 Good day everybody. This is Dr. Sanjay Sanyal, Professor Department Chair. We have focused a specimen of the sternum with attached coastal cartilages in front of you. Now if you were to take a good look at it, kind of reminds you of Excalibur, the legendary sword of King Arthur. So therefore, the parts of the sternum have been named according to that of a sword. In front of us we see this portion here. This is called the manabrium, which means the handle. This portion that we see is the body. This is called the gladiolus or the blade of the soul. And this is the Ziphoid process of the Ziphy sternum, which is the tip of the soul. So therefore, this has been likened to that of a sword. So let's take the manabrium sterni first and let's take a look at the parts of it. Up here we see this notch here. This is called the juggler notch. This is the notch which we can feel at the root of our neck. And in fact, this forms one of the boundaries of the root of the neck. On the other side, we have the clavicular notch. This is where the clavicle is attached and this forms what is known as the sternoclavicular joint. The sternoclavicular joint is a very strong joint. It is strengthened by an anterior and posterior sternoclavicular ligament and a costoclavicular ligament. So therefore, the sternoclavicular joint is hardly ever dislocated in clinical practice. And in between, inside the joint, there is a disc of fibrocartilage. So let's move the movement which occurs with the sternoclavicular joint is a sliding movement in movements of the pectoral girdle. Then we have the articulation of the first strip, costocartilage. This is the synchondrosis. And if you look closely here, this is the manabrium sternal joint. This constitutes what is known as the sternal angle of Louis. And if you were to take a look at it from the lateral aspect, and I'm turning it, you may be able to see a small anterior angulation, which of course is not so obvious in this model. That is the sternal angle. And in a living person and in yourself also, we can feel it in front of our chest. This is a very useful landmark because we cannot feel the first strip in a living person because it is covered by the clavicle. But we can feel the manabrium sternal angle of Louis. And we know that attached at the junction of the manabrium sternal joint is the second grid costocartilage. So once we have felt this, we know that the attached rib is the second one. And therefore we can count the intercostal spaces from there onwards. We know that this is the second intercostal space, third intercostal space, and so on and so forth. That is the importance of the manabrium sternal angle. Now let's come to the body here. Body, if you look very closely, it has got four segments. These are the embryonic remnants of what are known as sternipray, which correspond to the ossification centers. The manabrium comes from one ossification center, the sternum body comes from four ossification centers, or the sternipray, and the zephyrd process comes from one ossification center. Later on, after birth, they all fuse, and therefore they form a small ridge here. At the junction of fusion of the sternipray, we had the ribs. So starting from this one, we have the third rib here, we have the fourth rib, we have the fifth rib, we have the sixth rib, and of course the seventh rib fuses at the junction of the zephyr sternal joint. The second rib onwards junction with the sternum is a sanomial joint. So there is a small degree of movement possible. However, in old age, this articulation can get ossified. So this is the body of the sternum. This is the zephyrd process. This is the one which we can feel in our epigastrium, and therefore this is the zephyr sternal joint. Ideally, the seventh costal cartilage should be articulating here, and we can see that the seventh costal cartilage is articulating here. Sometimes the eighth costal cartilage can also articulate there. Let's mention the quick subdivisions of the sternum and use them to demarcate the mediastinum. This jugular notch corresponds to the upper border of vertebra T3. The mediasternal joint corresponds to the upper border of vertebra T5, and the zephyr sternal joint corresponds to T9 upper border. So therefore from this segment to this segment, this much is the superior mediastinum from here to here, from T5 to T9 is divided into an anterior middle and posterior mediastinum. So having subdivided the mediastinum into superior, inferior, anterior, middle and posterior mediastinum, let's now take a look at what are all the anatomical events that are taking place at the mediasternal joint level or the sternal angle of Louie, which we said is at the level of upper border of T5 vertebra. This is the place where the trachea divides into right and left principal bronchus. This is the place where the ascending aorta ends, the arch of aorta begins, the arch of aorta ends, the descending thoracic aorta begins. This is the level approximately where the pulmonary trunk divides, and this is the level where the thoracic duct deviates to the left, approximated to the level of T5 vertebra and goes to the left side. So these are all the anatomical events which are taking place at the level of the mediasternal angle of Louie, that is the T5 level. Antimidastinum is mostly empty, in children it can contain the thymus. We can have a superior sternopericardial ligament attached to the mediasternal and the pedicardium. We can have an inferior sternopericardial ligament attached to the pedicardium and to the zephoid process. These are some structures which can be present in the anterior mediastinum. Let's come to the muscles which are attached to each of these parts. Attached to the maripreum sterni, we have on the anterior surface is the sternal head of the sternocleid of mastoid muscle. If I turn it around, attached to the inner surface near the upper part, we have the sternohiaoid and the sternothiaeoid muscles, which are the intrahaeoid strap muscles. Attached to the jugular notch, we have the anterior and the posterior layers of the investing layer of deep cervical fascia. And in this location, there's a small space which is referred to as the suprasternal space of burns, which contains the jugular venous arch and a lymph node. Attached to the sides of the sternum, we have the sternocostal origin of the pectralis major along this. And on the inner surface of the sternum, we have attached the transversus thoracis muscle, which attaches by multiple slips like this. Three or four slips of the transversus thoracis, they constitute innermost layer of the intercostal muscles. And running on either side of the sternum on the inner surface, we have the internal thoracic artery and the internal thoracic vein, till the sixth space. So therefore this is the second, third, fourth, fifth, sixth space. And from the seventh space downwards, it becomes musculophrenic artery, which runs and it supplies the diaphragm. Let's come to a few clinical correlations pertaining to the sternum at this junction. Sternum surprisingly does not have too many clinical correlations. We can use the sternum for bone marrow biopsy, because it is filled with bone marrow inside, spongy bone inside. And therefore it can be used for bone marrow biopsy and bone marrow sphere. One more clinical correlation pertaining to the sternum refers to what is known as median sternotomy, when we split open the sternum in the midline to do an intrathoracic procedure. And thereafter we have to repair the sternum by means of steel sutures. Sternum fracture is not very common, but it can happen. Repeated punches to the chest can lead to sternum fractures. The sternum rarely can be biped because of failure of fusion of the two halves. And rarely there can be also an opening, again between failure of fusion of the two halves. When we are giving an external cardiac compression in cardiopulmonary resuscitation, we should usually compress in the lower half of the sternum. In old age, when we are giving a cardiopulmonary resuscitation, we can actually sometimes feel the costal cartilages and the sternocostal joints popping because they are calcified. And rarely they can also lead to surgical emphysema. It has also been documented that if by mistake if a person gives compression low down and over the zephysternal joint or below that, then the zephoid can fracture from the zephysternal joint and it can penetrate into the abdomen and can enter into the liver producing liver hemorrhage. So these are all the points which I want to mention about the sternum. Thank you very much for watching. Dr. Sanjay Sanyal is setting out. If you have any questions or comments, please put them in the comment section below. Please like and subscribe. Have a nice day.