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Hello everyone! This is Joao from Kenhub, and on this anatomy tutorial, we are going to be looking at the ribs and costal cartilages. We will cover the structure and major landmarks of ribs. We wil... Read more
Hello everyone! This is Joao from Kenhub, and on this anatomy tutorial, we are going to be looking at the ribs and costal cartilages. We will cover the structure and major landmarks of ribs. We will start by looking at the overall anatomy of the ribs – that is, their location and organization in the body and the two different types of ribs, including true ribs, and false ribs. Next, we will look at the bony landmarks found on all ribs and then examine the landmarks that can be found on only a few specific ribs. We'll then look at the joints of the ribs and then the floating ribs which are a subtype of the false ribs. Once we know our way around the ribs in the thorax, we'll look at what happens when something goes wrong with the ribs.
Now, ribs are part of the axial skeletal which is made up of the skull, spine, ribs, sternum, and sacrum. Ribs are long. They are thin bones that make up the thoracic cage. The rib cage protects vital organs found in the thorax like your heart and lungs. It also provides attachments for some of the muscles that move your arms and help you breathe.
Now, let's look at the types of ribs that we can find in the human body including true ribs, false ribs and floating ribs. We'll start by looking at the rib cage from the front to see the costal cartilages. Now, this is an image of the rib cage from the front. The sternum is highlighted in green and ribs are classified into two groups by how they attach to the sternum. The first seven pairs of ribs are what we call true ribs, and true ribs attach directly to the sternum through costal cartilage. Ribs eight through twelve are called false ribs. They also attach to the sternum but not directly. Instead, they attach to the costal cartilage of the true ribs. Note that the true and false ribs have a flat sternal end to accommodate the costal cartilage. The cartilage forms the joint between the rib and the sternum. Finally, the last two false ribs, ribs eleven and twelve do not attach to the sternum at all. These are called floating ribs and are considered a subsection of the false ribs. You can only see small part of them from this perspective because the floating ribs do not pass all the way around the body.
Before we move on to talk about the bony landmarks of the ribs, let's talk about costal cartilages, which we mentioned briefly earlier. As we mentioned, the ribs are connected medially to costal cartilages, which are cartilages that extend the ribs and make the thoracic wall more elastic for respiration. The first seven cartilages, and occasionally the eighth, are connected to the sternum as you can see in this image. The eighth to tenth cartilages on the other hand are connected to the cartilages immediately superior to them, which you can see in this image. The costal cartilages on ribs eleven and twelve are not visible on this image but form caps on the ends of the ribs.
Let's now have a look at some bony landmarks that are found on most ribs. To show you the landmarks, we have isolated here a rib for you. These landmarks include the head of the rib, the neck of the rib, the articular facet of the rib tubercle, the articulation between the rib and vertebra, the crest of the neck of the rib, the angle, and shaft of the rib.
Now this is an image of four ribs from different levels of the thoracic cage. This is the first rib, this is the second one, this is a true rib, and this is the eleventh rib. Although there are some exceptions, most ribs have the same bony landmarks. Let's go over some of the landmarks you would see on a typical rib and then we'll look at some special features seen only on a couple of ribs.
To start, the head of the rib is the part closes to the spine. All ribs have a head with a surface to articulate or form a joint with the vertebral body next to it. If we move a little further out, we reach this part here which is the neck of the rib. It is a slightly longer region between the head and angle of the rib. In this image, we have highlighted it in green. The neck has more surfaces for attaching the vertebrae to the ribs which we call articular tubercles.
The tubercles of the ribs are small, rough bumps that attach the neck of the rib to the thoracic vertebra. If you look closely at the tubercles, you will notice a smooth surface in the middle of the articular tubercle called the articular facet. This is where the tubercle of the rib articulates with the transverse process of a thoracic vertebra. Let's take a closer look at how the surfaces fit together.
This is what the joint between the ribs and spinal column looks like from above. This is the body and transverse process of the vertebra. You can see here that there are two articulations involved. This is the joint between the head of the rib and the vertebral body and here is the joint between the articular facet of the tubercle and the transverse process of the vertebra.
To reorient ourselves, these are four ribs from different levels of the thoracic cage. This is the first rib, this one here is the second one, this is a typical rib near the middle of the thoracic cage, and this is the eleventh rib. The uppermost part of the neck of the rib is referred to as the crest of the rib. In this image, it is the green line between the head of the rib and the tubercle of the neck.
We just looked at the head and neck of the ribs, and if we move a little further away from the spine, the bone curves. This is the angle of the rib. At this point, the rib begins to course around the lung towards the sternum. The rest of the rib from the angle to the joint with the sternum is called the body or shaft of the rib. The body of the rib has a small groove at the bottom on the inside of the rib cage. This is the costal groove. Nerves and arteries that supply the ribs and muscles follow this groove.
Now that we know the basic structure of the ribs, let's look at some of the features of atypical ribs. Remember, atypical ribs include ribs one, two, and ten through twelve. In this section, we will look at the scalene tubercle, the attachment for the subclavius, the groove for the subclavian vein, and also the groove for the subclavian artery. And lastly, we will look at the serratus anterior tuberosity.
Now, this is the first rib. Like a typical rib, it has a head, neck, shaft and articular tubercles but it is much shorter than other ribs and has a few extra bony landmarks made by muscle attachments and blood vessels passing across it. The landmark highlighted in this picture is called the scalene tubercle, and it is the attachment point for the anterior scalene muscle.
This is another bony landmark created by a muscle attachment. The subclavius muscle attaches to the clavicle and first rib. When this muscle is tensed, it pulls the clavicle closer to the first rib. Now, the subclavian vein is a large vein draining blood from the upper limb and it passes over the first rib on its way to the heart. The subclavian vein is large enough to create a small depression on the rib. This is what we call the groove for the subclavian vein and it is highlighted in green on the image right now.
The subclavian artery passes over the first rib next to the subclavian vein and also creates a groove. Blood pressure is higher in arteries than veins so the groove created by the subclavian artery is larger than the groove from the subclavian vein. The groove for the subclavian artery is highlighted in green here next to the groove for the subclavian vein.
Like the scalene muscles, the serratus anterior muscle also creates a unique bony landmark where it attaches to the ribs. The first eight or nine ribs feature a serratus anterior tuberosity. This is the serratus anterior tuberosity of the second rib.
Let's have a look now at some important joints associated with the ribs.
Sternochondral or sternocostal joints as they're sometimes called are joints that connect the medial aspect of the second to seventh costal cartilages to the lateral surface of the sternum. These joints are synovial plane joints moving with respiration. The sternochondral joints of the first pair of costal cartilages on the other hand articulate with the manubrium of the sternum as you can see in this image here. These joints are known as synchondroses which are strong and stable joints with little movement.
Moving laterally along the costal cartilages, costochondral joints are those found between the lateral end of the costal cartilage and the sternal or medial end of the ribs. The sternal ends of the ribs each have a small cup shaped depression into which the lateral end of the costal cartilage inserts. These joints are hyaline cartilaginous joints and are connected by the periosteum of both ribs and the cartilage so there is usually no movement in these joints.
And moving down the rib cage towards the lower ribs we have the interchondral joints which are articulations between the contiguous borders of costal cartilages six to ten. Do note however that while the articulations between the costal cartilages six to nine are synovial plane joints, the articulation between ninth and tenth costal cartilages is a fibrous joint. These joints are reinforced by interchondral ligaments and you can see them here.
Let's look at some features of floating ribs. Ribs three through ten show typical structure and landmarks, even though ribs eight to twelve are false ribs. Remember that false ribs do articulate with the sternum, but only through the costal cartilages of true ribs. Floating ribs are also very similar to a typical rib. Note here that on this image, we are looking at the floating ribs from the back. This is the eleventh rib. You can see here that it has a head, neck, angle, and shaft but the sternal end of this rib is tapered rather than flat.
Now that we are familiar with features of our thoracic ribs, let's take a look at the implications of having a cervical rib. This is a radiograph of the neck and upper part of the thorax. The spine and ribs are visible in a light gray color. The first four ribs are here. In some rare cases, an individual may present with another rib above it. This is called a cervical rib because it arises from a cervical vertebra. In this radiograph, the cervical rib is indicated with the red arrow. Usually, there is a cervical rib on only one side. Cervical ribs do not usually cause a person major distress but can sometimes alter the position of a major nerve plexus that runs from the cervical and thoracic spine to the arm. Supraclavicular nerve blocks used for shoulder surgery can still be performed with a cervical rib although a physician has to take extra care to work around it.
Now that we're finished looking at the features of the ribs and clinical correlations, let's take a quick moment to summarize what we have learned about the ribs. In this video, we looked at the classification and structure of ribs. Ribs are classified into two groups. True ribs connect directly to the sternum through their own costal cartilage. Ribs one through seven are true ribs. We also looked at false ribs which connect to the sternum through the costal cartilages of true ribs. Ribs eight to twelve are false ribs, and floating ribs do not connect to the sternum at all. Ribs eleven and twelve are floating ribs.
The costal cartilages are cartilage that attach to the medial end of the ribs and help make the thoracic wall more elastic for respiration. Costal cartilages one to seven attach to the sternum, while costal cartilages eight to ten attach to the cartilages above.
Then we looked at some common features seen on all ribs. The head of the rib is closest to the vertebral body. The neck of the rib is just distal to the head. The neck of the rib features an articular facet for attaching to the transverse process of a vertebra, and a crest, which is the highest point of the neck. Just distal to the neck is the angle of the rib. This is the point where the rib begins to curve around the front of the body. The long part of the rib that travels around the thorax is called the shaft of the rib.
Some of the ribs feature unique bony landmarks. The serratus anterior tuberosity is created by the origins of the serratus anterior muscle on the first eight or nine ribs. The scalene tubercle is created by the attachment of the scalene muscles on the first and second ribs. The subclavius muscle creates a small bony landmark where it attaches to the first rib. Finally, the subclavian artery and vein both create grooves on the first rib where they pass over it. The groove for the subclavian vein and subclavian artery are next to each other on the rib.
We also looked at joints of the rib, including the sternochondral joints, which connect the medial aspect of the second to seventh costal cartilages to the lateral surface of the sternum and the sternochondral joints of the first pair of costal cartilages which articulate with the manubrium. We looked at the costochondral joints which are found between the lateral end of the costal cartilage and the sternal end of the ribs. And we also looked at the interchondral joints, which are the articulations between the contiguous borders of costal cartilages six through ten.
And, finally, finally, we looked at a radiograph of a very unusual rib. Ribs articulate with the thoracic spine, however, they can also sometimes arise from a vertebra in the neck. This is then called a cervical rib. Although it is not usually a major cause for concern, cervical ribs can affect the location of nerves controlling the arms.
And that's it, we've reached the end of this tutorial. Thank you for watching and I hope to see you on the next one.