Sternum definitions and example sentences on Wordnik

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Definitions (9)

American Heritage Dictionary (1)

noun A long flat bone in most vertebrates that is situated along the ventral midline of the thorax and articulates with the ribs. The manubrium of the sternum articulates with the clavicles in humans and certain other vertebrates. Also called breastbone.

Century Dictionary (6)

The breast-bone of man and many other vertebrates; a bone or longitudinal series of bones in the middle line of the ventral aspect of the body, chiefly in its thoracic section, completing the thoracic wall by articulation with more or fewer ribs, or elements of the scapular arch, or both: theoretically, in Owen's system, the hemal spines of a series Of vertebræ. In man and most mammals the sternum consists of an anterior piece, the “handle,” manubrium, or presternum; of several (in man four) segments or sternebers constituting the body of the sternum, gladiolus, or mesosternum; and of a terminal piece, the xiphoid or ensiform cartilage, or xiphisternum. It articulates in man with the clavicles and with seven costal cartilages. The sternebers of a mammalian sternum may remain perfectly distinct, or be ankylosed in one. (See cut under mesosternum.) In cetaceans and sirenians the sternum is much reduced, and may be a single bone or quite rudimentary. In the monotrematous mammals a small median bone called proösteon is developed in front of the præsternum. The parts called episternum, omosternum, interclavicle, in the mammals just mentioned, or in various reptiles, or in batrachians, belong rather to the shoulder-girdle. There is no sternum in some reptiles, as serpents. See cuts under Catarrhina, Elephantinæ, interclavicle, omosternum, and skeleton. In birds the sternum is a large single bone without trace of its original composition of several parts, highly specialized in form and function, in relation to the muscular apparatus of the wings, articulating with several ribs, with the coracoids, and sometimes ankylosed with the clavicle; it appears under two principal modifications, known as the carinate and ratite. (See these words.) The carinate sternum normally develops from five ossific centers, having consequently as many separate pieces in early life. The single median ossification, which includes the keel, is the lophosteon; the anteriorlateral pieces, a pair, are the pleurostea, which become the costal or costiferous processes; the posterior pair are the metostea. In some birds are additional pieces, a pair of coracostea and a urosteon. The ratite sternum has no median ossification, or lophosteon. The passerine sternum normally develops a prominent forked manubrium. In a few birds, as cranes and swans, the sternum is hollowed out to receive convolutions of the windpipe. See cuts under carinate, Dinornis, and epipleura. In Chelonia, the plastron of a turtle, consisting of several bones, normally nine, one median, and four lateral in pairs. These bones have no homology with the sternum of other vertebrates. See cuts under carapace, plastron, and Chelonia.
In arthropods, as insects and crustaceans, a median sternal or ventral sclerite of any somite of the cephalothorax, thorax, or abdomen; a sternite: the opposite of a tergite or notum. In such cases, sternum and sternite are used interchangeably, sternum being seldom used of the series of sternites as a whole. (See cut under cephalothorax.) In insects the three thoracic sterna are specified as prosternum, mesosternum, and metasternum. In Diptera, sternum, generally means the mesosternum, as the other thoracic rings do not show a sternal piece. In Coleoptera, sternum is sometimes extended to include the episterna and epimera, or whole lower surface of a thoracic segment. See episternum, 3.
Antennary sternum. See antennary.

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Something lodged in her chest above her sternum, an ice cube, her panic building, crushing her chest. — EQMM, June 2005
He rested the heel of his left hand on the sternum, the heel of his right hand on top of the left, and interlaced his fingers. — Memory of Fire by Holly Lisle
Her heart was slamming against her sternum, and her head felt as though it had been split apart, the pain almost blinding as she stumbled forward. — Garwood, Julie - Mercy
Mouse's front paws hit Cassius squarely on the sternum, and a bloodcurdling snarl exploded from the huge dog's chest as they both went down. — Butcher, Jim - Dead Beat (v1.0) (html).html
Then they have a sternum which is located on the bottum of the cephalothorax, which is the flat structure that is surrounded by the leggs. — CreationWiki - Recent changes [en]

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sternum

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