Lung lobes and fissures play a fundamental role architecture of the human respiratory system. These structures not only demarcate the lungs’ anatomical divisions but also facilitate their essential function in gas exchange.
Understanding the configuration of lung lobes and fissures is crucial for comprehending how the lungs operate and how various respiratory diseases affect them.
This article explains the detailed anatomy of the lung lobes and fissures, highlighting their significance in both health and pathology.
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Lung Lobes and Fissures
The human lungs consist of five lobes, divided by fissures. The right lung has three lobes: the superior, middle, and inferior, separated by the horizontal and oblique fissures. The left lung has two lobes, the superior and inferior, separated by the oblique fissure.
Lung Lobes
A lung lobe is a large, distinct section of a lung, anatomically separated from other lobes by fissures. In humans, each lung is divided into lobes to increase its efficiency in gas exchange.
The right lung has three lobes – superior, middle, and inferior – while the left lung has two lobes – superior and inferior.
These lobes are made up of smaller segments called bronchopulmonary segments, which provide a systematic way for air to be distributed and exchanged in the lungs.
Lung Fissures
A lung fissure is a deep groove or cleft that separates the lobes of the lungs. In the human respiratory system, these fissures allow each lung to be divided into distinct lobes, facilitating efficient functioning and movement.
There are two types of fissures:
- Oblique Fissure: Present in both lungs, it separates the superior and inferior lobes. In the right lung, it also separates the inferior lobe from the middle lobe.
- Horizontal Fissure: Only found in the right lung, it divides the superior lobe from the middle lobe.
Note: These anatomical separations are important for both the organization of the bronchial tree and blood vessels, as well as for surgical procedures involving the lungs.
Anatomy of the Lungs
The anatomy of the lungs is intricate and designed for efficient gas exchange, crucial for respiration.
Here’s a general overview:
Right Lung
The right lung, larger and heavier than the left, is divided into three lobes – superior, middle, and inferior – by two major fissures.
- Superior Lobe: The topmost lobe, located just below the clavicle. It houses the apical segment, which is crucial for upper respiratory functions.
- Middle Lobe: Smaller and wedged between the superior and inferior lobes. Unique to the right lung, it plays a key role in ventilating the middle region of the thoracic cavity.
- Inferior Lobe: The largest lobe, occupying the bottom part of the lung. It extends from the base of the lung up to the oblique fissure.
The right lung is characterized by its broader and shorter structure due to the liver’s position beneath it. It contains three fissures:
- Oblique Fissure: Separates the inferior lobe from the superior and middle lobes.
- Horizontal Fissure: Divides the superior and middle lobes.
The bronchial tree of the right lung is more vertical and wider than the left, making it more prone to inhaled objects getting trapped.
Left Lung
The left lung is smaller due to the heart’s placement in the thoracic cavity and is divided into two lobes – superior and inferior – by a single oblique fissure.
- Superior Lobe: Extends from the top of the lung to the oblique fissure. It includes the lingula, a tongue-like projection that corresponds to the middle lobe of the right lung.
- Inferior Lobe: The larger lobe, occupying the lower half of the left lung. It is involved in the lower respiratory functions.
The left lung has a notable feature called the cardiac notch, an indentation on the lung’s surface to accommodate the heart. The bronchial tree in the left lung is more horizontal and narrower than in the right, influencing the pattern of air flow and distribution.
Note: Both lungs share similarities in their structure and function, with the main differences arising from their adaptation to accommodate other organs in the thoracic cavity.
FAQs About Lung Lobes and Fissures
What is the Difference Between a Fissure and a Lobe?
A fissure in the lungs is a deep groove or separation that serves as a boundary between different sections, known as lobes. These fissures create clear divisions between the lobes, which are large, distinct regions of the lungs.
Each lobe functions as a semi-independent unit, with its own bronchial tree, blood supply, and clusters of alveoli that facilitate the exchange of oxygen and carbon dioxide during respiration. While fissures act as the dividing lines, the lobes work together to maintain efficient lung function.
Which Lung Has Two Fissures and Three Lobes?
The right lung has two fissures and three lobes. The fissures are the oblique fissure and the horizontal fissure, which create the anatomical divisions between the lung’s three lobes: the superior (upper), middle, and inferior (lower) lobes.
The presence of two fissures allows the right lung to be divided into these three sections, each performing specific roles in the breathing process.
What is the Main Fissure of the Lungs?
The primary fissure in both lungs is the oblique fissure. In the right lung, it separates the superior lobe from the inferior and middle lobes, while in the left lung, it divides the superior and inferior lobes.
The oblique fissure is a significant anatomical feature, playing a key role in partitioning the lungs into functional sections, which helps optimize the flow of air and blood through each lobe.
What is the Fissure of the Left Lung?
The left lung contains only one fissure, called the oblique fissure. This fissure separates the left lung into two lobes: the superior and inferior lobes.
Unlike the right lung, the left lung lacks a horizontal fissure due to space limitations created by the heart’s position on the left side of the thoracic cavity, which reduces the size and complexity of the left lung’s structure.
What is a Pleural Fissure?
A pleural fissure refers to an incidental finding on lung imaging, such as a chest X-ray or CT scan, which appears similar to a true lung fissure but does not represent a natural anatomical division. It typically manifests as a thin, linear shadow and is often caused by the folding or movement of the pleural membranes or nearby structures.
These pseudo-fissures are distinct from the actual fissures that divide the lung lobes and usually have no significant impact on lung function.
What Fissure is Between the Right Upper and Middle Lobe?
The horizontal fissure is the anatomical division between the right upper (superior) lobe and the middle lobe. It runs horizontally across the lung, creating a boundary that separates these two lobes from each other.
This fissure is unique to the right lung, contributing to the distinct three-lobed structure that the left lung lacks.
Why Does the Left Lung Only Have Two Lobes?
The left lung has only two lobes—the superior and inferior lobes—primarily because of the space taken up by the heart in the left side of the chest cavity.
The heart’s position reduces the room available for the lung, which results in a simpler structure with fewer lobes compared to the right lung. This adaptation allows the left lung to function efficiently despite its reduced size.
How Many Fissures Does the Right Lung Have?
The right lung has two distinct fissures: the oblique fissure and the horizontal fissure. The oblique fissure divides the inferior lobe from the superior and middle lobes, while the horizontal fissure separates the superior lobe from the middle lobe.
These two fissures are key to the three-lobed structure of the right lung, which facilitates optimal lung function.
Final Thoughts
Lung lobes and fissures are more than just anatomical features; they are vital to the lung’s functionality and overall respiratory health.
The distinct lobes of the right and left lungs, separated by the oblique and horizontal fissures, facilitate efficient gas exchange and adapt to the unique spatial constraints within the thoracic cavity.
Recognizing the nuances of these structures aids in the diagnosis and treatment of pulmonary conditions, underscoring their importance in the field of pulmonology and respiratory care.
Written by:
John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.
References
- Kc S, Shrestha P, Shah AK, Jha AK. Variations in human pulmonary fissures and lobes: a study conducted in nepalese cadavers. Anat Cell Biol. 2018.