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Corpuscle of Stannius
The corpuscles of Stannius are special endocrine organs in the kidney in fish and are responsible for maintaining calcium balance. They are found only in bony fishes. They were discovered and described by a German anatomist Hermann Friedrich Stannius in 1839. Stannius considered them as functionally similar to adrenal glands in mammals. But they are later found to be anatomically different as they are derived from different tissues of the embryo. Structurally the corpuscles are a large number of spherical bodies separated from each other by loose connective tissues. Each body or lobule is in turn composed of several columnar cells, which contain secretory granules and are, thus, secretory in function. Each Secretory granule is spherical in shape and measures 0.5 to 1 μm in diameter. Their possible endocrine nature, i.e. producing hormone, was suspected from the complete anatomical description, and it was believed to be responsible for regulating calcium level in the blood. The hormone was identified as stanniocalcin.
==Structure==
The corpuscles of Stannius are small bodies embedded inside the kidney. They are spherical in shape and whitish in colour. In primitive bony fishes, such as the bowfin and garpike, they are extremely small and are distributed throughout the kidney. In some species (such as ''Oncostymchus Tshawytstha'' and ''O. Kisutch'') there are 5-6 corpuscles. The number of vary from 4-10 in ''Salnio solar'', and 6-8 in the brown trout (''Salmo trutta''). But in higher bony fishes, they are larger, occurring in a pair, and lies toward the posterior end of the kidney. The exact location differs from species to species, and is an anatomical diagnosis in taxonomy. Each pair measures about 0.5 to 2 mm in diameter. Each is enclosed in a fibrous capsule (and is called a lobe or lobule), which is surrounded by a layer of connective tissue. Inside the corpuscles are stacks of secretory cells which are arranged in strands.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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