Sternum: Difference between revisions

| Latin = Sternumsternum

The '''sternum''' ({{plural form}}: '''sternums''' or '''sterna''') or '''breastbone''' is a long [[flat bone]] located in the central part of the [[chest]]. many main [[Organ (biology)|organs]] are located around it. It connects to the [[rib]]s via [[cartilage]] and forms the front of the [[rib cage]], thus helping to protect the [[heart]], [[human lung|lungs]], and major [[blood vessel]]s from injury. Shaped roughly like a [[necktie]], it is one of the largest and longest flat bones of the body. Its three regions are the manubrium, the body, and the [[xiphoid process]].<ref name=KS>{{cite book |author=Saladin, Kenneth S. |year=2010 |title=Anatomy and Physiology: The Unity of Form and Function, Fifth Edition |url=https://archive.org/details/anatomyphysiolog00sala_868 |url-access=limited |publisher=McGraw-Hill |location=New York, NY |page= [https://archive.org/details/anatomyphysiolog00sala_868/page/n1218 266] |isbn= 978-0-07-352569-3}}</ref> The word ''sternum'' originates from Ancient Greek στέρνον (''stérnon'') 'chest'.

[[File:Xiphoid_process_-_close-up_-_animation.gif|220x124px|thumb|right|alt=Xiphoid process|3D illustration of the Xiphoidxiphoid process.]]

The sternum develops from two cartilaginous bars one on the left and one on the right, connected with the cartilages of the ribs on each side.<ref name="Openstax Anatomy & Physiology attribution">{{CC-notice|cc=by4|url=https://openstax.org/books/anatomy-and-physiology/pages/7-5-embryonic-development-of-the-axial-skeleton}} {{cite book|last1=Betts|first1=J Gordon|last2=Desaix|first2=Peter|last3=Johnson|first3=Eddie|last4=Johnson|first4=Jody E|last5=Korol|first5=Oksana|last6=Kruse|first6=Dean|last7=Poe|first7=Brandon|last8=Wise|first8=James|last9=Womble|first9=Mark D|last10=Young|first10=Kelly A|title=Anatomy & Physiology|location=Houston|publisher=OpenStax CNX|isbn=978-1-947172-04-3|date=May 14, 2023|at=7.5 Embryonic development of the axial skeleton}}</ref> These two bars fuse together along the middle to form the cartilaginous sternum which is ossified from six centers: one for the manubrium, four for the body, and one for the [[xiphoid process]].

In 2.5–13.5% of the population, a foramen known as [[sternal foramen]] may be presented at the lower third of the sternal body.<ref>{{Cite journal |last1=Choi |first1=Paul J |last2=Iwanaga |first2=Joe |last3=Tubbs |first3=R. Shane |title=A Comprehensive Review of the Sternal Foramina and its Clinical Significance |journal=Cureus |year=2017 |volume=9 |issue=12 |pages=e1929 |doi=10.7759/cureus.1929 |doi-access=free |issn=2168-8184 |pmc=5805319 |pmid=29456905}}</ref> In extremely rare cases, multiple foramina may be observed. Fusion of the manubriosternal joint also occurs in around 5% of the population.<ref>{{Cite journal |last1=Sebes |first1=Ji |last2=Salazar |first2=Je |date=1983-01-01 |title=The manubriosternal joint in rheumatoid disease |url=https://www.ajronline.org/doi/10.2214/ajr.140.1.117 |journal=American Journal of Roentgenology |volume=140 |issue=1 |pages=117–121 |doi=10.2214/ajr.140.1.117 |pmid=6600299 |issn=0361-803X}}</ref> Small ossicles known as [[episternal ossicles]] may also be present posterior to the superior end of the manubrium.<ref>{{Cite journal |last1=Stark |first1=P. |last2=Watkins |first2=G. E. |last3=Hildebrandt-Stark |first3=H. E. |last4=Dunbar |first4=R. D. |date=1987 |title=Episternal ossicles |url=https://pubmed.ncbi.nlm.nih.gov/3628759/ |journal=Radiology |volume=165 |issue=1 |pages=143–144 |doi=10.1148/radiology.165.1.3628759 |issn=0033-8419 |pmid=3628759}}</ref> Another variant called suprasternal tubercle is formed when the episternal ossicles fuse with the manubrium.<ref>{{Cite journal |last1=Duraikannu |first1=Chary |last2=Noronha |first2=Olma V |last3=Sundarrajan |first3=Pushparajan |date=2016 |title=MDCT evaluation of sternal variations: Pictorial essay |journal=The Indian Journal of Radiology & Imaging |volume=26 |issue=2 |pages=185–194 |doi=10.4103/0971-3026.184407 |issn=0971-3026 |pmc=4931775 |pmid=27413263 |doi-access=free }}</ref> {{Clear}}

A manubriosternal dislocation is rare and usually caused by severe trauma. It may also result from minor trauma where there is a precondition of arthritis.<ref>{{Cite journal |last1=El Ibrahimi |first1=Abdelhalim |last2=Sbai |first2=Hicham |last3=Kanjaa |first3=Nabil |last4=Shimi |first4=Mohammed |last5=Lakranbi |first5=Marouane |last6=Daoudi |first6=Abdelkrim |last7=Elmrini |first7=Abdelmajid |last8=Smahi |first8=Mohammed |title=Traumatic manubriosternal dislocation: A new method of stabilization postreduction |journal=Journal of Emergencies, Trauma, and Shock |date=2011 |volume=4 |issue=2 |pages=317–319 |doi=10.4103/0974-2700.82237 |pmid=21769224 |pmc=3132377 |doi-access=free }}</ref>

The breastbone is sometimes cut open (a [[median sternotomy]]) to gain access to the thoracic contents when performing [[cardiothoracic surgery]]. Surgical fixation of sternotomy is achieved through the use of either wire cerclage or a plate and screw technique. The incidence of sternotomy complications falls within the narrow range of 0.5% to 5%. Nevertheless, these complications can have severe consequences, including increased mortality rates, the need for reoperation, and a mortality rate as high as 40%. Such complications often entail issues like dehiscence and sternal non-union, primarily stemming from lateral forces exerted during post-operative activities such as coughing and sneezing.

A bifid sternum is an extremely rare congenital abnormality caused by the fusion failure of the sternum.<ref name=":0">{{Cite journal|last1=Das|first1=Sibes Kumar|last2=Jana|first2=Pulak Kumar|last3=Bairagya|first3=Tapan Das|last4=Ghoshal|first4=Bhaswati|date=2012-01-01|title=Bifid sternum|journal=Lung India |volume=29|issue=1|pages=73–75|doi=10.4103/0970-2113.92370|issn=0970-2113|pmc=3276042|pmid=22345921 |doi-access=free }}</ref> This condition results in [[sternal cleft]] which can be observed at birth without any symptom.<ref name=":0" />

The sternum, in vertebrate anatomy, is a [[flat bone]] that lies in the middle front part of the [[rib cage]]. It is [[endochondral]] in origin.<ref name="kardong">{{cite book|last=Kardong|first=Kenneth V.|title=Vertebrates: comparative anatomy, function, evolution|year=1995|publisher=McGraw-Hill|isbn=0-697-21991-7|pages=55, 57}}</ref> It probably first evolved in early [[tetrapod]]s as an extension of the [[pectoral girdle]]; it is not found in [[fish]]. In [[amphibian]]s and [[reptile]]s, it is typically a shield-shaped structure, often composed entirely of [[cartilage]]. It is absent in both [[turtle]]s and [[snake]]s. In [[bird]]s, it is a relatively large bone and typically bears an enormous projecting [[keel (bird anatomy)|keel]] to which the flight muscles are attached.<ref name=VB>{{cite book |author=Romer, Alfred Sherwood|author2=Parsons, Thomas S.|year=1977 |title=The Vertebrate Body |publisher=Holt-Saunders International |location= Philadelphia, PA|page= 188|isbn= 0-03-910284-X}}</ref> Only in [[mammal]]s does the sternum take on the elongated, segmented form seen in humans.

In [[arachnid]]sarthropods, thea sternum is the ventral[[Anatomical (lower) portionterms of thelocation#Dorsal [[cephalothoraxand ventral|ventral]]. It consistspart of a singlesegment [[sclerite]] situated between theof [[arthropod coxa|coxathorax]], opposite theor [[carapaceabdomen]].