Book Lung -

The folded design creates a massive surface area in a small space, maximizing oxygen absorption. How They Work

Book lungs are believed to have evolved from , which are found in aquatic ancestors like horseshoe crabs. When these creatures moved from water to land, the gills were internalized to prevent them from drying out, becoming the book lungs we see today. Comparison: Book Lungs vs. Tracheae book lung

The name comes from the organ's physical structure, which resembles the stacked pages of a book: The folded design creates a massive surface area

Most arachnids don't "inhale" or "exhale" like we do. Air simply flows into the spiracles and oxygen diffuses into the hemolymph naturally. book lung