Respiratory System in Frogs

Introduction to Frog Respiration

Frogs are amphibians characterized by their jumping ability, croaking sounds, and life cycles including aquatic and terrestrial stages. They form a part of most ecosystems and play the dual roles of being a predator and prey.

The anatomy of frogs explains a great deal about their strategies for survival, adaptation, and evolutionary biology, hence making them among the most important model organisms in scientific research and education. Understanding their physiology further provides indications for conservation, since many frog species are environmental indicators and their populations are already threatened due to habitat loss and climate change.

Structure of the Respiratory System in Frogs

The structure of the respiratory system is given below-

External Anatomy

Skin: The skin of frogs is thin, moist, and very well vascularised. Gas exchange can readily occur directly through the surface. Cutaneous respiration is very significant, particularly when the frogs are underwater.

External nares (nostrils): Frogs have a pair of small, external nostrils on top of the head that allows for air to move into the nasal passages when the frog is at the surface of the water. This allows respiration to occur even when most of the body is submerged.

Internal Anatomy

Mouth Cavity: The mouth cavity of the frogs constitutes a major portion of buccopharyngeal respiration. The lining of the mouth is richly supplied by blood vessels; thus, the presence of oxygen and carbon dioxide causes diffusion.

Pharynx: It connects the mouth cavity to the oesophagus posteriorly and to the larynx anteriorly. It serves both as a passage to food as well as air and thus forms a part of the respiratory system by providing a passageway to the air getting to the lungs.

Larynx: It is very simple in frogs. It just acts as a passage to the lungs. It has vocal cords, which it uses in making calls.

Lungs: A frog has two sac-like structures—organs of respiration—that are sac-like, making up the lungs. In comparison to mammals, the structures are too simplified and mainly help in the exchange of gases when the frog is active on land.

Diaphragm: Frogs do not have a diaphragm like mammals. Instead, it has buccal pumping. This is a way of ventilating the lungs by movements of the floor of the mouth to push air in and out of the lungs.

Types Of Respiration In Frogs

The types of respiration are given below:

Cutaneous Respiration

This involves gas exchange directly through the frog's skin. This kind of respiration mostly takes place when the frogs are underwater. It allows them to obtain oxygen from the water and eliminate excess carbon dioxide.

Cutaneous respiration can only take place in a dampened environment where the skin is kept moist because diffusion of gasses can only take place when moist.

Buccopharyngeal Respiration

Frogs respire via the buccopharyngeal mechanism, which involves exchange with mucous membranes inside their mouth and pharynx. A frog draws air into its mouth cavity and subsequently propels it over the mucous membranes by closing its nostrils.

The mouth and pharynx are extremely significant in this kind of respiration because they offer a large surface area where the exchange of gases occurs.

Pulmonary Respiration

Frogs use their lungs to breathe air when they are mostly on land in pulmonary respiration. Buccal pumping is performed through a rhythmically expanding and contracting throat by which air is passed in and out of the lungs.

Frogs do not possess a diaphragm. So, they force the air into their lungs through the muscles of the mouth and throat into their lungs, this mode of respiration is called positive pressure breathing.

The Respiratory Cycle

The respiratory is given below-

Inhalation Process

The frog depresses the floor of the mouth while inhaling, which draws air into the nostrils. The nostrils close, and then it raises the floor of its mouth, forcing the air into the lungs.

Exhalation Process

The frog in exhalation relaxes the muscles in the mouth and throat, and then the air is pushed out through the nostrils or the mouth. As the case may be, the lungs are deflated.

Adaptations of Frogs for Efficient Respiration

The adaptations are given below-

Structural Adaptations

• The skin in frogs is a unique structure that is thin and permeable enough to facilitate efficient gas exchange with their surroundings.

• The skin itself is profusely supplied with blood vessels, which ensures the quicker uptake of oxygen and release of carbon dioxide.

• Mucous glands in the skin keep it moist, which in turn becomes very relevant to gas diffusion during cutaneous respiration.

Behavioural Adaptations

• Frogs inhabit moist environments, which enhance cutaneous respiration and prevent the dehydration of their skin.

• Frogs hibernate and survive harsh winters by sleeping and surviving on the stored food in their body during winters.

• Similarly, farmed frog populations aestivate during summers to save energy to maintain their basal metabolism and then use that saved energy during aestivation to live in such harsh conditions.

Respiratory System in Frogs NEET MCQs (With Answers & Explanations)

This topic carries a significant weightage in NEET exam. Important topics to be covered are:

• Structure of Respiratory System

• Types of respiration (Cutaneous, buccopharyngeal, pulmonary)

• Respiratory Cycle

Practice Questions for NEET

Q1. One of the main functions of frog's skin is

1. Diffusion of respiratory gases

2. Diffusion of respiratory gases

3. Storage of excess food in the form of subcutaneous fat

4. Excretion of nitrogenous waste in the form of uric acid

Correct answer: 1) Diffusion of respiratory gases

Explanation:

The skin of a frog plays an important role in respiration through a process known as cutaneous respiration. It acts as an extensive surface for the exchange of gases, allowing oxygen to diffuse in and carbon dioxide to diffuse out directly through the skin.

Hence, the correct answer is option 1) Diffusion of respiratory gases.

Q2. Which of the following best describes the breathing mechanism in frogs?

1. Diaphragmatic breathing

2. Costal breathing

3. Buccal pumping

4. Pharyngeal pumping

Correct answer: 3) Buccal pumping

Explanation:

Buccal pumping is the breathing mechanism observed in frogs. It involves the rhythmic movement of the floor of the oral cavity, or buccal cavity, to facilitate respiration. In frogs, buccal pumping involves the coordinated action of the muscles in the buccal cavity, which leads to the inhalation and exhalation of air. As the floor of the buccal cavity moves down, fresh air is drawn in through the nostrils. When the floor moves up, the air is forced out of the lungs and through the nostrils. This mechanism helps facilitate gas exchange in the frog's respiratory system.

Hence, the correct answer is option 3) Buccal pumping.

Q3. What role does the glottis play in frog respiration?

1. It allows for the entry of air into the lungs.

2. It controls the opening and closing of the nostrils.

3. It aids in vocalization and sound production.

4. It helps in the regulation of body temperature.

Correct answer: 1) It allows for the entry of air into the lungs.

Explanation:

The glottis is a small opening located at the back of the oral cavity in frogs. It serves as the entrance to the respiratory system. When a frog breathes, the glottis opens, allowing air to enter the lungs. This air passes through the buccal cavity, where gas exchange occurs across the moist lining, and then continues into the lungs for further gas exchange. After oxygen is extracted from the air in the lungs, carbon dioxide is expelled from the body through the same pathway. So, the glottis plays a crucial role in facilitating the entry of air into the frog's lungs, enabling respiration to occur.

Hence, the correct answer is option 1) It allows for the entry of air into the lungs.

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