Lungs – Pulmonary Structures and Esophagus

by Craig Canby, PhD

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    00:01 The next slide that we’ll see will help you understand the various structures that are associated with the lungs in situ. And those structures will be the lobes, fissures and then two specific features that we see associated with the left lung: the cardiac notch and the lingula.

    00:24 Here’s your right lung. It has two fissures. One here: this is called the transverse fissure.

    00:34 We also have a little bit shown here of the oblique fissure. These two fissures help divide the right lung into its three lobes: a superior lobe, a middle lobe. And then we’re just seeing a very small portion of a large inferior lobe to the right lung.

    00:58 The left lung only has one fissure. It too is obliquely oriented and we just see kind of the terminal aspect of that oblique fissure here. That then means everything above the oblique fissure belongs to the superior lobe of the left lung. And then we’re seeing just a little bit of a much larger inferior lobe below the fissure.

    01:24 Two structural features of the superior lobe of the left lung would be the cardiac notch that we see here. And you can see it receives the heart as it projects to the left of the midline. And then this tongue-like extension here more inferiorly, but yet still associated with the superior lobe is referred to as the lingula.

    01:52 Each lung is going to present an apex, base and surfaces. The apex of the lung, this is the right lung, three lobes, the apex is shown here. And then the base is opposite the apex and is best demonstrated here. And we can see that the base of the lung is concave because of its relationship with the respective dome of the diaphragm. So, the right lung with its base will be related to the right dome of the diaphragm. The concave surface of the base of the left lung will be related to the left dome of the diaphragm. And then the surfaces of the lung: there are two. We have a more extensive costal surface, which is everything we see here. And then we’ll also be seeing here more posteriorly.

    02:49 So, it has relationships to the rib cage.

    02:53 The mediastinal surface is this area here and this is the surface of the lung that will face the mediastinum.

    03:02 Here we have the right lung in isolation and we can better appreciate the two fissures that are associated with the right lung as well as the fact that the lung has three lobes.

    03:17 Here is your transverse or horizontal fissure and then here we can see more clearly the extent of the oblique fissure. These two fissures then will separate the right lung into a superior lobe, a middle lobe and then this extensive inferior lobe that we see here. And again the lobes are supplied by secondary bronchi.

    03:51 Here we’re looking at the left lung. It only has one fissure: the oblique fissure.

    03:56 And so, we see the extent of the oblique fissure here. The area of lung above is the superior lobe. The area of the lung below our oblique fissure is going to be the left lobe.

    04:09 And again, we can see the cardiac notch.

    04:12 And you can see the lingula associated with that superior lobe.

    04:19 On the following slide, you’ll be able to understand the next concept about the lung and that is the hilum of the lung. The hilum represents the gateway into and out of the lung. This gateway provides for the entry of our respiratory passageways, the entry of our pulmonary artery and its subsequent branching pattern and then the exit of the pulmonary veins that will conduct blood back to the left atrium.

    04:51 And so, if we take a look here, we have the right lung above, its hilum is shown here.

    04:58 Down below, we have the hilum that’s associated with the left lung. And we can also see an outline here of the pleura. And so, here the pleura is approaching the lung surface itself and then it’s going to spread out and adhere to the lung and become the visceral pleura.

    05:22 And where that reflection is happening below the hilum, you’ll have this region here of pleural membranes that constitutes what is known as the pulmonary ligament.

    05:36 In the left lung, its hilum will also have a pulmonary ligament.

    05:42 Now, within the hilum, we’ll have a relationship of the airways to the vascular structures.

    05:47 It’s going to be a bit different between the right lung and the left lung.

    05:55 In the hilum of the right lung, your airways are located here in the posterior superior aspect of your hilum. If you look anterior to it, I can see the right pulmonary artery entering the hilum and it will start to branch. And then anterior to the artery and inferior to the artery and airway, you have your two pulmonary veins that are leaving the lung to transport blood back to the left atrium.

    06:26 In the left hilum, here is your airway posteriorly located, but if you look here, the artery is immediately above or superior to your airway. And then your veins lie anterior and inferior to those particular structures.

    06:45 There is a mnemonic to help your remember the anatomic relationship of the pulmonary artery to the airway in each hilum. That mnemonic is RALS. RALS stands for Right is Anterior and Left is Superior. So, in the right hilum, the artery is anterior to your airway and in the left the artery is superior to your airway.

    07:17 The following slide will introduce you to the concept of bronchopulmonary segments.

    07:23 Bronchopulmonary segments are their own individual anatomic unit. Each one is supplied by its own respiratory passageway. Each one is supplied by its own artery and also drains by its own venous system. The bronchopulmonary segments are also separated from one another by connective-tissue septum.

    07:49 As a consequence of these being their own individual units, it is possible to surgically resect or remove each one of these pieces like you would a piece from a jigsaw puzzle.

    08:04 The slide that you now see shows the various bronchopulmonary segments in the right lung.

    08:12 Each coloured region represents a separate bronchopulmonary segment. Here we see the numbering in a costal view. And then here is the mediastinal view of the right lung.

    08:26 And if you look at the numbering, you will see that there are 10 bronchopulmonary segments identified and this is what is normal in the right lung. The left lung will typically have two less bronchopulmonary segments. Thus, we’re at 8. However, it may in some cases have 9 or even 10.

    08:51 Here is the left lung in its costal view. And then, here’s the left lung in its mediastinal view. And if you count the number of each coloured segment here, you will see that there are 9. But, if you look at the numbering system, you’ll see that 10 is the maximum number here. And it’s missing one, so this really only shows 9, but that is within anatomic variation. And again you can kind of appreciate how you could surgically resect or remove each one of these units. And so, if there’s tumour involvement in two of the segments, you then remove those surgically and then you can leave the other bronchopulmonary segments intact or in place. And each segment is supplied by a tertiary or segmental bronchus.

    09:48 The bronchi can be visualized, if necessary, with bronchoscopy. And so, here we see a bronchoscopic view. And we’re at the level where we can actually see the segmental bronchi. So, here’s a segmental or tertiary bronchus, here’s another. Here’s one leading off here to the left. Above at this branching point we see some additional segmental or tertiary bronchi.

    10:26 This particular slide is demonstrating an area within a bronchopulmonary segment. This region of tissue within the bronchopulmonary segment is referred to as a pulmonary acinus.

    10:43 Each pulmonary acinus is going to be fed by a type of bronchiole called the terminal bronchiole.

    10:50 Terminal bronchioles will branch from your primary bronchioles. And so, this bronchiole that we see here is a terminal bronchiole. And the area defined within the region here represents the pulmonary acinus. Within the pulmonary acinus and even smaller divisions upstream of this level, what you’ll see is the pulmonary artery will follow the branching pattern of the bronchus or the airway. In this case, we’re at the level of the bronchioles.

    11:28 Venous blood is going to be drained at the periphery of this organizational unit, the acinus.

    About the Lecture

    The lecture Lungs – Pulmonary Structures and Esophagus by Craig Canby, PhD is from the course Thoracic Viscera.

    Included Quiz Questions

    1. 1
    2. 2
    3. 3
    4. 4
    5. 5
    1. Concave
    2. Slanted
    3. Straight
    4. Convex
    5. Wedge-like
    1. There are 2 more in right
    2. There are 3 more in right
    3. There are 2 less in the right
    4. There is 1 less in the right
    5. The same are found in both
    1. The pattern of the division of the bronchioles
    2. The pattern of the veins
    3. The pattern of the lymph vessels
    4. They travel superficially in their own unique pattern
    5. They travel on the superior surfaces of the alveoli only
    1. Tertiary
    2. Secondary
    3. Primary
    1. Superior lobe of left lung
    2. Inferior lobe of left lung
    3. Superior lobe of right lung
    4. Inferior lobe of right lung
    5. Middle lobe of right lung

    Author of lecture Lungs – Pulmonary Structures and Esophagus

     Craig Canby, PhD

    Craig Canby, PhD

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