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What is under a womans right rib cage?

rib cage

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  • National Library of Medicine — The rib cage stabilizes the human thoracic spine: An in vitro study using stepwise reduction of rib cage structures
  • WebMD — Rib Cage: What to know

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Also known as: thoracic basket
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Last Updated: Mar 28, 2023 • Article History
Table of Contents

human rib cage

human rib cage
Related Topics: rib sternum thoracic vertebra costal cartilage torso . (Show more)

rib cage, in vertebrate anatomy, basketlike skeletal structure that forms the chest, or thorax, and is made up of the ribs and their corresponding attachments to the sternum (breastbone) and the vertebral column. The rib cage surrounds the lungs and the heart, serving as an important means of bony protection for these vital organs.In total, the rib cage consists of the 12 thoracic vertebrae and the 24 ribs, in addition to the sternum. With each succeeding rib, from the first, or uppermost, the curvature of the rib cage becomes more open. The rib cage is semirigid but expansile, able to increase in size. The small joints between the ribs and the vertebrae permit a gliding motion of the ribs on the vertebrae during breathing and other activities.

The first seven ribs in the rib cage are attached to the sternum by pliable cartilages called costal cartilages; these ribs are called true ribs. Of the remaining five ribs, which are called false, the first three have their costal cartilages connected to the cartilage above them. The last two, the floating ribs, have their cartilages ending in the muscle in the abdominal wall. The configuration of the lower five ribs gives freedom for the expansion of the lower part of the rib cage and for the movements of the diaphragm, which has an extensive origin from the rib cage and the vertebral column. The motion is limited by the ligamentous attachments between ribs and vertebrae.

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The Editors of Encyclopaedia Britannica This article was most recently revised and updated by Kara Rogers.

Right upper quadrant of the abdomen

Right upper quadrant (Quadrans superior dexter); Image: Paul Kim

Since the abdomen is tightly packed with several different organs and tissues, it is commonly described according to quadrants, regions and/or planes to help localize the anatomical positions of various structures. The right upper quadrant, or RUQ, refers to the upper right part of the abdomen, more specifically what lies deep to this area of the abdominal wall.

Healthcare professional are commonly required to examine the abdomen of a patient in order to establish a preliminary diagnosis in many clinical situations. Abdominal examination starts from the observation; skin colour, any bulge or distension, abdominal respiration, bruising, scars, herniae and any visible peristalsis are noted. This is followed by palpation, percussion and auscultation. In order to perform a comprehensive examination and to understand any abdominal pathology, it is essential to have proper knowledge of the relevant anatomy and the relationship of the internal structures to the surface markings on the exterior.

Key facts about the right upper quadrant of the abdomen

DefinitionRegion of the abdomen above and to the right of the transumbilical and median lines, respectively.
OrgansRight lobe of the liver, gallbladder
Pylorus of stomach, duodenum, head of pancreas
Superior part of ascending colon/right colic flexure/right half of transverse colon.
Right kidney/suprarenal gland


  1. Overview
  2. Right upper quadrant organs
  3. Hepatobiliary system
    1. Liver
    2. Gallbladder

    + Show all


    Because the anterior and lateral walls of the abdomen do not have any bony landmarks (like those we see around the neck and hips, for example), clinicians often make reference to imaginary lines drawn on the abdomen. For general clinical descriptions, a four-quadrant model is used which describes a right upper, right lower, left upper, and left lower quadrant.

    Anterior median line
    Linea mediana anterior
    Synonyms: none

    These quadrants are defined by one imaginary line drawn horizontally across the belly button and one drawn vertically down the midline of the body. More specifically, the transumbilical plane passes through the umbilicus and the intervertebral disc between the third and fourth lumbar vertebrae and the median plane passes superoinferiorly through the midline of the body, dividing it into right and left halves.

    The right upper quadrant will be discussed in detail in the following article. It extends from the midline of the body to the right side of the abdomen, and from the umbilical plane to the right ribcage superiorly.

    Revise the muscles of the abdominal wall with the following quiz.

    Right upper quadrant organs

    The various viscera, or organs, found in the right upper quadrant are:

    • Right lobe of the liver
    • Gallbladder
    • Pylorus of stomach
    • Duodenum
    • Head of pancreas
    • Right kidney with right suprarenal gland
    • Right colic flexure
    • Superior part of ascending colon
    • Right half of transverse colon.

    The most clinically relevant organs that manifest themselves as symptomatic in a patient reporting right upper abdominal pain are the liver, gallbladder, duodenum and head of the pancreas. The liver and gallbladder, along with the biliary tree, occupy the majority of the region and will be the main focus of this article. We will also discuss common clinical conditions that lead to patients’ complaints of abdominal pain in the right upper quadrant, often abbreviated to RUQ pain.

    Hepatobiliary system

    Pain in the right upper quadrant (RUQ) can be caused by a wide variety of medical conditions. The hepatobiliary system is the term used to refer to how the liver and gallbladder organs work together to make and transport bile. It is often the culprit of RUQ pain.


    The liver occupies the upper part of the abdominal cavity just beneath the diaphragm. Its convex superior surface is molded to the under surface of the domes of the diaphragm muscle, and it extends from the right fifth intercostal space down to the right costal margin. Grossly, the liver is divided into right, left, caudate, and quadrate lobes due to peritoneal and ligamentous attachment. The larger right and smaller left lobes are demarcated by the falciform ligament. The quadrate lobe exists between the gallbladder and round ligament. In turn, inferior vena cava, ligamentum venosum, and porta hepatis make the boundaries of caudate lobe.

    The porta hepatis, or hilus of the liver, is a deep fissure in the inferior surface of the organ. It contains the hepatic ducts and branches of the portal vein and hepatic artery. The circulatory system of the liver is unlike that seen in any other organ. Roughly 75% of the blood entering the liver is venous blood from the portal vein, while the remaining 25% of the blood supply to the liver is arterial blood from the hepatic artery. Within the liver, the portal vein divides into right and left branches and then further into smaller channels (clinical fun fact: these smaller channels help define the liver segments used in surgical resections). On the other hand the hepatic arterial tree, that is often a branch of the celiac trunk, terminates in two plexuses: peribiliary plexus, which supports the functions of the biliary epithelium of the bile ducts and the periportal plexus that supplies the portal canals and drains into periportal sinusoids.


    The sternum or breastbone is a long flat bone located in the central part of the chest. 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. 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. [1] The word sternum originates from Ancient Greek στέρνον (stérnon) ‘chest’.

    Structure [ edit ]

    The sternum is a narrow, flat bone, forming the middle portion of the front of the chest. The top of the sternum supports the clavicles (collarbones) and its edges join with the costal cartilages of the first two pairs of ribs. The inner surface of the sternum is also the attachment of the sternopericardial ligaments. [2] Its top is also connected to the sternocleidomastoid muscle. The sternum consists of three main parts, listed from the top:

    • Manubrium
    • Body (gladiolus)
    • Xiphoid process

    In its natural position, the sternum is angled obliquely, downward and forward. 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. In adults the sternum is on average about 1.7 cm longer in the male than in the female. [ citation needed ]

    Manubrium [ edit ]

    Shape of manubrium

    The manubrium (Latin for ‘handle’) is the broad upper part of the sternum. It has a quadrangular shape, narrowing from the top, which gives it four borders. The suprasternal notch (jugular notch) is located in the middle at the upper broadest part of the manubrium. This notch can be felt between the two clavicles. On either side of this notch are the right and left clavicular notches. [1]

    The manubrium joins with the body of the sternum, the clavicles and the cartilages of the first pair of ribs. The inferior border, oval and rough, is covered with a thin layer of cartilage for articulation with the body. 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. 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. Also, the superior sternopericardial ligament attaches the pericardium to the posterior side of the manubrium.

    Body [ edit ]

    3D illustration of the body of sternum.

    The body, or gladiolus, is the longest sternal part. It is flat and considered to have only a front and back surface. 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. The pectoralis major attaches to it on either side. 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. 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.

    The sternal angle is located at the point where the body joins the manubrium. The sternal angle can be felt at the point where the sternum projects farthest forward. However, in some people the sternal angle is concave or rounded. During physical examinations, the sternal angle is a useful landmark because the second rib attaches here. [1]

    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. 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. 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. Most of the cartilages belonging to the true ribs, articulate with the sternum at the lines of junction of its primitive component segments. This is well seen in some other vertebrates, where the parts of the bone remain separated for longer. [ citation needed ]

    The upper border is oval and articulates with the manubrium, at the sternal angle. The lower border is narrow, and articulates with the xiphoid process.

    Xiphoid process [ edit ]

    Main article: Xiphoid process
    3D illustration of the Xiphoid process.

    Located at the inferior end of the sternum is the pointed xiphoid process. 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. [1]

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

    Joints [ edit ]

    The cartilages of the top five ribs join with the sternum at the sternocostal joints. The right and left clavicular notches articulate with the right and left clavicles, respectively. The costal cartilage of the second rib articulates with the sternum at the sternal angle making it easy to locate. [3]

    The transversus thoracis muscle is innervated by one of the intercostal nerves and superiorly attaches at the posterior surface of the lower sternum. Its inferior attachment is the internal surface of costal cartilages two through six and works to depress the ribs. [4]

    Development [ edit ]

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    Figure 4 Ossification

    Figure 5

    Figure 6 Peculiarities

    Figure 7

    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. 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.

    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.

    The centers make their appearance at the upper parts of the segments, and proceed gradually downward. 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. [ citation needed ]

    Occasionally some of the segments are formed from more than one center, the number and position of which vary [Fig. 6]. Thus, the first piece may have two, three, or even six centers.

    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. 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.

    More rarely still the upper end of the sternum may be divided by a fissure. Union of the various centers of the body begins about puberty, and proceeds from below upward [Fig. 5]; by the age of 25 they are all united.

    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. In advanced life the manubrium is occasionally joined to the body by bone. When this takes place, however, the bony tissue is generally only superficial, the central portion of the intervening cartilage remaining unossified.

    In early life, the sternum’s body is divided into four segments, not three, called sternebrae (singular: sternebra). [5]

    Variations [ edit ]

    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. [6] In extremely rare cases, multiple foramina may be observed. Fusion of the manubriosternal joint also occurs in around 5% of the population. [7] Small ossicles known as episternal ossicles may also be present posterior to the superior end of the manubrium. [8] Another variant called suprasternal tubercle is formed when the episternal ossicles fuse with the manubrium. [9]

    Clinical significance [ edit ]

    Bone marrow biopsy [ edit ]

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

    Sternal opening [ edit ]

    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. Congenital sternal foramina can often be mistaken for bullet holes. [10] They are usually without symptoms but can be problematic if acupuncture in the area is intended. [11]

    Manubrium sternal dislocation

    Fractures [ edit ]

    Main article: Sternal fracture

    Fractures of the sternum are rather uncommon. 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. A fracture of the sternum is usually a comminuted fracture. The most common site of sternal fractures is at the sternal angle. Some studies reveal that repeated punches or continual beatings, sometimes called «breastbone punches», to the sternum area have also caused fractured sternums. Those are known to have occurred in contact sports such as hockey and football. Sternal fractures are frequently associated with underlying injuries such as pulmonary contusions, or bruised lung tissue. [12]

    Dislocation [ edit ]

    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. [13]

    Sternotomy [ edit ]

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

    Resection [ edit ]

    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).

    Bifid sternum or sternal cleft [ edit ]

    A bifid sternum is an extremely rare congenital abnormality caused by the fusion failure of the sternum. [14] This condition results in sternal cleft which can be observed at birth without any symptom. [14]

    Other animals [ edit ]

    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. [15] It probably first evolved in early tetrapods as an extension of the pectoral girdle; it is not found in fish. In amphibians and reptiles it is typically a shield-shaped structure, often composed entirely of cartilage. It is absent in both turtles and snakes. In birds it is a relatively large bone and typically bears an enormous projecting keel to which the flight muscles are attached. [16] Only in mammals does the sternum take on the elongated, segmented form seen in humans.

    Arthropods [ edit ]

    Main article: Sternum (arthropod anatomy)

    In arachnids, the sternum is the ventral (lower) portion of the cephalothorax. It consists of a single sclerite situated between the coxa, opposite the carapace.

    Etymology [ edit ]

    English sternum is a translation of Ancient Greek στέρνον , sternon . [17] The Greek writer Homer used the term στέρνον to refer to the male chest, [18] [19] and the term στῆθος , stithos to refer to the chest of both sexes. [18] [19] The Greek physician Hippocrates used στέρνον to refer to the chest, [18] [19] and στῆθος to the breastbone. [18] [19] The Greek physician Galen was the first to use στέρνον in the present meaning of breastbone. [18] [19] The sternum as the solid bony part of the chest [20] can be related to Ancient Greek στερεός/στερρός , ( stereόs/sterrόs ), [20] meaning firm or solid. [19] The English term breastbone is actually more like the Latin os pectoris, [21] [22] derived from classical Latin os, bone [23] and pectus, chest or breast. [23] Confusingly, pectus is also used in classical Latin as breastbone. [23]

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