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Insects have spiracles on their exoskeletons to allow air to enter the trachea. [1] [page needed] In insects, the tracheal tubes primarily deliver oxygen directly into the insects' tissues. The spiracles can be opened and closed in an efficient manner to reduce water loss. This is done by contracting closer muscles surrounding the spiracle.
Although all insects have spiracles, only some arachnids have them. Some spiders such as orb weavers and wolf spiders have spiracles. Ancestrally, spiders have book lungs, not trachea. However, some spiders evolved a tracheal system independently of the tracheal system in insects, which includes independent evolution of the spiracles as well ...
The trachea open through spiracles into this air film, allowing access to oxygen. In many such cases, when the insect dives into the water, it carries a layer of air over parts of its surface, and breathes using this trapped air bubble until it is depleted, then returns to the surface to repeat the process.
Depending on the number and position of the tracheal spiracles, the following types of breathing apparatus can be distinguished. apneustic, with absence of stigmas ; metapneustic, with only one pair of stigmata. These are on the abdomen. amphipneustic, with two pairs of stigmas. On pair on the prothorax, one pair on the abdomen.
Instead, the insect respiratory system uses a system of internal tubes and sacs through which gases either diffuse or are actively pumped, delivering oxygen directly to tissues that need it via their trachea (element 8 in numbered diagram). Since oxygen is delivered directly, the circulatory system is not used to carry oxygen, and is therefore ...
During the closed phase of discontinuous gas exchange cycles, the spiracle muscles contract, causing the spiracles to shut tight. At the initiation of the closed phase, the partial pressure of both O 2 and CO 2 is close to that of the external environment, but closure of the spiracles drastically reduces the capacity for the exchange of gases with the external environment. [2]
The abdominal spiracles are located on each side of the body on the first eight abdominal segments. [64] Caterpillars have different types of projections; setae (hairs), spines, warts, tubercles, and horns. The hairs come in an assortment of colours and may be long or short; single, in clusters, or in tufts; thinner at the point or clubbed at ...
The trachea (pl.: tracheae or tracheas), also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all animals lungs. The trachea extends from the larynx and branches into the two primary bronchi.