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Respiratory system and lymphatic system of frog

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Respiratory System of Frog

The process of gaseous exchange (O2 and CO2) and the utilisation of oxygen to break down food to release energy is called respiration. The oxygen is taken through the blood.

C6H12O6+ 6O2→ 6CO2+ 6H2O + energy
glucose + O2→ Carbon dioxide + water + energy
The inhale of oxygen and exhale of carbon dioxide is done through respiration which involves three stages.

External respiration:

It 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 the utilisation 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 different types of respiration in frog which are as follows,

By gills
For many frogs, their life cycle includes a "tadpole" or larval stage of
development. Eggs are laid in ponds or lakes, and upon hatching, the tadpole uses internal and external gills in order to respire within their aquatic environment. The gills absorb and filter oxygen from the water and dispose of respiratory waste products through the process of diffusion. During maturation from a tadpole into a frog, these gills are disappeared.

Skin or Cutaneous respiration
The respiration through the skin is called coetaneous respiration. It occurs in hibernation and aestivation and in water.The skin of many frogs is thin and highly vascular to allow for gas exchange. Because of their thin skin, frogs must live in moist environments and secrete mucus from their skin to avoid desiccation. Cutaneous respiration also allows for the frog to remain almost completely submerged under water for long periods of time while still oxygenating their blood.
Inside the body of frog, the atmospheric oxygen ( dissolved ) diffuses into the blood capillaries which combines with haemoglobin forming oxyhaemoglobin which is taken into the different parts of the body and is converted into oxygen and haemoglobin in which haemoglobin again mix with waste gas CO2forming carboxyhaemoglobin that is later passed out through skin.

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. This includes following parts,

External nares: These are small opening between eyes and snout through which inhaling and exhaling occur.

Internal nares: The nostril is situated between maxillary and vomerine teeth of mouth cavity through which the external and internal nares are attached by a small tube like structure.

Buccal cavity: It is the area between upper and lower jaws which helps to pass air into the lungs. It is also called conducting organs.

Lungs: It is the pair of thin-walled, soft, spongy, pink coloured structure consisting a network of tissues where the exchange of gases takes place. Internally it is divided by septa into a large number of small air sac called alveoli that are richly supplied with blood vessels. It increases the surface area for respiration. The power of contraction and expansion of lungs is produced by inner- epithelial lining of the alveoli containing the alveolar type of connective tissue comprising vessels and smooth muscle fibres.

Mechanism of pulmonary respiration

inspiration and expiration of frog
fig:inspiration and the expiration of frog

Inspiration: During inspiration the sternohyal muscle contracts and lowers the floor of the mouth cavity and increases the mouth cavity that results in the decrease of pressure. Therefore, air is taken into the cavity through nares. Soon the nares remain closed and betrayals contract and the floor is raised up. Space in the cavity is decreased and pressure is increased. The air passed through lungs for the gaseous exchange.
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 submental muscles relax and external nares are opened. Due to the contraction of the lungs, the air from the lungs escapes and passed out through the nares.During this process there is no role of sternohyal and petrohyal muscles so, it is a passive process.

Bucco- pharyngeal Respiration

Frog also can have gas exchange through the buccal cavity that consists of moist mucus membrane and richly supplied blood vessels.The air enters the cavity through nares and gaseous exchange takes place through the lining of the buccal cavity between blood and air present in the cavity. This respiration takes place by the rhythmic up and down movement of the buccal cavity which is helped by petrohydal muscles and sternohyal muscles. During the contraction of the petrohydal muscles, mouth cavity is pushed upward and expiration occurs. Whereas during the contraction of petrohydal muscles, mouth cavity is lowered downwards and inspiration occurs. like this, the oxygen is taken in and carbon dioxide is diffused out. Now, the petrohydal muscle contracts and the carbon dioxide is thrown outside.

Sound production in Frog

The sound production is done from the laryngo tracheal chamber which consists two cartilage, arytenoid and cricoid one from outside and the other from inside which are both attached by ligaments. This chamber lies in the middle portion of hyoid arches. Two tracheal process from cricoid unites with lungs keeping it in position. Arytenoids cartilage encircles the glottis also. Two elastic bands called vocal chords are situated across the laryngo tracheal chamber which can contract and altered it's in its tension with the help of muscles and variation in sound also occurs. The vocal chords in male frog are large and thick in structure then female and vocal sacs in male frog act as resonators and intensity pitch of the sound.

Lymphatic System of Frog

In the circulatory system, due to blood pressure, many components of blood plasma come out of the capillaries and fill the intercellular spaces. These components are also in the form of a fluid and are called tissue fluid or interstitial fluid. Much of it reenters the capillaries and some of it enter the lymph vessels where it is known as lymph. The flow of lymph is unidirectional. Through lymph “vessels” lymph goes to big veins. Thus, lymph again enters the blood.

Instead of lymph vessels, lymph sinus is present in the frog. It is found in different body parts which are as follows,

Subcutaneous lymph sinus: Lies below the skin and are separated by connective tissue. It consists of following types,

Dorsal lymph sinus: found on the dorsal side and runs fro back up to

Lateral lymph sinus: from the tympanum to hind limbs of its lateral sides
Pectoral lymph sinus: pectoral regions of dorsal and ventral sides
Sub- maxillary lymph sinus: lower jaw regions
Abdominal lymph sinus: lies on the ventral side.
Pelvic lymph sinus: pelvic region

Sub- vertebral lymph sinus: It encircles the vertebral column and kidneys of the body cavity.

Coelom: It is the real body cavity where all the internal organs exist.

Pericardial sinus: It encircles heart and situated in the midst of pericardium.

Lymph vessels: Two pairs of lymph hearts are formed in the fusion part of veins. It is a transparent bag like structure, and always, pulsates.

Functions of Lymph

  • Lymph nodes produce lymphocytes.
  • Kills the foreign bodies like viruses, bacteria etc.
  • Keeps the percentage of proteins constant.
  • Absorbs food in the small intestine.


Small, globular reddish brown gland at the meeting point of the large and small intestine. It contains spleen pulp that consists network of blood capillaries, lies around arteries and produces the colourless corpuscles called white pulp, and red corpuscles called red pulp. A branch of anterior mesenteric artery supplies blood to the spleen.

Functions of spleen

  • Acts as the blood bank of the body.
  • Produces lymphocytes and antibodies.
  • Produces white and red blood corpuscles.
  • Produce nitrogen and urea from carbon dioxide.

  • Respiration can be defined as a process by which living beings obtain oxygen to oxidise their reserve digested food in order to release energy.
  • Cutaneous respiration is done during hibernation and aestivation periods.
  • The respiration through the buccal pharyngeal cavity is known as bucco- pharyngeal respiration.
  • The buccal cavity consists of moist mucous membrane and richy supplied with blood vessels.
  • Pulmonary respiration occurs only when the need of oxygen is more during swimming and jumping.
  • Numerous small air sac is present in the lungs called alveoli.
  • Sound production is due to the movement of vocal chords caused by air.

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