Tag: Sheath
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Thecal Sac or Dural Sac
The thecal sac or dural sac is the membranous sheath (theca) or tube of dura mater that surrounds the spinal cord and the cauda equina. The thecal sac contains the cerebrospinal fluid which provides nutrients and buoyancy to the spinal cord.[1] From the skull the tube adheres to bone at the foramen magnum and extends down to the second sacral vertebra where it tapers to cover over the filum terminale. Along most of the spinal canal it is separated…
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Theca
In biology, a theca (pl.: thecae) is a sheath or a covering. Botany The typical anther is bilocular, i.e. it consists of two thecae. Each theca contains two microsporangia, also known as pollen sacs. The microsporangia produce the microspores, which for seed plants are known as pollen grains. If the pollen sacs are not adjacent, or if they open separately, then no thecae are…
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Xylotheque
A xylotheque or xylothek (from the Greek xylon for “wood” and theque meaning “repository”) is special form of herbarium that consists of a collection of authenticated wood specimens.[1] It is also known as a xylarium (from the Greek xylon for “wood” and Latin arium meaning “separate place”). Traditionally, xylotheque specimens were in the form of book-shaped volumes, each made of a particular kind of wood and holding samples of the different parts…