The Invertebrate Heart
In invertebrates that possess a circulatory system, the heart is typically a tube or small sac and pumps fluid that contains water and nutrients such as proteins, fats, and sugars. In insects, the "heart" is often called the dorsal tube and insect "blood" is almost always not oxygenated since they usually respirate (breathe) directly from their body surfaces (internal and external) to air. However, the hearts of some other arthropods (including spiders and crustaceans such as crabs and shrimp) and some other animals pump hemolymph, which contains the copper-based protein hemocyanin as an oxygen transporter similar to the iron-based hemoglobin in red blood cells found in vertebrates.
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Famous quotes containing the word heart:
“Royalty is a government in which the attention of the nation is concentrated on one person doing interesting actions. A Republic is a government in which that attention is divided between many, who are all doing uninteresting actions. Accordingly, so long as the human heart is strong and the human reason weak, Royalty will be strong because it appeals to diffused feeling, and Republics weak because they appeal to the understanding.”
—Walter Bagehot (1826–1877)