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:
“We talk about a representative government; but what a monster of a government is that where the noblest faculties of the mind, and the whole heart, are not represented! A semihuman tiger or ox, stalking over the earth, with its heart taken out and the top of its brain shot away. Heroes have fought well on their stumps when their legs were shot off, but I never heard of any good done by such a government as that.”
—Henry David Thoreau (1817–1862)