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Various elongated or spindle-shaped structures in body parts or organs of plants and animals are referred to as rhachis (from ancient Greek ῥάχις rhachis ' backbone ', 'backbone-like structure').

In botany , Rhachis is the name

  • for the central main axis of simple pinnate leaves , the leaf spindle (rachis 1st order, for spindles of the pinnate on multi-pinnate leaves it is the rachis 2nd to nth order)
  • or for the main axis of an inflorescence .

In zoology , Rhachis u. a. the designation

  • for the shaft of bird feathers . Next to it is rachis the technical term
  • for the middle part of the trilobite's dorsal carapace separated by two longitudinal furrows ,
  • for the front end of the gladius, called the skeletal element of some squids , which is extended to form a free stalk ,
  • for the middle tooth in the narrow-tongued type of radula called rasping tongue of molluscs , e.g. B. Kraken ,
  • or for the nucleated cytoplasmic cord, which is particularly pronounced in the gonads of roundworms , which originates in the testes from spermatogonia and in the ovary from oogonia and which lie against the spermatocytes or oocytes.

In medicine , the formation of a gap in the spine in spina bifida is also known as rachischisis ; This expression uses the Greek words with their original meaning ( ancient Greek σχίζειν s'chizein 'column).

Individual evidence

  1. ^ Liddell-Scott-Jones: A Greek-English Lexicon . 9th edition, Clarendon Press, Oxford 1940, ῥάχις
  2. see entry Rhachis in the Lexicon Biologie on Spektrum.de, accessed on September 15, 2018.