【医】 半月瓣

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

{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.


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].

{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}.