Which lobes does the oblique fissure separate?
The lungs (pulmones) are paired asymmetric organs of the thoracic cavity, separated by the mediastinum. The oblique fissure is the main structure forming their lobar architecture. It is visible in all projections (anterior, posterior, and lateral).
- In the left lung — the organ consists of two lobes. The oblique fissure separates the superior lobe (lobus superior), occupying the upper regions of the thoracic cavity, and the inferior lobe (lobus inferior), the main mass of which is located in the posteroinferior regions.
- In the right lung — the organ consists of three lobes. Here, the oblique fissure separates the superior and middle lobes (lobus medius) from the inferior lobe.
Additionally, the right lung features a horizontal fissure (fissura horizontalis), which branches off from the oblique fissure on the costal surface and demarcates the superior lobe from the middle lobe.
How is the oblique fissure projected onto the thoracic wall?
The projection of the oblique fissure (fissura obliqua) is identical for the right and left halves of the thorax. Its topographic line runs through the following landmarks:
- Origin — posteriorly, at the level of the spinous process of the third thoracic vertebra (Th3).
- Course of the line — the fissure runs obliquely downward and forward, curving around the thorax along the outer (costal) surface, which is adjacent to the ribs.
- Termination — anteriorly, at the 6th rib along the mid-clavicular line, at the transition of the bony part of the 6th rib into the cartilaginous part.
Topographic relationship with the horizontal fissure
The middle lobe (lobus medius) is only present on the right, so the horizontal fissure is considered in relation to the right lung.
- Site of confluence — the horizontal fissure joins the oblique fissure on the outer surface of the lung. Topographically, this point is projected at the level of the 5th rib along the mid-axillary line.
- Further course — from the intersection with the oblique fissure, the horizontal fissure runs forward, corresponding to the projection of the 4th rib, and ends at the attachment site of the 4th rib cartilage to the sternum.
Anatomic context and surfaces of the lung
The lungs are paired organs located in the thoracic cavity. The lung tissue is elastic, spongy, and pinkish-gray in color.
Each lung has an apex (apex pulmonis), a base (basis pulmonis), and surfaces:
- Costal surface (facies costalis) — adjacent to the ribs.
- Mediastinal surface (facies mediastinalis) — adjacent to the mediastinal organs.
- Diaphragmatic surface (facies diaphragmatica) — adjacent to the diaphragm.
The lung apex projects above the clavicles. The mediastinal surface features the hilum of the lung (hilum pulmonis), through which the main bronchus, pulmonary artery, and pulmonary veins pass. Together, these structures form the root of the lung (radix pulmonis). The right dome of the diaphragm is positioned higher than the left.
Class and exam questions
In which lung is the oblique fissure located?
The oblique fissure (fissura obliqua) is present in both lungs — right and left. Unlike it, the horizontal fissure is only present in the right lung.
Where does the projection of the oblique fissure begin and end?
The projection begins posteriorly at the level of the spinous process of the third thoracic vertebra (Th3). Then the line runs obliquely downward and forward, ending anteriorly at the 6th rib, at the transition from bone to cartilage, along the mid-clavicular line.
Where does the oblique fissure join the horizontal fissure?
This confluence occurs in the right lung on the outer surface. The point of their junction is projected at the level of the 5th rib along the mid-axillary line.
Which lobes does the oblique fissure separate in the left lung?
In the left lung, which consists of only two lobes, the oblique fissure separates the superior lobe (lobus superior) and the inferior lobe (lobus inferior).
What else to study on this topic
- Horizontal fissure of the right lung
- Lung lobes (lobi pulmones)
- Topography and borders of the lungs
- Root and hilum of the lung
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