Knowra Book lung Book lung A respiratory organ in some arachnids, formed by stacked, thin plates within an internal chamber. Air flows around the plates, while gases diffuse across their surfaces.
Phyllotrachea : A book lung: an arachnid respiratory organ made of stacked, leaflike plates. This name emphasizes the plate-like anatomy that gives book lungs their structure.
Arachnid : A joint-legged invertebrate in the class Arachnida, including spiders, scorpions, mites, and ticks. Book lungs occur in several arachnid groups, though not in all arachnids.
Spider : An arachnid in the order Araneae, typically with eight legs and silk-producing spinnerets. Many spiders have one or two pairs of book lungs in the abdomen.
Arachnid evolution : The evolutionary history of arachnids, a diverse lineage of chelicerate arthropods. Book lungs are often considered in studies of how arachnids adapted to terrestrial life.
Spiracle : An external opening through which air enters or leaves an animal's respiratory system. Air reaches many book lungs through a spiracle in the body wall.
Arthropod : An invertebrate animal with a segmented body, jointed appendages, and an external skeleton. Arachnids belong to this broader animal group, whose respiratory systems vary widely.
Scorpion : An arachnid in the order Scorpiones, distinguished by pincers and a segmented tail ending in a venomous stinger. Scorpions typically rely on four pairs of book lungs.
Eurypterid : An extinct aquatic chelicerate arthropod, commonly known as a sea scorpion. Fossil comparisons with eurypterids inform hypotheses about the ancestry of arachnid respiratory organs.
Hemolymph : The circulating fluid of arthropods and some other invertebrates, serving functions analogous to blood and tissue fluid. Oxygen diffusing across book-lung plates enters the hemolymph.
Trachea : A tube that conducts air into an animal's body, especially in insects and some arachnids. Some arachnids use tracheae instead of, or alongside, book lungs.
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