Frog - Anatomy of Frog

Digestive System

• The alimentary canal runs from the mouth through the buccal cavity, pharynx, oesophagus, stomach, intestine, rectum and exits via the cloaca. It is short due to a carnivorous diet.
• Digestive glands include the liver (produces bile), the pancreas (secretes digestive enzymes) and the stomach glands (secrete HCl and gastric juices).

Respiratory System

• Frogs use three modes of respiration: cutaneous (through skin in water), buccal (on land) and pulmonary (through lungs). During aestivation and hibernation, gas exchange occurs only through the skin.

Circulatory System

• Frogs have a closed blood vascular system with a three-chambered heart (two atria + one ventricle). RBCs are nucleated and contain haemoglobin.

Excretory System

• Frogs are ureotelic (excrete urea). Kidneys are dark red, bean-shaped organs composed of nephrons. In males, ureters act as urinogenital ducts; in females, ureters and oviducts open separately into the cloaca.

Nervous System

• The brain is divided into the forebrain (olfactory lobes, cerebral hemispheres, diencephalon), midbrain (optic lobes) and hindbrain (cerebellum, medulla oblongata). Ten pairs of cranial nerves arise from the brain.

Reproductive System

• Fertilisation is external and occurs in water. Males have testes connected to the kidneys via 10-12 vasa efferentia. Females can lay 2500-3000 ova at once. Development includes the tadpole stage followed by metamorphosis.