph, lymph nodes and lymphatic vessels.
- Heart is three chambered with two atria and one ventricle.
- Heart is covered by a membrane called pericardium.
- A triangular sinus venosus opens into right atrium. It receives the deoxygenated blood through vena cava.
- The ventricle opens into conus atreriosus on the ventral side of the heart.
- Form the conus atreriosus the blood circulated to different part of the body by arterial system.
- Blood collected from the body to the heart by venous system.
- Special venous connection between liver and intestine is called hepatic portal system.
- Venous connection between lower part of the body and kidney is called renal portal system.
- The blood is composed of plasma and cells.
- The blood cells are; erythrocytes (RBC), leucocytes (WBC) and Thrombocytes (Platelets).
- RBC is nucleated and contains hemoglobin.
- The lymph differs from in, it lack proteins and RBC.
Excretory system :
- The excretory system consists of a pair of kidneys, ureters, cloaca and urinary bladder.
- Each kidney composed of several uriniferous tubules or nephrons.
- The ureter arises from the kidney act as urinogenital duct which opens into cloaca in male.
- In female the ureters and oviduct open separately into the cloaca.
- Thin walled urinary bladder located ventral to rectum, opens to the cloaca.
- The frog excretes nitrogenous waste in the form of urea, hence ureotelic.
Control and coordination system :
- It includes both nervous and endocrine system.
- Chemical coordination is carried out by hormones secreted by endocrine glands.
- Endocrine glands found in frog are pituitary, thyroid, parathyroid, thymus, pineal body, pancreas, adrenal and gonads.
- The nervous system organized into;
- Central nervous system- brain and spinal cord.
- Peripheral nervous system – cranial and spinal nerves.
- Autonomic nervous system – sympathetic and parasympathetic.
- There are 10 pairs of cranial nerves arises from the brain.
- Brain is enclosed in side the cranium.
- The brain differentiated into; fore brain, mid brain and hind brain.
- Fore brain includes;
- Paired olfactory lobe.
- Paired cerebral hemisphere
- Unpaired diencephalon.
- The mid brain is characterized by a pair of optic lobes.
- Hind brain consists of cerebellum and medulla oblongata.
- Medulla oblongata passes through foramen of magnum and continues as spinal cord which runs inside the vertebral column.
Sense organs:
- Frog has different types of sense organs;
- Organs of touch (sensory papillae)
- Taste (taste buds)
- Smell (nasal epithelium)
- Vision (eye)
- Hearing (tympanum with internal ear)
- Eye is well organized inside the orbit of the skull.
- Ear is an organ for hearing and equilibrium (balancing).
Male reproductive system:
- Consists of a pair of yellowish ovoid testes, attached to the upper part of kidneys, by mesorchium.
- Vasa efferentia are 10-12 in number arises from the testes.
- They enter into the kidney and opens into Bidder’s canal.
- Bidder’s canal communicates with the urinogenital duct that comes out of the kidneys and opens into the cloaca.
- The cloaca is a small median chamber that is used to pass faecal matter, urine and sperms to the exterior.
Female reproductive system:
- Includes a pair of ovaries present near the kidneys.
- A pair of oviduct arising from ovaries opens into the cloaca separately.
- A mature female lays 2500 to 3000 ova at a time.
- Fertilization is external i.e. in water
- Development is indirect involved a larval stage called tadpole larva.
- Tadpole larva metamorphoses into adult frog.
