Human chest bone structure Parts of the Chest Bones
For many, the chest is made up of a single rigid bone called the sternum. However, this is not true. Other than the sternum, there are other bones in the chest region, such as the ribs and even the spine at the back. All these bones are vital for several different functions that they play in the human body. All bones in the body are actually very important, ranging from the smallest of them all – the oscicles – to the largest, the femur.
Despite their uniqueness, chestbones are just like any other bones in the body. They are made of a combination of collagen and calcium which make up certain bone cells known as osteocytes. The osteocytes together with other bone cells (the osteoblasts and osteoproginator cells) are arrange in a manner that allows the growth and development of bones, as well as repair of worn out or damaged bone cells. This arrangement is also responsible for the tough nature of the bones, which is exactly what enables them to perform their functions so perfectly.
But what exactly do we need chest bones for? People live without some of their ribs anyway, so are they that important? What implications do broken chest bones have on a person’ health?
The truth of the matter is, all chest bones are very useful and can be extremely painful and threatening to lose. Given how vital the chest is, one can only imagine what would happen to a boneless chest.But it is not enough to just state that they are important. The rest of this article explains why the parts of the chest bones are so paramount.
The sternum is a nearly flat rigid bone in the middle of human chest. It extends from the position of the diaphragm to the clavicle or the collar bone. It consists of the manubrium on its uppermost end, its body in the intermediate region and the small xiphoid process on its lowermost end. Manubrium and the body are connected by a secondary joint made of cartilage. Most of the sternum is made of cancellous bone, just like the ribs, which is filled with red marrowthroughout life.
The manubrium is a flat bone, with its concave upper margin, the jugular notch, which provides attachment surface for adherent ligaments that connect it to the clavicle. The upper angles of the manubrium are scooped out into a concavity for the joint between the sternum and the clavicle which is a synovial joint though atypical. Below, the lateral border is excavated. This is to give space for the first costal cartilage that articulates here by a cartilaginous joint. At the lower angle is a small facet for articulation with the second costal cartilage. The anterior surface of the manubrium is mainly covered by the pectoralismajor – one of the chest muscles – and also gives attachment to the tendon of another chest muscle – the sternocleidomastoid. Forming the anterior wall of the superior mediastinum, the manubrium provides attachment between the sternum and two neck bones, the hyoid and thyroid, on its upper part of the posterior surface.
Clearly, the sternum is out here to aid attachment of muscles that control other body parts, but not only that. Ribs and other costal cartilage attach to it as will be examined in the following part of the article. However, it is important to note that the sternum, via the manubrium, connects to the neck bones. This shows that the chest, despite its lonely seeming nature, is attached to other parts of the body. This interconnection, as seen throughout the body, is important for certain structures that frame the body.
The body of the sternum possesses facets (auricular) along its lateral border for the attachment of the lower part of the second costal cartilage as well as for the third through seventh costal cartilages which are all synovial joints. The body also gives attachment to the anterior intercostal membrane between the costal facets lateral bodyas well as for other intercostal muscles that are internal – the pectoralis major and the transversus thoracis on the anterior and posterior surfaces respectively. Some lame sternopericardial ligaments also arise from the posterior surface to pass to the fibrous pericardium where they attach.
The xiphoid process (also known as the xiphisternum) projects downwards in order to allow for attachment of the linea alba from the lower end of the body of the sternum on its posterior margin. Here, it articulates with the sternal body by means of a symphysiswhich usually grows in mid-age, about 20 years of age.
Given that the sternum is not a single bone as most people think, it provides attachment for its other bones as well as for other bones, costal cartilages, ligaments and muscles mentioned above. This makes its role as vital as the roles these bones and other attachments play as it provides an attachment for them.
Even then, aside from the sternum, other parts of the chest bones exist as aforementioned. They play different roles in the chest as well as general body. Details are provided herein.
A typical rib (the 6th rib)
Ribs together form the rib cage, which as the name suggests, is a protective cage for the delicate thoracic organs such as lungs and heart. A rib is a long curved boned that attaches to the sternum on its anterior end via costal cartilage and to the spine on its posterior end. A typical rib has several parts that are displayed in the diagram above and discussed below.
The head of the rib is beveledout by its two articular facets that slope away from thedividing ridge thus formed. Articulating with its own vertebra, the lower facet is vertical while the upper facet slopes and articulates with thevertebra above it. The facets make synovial joints, with the cavities separated by ligaments that attach to the ridge of the head as well as to the intervertebral disc.
The neck of the rib is flattened, with its upper border formed by a sharp crest. To the crest are attached two laminae of the upper costotransverse ligaments. When traced from head to tubercle, it inclines backwards.
The tubercle hosts two facets as shown in the diagram. The medial facet issmooth and makes a synovial joint with its own vertebra. Since upper ribs have slightly convex facets, the lower ribs have flat facets, which is complementary to their nature. The lateral costotransverse ligament attach to the lateral facet, which is suitable for the attachment due to its rough nature.
The shaft has quite a complex shape. It slopes downwards and backwards to the angle where it twists forward in its characteristic curvature that makes it unique. The shaft then curves to form arcs whose diameter increasesdownwards from the anterior angle. When it comes to torsion at the angle, rib head lies at a more superior level than its anterior ends. The degree of torsion is most remarkably visible on the seventh through ninth ribs.
Unlike its lower border, the upper border of a rib is blunt. External intercostal muscles attach to the whole length whereas internal intercostal muscles attach to the. The lower edge of the shaft is sharp as mentioned and hangs down,producing a well-marked costal groove on the rib’s inner surface. This sharp lower border is where external intercostal muscles arise. Internal intercostal muscles are attached to the costal groove.
A group of transverse thoracic muscles are attached to the inner surface of the shaft, which provides a much convenient space for the attachment. A group of nerves and blood vessels lies between this layer of muscles and the internal intercostal muscle, under the costal groove. The rib is excavated into a concave fossa anteriorly. This anterior concavity is plugged by the costal cartilage into an immobile cartilaginous joint.
Whereas the above discussed are the features of a typical rib, atypical ribs do not possess many features so different from the typical ribs. For example, the first rib resembles a sickle, only without teeth. Its head carries a single facet unlike other ribs however. This is necessary due to its attachment, which is, needless to say, different from other ribs. Have a look.
The first rib: an atypical rib
One look at it is enough to tell that however rib it might seem, it is not really a rib thing. Here are the features of an atypical rib.
The head is of an atypical rib is usually small and carries a single facet for the synovial joint between itself and the body of the first thoracic vertebra. Lying in contact with the frontal border of the neck is the sympathetic trunk (also known as cervicothoracic ganglion) alongside the head. On its lateral side is the first posterior intercostal vein, which is followed by superior intercostal artery lying in contact, and ultimately, even more lateral still is the first thoracic nerve lying in front of the neck. These nerves and vessels are held against the font of the rib neck by the cervical dome of the pleura. The apex of the lung also contributes to this function.
The rib then becomes broad at the junction of the neck and the shaft, where a tubercle prominently projects backwards to form the posterior convexity of the rib – recall the anterior concavity. This is formed by a fusion of the tubercle and the angle. A convex facet is found mediallypurposefully to form a corresponding concavity on the first transverse process in on the side. Thetubercle receives the lateral costotransverse ligament on this lateral prominent part.
The lower surface of the shaft, which is obliquely crossed by the small first intercostal nerve and vessels, is covered by sticky pleura of the parietal variety. The outer rim of this surface is formed by the internal and external intercostal muscles, which are attached together. A muscle, serratus anterior, hasits first digitation attached to the anterior part of the outer border, which is blunt between the tubercle and the subclavian groove. The suprapleural membrane is attached to the internal border, which is concave, in front of thesubclavian groove.
Aside from the first rib, the other atypical ribs are not so much of a difference to the other ribs. It is worth mentioning though, that only the first through seventh ribs are considered as true ribs whereas the rest being referred to as false ribs. The false ribs are not attached onto the sternum, but onto other ribs. Some of them even hang without an anterior attachment. All the ribs, even false ones possess the costal cartilage that aids them in attachment. The floating eleventh and twelfth ribs, surprisingly, possess the costal cartilage although they do not have an anterior bony attachment.
The human chest, aside from bones, is made up of a lot of delicate organs and tissue. The lungs and the heart, the diaphragm and other tissue found in the pleural space are some of the examples of these organs. All of them require protection from the external hard environment, which is why it is necessary to have a rigid wall that separates them from the world. This rigid wall is formed by the ribs.
The ribs require an attachment surface, which the sternum provides. The sternum itself is not a single rigid bone as the chest needs flexibility. A rigid bone would hinder the heaving of the chest, which is important for breathing. And it goes without saying that breathing is an important aspect of the human survival.
Broken ribs and sternum can lead to serious implications if not attended to on time. The problem with these is because it worsens since the chest can never be perfectly still for a living human being. It is therefore important to be in close contact with an osteologist whenever need arises from an accidental occurrence on these vital bones in the body. Not that other bones in the body are not important – not a single bone in the body serves no purpose, but that these ones are just too vital.