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).