Respiratory system of Frog

Respiratory system of Frog

organs concerned with the exchange of gases forms respiratory system. In frog, respiration takes place through moist skin, lining of bucco-pharyngeal cavity and lungs. However in tadpole larva, respiration takes through gills.

Types of respiration

1. Cutaneous respiration:
respiration through moist skin is called as cutaneous respiration. Skin is richly supplyed with alone vessels and is permeable to gases. Oxygen get dissolved in moist surface of skin them exchange of gases takes place by diffusion. It goes on all the time wheather frog is in water or on land. It is only mode of respiration during hibernation or aestivation or when frog is under water.

2. Buccal respiration:

it takes place on land during mouth and glottis remains closed while nostrils remain open. The floor of buccal cavity is alternately raised and lowered so that air is drawn into and expelled out of buccal cavity through. Nostrils. The epithelial lining of buccal cavity is moist and highly supplied with alone capillaries and exchange of gases takes place through it.

3. Pulmonary respirations

 Organs associated with respiration:


It consists of respiratory tract and lungs.

 Respiratory tract: the passage through which air enters and leaves lungs is called respiratory tract and it consists of external nares, nasal chambers, internal nares, bucco-pharyngeal cavity, glottis, laryngo-tracheal chamber and two bronchi. The glottis opens into small, thin walled chamber called as laryngo-tracheal chamber. It's wall remain supported by 2 arytenoid and 1 chricoid cartilage. Internally it contains a pair of elastic horizontal bands called as vocal cords. Vibration of vocal cords produce sound. Thus larynx or laryngo-tracheal chamber is called as voice box. 

When air from lungs is forced out between vocal cords, they vibrate producing croaking sound. Vocal sacs of male frog amplify the croaking sound.
From larynx a very small tube, the bronchus, leads to each lung.

Lungs: a pair of lungs, each on either side of heart in anterior body cavity are present. Each lungs is ovoid, thin walled and highly elastic. Externally, they remain covered by peritoneum. Internally, each lung is divided by a network of folds or septa forming a number of small air scar or alveoli with a large central cavity. The alveoli are linked with thin epithelum highly pursuied with capillaries. Exchange of gases takes place through these alveoli.






















Mechanism of pulmonary respiration

pulmonary respiration takes place between buccal respiration and during it buccal cavity acts a force pump. The up and down movements of the floor of buccal cavity is brought by the action of two muscles, sternohyal muscles and petrohyal muscles. The sternohyal are attached at the lower and to sternum and at the upper end to under surface of hyod bone in the floor of buccal cavity. The petrohyal muscles are attached below to the upper surface of hyoid bone and above to squamosal bone of skull. The whole process consists of two steps. Inspiration and expiration.

Inspiration
the process in which lungs are filled up with air is called inspiration. During it, glottis and mouth remains closed while nostrils remain open. The sternohyal muscles contract due to which the floor of buccal cavity is lowered. Thus, the buccal cavity get enlarged and air comes into buccal cavity through nostrils. Now the glottis opens and nostrils are closed. Now petrohyal muscles contract which raises the floor of buccal cavity. This decreases size of buccal cavity and air passes into lungs through glottis. This completes inspiration.

Expiration
when longs are filled with air glottis closes and air remains in lungs for some time. At this time, the floor of buccal cavity is raised and lowered to carry buccal respiration. Now glottis opens and floor of buccal cavity is towered by the contraction of sternohyal muscles. This process in which lungs are emptied is called expiration.


According to recent findings, when the floor of buccal cavity is lowered fresh atmospheric air from nostrils and air of lungs from glottis come in buccal cavity and get mixed with each other. When floor of buccal cavity is raised, the mixed air of buccal cavity goes into the lungs through glottis and goes outside through nostrils. This proves inefficiency of lungs for respiration.