 Hello everyone, I am Dr. Reina Tembe and today we shall be discussing about the normal anatomy of the tracheobronchial tree and how to identify the various low bar and segmental bronchi. We have here a CT chest with a lung window setting in an egg shell and coronal plane. Let us start by having a look at the trachea. The trachea is a midline structure that divides at the level of carina into the right and the left main stem bronchus. These main stem bronchi then further divide into the various low bar and segmental bronchi. We shall first have a look at the right main bronchus followed by the left main bronchus. As we can see in this coronal plane, the right main bronchus is dividing into the right upper low bar bronchus and bronchus intermedius. We shall go to the egg shell plane now and identify the various low bar and segmental bronchi. This is the egg shell plane at the level of carina. We see the right main bronchus and the left main bronchus. This is the upper low bar bronchus arising from the right main bronchus. We shall be following this upper low bar bronchus now. So let us scroll through these images. As we scroll superiorly, we see that a segmental branch is arising from the upper low bar bronchus. This is going superiorly towards the apex of the right upper low. This will be the apical segment of the right upper low. As we go down inferiorly, we see that the upper low bar bronchus is dividing into two segments. The one which is going anteriorly is the anterior segmental bronchus. So this here is the anterior segmental bronchus and the one which is going posteriorly is the posterior segmental bronchus. Now as we go inferiorly, we see the bronchus intermedius. This bronchus intermedius divides into the middle low bar bronchus and the lower low bar bronchus. The middle low bar bronchus has two segments. The one segment which goes medially. We can see that this segment which is arising from the right middle low bronchus is going medially. It will be the medial segmental bronchus and the one which is going laterally will be the lateral segmental bronchus. We go back up again at the level of bronchus intermedius and identify its division and then identify the lower low bar bronchus. The first division that is coming is the superior segmental bronchus. We go inferiorly and identify one more segment which is arising from the medial aspect. This segment is the medial segmental bronchus as it is going towards the medial basal segment of the right lower low. The lower low bar bronchus then divides into three segments. We can see that this bronchus is dividing into three segments. This segment which is going anteriorly will be the anterior segmental bronchus. This segment we trace it and we see that it is going laterally. This will be the lateral segmental bronchus and this segment which is going posteriorly is the posterior segmental bronchus. Let us now have a look at the anatomy of the left bronchial tree. We go back to our coronal plane, see the trachea right and the left main bronchus. Let us scroll through these images now. We can see that the left main bronchus is dividing into the upper low bar bronchus and the lower low bar bronchus. So we go back to our axial plane at the level of carina, identify the left main bronchus and follow this left main bronchus now. As we follow this left main bronchus and scroll through the images, we can see that it is dividing into the upper low bar bronchus and the lower low bar bronchus. Now let us first have a look at the anatomy of the upper low bar bronchus. The upper lobe of the left lung has four segments. A pycoposterior segment, anterior segment, superior and inferior lingular segment. We shall be identifying the various segmental bronchi now. We go back to the level of the left main bronchus and we now identify the left upper low bar bronchus. So this is the upper low bar bronchus. Now we are going to go through periodically again. So when we scroll upwards, we see that there is a segmental branch which is going towards the apical and posterior aspects of the left upper lobe. This branch will be the apicoposterior segmental branch of the left upper lobe. As we go inferiorly, we see another branch which is arising and going anteriorly. So we trace this branch and we see that it is going anteriorly. This is the anterior segmental bronchus. When we go further inferiorly, we see another bronchus. This is the lingular bronchus. This lingular bronchus will be dividing into superior and inferior lingular segments. It shall be easier for us to identify these segments on the coronal plane. So we are going to switch back to the coronal image. We can see the left main bronchus here. We can see the upper low bar bronchus. Now follow this upper low bar bronchus. As we follow this upper low bar bronchus, we see the first division which is the apicoposterior segmental bronchus. Now we follow this segment which is going anteriorly. We see that there are two segments arising anteriorly. The one which is superior is the anterior segmental bronchus and the one which is inferiorly is the lingular segmental bronchus. Now we follow this lingular bronchus and we see that it is dividing into two segments, the superior and inferior lingular segments. Now we shall have a look at the left lower low bronchus. So let us go back to our axial plane and we identify the left main bronchus. As we scroll inferiorly, we identify the upper low bar bronchus and the lower low bar bronchus. The first division arising will be the superior segmental bronchus. As we go inferiorly, we see that the left lower low bar bronchus is dividing into three segments. The one which is going towards the anterior and medial aspect of the left lower low will be the anterior medial segment. Let us trace this back again. Here we can see that this segment is the anterior medial segment. Now we go back at the division of the left lower low bar bronchus and identify this segment. Now this segment is going laterally and will be the lateral segmental bronchus. This another segment which is going posteriorly will be the posterior segmental bronchus.