Frog Morphology and Anatomy Explained for Students

Frogs are remarkable amphibians found in diverse habitats across the globe. In India, the most common species is the Indian bullfrog (Rana tigrina). As cold-blooded vertebrates, they rely on their surroundings to regulate body temperature. This detailed guide will help you understand the external features, internal structures, and viscera of frogs in a simple, clear manner—ideal for learners of all grades!

Introduction to Frogs

Frogs belong to the class Amphibia of the phylum Chordata. Being poikilothermic (cold-blooded), they must adapt to environmental fluctuations. Therefore, they undergo:

• Aestivation (summer sleep) when temperatures are extremely high.

• Hibernation (winter sleep) when it is too cold.

Frogs also exhibit camouflage, changing their skin colour to blend in with their surroundings. Their life cycle includes a larval stage (tadpole), which has a tail, but as adults, they are completely tailless.

Morphology of Frogs

Adult frogs have a compact body divided into the head and trunk. They lack a neck and tail. Key external features include:

1. Nostrils: A pair of small openings on the snout that allow breathing when the frog’s head is above water.

2. Protruding Eyes: Enable nearly 360° vision, helping frogs detect predators and prey.

3. Tympanum (Ear): A membrane located behind each eye; it vibrates with sound waves, acting as an external ear.

4. Moist, Permeable Skin: A vital organ for both respiration and water absorption.

5. Limbs: Frogs have four limbs—two forelimbs and two powerful hind limbs adapted for jumping and swimming.

Frogs are unisexual, showing clear sexual dimorphism:

• Male frogs possess vocal sacs and a copulatory pad on the forelimbs.

• Female frogs lack both of these features.

The moist frog skin helps them breathe (cutaneous respiration) and contains mucus-producing glands that keep the skin slippery. Some species also produce mild toxins as a defence against predators.

Viscera of Frog

If you’ve ever wondered, What is the viscera of a frog? The term “viscera” generally refers to the internal organs contained within the body cavity. In frogs, the viscera of frogs typically include the liver, lungs, heart, stomach, intestines, kidneys, and other soft internal organs.

Understanding the Viscera of Frog Function

The viscera of frogs function collectively to maintain life processes. For instance:

• The liver aids in bile production and metabolism.

• The kidneys filter waste from the bloodstream.

• The stomach and intestines digest and absorb nutrients.

• The lungs enable pulmonary respiration on land.

• The heart pumps blood through the body.

Viscera of Frog Diagram and Labelled Representation

A viscera of frog diagram or viscera of frog labelled diagram illustrates these organs positioned in the frog’s body cavity. Observing such a diagram clarifies how the frog’s systems are compactly arranged and interconnected, allowing for efficient regulation and function of each organ.

Below is a simplified overview of the major viscera:

1. Heart (3-chambered)

2. Lungs (paired structures)

3. Liver (large, lobed organ)

4. Stomach (curved, muscular sac)

5. Intestines (short and coiled)

6. Kidneys (elongated structures near the dorsal body wall)

7. Urinary Bladder (thin-walled sac at the cloacal end)

Frogs are amphibians that showcase unique survival strategies like camouflage, cutaneous and pulmonary respiration, and seasonal dormancy. Their morphological adaptations—strong hind limbs, moist skin, and specialised sensory organs—enable them to thrive both on land and in aquatic environments. Internally, all vital organ systems and the viscera of frogs work together to perform essential functions, from digestion and excretion to reproduction and respiration.

Anatomy of Frogs

The internal organisation of frogs encompasses several organ systems. These systems are arranged within the body cavity to perform vital physiological functions.

Digestive System

Frogs are carnivorous, feeding mainly on insects, worms, and other small animals. Their alimentary canal is relatively short and composed of:

• Mouth (Buccal Cavity): Captures and grinds food.

• Pharynx: Common passage for food and air.

• Oesophagus: Tube carrying food to the stomach.

• Stomach: Main site for digestion.

• Small Intestine: Further digestion and nutrient absorption.

• Large Intestine and Rectum: Water absorption and waste accumulation.

• Cloaca: Final exit chamber for digestive wastes, urine, and reproductive cells.

Respiratory System

Frogs use cutaneous respiration (through the skin) when in water. On land, they primarily use their lungs, though the skin still contributes significantly to gas exchange. During hibernation or aestivation, frogs rely heavily on their skin for respiration.

Circulatory System

The frog’s heart has three chambers—two atria and one ventricle. Blood (carrying nutrients, oxygen, and waste) and lymph flow through a network of vessels, ensuring efficient transport. Frog blood contains red blood cells (RBCs), white blood cells (WBCs), and platelets.

Excretory System

Frogs are ureotelic, excreting urea as their primary nitrogenous waste. Each frog has:

• A pair of kidneys (containing nephrons that filter blood).

• Ureters carry urine from the kidneys.

• A urinary bladder for temporary storage.

• The cloaca, where urine is finally expelled.

Coordination and Control

Frogs coordinate their activities via:

• Nervous System: Divided into the central nervous system (CNS)—with the brain (forebrain, midbrain, hindbrain) and spinal cord—and the peripheral nervous system (PNS).

• Endocrine System: Includes glands like the pituitary, thyroid, parathyroid, thymus, pineal body, pancreatic islets, adrenals, and gonads. Hormones from these glands regulate growth, metamorphosis, reproduction, and more.

Reproductive System

Frogs reproduce sexually.

• Male frogs Possess testes that produce sperm, which exit through the cloaca.

• Female frogs: Possess ovaries that release eggs into the oviduct. The oviducts open into the cloaca. External fertilisation occurs in water, where females can lay 2,500–3,000 eggs at a time.

Fun Mnemonics for Frog Anatomy

Here is a simple mnemonic to recall the main internal organs (viscera) of a frog

:
“He Loved Soft Ice Cream Kindly, Usually.”

What each first letter stands for:

• H – Heart

• L – Lungs

• S – Stomach

• I – Intestines

• C – Cloaca

• K – Kidneys

• U – Urinary Bladder

Quick Quiz on Frogs

1. Which hormone regulates metamorphosis in frogs?
a) Insulin
b) Thyroxine
c) Adrenaline
d) Oestrogen

2. How many chambers does a frog’s heart possess?
a) 2
b) 3
c) 4
d) 5

3. Which organ system in frogs filters out waste from the blood?
a) Respiratory System
b) Nervous System
c) Excretory System
d) Circulatory System

4. Name the primary excretory product in frogs.
a) Ammonia
b) Urea
c) Uric acid
d) Carbon dioxide

5. The moist skin of a frog plays a major role in which type of respiration?
a) Buccal
b) Pulmonary
c) Cutaneous
d) None of the above

(Answers: 1-b, 2-b, 3-c, 4-b, 5-c)

Explore More:

• Sexual Reproduction In Fungi

• Planaria

• Circulatory System Function