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LatinSternum_header_cell_0_3_0 SternumSternum_cell_0_3_1
MeSHSternum_header_cell_0_4_0 Sternum_cell_0_4_1
TA98Sternum_header_cell_0_5_0 Sternum_cell_0_5_1
TA2Sternum_header_cell_0_6_0 Sternum_cell_0_6_1
FMASternum_header_cell_0_7_0 Sternum_cell_0_7_1

The sternum or breastbone is a long flat bone located in the central part of the chest. Sternum_sentence_0

It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sternum_sentence_1

Shaped roughly like a necktie, it is one of the largest and longest flat bones of the body. Sternum_sentence_2

Its three regions are the manubrium, the body, and the xiphoid process. Sternum_sentence_3

The word "sternum" originates from the Ancient Greek στέρνον (stérnon), meaning "chest". Sternum_sentence_4

Structure Sternum_section_0

The sternum is a long, flat bone, forming the middle portion of the front of the chest. Sternum_sentence_5

The top of the sternum supports the clavicles (collarbones) and its edges join with the costal cartilages of the first two pairs of ribs. Sternum_sentence_6

The inner surface of the sternum is also the attachment of the sternopericardial ligaments. Sternum_sentence_7

Its top is also connected to the sternocleidomastoid muscle. Sternum_sentence_8

The sternum consists of three main parts, listed from the top: Sternum_sentence_9


  • ManubriumSternum_item_0_0
  • Body (gladiolus)Sternum_item_0_1
  • Xiphoid processSternum_item_0_2

In its natural position, the sternum is angled obliquely, downward and forward. Sternum_sentence_10

It is slightly convex in front and concave behind; broad above, shaped like a "T", becoming narrowed at the point where the manubrium joins the body, after which it again widens a little to below the middle of the body, and then narrows to its lower extremity. Sternum_sentence_11

In adults the sternum is on average about 17 cm, longer in the male than in the female. Sternum_sentence_12

Manubrium Sternum_section_1

The manubrium (Latin: handle) is the broad upper part of the sternum. Sternum_sentence_13

It has a quadrangular shape, narrowing from the top, which gives it four borders. Sternum_sentence_14

The suprasternal notch (jugular notch) is located in the middle at the upper broadest part of the manubrium. Sternum_sentence_15

This notch can be felt between the two clavicles. Sternum_sentence_16

On either side of this notch are the right and left clavicular notches. Sternum_sentence_17

The manubrium joins with the body of the sternum, the clavicles and the cartilages of the first pair of ribs. Sternum_sentence_18

The inferior border, oval and rough, is covered with a thin layer of cartilage for articulation with the body. Sternum_sentence_19

The lateral borders are each marked above by a depression for the first costal cartilage, and below by a small facet, which, with a similar facet on the upper angle of the body, forms a notch for the reception of the costal cartilage of the second rib. Sternum_sentence_20

Between the depression for the first costal cartilage and the demi-facet for the second is a narrow, curved edge, which slopes from above downward towards the middle. Sternum_sentence_21

Also, the superior sternopericardial ligament attaches the pericardium to the posterior side of the manubrium. Sternum_sentence_22

Body Sternum_section_2

The body, or gladiolus, is the longest part. Sternum_sentence_23

It is flat and considered to have only a front and back surface. Sternum_sentence_24

It is flat on the front, directed upward and forward, and marked by three transverse ridges which cross the bone opposite the third, fourth, and fifth articular depressions. Sternum_sentence_25

The pectoralis major attaches to it on either side. Sternum_sentence_26

At the junction of the third and fourth parts of the body is occasionally seen an orifice, the sternal foramen, of varying size and form. Sternum_sentence_27

The posterior surface, slightly concave, is also marked by three transverse lines, less distinct, however, than those in front; from its lower part, on either side, the transversus thoracis takes origin. Sternum_sentence_28

The sternal angle is located at the point where the body joins the manubrium. Sternum_sentence_29

The sternal angle can be felt at the point where the sternum projects farthest forward. Sternum_sentence_30

However, in some people the sternal angle is concave or rounded. Sternum_sentence_31

During physical examinations, the sternal angle is a useful landmark because the second rib attaches here. Sternum_sentence_32

Each outer border, at its superior angle, has a small facet, which with a similar facet on the manubrium, forms a cavity for the cartilage of the second rib; below this are four angular depressions which receive the cartilages of the third, fourth, fifth, and sixth ribs. Sternum_sentence_33

The inferior angle has a small facet, which, with a corresponding one on the xiphoid process, forms a notch for the cartilage of the seventh rib. Sternum_sentence_34

These articular depressions are separated by a series of curved interarticular intervals, which diminish in length from above downward, and correspond to the intercostal spaces. Sternum_sentence_35

Most of the cartilages belonging to the true ribs, articulate with the sternum at the lines of junction of its primitive component segments. Sternum_sentence_36

This is well seen in some other vertebrates, where the parts of the bone remain separated for longer. Sternum_sentence_37

The upper border is oval and articulates with the manubrium, at the sternal angle. Sternum_sentence_38

The lower border is narrow, and articulates with the xiphoid process. Sternum_sentence_39

Xiphoid process Sternum_section_3

Main article: Xiphoid process Sternum_sentence_40

Located at the inferior end of the sternum is the pointed xiphoid process. Sternum_sentence_41

Improperly performed chest compressions during cardiopulmonary resuscitation can cause the xiphoid process to snap off, driving it into the liver which can cause a fatal hemorrhage. Sternum_sentence_42

The sternum is composed of highly vascular tissue, covered by a thin layer of compact bone which is thickest in the manubrium between the articular facets for the clavicles. Sternum_sentence_43

The inferior sternopericardial ligament attaches the pericardium to the posterior xiphoid process. Sternum_sentence_44

Joints Sternum_section_4

The cartilages of the top five ribs join with the sternum at the sternocostal joints. Sternum_sentence_45

The right and left clavicular notches articulate with the right and left clavicles, respectively. Sternum_sentence_46

The costal cartilage of the second rib articulates with the sternum at the sternal angle making it easy to locate. Sternum_sentence_47

The transversus thoracis muscle is innervated by one of the intercostal nerves and superiorly attaches at the posterior surface of the lower sternum. Sternum_sentence_48

Its inferior attachment is the internal surface of costal cartilages two through six and works to depress the ribs. Sternum_sentence_49

Development Sternum_section_5

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. Sternum_sentence_50

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. Sternum_sentence_51

The ossification centers appear in the intervals between the articular depressions for the costal cartilages, in the following order: in the manubrium and first piece of the body, during the sixth month of fetal life; in the second and third pieces of the body, during the seventh month of fetal life; in its fourth piece, during the first year after birth; and in the xiphoid process, between the fifth and eighteenth years. Sternum_sentence_52

The centers make their appearance at the upper parts of the segments, and proceed gradually downward. Sternum_sentence_53

To these may be added the occasional existence of two small episternal centers, which make their appearance one on either side of the jugular notch; they are probably vestiges of the episternal bone of the monotremata and lizards. Sternum_sentence_54

Occasionally some of the segments are formed from more than one center, the number and position of which vary [Fig. Sternum_sentence_55

6]. Sternum_sentence_56

Thus, the first piece may have two, three, or even six centers. Sternum_sentence_57

When two are present, they are generally situated one above the other, the upper being the larger; the second piece has seldom more than one; the third, fourth, and fifth pieces are often formed from two centers placed laterally, the irregular union of which explains the rare occurrence of the sternal foramen [Fig. Sternum_sentence_58

7], or of the vertical fissure which occasionally intersects this part of the bone constituting the malformation known as fissura sterni; these conditions are further explained by the manner in which the cartilaginous sternum is formed. Sternum_sentence_59

More rarely still the upper end of the sternum may be divided by a fissure. Sternum_sentence_60

Union of the various centers of the body begins about puberty, and proceeds from below upward [Fig. Sternum_sentence_61

5]; by the age of twenty-five they are all united. Sternum_sentence_62

The xiphoid process may become joined to the body before the age of thirty, but this occurs more frequently after forty; on the other hand, it sometimes remains ununited in old age. Sternum_sentence_63

In advanced life the manubrium is occasionally joined to the body by bone. Sternum_sentence_64

When this takes place, however, the bony tissue is generally only superficial, the central portion of the intervening cartilage remaining unossified. Sternum_sentence_65

In early life, the sternum's body is divided into four segments, not three, called sternebrae (singular: sternebra). Sternum_sentence_66

Clinical significance Sternum_section_6

Bone marrow biopsy Sternum_section_7

Because the sternum contains bone marrow, it is sometimes used as a site for bone marrow biopsy. Sternum_sentence_67

In particular, patients with a high BMI (obese or grossly overweight) may present with excess tissue that makes access to traditional marrow biopsy sites such as the pelvis difficult. Sternum_sentence_68

Sternal opening Sternum_section_8

A somewhat rare congenital disorder of the sternum sometimes referred to as an anatomical variation is a sternal foramen, a single round hole in the sternum that is present from birth and usually is off-centered to the right or left, commonly forming in the 2nd, 3rd, and 4th segments of the breastbone body. Sternum_sentence_69

Congenital sternal foramina can often be mistaken for bullet holes. Sternum_sentence_70

They are usually without symptoms but can be problematic if acupuncture in the area is intended. Sternum_sentence_71

Fractures Sternum_section_9

Main article: Sternal fracture Sternum_sentence_72

Fractures of the sternum are rather uncommon. Sternum_sentence_73

They may result from trauma, such as when a driver's chest is forced into the steering column of a car in a car accident. Sternum_sentence_74

A fracture of the sternum is usually a fracture. Sternum_sentence_75

The most common site of sternal fractures is at the sternal angle. Sternum_sentence_76

Some studies reveal that repeated punches or continual beatings, sometimes called "breastbone punches", to the sternum area have also caused fractured sternums. Sternum_sentence_77

Those are known to have occurred in contact sports such as hockey and football. Sternum_sentence_78

Sternal fractures are frequently associated with underlying injuries such as pulmonary contusions, or bruised lung tissue. Sternum_sentence_79

Dislocation Sternum_section_10

A manubriosternal dislocation is rare and usually caused by severe trauma. Sternum_sentence_80

It may also result from minor trauma where there is a precondition of arthritis. Sternum_sentence_81

Sternotomy Sternum_section_11

The breastbone is sometimes cut open (a median sternotomy) to gain access to the thoracic contents when performing cardiothoracic surgery. Sternum_sentence_82

Resection Sternum_section_12

The sternum can be totally removed (resected) as part of a radical surgery, usually to surgically treat a malignancy, either with or without a mediastinal lymphadenectomy (Current Procedural Terminology codes # 21632 and # 21630, respectively). Sternum_sentence_83

Bifid sternum or sternal cleft Sternum_section_13

A bifid sternum is an extremely rare congenital abnormality caused by the fusion failure of the sternum. Sternum_sentence_84

This condition results in sternal cleft which can be observed at birth without any symptom. Sternum_sentence_85

Other animals Sternum_section_14

The sternum, in vertebrate anatomy, is a flat bone that lies in the middle front part of the rib cage. Sternum_sentence_86

It is endochondral in origin. Sternum_sentence_87

It probably first evolved in early tetrapods as an extension of the pectoral girdle; it is not found in fish. Sternum_sentence_88

In amphibians and reptiles it is typically a shield-shaped structure, often composed entirely of cartilage. Sternum_sentence_89

It is absent in both turtles and snakes. Sternum_sentence_90

In birds it is a relatively large bone and typically bears an enormous projecting keel to which the flight muscles are attached. Sternum_sentence_91

Only in mammals does the sternum take on the elongated, segmented form seen in humans. Sternum_sentence_92

Arthropods Sternum_section_15

Main article: Sternum (arthropod anatomy) Sternum_sentence_93

In arachnids, the sternum is the ventral (lower) portion of the cephalothorax. Sternum_sentence_94

It consists of a single sclerite situated between the coxa, opposite the carapace. Sternum_sentence_95

Etymology Sternum_section_16

English sternum is a translation of Ancient Greek στέρνον, sternon. Sternum_sentence_96

The Greek writer Homer used the term στέρνον to refer to the male chest, and the term στῆθος, stithos to refer to the chest of both sexes. Sternum_sentence_97

The Greek physician Hippocrates used στέρνον to refer to the chest, and στῆθος to the breastbone. Sternum_sentence_98

The Greek physician Galen was the first to use στέρνον in the present meaning of breastbone. Sternum_sentence_99

The sternum as the solid bony part of the chest can be related to Ancient Greek στερεός/στερρός, (stereόs/sterrόs), meaning firm or solid. Sternum_sentence_100

The English term breastbone is actually more like the Latin os pectoris, derived from classical Latin os, bone and pectus, chest or breast. Sternum_sentence_101

Confusingly, pectus is also used in classical Latin as breastbone. Sternum_sentence_102

Additional Images Sternum_section_17


  • Sternum_item_1_3
  • Sternum_item_1_4
  • Sternum_item_1_5
  • Sternum_item_1_6
  • Sternum_item_1_7
  • Sternum_item_1_8

See also Sternum_section_18

This article uses anatomical terminology. Sternum_sentence_103


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