![]() ![]() The outer surface of the lung is coated with coelomic epithelium called peritoneum. On the inner side of the epithelium there is aerolar type of connective tissue comprising blood and lymph vessels and unstriped muscle fibres which give remarkable power of contraction and expansion to the lungs. The inner surface of the aveoli is covered with a single layer of epithelial cells which are very thin and flattened except on the edges of the septa where they are ciliated and cylindrical. These are separated from each other through septa. They are ovoid, thin-walled, elastic sacs with shallow internal folds or septa that increase the inner surface to form many chambers called alveoli. The larynx opens behind into a pair of very small tubes, the bronchi, which lead to corresponding lung.Ī pair of lungs are found in the anterior part of the body cavity, one on the either side of the heart. Vocal sacs found only in male frog serve as resonators to increase the croaking sound produced by the vocal cords. The vocal apparatus of the male frog is much larger than that of the female. Vibrations in the sound are caused by altering the tension on the cords through the action of laryngeal muscles. Sound is produced by the expulsion of air from the lungs which set the free edges of the vocal cords in vibration. Their median edges are thickened and lie near each other in the middle line. The true sound producing organs are a pair of elastic bands, the vocal cords, extending longitudinally across the larynx. They afford attachment to muscles by which glottis may be opened or closed. Their upper edges form the lateral margins of the glottis. The arytenoid cartilages are a pair of semilunar valves, which rest upon the cricoid cartilage. Cricoid cartilage is a slender ring surrounding the larynx. Larynx is a small sac whose walls are supported by two arytenoid and one cricoid cartilages. The median slit-like glottis on the floor of pharynx opens into larynx (laryngo-tracheal chamber). It includes the external nostrils, nasal chambers, internal nostrils, bucco-pharyngeal cavity, glottis, laryngo-tracheal chamber and a pair of bronchi. The air enters and leaves the lungs through the respiratory fact. ![]() The lungs are not only the organs of respiration but are also hydrostatic organs as they enable frog to float in water when they are inflated. The organs of aerial respiration are a pair of lungs. Therefore, oxygen intake through moist skin and buccal cavity is needed. The intake of oxygen by lungs is not sufficient to the body. Respiration on land in air with the help of lungs is the pulmonary respiration. At the same time carbon dioxide is given out into the buccal cavity from the blood which is expelled along with residual air through the nostrils when the floor of the buccal cavity is raised. The oxygen of air dissolves in the layer of mucus and then goes into blood. When the floor of the buccal cavity is lowered, the air enters the buccal cavity through the nostrils or the nares. Thus, no air enters or goes out from the lungs. ![]() In this type of respiration, the mouth and glottis remain closed. Similarly, when frog undergoes summer sleep (aestivation) and winter sleep (hibernation), the skin is the only organ of respiration. During this period the skin only serves as an organ of respiration for gaseous exchange. The frog, due to amphibious mode of life, passes most of the time of its life in water. The skin of frog is an important organ of respiration. ![]() Ordinary respiratory requirements are met by the skin and bucco-pharyngeal cavity, lungs are used only when the need of oxygen is great. In adult frog, due to its amphibian life, respiration occurs through skin (cutaneous respiration), lining of the bucco-pharyngeal cavity (buccal respiration) and the lungs (pulmonary respiration). Respiration in tadpole of frog occurs by means of gills as in fishes. Organs which help in the intake of oxygen and supplying it to the body tissues and removal of carbon dioxide constitute the respiratory system. In the course of this reaction carbon dioxide is also formed which is removed regularly from the body due to its injurious property. Respiration can be defined as a process by which living beings obtain oxygen to oxidise their reserve digested food in order to release energy of which they are in constant need to maintain their existence by keeping their all other metabolic activities in order. ![]()
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