Respiratory System of Earthworm, Cockroach and Frog

Introduction

Morphology is a term that defines the forms and external structure of a living organism, which includes its size, shape, and structure. Morphology is primarily of three types – cellular morphology, tissue morphology, and organ morphology. Animal morphology is very distinct from plant morphology. You can easily understand it with the help of respiratory processes in earthworms, cockroaches and frogs.

Respiratory System in Earthworm

An earthworm is a terrestrial invertebrate that lives on the earth surface. They help in keeping the soil porous and suitable for agriculture and rely on the dead organic matter found in the soil. They can breathe through their skin. 

Earthworm’s Inhalation Process 

Earthworms perform the process of respiration with the help of thin permeable skin. The oxygen does not pass through the skin directly; it must first combine with the moist slime before passing through. As a result, wet skin is required for earthworms to avoid asphyxia. Blood capillaries run beneath the skin’s surface, and this is where the slime and air mix reaches. In addition to skin and capillaries, earthworms have blood vessels, with dorsal blood vessels transporting oxygen to the head (anterior region) and ventral blood vessels transporting it to the posterior region. Oxygen is circulated throughout the body in this manner.

Earthworm’s Exhalation Process

The exhalation process of the earthworm is very similar to the inhalation process. An earthworm’s body is divided into several segments, which are segmented by multiple septa and contain nephridia, which aid in exhalation.

Respiratory Organ of an Earthworm

Earthworms lack specialised respiratory organs. Except for the first three anterior segments and the last posterior segment, all body segments include nephridia. They use nephridia, coiled tubular duct-like organs that filter and eliminate waste from their bodies, made of apertures that extend to the skin. Each segment can expel waste gases through these openings in the earthworm’s skin.

Respiratory System in Cockroach

A cockroach is an insect that lives in damp places. It is omnivorous, eating small insects, grains, cereals, other plants, and animal products; as a result, it consumes all organic materials. The body of the cockroach is divided into three parts – head, thorax, and abdomen

Respiration Process of a Cockroach

Cockroaches have a unique respiratory system, which is called the tracheal system. The trachea, often known as the windpipe, is a tubular structure that helps to transmit air. The tracheal system is a network of tracheal tubes that insects, especially cockroaches, use to extract oxygen from the air around them.

Respiratory Organ of a Cockroach

The respiratory system of a cockroach is segmented into three different parts:

• Spiracles – These are tiny holes seen on the main body’s lateral surface. These are similar to human noses in that they are open to the air and have apertures. As a result, the air is inhaled through spiracles, and it goes through the tracheal tube. Muscle sphincters control the opening of the spiracles. When the sphincters open, air enters the holes; when they close, air does not pass anymore
• Trachea – This portion transports oxygen from the air (received through spiracles) to other body parts through tube-like structures that open through spiracles
• Tracheoles – These are trachea portions that have been subdivided into thinner tube-like structures. Tracheoles have a fluid network (hemolymph), and they are the places where gaseous exchange occurs by diffusion

Respiratory System in Frog

Frogs come under the amphibian species. It means that these species can live on both land and water. Frogs are characterised by prominent eyes, a lack of a tail, and strong, webbed hind feet that are specialised for leaping and swimming. They also have soft, supple skin. Many dwell in water, but others live on land, burrows, or trees.  

Respiration Process of a Frog

Frogs breathe through various processes. In the case of tadpoles or larval stages, branchial respiration occurs. Branchial respiration is accomplished through the use of external gills. An adult frog has three respiratory processes – cutaneous respiration, buccal respiration, and pulmonary respiration. Each respiration type utilises specialised organs and functions according to the surroundings of the frog. Buccal and pulmonary respiration functions on land, while cutaneous respiration takes place on land and water.

• Cutaneous Respiration

Whether the frog is on land or in water, it breathes through its skin. This form of respiration occurs when a frog is submerged in water or hibernating. The skin has a plentiful supply of blood and is permeable to gases. Before oxygen can penetrate blood, it must first dissolve on a moist surface. It is one of the reasons why frogs have wet skin and prefer to live near water. Mucous glands also release mucous to prevent the skin from drying out. Because the skin is exposed to air or water, cutaneous respiration does not necessitate movement.

• Buccal Respiration

In buccal respiration on land, the mouth is kept closed while the nostrils remain open. The bottom structure of the buccal cavity is alternately elevated and lowered. The open nostrils allow air to be sucked into and discharged from the buccal cavity regularly. During buccal respiration, the glottis is kept closed. Furthermore, this happens in such a way that air doesn’t enter or exit the lungs through the buccal cavity. Blood capillaries abound in the mucous epithelial lining of the buccal cavity, which receives O2 from the air and expels CO2.

• Pulmonary Respiration  

Pulmonary respiration is the breathing that takes place on land with the help of the lungs in the ambient air. The lungs of frogs are not fully developed. As a result, the wet skin and buccal cavity replace the limited supply of O2 acquired through the lungs.

Respiratory Organs of the Frog

The respiratory system of the frog is divided into two parts – the respiratory tract and the lungs. 

• Respiratory tract

The respiratory tract is the organ through which the air moves in and out of the lungs. It has various segments which function together to perform the task smoothly. Nasal chambers, Glottis, Bucco-pharyngeal cavity and tracheal chambers are some of the parts of the respiratory tract that aid in the breathing process. It is also the reason why frogs have a distinct croaking sound.

• Lungs

Lungs perform the function of mixing the O2 from the air and fusing it in the blood. In the case of the frog, the lungs are not well-developed. The internal surface of each lung is separated into many little air sacs, also known as alveoli, leaving a clear big centre space. A thin epithelium lines the alveoli. This epithelium is densely packed with blood capillaries that carry deoxygenated blood for gas exchange. Inhaled oxygen diffuses to the bloodstream, whilst CO2 is discharged into the alveoli.