Author: Benjamin Aghoghovwia •Reviewer: Latitia KenchLast reviewed: October 09, 2021Reading time: 17 minutes


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The thoracic cage (rib cage) is the skeleton the the thoracic wall. That is created by the 12 thoracic vertebrae, 12 bag of ribs and associated costal cartilages and also the sternum.

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The thoracic cage bring away the form of a domed bird cage v the horizontal bars created by ribs and costal cartilages. It is supported through the upright sternum or breastbone (anteriorly) and the 12 thoracic vertebrae (posteriorly). The thoracic cage can additionally be explained as an osteocartilaginous cage formed by the sternum, 12 pairs of ribs and costal cartilages, 12 thoracic vertebrae and also the intervertebral (IV) discs interposed between them.

The thoracic cage, like skeletal tissue in many parts that the body, serves to support the thorax. It additionally has several functions, such as:

protecticting vital thoracic and ab internal guts from external forces providing the anchoring attachments (origin) of many of the muscles the move and maintain the place of the upper limbs relative to the trunk. an essential facts
Sternum Manubrium: suprasternal and also clavicular notches, articulates with the body, an initial two ribs, and claviclesBody: articulates v the costal cartilages of 2nd to saturday ribs and also the xiphoid process (xiphisternal joint)Xiphoid process: T10 level, inferior limit of the central part the the thorax
Thoracic Vertebrae Twelve in total, include a body, arch, and also costal facets
Ribs Typical: head, beck, tubercle, bodyAtypical: one or two facets and also a tuberosity (1st, 2nd, 10th-12th)True: first to 7th, contain their own costal cartilages and attach straight to the sternumFalse: 8th, 9th, 10th of i m sorry their respective cartilages connect to the costal cartilage the the rib aboveFloating: 11th and 12th rib hang freely and also only articulate v the vertebra
Intercostal Spaces called according to the rib developing the superior border and also contain intercostal muscles, vessels, and nerves
Joints Xiphisternal: xiphoid process and body of sternumIntervertebral: between vertebraeSternochondral: sternum and also costal cartilagesSternoclavicular: manubrium and claviclesManubriosternal: manubrium and body that sternumCostochondral: costal cartilage and ribCostovertebral: developed by the ribs and also bodies of the vertebrae.Interchondral: authorized the costal cartilages to one another

Ossification and also development

During the intrauterine duration of development, the rib cage starts to ossify. This procedure continues until about the 25th year the extra-uterine life. Of all the three groups of bones developing the thoracic cage, the vertebral and ribs ossification start by the end of the embryonic duration (at approximately the 7th week of gestation). Sternal ossification begins during the 5th month that fetal development.

Although ossification is complete, top top average, by age 25 years, steady calcification that the costal cartilages can continue into old age. A notably far-ranging development that the thoracic cage is the expansion of the rib cage i beg your pardon contributes significantly to the vast shoulders observed specifically in males. In males, expansion of the rib cage is caused by the results of testosterone hormone throughout puberty; therefore males generally have large shoulders and expanded thoraces, allowing them to inhale much more air come supply their muscles with oxygen.

Sternum

The sternum (derived from the Greek word, sternon meaning chest) is a flat, elongated bone forming the middle of the anterior part of the thoracic cage.

The sternum is composed of three parts, namely, the manubrium, body of sternum and also the xiphoid process.

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Overview that the sternum

Manubrium

The manubrium is a around trapezoidal bone. That is the widest and also thickest the the three components of the sternum. Its premium border has actually an conveniently palpated concave centre, called the jugular notch (or suprasternal notch). Lateral come the suprasternal notch room the clavicular notches, which obtain the sternal finish (medial end) of the clavicle. In one articulated skeleton, the jugular notch is deepened by the medial ends of the left and also right clavicles.

The manubrium also articulates v the costal cartilage the the first rib – the synchondrosis the the first rib, and also the superior half of the articular surface ar of the costal cartilage that the 2nd rib.

The manubrium and also body of the sternum lied in slightly various planes superiorly and also inferiorly to their junction, the manubriosternal joint; hence, their junction creates a projecting sternal angle (of Louis).

Body

The body of the sternum is longer, narrower and thinner 보다 the manubrium. The is interposed between the manubrium and also the xiphoid process, and also is situated at the level of the T5 – T9 vertebrae. On the lateral borders, the human body articulates with the costal cartilages of the second to seventh ribs, and forms a xiphisternal joint at its junction through the xiphoid process.


Xiphoid process

The xiphoid process is the smallest and also most variable component of the sternum. That is thin, elongated and lies in ~ the level of the T10 vertebra. Although regularly pointed in some individuals, the procedure may be blunt, bifid, curved or deflected come one side or anteriorly. The xiphoid procedure is tiny and cartilaginous in young people yet gets ossified in adults older than age 40, with significant pains accompanying the procedure of ossification. Ossification of the xiphoid procedure in the elderly human being may likewise cause fusion of the xiphoid process with the sternal body.

The xiphoid procedure is crucial landmark in the median plane, describe the inferior limit of the central part that the thoracic cavity. This worse limit coincides to the xiphisternal joint, and it is likewise the site of the infrasternal angle (subcostal angle) of the worse thoracic aperture. Additionally, the xiphoid process is a midline marker because that the superior limit that the liver, the main tendon of the diaphragm, and the inferior border that the heart.

Test your expertise on the sternum v the adhering to quiz!


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The thoracic vertebrae are a team of 12 little bones that form the vertebral spine of the thorax. They are intermediate in size in between those of the cervical region and lumbar region, come which castle are likewise interposed, and also increase in size from above downwards.

They room mostly typical vertebrae in that they room independent, have bodies, vertebral arches, and also seven procedures for muscular and also articular connections. Most of them additionally have costal facets on your transverse processes for articulation with the tubercles of ribs. They are likewise characterized v bilateral costal facets (demifacets) on your bodies, and also long, inferiorly slanting spinous processes.

Atypical thoracic vertebrae have actually “whole costal facets” in place of demifacets. The T1 vertebrae, T10, T11 and also T12 are all atypical, having only solitary whole costal facets.

Learn the bones of the thoracic cavity with the complying with study unit:


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Sternum check out study unit

Ribs and also costal cartilages

The ribs (derived from the Latin word costae) are curved, long bones connecting the sternum and most of the thoracic vertebrae (specifically T1-T10). They consist of the highest variety of bones forming the thoracic cage. They space remarkably irradiate in weight yet highly long lasting to press from within the thorax, e.g., push generated during inspiration.

There space three varieties of ribs, and all teams have a spongy interior containing bone marrow (hematopoietic tissue), which creates blood cells. All of the ribs the articulate (rib 1-10) with the sternum are an extensive anteriorly, v their enclosed costal cartilages with which castle articulate v the sternum. This costal cartilages likewise contribute to the elasticity the the thoracic wall, giving a functional attachment for their anterior or distal ends.

The cartilages of the an initial 8 ribs rise in size in to decrease order, through the length then decreasing after ~ the 8th. The very first seven (and sometimes the 8th) cartilages attach directly and independently to the sternum. The 8th, 9th and also 10th cartilages articulate through the costal cartilages simply superior to them, forming a continuous, articulated, cartilaginous costal margin of the rib cage. The ribs have the right to be split into 2 groups, typical and atypical.

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Overview the the ribs

Typical ribs

The usual ribs encompass ribs 3 come 9th and have the adhering to components:

Wedge shame head through two facets, be separate by the comb of the head.Neck connecting the head through the body at the level of the tubercle.A tubercle at the junction the the neck and body, which and has a smooth articular component for articulating with the transverse process of the corresponding vertebra.A thin, flat and curved body (shaft), most markedly at the costal angle whereby the rib turns anterolaterally.

Atypical ribs

The patent ribs room the 1st, 2nd, and also the 10th – 12th ribs identified with the adhering to features:

Have one or two facets, and also a stormy area top top the exceptional surface, e.g, the tuberosity for serratus anterior that the 2nd rib.

True, false, floating ribs


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All 12 pairs of ribs can additionally be separated into the following varieties or groups:

True (Vertebrocostal) ribs: The 1st to 7th ribs loss under this group, and they attach directly come the sternum v their very own costal cartilages.False (vertebrochondral) ribs: The 8th, 9th, and also 10th ribs are referred to as false ribs because their cartilages are connected to the costal cartilage of the rib over them; thus their connection with the sternum is indirect.

Reinforce your knowledge about the ribs through this quiz:


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tradition quiz: Ribs start quiz

The bones forming the thoracic cage are arranged in a pattern that enables some room between them. Those spaces are referred to as the intercostal spaces . The intercostal spaces separate the ribs and also their costal cartilages indigenous one another and enable smooth growth of the cage during inspiration. The spaces are named according to the rib creating the remarkable border of the space, for example, the 4th intercostal space lies in between the fourth rib and 5th rib; therefore, there space 11 intercostal spaces in the rib cage.

Intercostal spaces are inhabited by intercostal muscle and membranes, 11 intercostal nerves and two to adjust (main and collateral) that intercostal blood vessels likewise identified through the very same number assigned come the intercostal space. Below the 12th rib, is described as the subcostal space and also the anterior ramus that the spinal nerve T12 runs v this space, and also it is therefore referred to as the subcostal nerve.

Have you to be wondering even if it is you have to use 3D anatomy tools to learn about the thoracic cage? Here"s why you should think again. 

Joints

The joints developing the domed-shaped thoracic cage include the:

Xiphisternal joint – xiphoid process and human body of sternumIntervertebral joints – in between vertebraeSternochondral joints – sternum and costal cartilagesManubriosternal joints – manubrium and also body that sternumCostovertebral joints – created by the ribs and bodies of the vertebrae.

Some that the over joints are briefly described below.


Costochondral joints

The costochondral joints are the articulations between each rib and its costal cartilage. The is a hyaline cartilaginous type the joint. The coupling is between the cup-shaped depression in the sternal finish of a rib and the lateral end of a costal cartilage. The rib and also its cartilage space firmly bound together by the continuous of the periosteum of the rib through the perichondrium that the cartilage. No movement normally occurs at these joints.

Interchondral joints

The interchondral joints are plane synovial joints between the surrounding borders that the sixth and 7th, 7th and also 8th, and 8th and 9th costal cartilages. The joints room usually strengthened by interchondral ligaments, and also they likewise have synovial caries that space enclosed by share capsules.

Sternocostal joints

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Sternocostal share (anterior view)

These room joints developed by the lateral boundaries of the sternum and also the costal cartilages that the 1st to 7th ribs, and sometimes the 8 hours rib. The an initial pair of costal cartilages articulate v the manubrium by way of a thin thick layer of strictly adherent fibrocartilage interposed in between cartilage and the manubrium, the synchondrosis the the very first rib. The 2nd to seventh pairs of costal cartilages articulate through the sternum in ~ synovial joints with fibrocartilaginous articular surface on both the chondral and sternal aspects, enabling movement during respiration. The sternocostal joints are also referred to as sternochondral joints.

Costovertebral joints


Articulation of the left and right ribs with the vertebral tower (thoracic vertebrae) finish the domed birdcage-like thoracic cage posteriorly. The costovertebral joints are synovial joints, and also they room richly surrounded by share capsule. Of all the joints of the rib cage, this joints have actually the largest amount that ligaments crossing and also stabilizing them.

Most the the ribs room attached firmly to the intervertebral (IV) discs through intra-articular ligament within the joints. Fanning approximately from the anterior margin that the heads of the ribs come the sides of the bodies of vertebrae and the IV discs in between them is a radiate sternocostal ligament. Also crossing these joints is the costotransverse ligament passing indigenous the neck the the rib to the transverse process, and also a lateral costotransverse ligament passing native the tubercle the the rib come the reminder of the transverse process. These ligaments strengthen the anterior and also posterior elements of the joints respectively. Over there is a superior costotransverse ligament which might be split into a strong anterior costotransverse ligament and a weak posterior costotransverse ligament, both joining the crests the the neck of the ribs come the transverse processes superior to every of the ribs.

Master the costovertebral joints v our tailored quiz!


Clinical notes 

Dislocation that costochondral joint

Dislocation at this joint leader to separation that a rib indigenous its costal cartilage. This usually occurs as a result of tearing of the perichondrium and also periosteum resulting in an upward movement of the influenced rib, overriding the rib over and resulting in severe pains.

Dislocation the sternocostal and also interchondral joints

Sternocostal and/or interchondral share dislocation is the displacement of a costal cartilage from the sternum. This leader to dislocation that the matching rib, a condition referred to together slipping rib syndrome. Displacement that interchondral joints generally occurs unilaterally and involves ribs 8,9, and also 10. Trauma sufficient to displace this joints frequently injures underlying frameworks such as the diaphragm and/or liver, leading to severe pain, an especially during deep inspiratory movements. Rib dislocations are usual in body contact sports, and also complications may an outcome from press on or damages to surrounding nerves, blood vessels, and muscles.

Flail chest

Multiple rib fractures may allow a segment that the anterior and/or lateral thoracic wall surface to move freely but paradoxically inward on inspiration and outward ~ above expiration. Flail chest is really painful injury and impairs ventilation thereby affecting oxygenation the the blood.

Supernumerary ribs

As the name suggests, this is a clinically far-reaching condition in which there is distortion the the normal number of ribs forming the thoracic cage. Supernumerary or extra ribs have clinical meaning in that they might confuse the to know of vertebral levels in radiographs and other diagnostic images. Usually, there room 12 ribs on every side that the vertebral column, however the number is enhanced by the existence of cervical and/or lumbar ribs, or diminished by failure of the 12th pair come form.

Ossified xiphoid processes

Many human being in their beforehand 40s unexpectedly become aware of their partially ossified xiphoid procedure and consult their physician around the tough lump in the “pit of your stomach” (epigastric fossa). Never having been conscious of your xiphoid procedure before, they fear they have arisen a tumour.

Other clinically relevant instances include:

sternal anomaliessternal fracturessternal biopsymedian sternotomy

Sources

References:

K. L. Moore and also A. F. Dalley: Clinically oriented anatomy, 5th edition, (2006), p.74 – 84.

Illustrators:

Overview of the sternum - Yousun KohOverview that the ribs - Begoña RodriguezSternocostal joint (anterior view) - Yousun Koh

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