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| Respiratory system of a scorpion |
By:
Snigdha |
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The respiratory system consists of four pairs of cuticular book-lungs or pulmonary sacs.
One pair of them lies inside each mesosomatic segment from 3 to 6. Each book-lung consists of two parts. The proximal or ventral part is in the form of a small and compressed air cavity, called the atrial chamber, which communicares with the outer air by a slit-like stigma, placed obliquely on the ventrolateral side of the sternum. The dorsal hpart, or the pulmonary chamber, is filled with about 150 lamellae , running parallel to each other and arranged one over the other like the leaves of a book. Each lamella is a hollow structure made of two thin layers of cuticle united at their edges. A thin air-space is bounded in between the two adjacent la onellae. The ,roof of the atrial chamber is perforated by many linear, slit- like openings, set parallel with one another. The atrial chamber communicates with the inter-lamellar air-spaces through those openings.The venous blood from the ventral sinus is sent to each book-lung by a diverticulum from which it enters the lamellac at their
base. The aerated blood from the lamellae of each book lung is collected into a pulmonary vein, which runs dorsally to open into the pericardium.
The inflow and outflow of air in the book-lungs seem to be controlled by the action of the dorso-ventral muscles and the atrial muscles. On the contraction of these muscles the book lungs are compressed and the air of inter-lamellar spaces is forced out into the atrial chamber and then to the outside through the stigma fa. When the muscles relax, the book-lungs resume their normal shape, so that fresh air enters through stigmata first into the arrial chamber and then into the inter lamellar spaces.
The air lies in between the lamellae and the venous blood inside them. The exchange of gases takes place through the thin membranous walls of the lamellae, the blood becoming oxygenated and its CO2 passed out into the air. |
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