The process of intake of oxygen to oxidise food to release energy and throw out of Carbondioxide is Called respiration.
The process of intake of oxygen and through out of Carbondioxide is called breathing or External respiration while oxidation of food to release energy is Called respiration or internal respiration or Cellular respiration.The part of body where exchange of gases takes place is Called respiratory Surface. In adult frog, 3 types of respiration are present on the basis of respiratory surface which are Cutaneous respiration, buccal respiration and pulmonary respiration.
* In tadpole larva, Branchial respiration is present in which exchange of gases takes place through gills (Respiratory surface) as it lives in Water.
In tadpole, 3 pairs of external gills, 4 pairs of internal gills and 5 pairs of gill pouches are present.
* cutaneous respiration: In it, exchange of gases takes place through skin. The skin of frog is thin, moist and highly vascular (dermis).
During this process oxygen present in air On the Contact of Skin get dissolved in the Water present on the surface of Skin. The concentration of Oxygen is more on the surface of Skin while concentration of carbon dioxide is less. on the other side , in blood Capillaries of skin with deoxygenated blood has low concentration of oxygen and higher concentration of Carbon dioxide. Thus, exchange of gases takes place by the process of diffusion during which dissolved oxygen passes into blood while Carbondioxide in blood passes out to air.
It takes place when Frog is on land, in water, during hibernation and
aestivation. It is only one mode of respiration during hibernation and activation. The Skin must be moist for it. It does not take place through dry Skin.
It fulfils 30% oxygen demand of body.
waxing of skin prevents Cutaneous respiration and Frog dies due to asphyxia (scarcity of oxygen).
* pulmonary respiration: In it, exchange of gases takes place through lungs. It fulfils about 65% oxygen demand of body. It takes place when frog is active specially during leaping on land.
organs concerned with the process of respiration form respiratory system which Consists of respiratory tract and respiratory surface.
The passage through which atmospheric air passes upto lungs and
vice-verca is called respiratory tract while the part where exchange of gases takes place is called respiratory Surface.
The respiratory organs are External nostrils, nasal Chambers, internal Nostrils, bucco-pharyngeal cavity, laryngo-tracheal Chamber, bronchus and lungs.
• External nostrils/ nares: TWO Small openings above mouth in upper jaw through which air passes in lout during respiration.
• Nasal chambers: Each external nares opens into a Small Chamber Called nasal Chamber through which air Passes during respiration.
• Internal nostrils: Each nasal Chamber opens into the anterior roof of buccal Cavity by an opening called internal nostril. Thus, a pair of internal nostrils are present. Air passes through them during respiration.
The external nostrils, nasal chambers and internal nostrils are Collectively called nasal passage.
• Bucco-pharyngeal Cavity: is a wide Cavity lying between upper jaw and lower jaw which remains lined by epithelium with mucus cells. It contains different structures. It's anterior part is buccal cavity while Posterior is pharynx. The pharynx opens into laryngo-tracheal Chamber.
•Laryngo-tracheal Chamber : In Frog, neck is absent. Thus, both larynx and trachea are very short and they remain fused with each other to form a Chamber Called laryngo-tracheal Chamber.
It's Wall remains supported by 3 Cartilages ; one ring like cricoid Cartilage and two Crescentric arytenoid Cartilage.
Two fibrous elastic bands are present in its Cavity Called as Vocal Cords. when air forcely passes through laryngo-tracheal chamber ,these vocal cords vibrate and Sound is produced. Thus, sound is produced by vibration of vocal cords. so, laryrgo-tracheal Chamber is Called voice box.
• Bronchus: From Posterior end of laryngo - tracheal Chamber a short tubular structure arises each on either side Called as bronchus. These bronchus Connects laryngo-tracheal Chamber with lungs.
• Lungs: A pair of lungs are present in the anterior region of body Cavity each on either side of heart at the level of fore limbs. Each lung is thin walled, elastic, spongy, highly Vascular , pink Coloured and ovoid in shape.
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| Frog: T.s. of lungs |
Histologically, lungs remain Covered by a layer of peritoneum inner to which a layer of muscles is present and inner to muscles a layer of connective tissue with blood vessels and nerves is present. Internally, it remains Covered by epithelium with folds. These folds remain lined by squamous epithelium towards periphery While by Columnar epithelium towards Centre. Due to these folds Cavity of lungs remain differentiated into a number of Smaller Chambers Called air sacs or alveolie where exchange of gases takes place.
• Muscles involved in pulmonary respiration:
Two muscles are involved in the process of pulmonary respiration which are sternohyal muscles and petronyal muscles.
The sternohyal muscles remain attached with under surface of hyoid bone in front and with sternum at back. The Petrolyal muscles remain attached with upper surface of hyoid bone in down side while with Squamosal bone of Skull in upside.
when Sternohyal muscle contract , the petrohyal muscle relaxes and the hyoid bone along with floor of buccal Cavity moves down and size of buccal Cavity increases. when Petrolyal muscles Contract , the sternohyal muscles relaxes and the floor of buccal Cavity moves up decreasing size of buccal Cavity. Thus, Contraction and relaxation of these two muscles make bucco-pharyngeal Cavity act as force pump and brings atmospheric air into buccal Cavity and pumps that air into lungs and vice-verca.
• Mechanism of pulmonary respiration: the process of pulmonary respiration gets Completed in two steps; inspiration and expiration.
• Inspiration: The process by which atmospheric air is reaches upto lungs is Called inspiration.
During it, nostrils remain open while glottis remains closed. The sternohyal muscles contract while petrolyal muscles relax. Due to this the hyoid bone along with floor of buccal Cavity moves down and size of buccal Cavity increases. Thus, air pressure inside buccal Cavity decreases and atmospheric air comes into buccal Cavity through nostrils.
NOW nostrils get closed due to Contraction of submental muscles which raises mentomeckelian bone while glottis opens. The petroyal muscles Contract and Sternohyal muscles relax. Due to this the hyoid bone along with floor of buccal Cavity moves up and size of buccal Cavity decreases. Thus, air pressure inside buccal Cavity increases and air in buccal Cavity passes into lungs through glottis. this Completes inspiration.
Now glottis get closed for Sometime and exchange of gases takes place inside lungs by diffusion.
• Expiration: the process by which air in lungs passes out to atmosphere is Called expiration. During it, glottis remain open while nostrils remain closed. The sternohyal muscles Contract while petrolyal muscles relax. Due to this size of buccal Cavity increases and air pressure inside it decreases. Thus, air in lungs come into buccal Cavity through glottis.
Now the glottis get closed while nostrils open. the petrolyal muscles Contract and sternohyal muscles relax. Due to this size of buccal Cavity decreases and air pressure inside it increases. Thus, air in buccal Cavity passes out to atmosphere through nostrils. This Completes expiration.
According to recent findings, both nostrils and glottis remain open during pulmonary respiration. Thus, when size of buccal Cavity increases , the atmospheric air Comes into buccal Cavity through nostrils and at the same time air in lungs also Comes into buccal Cavity through glottis. Both air get mixed with each other in buccal Cavity. when size of buccal Cavity decreases, some amount of the mixed air in it passes out to atmosphere through nostrils while some amount Passes into lungs through glottis.
This proves the inefficiency of lungs to fulfil the demand of oxygen in body as fresh atmospheric air Cannot reach up to lungs.
• In pulmonary respiration, both sternohyal and petroyal muscles Contract for 2 times.
* Buccal respiration: also Called bucco-pharyngeal respiration. In it, respiratory surface is lining of buccal Cavity.
It takes place when the frog is on land and floating on water. It also takes place in between inspiration and expiration of pulmonary respiration.
During it, mouth and glottis remains closed while nostrils remain open.
when size of buccal Cavity increases by contraction of Sternohyal muscles, the atmospheric air comes into buccal Cavity through nostrils and exchange of gases takes place in the lining of buccal Cavity by diffusion. Again, when the size of buccal Cavity decreases by Contraction of petrohyal muscles, the air in buccal Cavity passes out to atmosphere through nostrils. This Completes buccal respiration.
• In buccal respiration, both sternohyal and petrohyal muscles Contract for
1 time.
