Sternum

Sternum
Name	Sternum
Latin	sternum
System	Thoracic cavity
Location	Human body
Components	Manubrium; Body; Xiphoid process
Precursor	Sclerotome derivatives
Artery	Internal thoracic artery; Pericardiacophrenic artery
Nerve	Intercostal nerves

Sternum The sternum is a flat, elongated bone forming the anterior midline of the Thoracic cavity that articulates with Clavicle, Rib pairs, and provides attachment for major Muscles of respiration and posture. It has three principal regions: the manubrium, the body (gladiolus), and the xiphoid process, each with distinct embryologic origins and ossification patterns. Clinically it is a landmark for procedures such as median sternotomy and chest compressions, and a site of pathology in trauma, infection, and neoplasm.

Anatomy

The manubrium articulates superiorly with the medial ends of the Clavicle at the sternoclavicular joints and with the first costal cartilages and the superior aspect of the body at the manubriosternal joint, a location historically referenced in descriptions by anatomists like Andreas Vesalius and Henry Gray. The body extends inferiorly, providing costal notches for ribs two through seven; classical anatomical atlases by Jean-Martin Charcot and surgical texts by William Halsted depict these relations. The xiphoid process varies widely and may be ossified or cartilaginous, as discussed in comparative descriptions by Sir William Turner. The posterior surface is adjacent to the Mediastinum and vital structures such as the Heart, Pericardium, and portions of the Lung and great vessels, noted in operative reports from Cleveland Clinic and historical dissections at Guy's Hospital.

Vascular supply derives from branches of the Internal thoracic artery including superior and inferior epigastric distributions; venous drainage parallels arterial routes to the Internal thoracic vein and systemic circuits described in classic works by Paul Broca. Innervation arises from anterior branches of the upper Intercostal nerves, with nociceptive pathways characterized in neuroanatomical studies at institutions such as Johns Hopkins Hospital.

Development

Embryologically, the sternum originates from paired sternal bars formed in the ventral body wall from mesenchyme derived from Sclerotome and somatic lateral plate mesoderm, a process detailed in classic embryology by Ernst Haeckel. These bars fuse in the midline cranio-caudally; ossification centers appear in the body during fetal life and postnatal years, with the xiphoid sometimes ossifying only in adulthood, observations corroborated by developmental series at Karolinska Institutet and anatomical surveys at Smithsonian Institution. Variations in timing and the number of ossification centers contribute to anatomical diversity noted in forensic collections at Metropolitan Museum of Art and medico-legal reports from FBI casework. Endochondral and intramembranous ossification patterns are summarized in monographs by Wilhelm His and modern reviews from National Institutes of Health laboratories.

Function

Mechanically, the sternum serves as a keystone for the anterior thoracic cage, transmitting forces between the Clavicles and ribs during upper limb motion and respiration, a role emphasized in biomechanical analyses at Massachusetts Institute of Technology and Imperial College London. It provides attachment sites for muscles such as the Pectoralis major, Sternocleidomastoid (via manubrial portions), and portions of the Diaphragm and Transversus thoracis; these myological relationships were cataloged by Henry Gray and reanalyzed in functional studies at University of Oxford. The sternum contributes to protection of the Heart and great vessels during blunt trauma, an aspect evaluated in trauma registries at St Thomas' Hospital and epidemiological reviews by World Health Organization.

Clinical significance

Sternal fractures commonly result from blunt anterior chest trauma in vehicular collisions, with management guidelines developed by trauma centers such as R Adams Cowley Shock Trauma Center. Median sternotomy, pioneered by surgeons including Julian Lewis and refined at Mayo Clinic, provides access for cardiac procedures like Coronary artery bypass grafting and Valve replacement surgery; complications include sternal wound infection and mediastinitis noted in quality audits by Centers for Disease Control and Prevention. Pathologies include osteomyelitis seen in intravenous drug users documented by public health reports from Harvard Medical School, primary malignancies like chondrosarcoma described in oncologic series at Memorial Sloan Kettering Cancer Center, and sternal clefts reported as congenital anomalies in case series from Great Ormond Street Hospital. The xiphoid process can be a source of anterior chest pain or be mistaken for a palpable mass in physicals recorded in family medicine literature at Mayo Clinic.

Comparative anatomy

Across vertebrates, the sternum exhibits marked diversity: in birds like Gallus gallus domesticus a pronounced keel (carina) supports flight muscles, a feature analyzed in evolutionary studies at Smithsonian National Museum of Natural History and described by Thomas Henry Huxley. Reptilian and amphibian taxa show variable ossification or cartilaginous sterna, as cataloged in comparative atlases housed at Natural History Museum, London and research from University of California, Berkeley. Mammalian sterna range from fused plates in ungulates described by veterinary anatomists at Royal Veterinary College to reduced elements in cetaceans documented by investigators at Scripps Institution of Oceanography. Paleontological records, including specimens at American Museum of Natural History, trace modifications of the sternum in the transition to powered flight in theropod relatives of Archaeopteryx.

Imaging and surgical approaches

Radiographic evaluation employs chest radiography, computed tomography, and magnetic resonance imaging protocols standardized by radiology departments at Mayo Clinic and Royal College of Radiologists for assessment of fracture, infection, and tumor. Postoperative imaging after sternotomy is guided by institutional protocols from Johns Hopkins Hospital and Cleveland Clinic to monitor sternal wires, mediastinal drains, and evidence of dehiscence. Surgical approaches include median sternotomy, parasternal and subxiphoid incisions as taught in operative manuals from American College of Surgeons and practiced in cardiothoracic units at Brigham and Women's Hospital. Minimally invasive and robotic-assisted techniques developed at centers like Stanford Health Care reduce sternal disruption for select procedures, while sternal plating and rigid fixation systems are utilized per device evaluations by Food and Drug Administration reports.

Category:Human bones