Respiratory System of Frog | Zoology : Biology

UNIT SEVEN | DETAILED STUDY OF FROG
Class 11

Respiratory System of Frog

The process of gaseous exchange (O2 and CO2) and utilization of oxygen to breakdown food to release energy is called respiration. The process of respiration involves three stages. 

External respiration 

It also refers to breathing. In this process, the O2 is taken into the body and the CO2 is thrown out from the body into the environment. 

Internal respiration 

It refers to utilization of O2 to break down food to release energy and release of CO2 during the process. 

Transport of gases 

It refers to transportation of O2 from the respiratory surface to the cell and tissues and the CO2 from cell and tissues to the respiratory surface. There are three types of respiration in frog 

1. Coetaneous respiration 

· The respiration through skin is called coetaneous respiration. 

· The coetaneous respiration occurs in hibernation and aestivation and in water. 

· The skin of frog is thin and vascularised (skin is supplied with fine blood vessels). 

· The skin is always becomes moist by mucous secreted from the mucous glands. 

· Due to moist skin, the oxygen from the environment diffuses into the blood through skin and the carbondioxide diffuses out from the blood into the environment. 

2. Buccopharyngeal respiration 

· The respiration through the buccopharyngeal cavity is called buccopharyngeal respiration. 

· The buccal cavity consists of moist mucous membrane and richly supplied with blood vessels. 

· The air enters into the cavity through nares and gaseous exchange takes place through the lining of buccal cavity between blood and air present in the cavity. 

3. Pulmonary respiration 

· The respiration through the lungs is called pulmonary respiration. 

· This respiration occurs only when the need of oxygen is more during swimming and jumping. 

· There is a pair of lungs. The lungs are thin walled elastic sacs. They are present within thoracic cavity on either side of heart. 

· Numerous small air sacs are present in the lungs called alveoli. 

· The alveoli are very thin walled and supplied by blood vessels. The air enters into the alveoli of the lungs through the external nares, internal nares, buccopharyngel cavity, glottis, laryngotrachial camber, and bronchi. 

Mechanism of pulmonary respiration 

Inspiraton 

· Process of inhaling of air is called inspiration. 

· The mouth remains closed. The sternohyalas contract and the floor of buccal cavity is lowered. The space in cavity is increased and air pressure is decreased. Therefore, air is taken in into cavity through nare. 

· The nares remain closed and petrohyals contract and floor is raised up. Space in cavity is decreased and pressure is increased. The air passed into lungs. 

· In lungs, alveoli are filled with air and gaseous exchange takes place between blood and alveoli. Then oxygen is carried to cells and tissues in the same manner as in cutaneous respiration. 

Expiration 

· The process of exhaling of CO2 is called expiration. 

· The lungs get contracted. The external nare remains closed. 

· The floor of the cavity is lowered and the air is drawn into the cavity from the lungs. 

· The nares then open and the cavity raises and then the air is passed out through the nares. 

Transportation of gases 

The oxygen diffused into the blood through coetaneous, buccopharyngeal and pulmonary respiration is carried to the cells and tissues by hemoglobin of the blood RBC. When the oxygen reacts with hemoglobin, the oxyhemoglobin is formed, this is unstable and soon dissociates into hemoglobin and oxygen in cell surface. The released oxygen in cell surface from oxyhemoglobin diffuses into the cytoplasm of the cell. In the cytoplasm, the oxygen is utilized to break down the food to release energy. The process is called internal Respiration or cell Respiration. During the process, the CO2 is produced. 

C6H12O6 + O2---------------------------------CO2 + H2O + energy 

The released CO2 from the cell cytoplasm diffuses out through cell membrane into the blood. In the blood CO2 may reacts with water in plasma to form carbonic acid (H2CO3) or carbonic acid dissociates into HCO3 and H ions, which may react with sodium and potassium ions to form sodium and potassium bicarbonates. The carbondioxide is transported to respiratory surface in the form of these compounds.