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theca

Line breaks: theca
Pronunciation: /ˈθiːkə
 
/

Definition of theca in English:

noun (plural thecae /-siː/)

1A receptacle, sheath, or cell enclosing an organ, part, or structure, in particular:
1.1 Anatomy The loose sheath enclosing the spinal cord.
Example sentences
  • The vertebral foramen houses the theca and spinal nerves.
  • The theca contains the cauda equina or nerve roots.
1.2 Zoology A cup-like or tubular structure containing a coral polyp.
Example sentences
  • It is notable that both specimens also display asymmetry in the overall structure of their thecae.
  • In the ‘echinoderm’ reconstruction, the theca lies with the convex side upwards and the appendage is interpreted as an anterior feeding arm.
  • The theca around the column is smooth, sometimes with weak longitudinal muscles.
1.3 Botany Either of the lobes of an anther, each containing two pollen sacs.
Example sentences
  • As pollinators removed pollen from the thecae, their walls collapsed and the anthers curled down gradually.
  • The percentage of thecae that dehisced longitudinally varied greatly among rice varieties.
  • Stamens are didynamous, but the yellow anthers occur close together, with their divergent thecae spreading to the outside.
1.4 (also theca folliculi /fəˈlɪkjʊlʌɪ/) Anatomy The outer layer of cells of a Graafian follicle.
Example sentences
  • The term ‘follicle complex’ has been proposed to include the follicle, basement membrane, and the theca, including its blood vessels.
  • The follicle is surrounded by a theca, derived from the stromal compartment of the ovary and is always separated from this compartment, throughout development and final oocyte maturation, by a basement membrane.

Origin

early 17th century: via Latin from Greek thēkē 'case'.

Derivatives

thecate

1
adjective
Example sentences
  • It is a widespread Paleozoic marine taxon that has been interpreted most recently as a tubiculous annelid or other ‘worm’ or as a thecate hydrozoan or scyphozoan cnidarian.
  • The results suggest that intensive regenerative nutrient cycling or external nutrient inputs are a necessary precondition for an efficient trophic transfer of the energy stored in blooms of thecate dinoflagellates.
  • This is a small thecate dinoflagellate, almost pear-shaped, with a conical anterior end and a round posterior.

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