Okay, let’s get into some basic anatomy of the lungs. First off it is critical for you to know that there is an “anatomic” position, meaning there is a standard convention for locating body parts. A person could be pictured laying on their back with hands down at their sides and palms up. Viewing is done from head/cranial/cephalad to feet/caudad with the patient’s right side of their body appearing on the left side of the image. For chest X-ray this usually not a problem. The heart is on the left, virtually always (situs inversus!).
The chest/thorax contains two lungs, conveniently named right and left. The right lung has 3 lobes. The left lung has 2 lobes. The lobes are separated by fissures/clefts and membranes surrounding each lobe. These fissures may or may not be visible on chest X-ray, but are always seen on CT scan.
Right Lung: The right lung has upper, middle, and lower lobes.
The minor/horizontal fissure separates the right upper lobe from the right middle lobe and is seen best on the frontal view.
The major/oblique fissure separates the right upper lobe, and right middle lobe from the right lower lobe and is seen best on the lateral view.
As you can see from this lateral image, the right lower lobe actually overlaps with the right upper and right middle lobes on the frontal view as depicted below.
Left Lung: The left lung has only two lobes separated by an oblique/major fissure. However, the left upper lobe includes the lingula, which anatomically corresponds to the middle lobe on the right lung. But it is not demarcated by a left minor/horizontal fissure, hence only two lobes.
The oblique fissure best seen on the lateral view shows the upper and lower lobes.
On this lateral image, there is shown tremendous overlap between the left upper and left lower lobes on the frontal view.
Okay that was a quick tour of some very basic chest X-ray anatomy where we only talked about the lungs, and just the lobes! There is much deeper anatomy than that and maybe we will touch on segmental airway anatomy when we tackle CT of the chest, but for now this is definitely enough. I think we will continue next time with more anatomy covering the heart and mediastinum (all the stuff in the middle of the chest). I was given some advice today to shorten my articles and make them more accessible to the lay public. Believe me I am trying. Medicine has a language to itself, seriously!
So if you can think of anyway I can make this more simplified, please help me by sounding off in the comments below.
Images within post from prior powerpoint. Appreciate the help!