Animal

:For the Muppet Show character, see Animal (Muppet). For the professional wrestler, see Joseph Laurinaitis.

Structure

With a few exceptions, most notably the sponges (Phylum Porifera), animals have bodies differentiated into separate tissues. These include muscles, which are able to contract and control locomotion, and a nervous system, which sends and processes signals. There is also typically an internal digestive chamber, with one or two openings. Animals with this sort of organization are called metazoans, or eumetazoans when the former is used for animals in general.

Related Topics:
Sponge - Porifera - Tissues - Muscle - Nervous system - Digestive

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All animals have eukaryotic cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. This may be calcified to form structures like shells, bones, and spicules. During development it forms a relatively flexible framework upon which cells can move about and be reorganized, making complex structures possible. In contrast, other multicellular organisms like plants and fungi have cells held in place by cell walls, so develop by progressive growth. Also, unique to animal cells are the following intercellular junctions: tight junctions, gap junctions, and desmosomes.

Related Topics:
Eukaryotic - Extracellular matrix - Collagen - Glycoprotein - Calcified - Plant - Fungi - Cell wall - Tight junction - Gap junction - Desmosome

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