There are 4 types of Respiration seen in the Frogs:
a. Branchial Respiration via Gills
b. Cutaneous Respiration via Skin
c. Pulmonary Respiration via Lungs
d. Buccopharyngeal Respiration.
· Respiration in frogs during the larval stage occurs by gills.
A. Branchial or Gill respiration
· It is found in the tadpole stage.
· External gills – 3 pairs
· Internal gills – 4 pairs
· Gill pouches - 5 pairs
· 4 pairs in a number
· Richly supplied with blood vessels.
· Tadpoles can’t survive outside water.
· In adults, in accordance with the amphibious mode of life, frog respires by skin, buccopharyngeal cavity and lungs.
· Ordinary Oxygen requirement is met by cutaneous and buccopharyngeal respiration.
· It is found in the tadpole stage.
· External gills – 3 pairs
· Internal gills – 4 pairs
· Gill pouches - 5 pairs
· 4 pairs in a number
· Richly supplied with blood vessels.
· Tadpoles can’t survive outside water.
· In adults, in accordance with the amphibious mode of life, frog respires by skin, buccopharyngeal cavity and lungs.
· Ordinary Oxygen requirement is met by cutaneous and buccopharyngeal respiration.
· Pulmonary respiration takes place when there is more demand.
B. Cutaneous respiration (Respiration by Skin)
· Usual mode of respiration.
· Occurs when in water, on land and during hibernation and aestivation.
a. Skin
· Thin and highly vascular
· Always kept moist by mucus secretion and by frequent plunging into the water.
· Oxygen dissolved in water (when the frog is in water) or atmospheric Oxygen dissolved in a thin film of moisture around the body (when the frog is on land) diffuses through the skin in the blood and CO2 diffuses back.
· Skin is a favourable site for respiration because of the mucous gland.
· It fulfils about 30% of the total amount of oxygen intakes
· Dermis acts as alveoli of lungs/surface of gaseous exchanges.
· Waxing of skin or when exposed to intense sunlight for a long time leads to death of frog due to asphyxia.
· Thin and highly vascular
· Always kept moist by mucus secretion and by frequent plunging into the water.
· Oxygen dissolved in water (when the frog is in water) or atmospheric Oxygen dissolved in a thin film of moisture around the body (when the frog is on land) diffuses through the skin in the blood and CO2 diffuses back.
· Skin is a favourable site for respiration because of the mucous gland.
· It fulfils about 30% of the total amount of oxygen intakes
· Dermis acts as alveoli of lungs/surface of gaseous exchanges.
· Waxing of skin or when exposed to intense sunlight for a long time leads to death of frog due to asphyxia.
C. Buccopharyngeal respiration
· Buccopharyngeal cavity is richly vascular and kept moistened by mucus secretion so that gas diffusion can occur.
· Buccopharyngeal cavity is richly vascular and kept moistened by mucus secretion so that gas diffusion can occur.
· It takes place when frog rests on land or semi-aquatic condition.
· It accounts for 5% of total oxygen intake.
D. Pulmonary respiration
· It occurs when the frog is more active such as during swimming or leaping and jumping.
· Structures concerned in this respiration:
· No trachea due to absence of neck in frog
· So laryngotracheal chamber is formed by fusion of the larynx and trachea.
· It occurs when the frog is more active such as during swimming or leaping and jumping.
· Structures concerned in this respiration:
- External nares
- Olfactory chambers
- Internal nares
- Buccopharyngeal cavity
· No trachea due to absence of neck in frog
· So laryngotracheal chamber is formed by fusion of the larynx and trachea.
· It is a voice box or sound-producing organ in the frog.
· Its walls are supported by 2 types of cartilages – 2 arytenoid cartilages (C-shaped) and one y shaped cricoids cartilage.
· Its internal lining forms a pair of elastic horizontal bands called vocal cords for sound production.
· Vocal sacs present in males act as resonators.
· Vocal sacs present in males act as resonators.
b. Lungs
· Lungs are non–lobulated.
· Externally lung is covered by visceral peritoneum
· Middle layer has connective tissue with smooth spongy muscle and blood vessel.
· Externally lung is covered by visceral peritoneum
· Middle layer has connective tissue with smooth spongy muscle and blood vessel.
· Innermost layer is the epithelium.
· Wall of alveoli is lined by externally thin flatted cells of squamous epithelium.
· Wall of alveoli is lined by externally thin flatted cells of squamous epithelium.
· The size of alveoli is larger but their number is fewer than the lungs of humans.
· Alveoli are the structural and functional unit of the lung.
· Lungs are a pair of thin-walled distensible sacs lying on the anterior part of the body cavity on either side of the heart partly overlapped by the liver.
· Internally surface of each lung is divided by a series of irregular septa into large no. of alveoli.
· Walls of alveoli are made up of extremely thin flattened cells and are richly supplied with blood vessels.
· Lungs are a pair of thin-walled distensible sacs lying on the anterior part of the body cavity on either side of the heart partly overlapped by the liver.
· Internally surface of each lung is divided by a series of irregular septa into large no. of alveoli.
· Walls of alveoli are made up of extremely thin flattened cells and are richly supplied with blood vessels.
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| Structure of lung of the frog |
MECHANISM OF PULMONARY RESPIRATION OR BREATHING OR VENTILATION OF AIR
· Pulmonary ventilation is brought about by two sets of muscles (Petrohyal and Sternohyal) that elevate and depress the floor of the buccal cavity which acts as a force pump.
· It is completed in 2 phases.
- Inspiration
- Expiration
1. Inspiration
· Process of withdrawal of atmospheric Oxygen into Lungs
Steps:
· Mouth, Glottis, Gullet are closed and external nostril is opened.
· Sternohyal muscles contract but petrohyal muscles relax so that volume of the buccopharyngeal cavity is increased and pressure decreases.
· Atmospheric Oxygen enters into the buccal cavity.
· Mentomecklian bone raises to close external nares
· Then petrohyal muscle contracts, the volume of the buccal cavity decreases and pressure increases.
· As a result of which O2 enters the lungs.
2. Expiration
· Process of expels out of CO2 from lungs into atmosphere.
Steps:
Contraction of lungs – contraction of the sternohyoid muscle to increase the volume of buccal cavity – air comes into the buccal cavity from lungs – Mentomecklian bone shifts in its original position to open external nares – Petrohyal muscle contracts to reduce the volume of buccal cavity – so air is expelled out into the atmosphere through the buccal cavity.
Steps:
· Mouth, Glottis, Gullet are closed and external nostril is opened.
· Sternohyal muscles contract but petrohyal muscles relax so that volume of the buccopharyngeal cavity is increased and pressure decreases.
· Atmospheric Oxygen enters into the buccal cavity.
· Mentomecklian bone raises to close external nares
· Then petrohyal muscle contracts, the volume of the buccal cavity decreases and pressure increases.
· As a result of which O2 enters the lungs.
2. Expiration
· Process of expels out of CO2 from lungs into atmosphere.
Steps:
Contraction of lungs – contraction of the sternohyoid muscle to increase the volume of buccal cavity – air comes into the buccal cavity from lungs – Mentomecklian bone shifts in its original position to open external nares – Petrohyal muscle contracts to reduce the volume of buccal cavity – so air is expelled out into the atmosphere through the buccal cavity.
Note:
1. Sternohyoid or sternohyal muscle
· It joins hyoid bone to the coracoids and clavicle bones of the pectoral girdle
· Its contraction lowers the floor of the buccopharyngeal cavity.
2. Petrohyal or petro-hyoid muscle
· It joins the upper surface of hyoid bone and pro-otics of the auditory capsule (skull)
· Its contraction raises the floor of the buccopharyngeal cavity (decrease the volume)
· Both sternohyal and petrohyal muscles contract 2 times for complete breathing.
· But in are complete buccopharyngeal respiration, sternohyal and petrohyal muscles contract one time only.
a. Breathing or external respiration
b. Gaseous exchange by diffusion
c. Internal respiration or tissue respiration or biological oxidation of foodstuffs.
Sound production
· By laryngotracheal chamber.
· Opens into the buccopharyngeal cavity through the glottis.
· Consists of cricoid and arytenoid cartilages and a pair of vocal cords with a narrow gap, rima glottidis between them.
· When air is forced from lunge through rima glottidis, vocal cards vibrate to produce characteristic croak sound.
· In males, vocal sacs act as resonators to raise the pitch of the sound.
1. Sternohyoid or sternohyal muscle
· It joins hyoid bone to the coracoids and clavicle bones of the pectoral girdle
· Its contraction lowers the floor of the buccopharyngeal cavity.
2. Petrohyal or petro-hyoid muscle
· It joins the upper surface of hyoid bone and pro-otics of the auditory capsule (skull)
· Its contraction raises the floor of the buccopharyngeal cavity (decrease the volume)
· Both sternohyal and petrohyal muscles contract 2 times for complete breathing.
· But in are complete buccopharyngeal respiration, sternohyal and petrohyal muscles contract one time only.
Physiology of Respiration
· It completes in three steps.a. Breathing or external respiration
b. Gaseous exchange by diffusion
c. Internal respiration or tissue respiration or biological oxidation of foodstuffs.
Sound production
· By laryngotracheal chamber.
· Opens into the buccopharyngeal cavity through the glottis.
· Consists of cricoid and arytenoid cartilages and a pair of vocal cords with a narrow gap, rima glottidis between them.
· When air is forced from lunge through rima glottidis, vocal cards vibrate to produce characteristic croak sound.
· In males, vocal sacs act as resonators to raise the pitch of the sound.
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