Index
The human lungs are divided into multiple smaller sections by fissures. These sections are called pulmonary lobes.
The number of lobes varies between the right and left lungs in a normal human being. The right lung has three upper, middle, and lower lobes.
There are only two lobes in the left lung, the upper and lower lobes, unlike the right lung.
The left lung is a little smaller than the right lung because it has to leave space for the heart on the left side of the chest cavity. As a result, the right lung is more significant and has three lobes, while the left has only two.
The function of the pulmonary lobes
All lung lobes have the same primary function: to receive oxygen-rich air as it travels through the respiratory tract and harbor oxygen and carbon dioxide exchange in the alveoli.
It is possible to remove one of the lobes surgically (lobectomy) in a life-threatening situation, such as in a severe case of tuberculosis or lung cancer.
This affects the lung’s ability, but the person can still lead a normal lifestyle in most cases.
Segments of the pulmonary lobes
In the right lung
Right upper lobe:
- Apical segment.
- Subsequent segment.
- Previous segment.
Middle lobe:
- Lateral segment.
- Medial segment.
Right lower lobe:
- Upper segment.
- Segmento basal medial.
- Previous basal segment.
- Segmento basal lateral.
- Posterior basal segment.
In the left lung
Although the left lung has only two lobes, an evident projection from the upper lobe, known as the lingula, has two segments.
Upper left lobe:
- Apicoposterior segment.
- Previous segment.
Lingula:
- Upper lingual segment.
- Lower lingual segment.
Lower left lobe:
- Upper segment.
- Segmento anteromedial.
- Lateral segment.
- Subsequent segment.
The lingula is equivalent to the middle lobe of the right lung in the left lung.
Lungs
Oblique fractures: separates the upper lobe of the lower lobes of both lungs.
Horizontal fissure: present only in the right lung, separating the middle lobe of the upper and lower right pulmonary lobes.
Supply of air to the pulmonary lobes
After entering the lungs, the right bronchus divides into three lobar bronchi, while the left bronchus divides into two lobar bronchi, one for each pulmonary lobes.
These lobar bronchi are divided into tertiary or segmental bronchi. There are ten tertiary bronchi in the right lung and 9 in the left, so each lung segment is supplied by one of these bronchial branches.
The tertiary bronchi branch out into bronchioles to drive the inhaled air to the alveoli.
Anatomy of the right upper lobe
The right upper lobe of the lung is located in the upper right corner of the thoracic cavity lateral to the trachea and esophagus. It is superior to horizontal and oblique fissures, which separate the upper lobe from the middle and lower lobes of the right lung.
The right upper lobe begins at the apex, the slightly superior tip of the lung. From the height, the upper lobe widens and extends laterally, where its convex curvature follows the interior of the rib cage.
At its medial end, the right upper lobe is concave and has several prominent notches that accommodate the trachea, esophagus, and major blood vessels of the mediastinum.
The root of the right lung, which contains the primary bronchus, blood vessels, and nerves entering the lung, protrudes just below the right upper lobe.
The air enters the root of the right lung through the right primary bronchus, which is divided into three secondary bronchi. The right upper lobar bronchus extends upward to provide air to the right upper lobe of these three secondary bronchi.
Within the right upper lobe, the superior lobar bronchus divides into three tertiary bronchi, which provide air to the three bronchopulmonary segments: apical, anterior, and posterior.
The apical segment includes the apex tissue and extends medially to the root of the lung. The anterior and posterior segments constitute the anterior and posterior regions, respectively, of the lower areas of the upper lobe.
Physiology
The air inhaled during respiration passes through the upper respiratory tract and the trachea on its way to the lungs. The primary bronchi separate to bring perspective to each lung at the lower end of the trachea.
The air in the right primary bronchus is divided between the three lobes by the secondary bronchi in the right lung.
The upper right lobar bronchus carries air to the right upper lobe, extending through the tertiary bronchi in each bronchopulmonary segment.
Each segment is filled with small bronchioles extending throughout the lung tissue and branching into terminal bronchioles. All terminal bronchioles end in a group of cup-like structures known as alveoli.
Each alveolus is made of a simple squamous epithelium surrounded by tiny capillaries.
When the air reaches the alveoli, the walls are so thin that the gases diffuse and concentrate between the blood in the capillaries and the air inside the alveoli.
Oxygen, which is at a higher concentration in the air, diffuses into the blood to be transported to the body’s tissues.
