Sigmoid valves

from The Collaborative International Dictionary of English v.0.48

Semilunar \Sem`i*lu"nar\, a.
   Shaped like a half moon.
   [1913 Webster]

   {Semilunar bone} (Anat.), a bone of the carpus; the lunar.
      See {Lunar}, n.

   {Semilunar valves}, or {Sigmoid valves} (Anat.), the valves
      at the beginning of the aorta and of the pulmonary artery
      which prevent the blood from flowing back into the
      ventricle.
      [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Sigmoid \Sig"moid\, Sigmoidal \Sig*moid"al\, a. [Gr. ???; ???
   sigma + e'i^dos form, likeness: cf. F. sigmo["i]de.]
   Curved in two directions, like the letter S, or the Greek
   [sigmat].
   [1913 Webster]

   {Sigmoid flexure} (Anat.), the last curve of the colon before
      it terminates in the rectum. See Illust. under
      {Digestive}.

   {Sigmoid valves}. (Anat.) See {Semilunar valves}, under
      {Semilunar}.
      [1913 Webster]

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