The pulmonary lobes are the well-defined sections into which the lungs are divided, demarcated by a series of folds in the membrane that covers these organs.
A lobe refers to the rounded, protruding part of an organ, which marks a clear division or extension of the organ, and which can be determined without the use of a microscope . A lobe marks the division of an organ through a fold or indentation on its surface.
The lungs are two of the organs of the human anatomy (and of other mammals) that are divided by lobes. These lobes allow the lungs to be divided into sections, which at a scientific and medical level facilitates their study and understanding, while at the level of the human body, they allow the extension of these in respiration.
The lungs in humans belong to the respiratory system and are located in the rib cage. These are classified into two; the left lung and the right lung , both divided into lobes.
Both lungs present some differences between them, although they both perform the same function. The left lung is slightly smaller, in order to make room for the heart, and both are divided by the so-called pulmonary lobes.
These lobes divide the lungs into two and three sections. The right lung, which is larger, has three lobes: upper , middle, and lower . While the left lung, smaller in size, has two lobes: lower and upper . In addition, the pulmonary lobes are in turn divided into bronchopulmonary segments .
The lungs are covered by a membrane called the pleura , made up of connective tissue, which prevents the lungs from rubbing directly with the inner wall of the rib cage.
The pulmonary lobes are formed by the formation of folds in the pleura , which give rise to the so-called interlobar fissures , which demarcate the division of the lungs between the lobes.
Fissures of the lungs
It has been mentioned that each lung (right and left) has its own number of lobes; three lobes in the right lung and two lobes in the left. Thus, the lungs in turn present a different number of interlobar fissures each.
Both lungs share one of the fissures , while only the right, which has one more lobe than the left, also has another fissure.
Therefore, the left lung has two lobes, divided by a fissure, while the right lung has three lobes, which are divided by two fissures.
The fissure that both lungs have in common is called oblique fissure , while the right lung also has another fissure, called horizontal fissure , which together with the oblique fissure , form the three lobes of the right lung.
Left lung fissures
The left lung, divided into two lobes, has a single interlobar fissure, which it also shares with the right lung, but which divides two different lobes, through the difference in the number of lobes of these.
The oblique fissure is the fold of the pleura that divides the upper and lower lobes of the left lung.
This fissure extends to the mediastinum (anatomical compartment where the heart is located, among other structures), and both above and below the pulmonary hilum (triangular depression, where the structures that form the root of the lung enter and leave the viscus) .
Right lung fissures
The right lung, as mentioned, shares the oblique fissure with the right lung , which divides two of the three lobes that make it up. But, in addition to this, the right lung has another fissure, called a horizontal fissure .
The horizontal fissure is the one that is found higher, and that begins in the oblique fissure , near the posterior border of the lung, and advances horizontally forward, cutting the anterior border at the same level as the sternal end of the fourth costal cartilage. This fissure is what separates the lower and middle lobes, the latter being the one that only has the right lung.
The oblique fissure , which lies lower, is closely aligned with the oblique fissure of the left lung. This fissure is what separates the middle lobe from the upper lobe in the right lung.
Classification of the pulmonary lobes
The left lung is smaller than the right lung, due to the presence of the heart, so it has a single fissure, which divides it into two lobes. These lobes are the upper lobe and the lower lobe.
The left lung also has a projection of the upper lobe called the lingula , which means “small tongue.” This language serves as an anatomical parallel to the middle lobe of the right lung.
Each lobe of the left lung is divided into bronchupulmonary segments. The upper lobe is divided into the anterior and apicoposterior segments . The lower lobe is divided into the upper , anterior , posterior , middle, and lateral segments . Also, the lingula is divided into the upper and lower segments .
On the other hand, the right lung, being larger than the left, is divided into three lobes, separated from each other by oblique and horizontal fissures. The lobes of the right lung are called superior and inferior, plus the middle lobe, which differentiates it from the left lung.
Similarly, the lobes of the right lung are divided into bronchopulmonary segments. The upper lobe is divided into apical , anterior, and posterior. The middle lobe is divided into the medial and lateral segments . And the lower lobe is divided into the upper , anterior , posterior , middle and lateral segments .
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