Hello, everyone! This is Joao from Kenhub, and welcome to another anatomy tutorial where, this time, I'm going to be talking about the bones of the dorsal trunk.
And before we start dissecting what are the different bones that you find on the dorsal trunk, why not just go briefly over the definition of trunk—what exactly I mean by trunk. And in anatomy, this is what we define as the central part of your body. So this is what we define as the chest cavity or the thorax, the abdomen as well. This is what is defined or included as the trunk.
Now, do not include in this definition the upper and lower limbs, and also the neck and the head. Do not include these structures as part of the trunk.
And on this tutorial, we will be focusing on the different bones that you find on the dorsal part or the back portion of your trunk, as you can now see on the screen—a general overview of the different bones, of some of the different bones that will be mentioned on this tutorial.
And without further ado, without keeping you waiting, I'm going to start off with this group of bones here that you see now, highlighted in green. These are known as the cervical vertebrae, which are the smallest vertebrae in the spinal column.
The cervical spinal column is comprised of seven vertebrae. Now, the first cervical vertebra is known as the atlas, and the second one is known as the axis. And the seven vertebra are… or the seven "vertebrae," plural, are unique in structure compared to the other cervical vertebrae.
We’re going to go a bit further down and talk about, now, this other set of bones, set of vertebrae, known as the thoracic vertebrae. And the thoracic vertebral part of the spinal column is the middle part of the spinal column and is comprised of, now, twelve vertebrae.
Each thoracic vertebra has a superior costal facet, and inferior costal facet, and a costal facet on the transverse process. Each vertebra also has an intervertebral foramen, a vertebral foramen, a spinous process, and transverse process—all of these structures that will be discussed in more detail in one of the tutorials that we have here on Kenhub where we focus on the different thoracic and lumbar vertebrae. So please check that one out.
A bit further down, we’re going to find the last set of vertebrae. These are the lumbar vertebrae. They are located between the thoracic vertebrae and this bone here that is known as the sacrum. And there are five lumbar vertebrae. That’s important point to make here, five lumbar vertebrae.
Now, the lumbar vertebrae are numbered from L-1 to L-5, and L-5 is going to be articulating with the sacrum on a joint known as the lumbosacral joint. And unlike the cervical and thoracic vertebrae, these vertebrae, the lumbar vertebrae, have no transverse foramina. And transverse foramina are openings that you find on the transverse processes of different vertebrae, but on the lumbar vertebrae, you cannot find.
Even on this image, you don’t find any transverse foramina, any openings here. So for that reason, it’s important to highlight here that these structures, these lumbar vertebrae, have no transverse foramina. And these transverse foramina are openings that serve as passages for the different spinal nerves.
The next set of structures that we’re going to be talking about on this tutorial are known as the true ribs, seen here highlighted in green. They are true ribs because they are the first seven ribs that you find on your rib cage. And also important to mention that we call them true ribs because they are the only ribs that actually articulate with the sternum.
But they do not articulate directly. They do so through their rib cartilages. They have some sort of direct connection, which are different from the next set of ribs that we call the false ribs. And these are the last ribs, last five ribs of the rib cage. They are called false ribs as they do not have any cartilaginous articulation with the sternum—so main important point happening here, main distinction made here between all the ribs that you find on the rib cage.
The last false ribs that you can see here, these last two, are also referred to as the floating ribs as they have no connection with the costal arch.
We’re going to move on and talk a little bit about the clavicle. And we have here a structure highlighted in green. And this is the sternal facet of the clavicle.
Now, the sternal facet of the clavicle is the articular surface on the medial end of the clavicle that articulates with the manubrium of the sternum.
We are still talking about the clavicle, but this time, about the body or shaft of the clavicle, which is the middle portion of this bone. And this part of the clavicle is curved in its structure with the thicker medial two-thirds of the body being convex, while the lateral thinner one-third is concave.
A groove for the subclavius muscle where this muscle attaches to the clavicle can be found on the shaft as well.
You can also find other structures, other structures that are worth just listing on this tutorial, but we will have another tutorial where I'm going to show you exactly where they’re found. But two structures worth mentioning are the conoid tubercle and also the costal tuberosity.
There are other muscles that will be attaching to the body of the clavicle, namely the pectoralis major, the sternocleidomastoid muscle, the deltoid, and also the trapezius—so a lot of muscles attaching to the body of the clavicle.
We’re going to move on to another structure still on this bone, the clavicle. This is known as the opposite as the sternal facet. This is the acromial facet. And the acromial facet of the clavicle is found on the lateral end of the clavicle. It is at this end that the clavicle attaches to the acromion of the scapula, as you can clearly see here on this image. So this is the acromion of the scapula, this triangular-shaped bone that is now articulating with the acromial facet of the clavicle. And this articulation forms a joint, the, then, known as the acromioclavicular joint.
Another structure worth mentioning on this tutorial found on the set of bones that we talked about previously: the ribs. This is known as the head of the rib.
The head of the ribs is the most proximal part of the rib to the vertebral column. This is the part of the ribs that articulates with the vertebrae as you can see here on this image. And the head of the rib has an articular surface and a ridge that separates two articular facets called the interarticular crest.
The ribs also have what you see now, highlighted: a neck. So this is the neck of the rib. And the neck of the rib sits between the head of the rib and the body of the ribs, as you can see here on this image. The neck of the rib is marked by a ridge on its upper part called the crest of the neck of the rib.
The next structure here on our list is going to also be part of the rib, this long structure known as the body of the ribs. So the ribs have a body. And the body of the rib is the main part of this bone and has some important identifiable structures that are worth noting here on this tutorial.
Now, the first one is known as the costal tubercle which is found between the shaft and also the neck of the ribs. So somewhere about here, this is where you would find the different tubercles, the different costal tubercles of the ribs.
The other structure would be the articular facet for the costal tubercle where the rib is going to articulate—as you can see here—where the rib is going to articulate with the transverse process of the thoracic vertebrae.
The other structure worth listing on the body of the rib is the angle of the rib. And the other one, the last one, is the costal groove which is a groove for the intercostal vessels and nerve. This groove is located on the internal lower margin of the body of the rib.
We’re going to move on to the last structure that we’re going to be highlighting here on this tutorial, known as the costal tubercle.
Now, the costal tubercle is located between the body and the neck of the rib, and we mentioned this before on the previous slides. And this eminence has an articular part where the rib is going to be articulating with the transverse process of the vertebrae—as you can see here on this image—and a non-articulating part to which the ligament of the tubercle will be attaching to.