Book Lungs Meaning

Book gills and book lungs are the types of respiratory organs that are present in insects or arthropods. There are some lamellae that are present in these structures. These lamellae are then arranged in the form of a book and so they are called the book lungs or the book gills. They are present in scorpions and spiders. To understand more about them, we need to understand the kingdom Arthropoda. 


The Arthropoda kingdom mainly comprises all the insects and they are the largest phylum on the earth. More than nine lakh species of insects are present on the earth. As they are the largest phylum, so they have the most diverse types of organisms present such as cockroaches, scorpions, spiders, prawns, centipede, millipede, and many more. We will study what are book lungs and about book lungs and book gills. 

Characteristics of Arthropods

 Some General Characteristics of This Phylum are Listed below.

  • These organisms have their habitat in almost all places on the earth. They are present in oceans, air, grass, and even in houses. 

  • Their body is bilaterally symmetrical.

  • The Organ-system level of organization is present in the body of these organisms.

  • They have a segmented body and different segments are present in their body. 

  • Their coelom is triploblastic in nature.

  • Their body cavity has visceral organs and they have a true coelom.

  • The Head, thorax, and abdomen are the parts in which their body is divided. 

  • Chitin helps to form a protective cover on the body of these organisms. This chitin helps them in retaining the moisture in their body. The appendages in these organisms are joined together. And this is the reason why they are named arthropods because arthro means jointed and pod means appendages. 

  • There is a process of shedding that occurs in these organisms. Through this process, their chitinous exoskeleton is shredded away and a new exoskeleton replaces it. This shedding process is termed ecdysis or moulting. 

  • A complete digestive system is present in these organisms. This means that all the organs required for digestion are present in them. 

  • The scorpion presents book lungs and they are known as scorpion book lungs. 

Respiratory Structures

For the process of respiration, there are special respiratory organs present in these organisms. These different structures are present in them for the adaptation to facilitate the passage of oxygen throughout their body. These structures are:

  • Gills: In prawns and crabs these structures are present. As these insects live in water so they have the presence of gills in them. 

  • Book-Gills: They are a modified version of gills. Lamellae are present in them. The lamellae are a plate-like structure and these lamellae lie parallel to each other and in this course, they are arranged in the form of a book, therefore they are called book gills. These structures are present in the Limulus. 

  • Book-Lungs: These are the modified structures of book-gills. An example is book lungs in scorpion. This helps us to understand book lungs meaning. 

  • Tracheal System: This comprises the major respiratory system in the insects. Elastic air tubes that are called the trachea are present in them. Some pores that are known as spiracles are present on the outside of their body. This system is present in cockroaches and mosquitoes. 

The above paragraph gives us a clear understanding of what are book lungs and book lung meaning. 

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Circulatory and Sensory System

As we read above about what are book lungs, now we will study the circulatory and sensory systems in insects. We know that in insects an open type of circulatory system is present. With the help of this system, the blood flows to all the cavities that are present in the organism. As the open type circulatory system is poor in nature, so to compensate for that, the insects have a very well-developed respiratory system. For the senses such as smell, taste, touch, sight, these organisms have special sensory structures that help them in this process. They are: 

  • Antennae: They are movable in nature and a type of appendage. These are present on the anterior end of their body. These antennae have receptors of touch and smell. Some tactile receptors are also present on the surface of the antennae that are associated with the senses of touch.

  • Eyes: The insects have compound eyes. This means that their one eye is further divided into small compartments and these compartments join together to form a big eye. 

  • Statocysts: As the name suggests, these organs serve the purpose of balancing the life of insects. They provide the information to the brain and then the brain helps in maintaining the balance of the body. 

FAQs (Frequently Asked Questions)

1. What are Different Types of Mouthparts That are Present in the Insects?

Answer: The mouthparts that are present in the insects comprise one labrum, one labium, one hypopharynx, and two mandibles, and two maxillae. These structures are then modified into different types that are listed below: 

  • Biting Type: They are also known as a chewing type of modification. They are present in the grasshoppers and crickets. The mandibles are well developed in this type of modification.

  • Piercing Type: They are also known as sucking type of modification. They are seen in mosquitos and the proboscis in them is modified by the labium. 

  • Sponging Type: They are present in the housefly. In this type they feed on sugars and secrete saliva on it, making it in liquid form and then sucking the liquid. 

  • Siphoning Type: This type of mouthpart is present in moths and butterflies. The maxilla is modified to form the proboscis. 

  • Chewing Type: It is also known as the lapping type of mouth modification. They are present in the honeybees. 

2. What Function is Served by the Jointed Appendages in the Body of Arthropods and also Explain About Chilopoda?

Answer: As we read above that the arthropods have jointed legs. These legs or appendages help them to have good mobility. As and when the legs are joined, then they serve the purpose of providing the movement in multiple directions. So, this gives them an edge to perform various activities, without much effort. The Chilopoda is one of the classes in which the arthropods are divided. They have the presence of many legs and their body is long and segmented. Excretion occurs with the help of Malpighian tubules and respirations occur by the trachea. Direct type of development is present in these organisms.