| 31. | Muscles within the body wall force the air back and forth between the lungs and vocal sac.
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| 32. | The spines are essentially moveable extensions of the body wall, and are hollow and covered by cuticle.
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| 33. | These outgrowths of the body wall are distinguished from chaeta, which grow from follicles and thus possess roots.
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| 34. | The last two to three pairs of ribs are not connected and hang freely in the body wall.
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| 35. | The body wall consists of the epidermis and an external cuticle, which consists mainly of criss-cross collagen fibers.
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| 36. | The outer body wall consists of connective tissue, muscle fibres, and a simple epithelium directly underlying the tunic.
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| 37. | Histolysis then occurs and the body wall becomes brittle and eventually bursts, liberating the eggs into the burrow.
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| 38. | The parietal pleura receives its blood supply from the intercostal arteries, which also supply the overlying body wall.
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| 39. | The main feature conssted of five arms, or ambulacra, in the body wall radiating outwards from the central mouth.
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| 40. | The gastrovascular cavity itself is divided into a number of chambers by mesenteries radiating inwards from the body wall.
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