General information
The bronchial system refers to the airways of the lungs. It is divided into an air conducting and a respiratory part. The air-conducting part is the sole conduit for breathing air and consists of the main bronchi and the bronchioles.
It is also known as dead space, as no gas exchange takes place here. The respiratory part, which is responsible for the exchange of oxygen-poor blood for oxygen-rich blood, consists of the smaller bronchioli and the alveoli. Especially in the winter and autumn months, infections of the upper respiratory tract are a very common clinical picture, which is why those affected go to their family doctor.
In addition to the nose and throat, in many cases the lungs with the associated bronchi (bronchitis) are also affected. – Right lung – Pulmo dexter
- Left lung – Pulmo sinister
- Nasal cavity – Cavitas nasi
- Oral cavity – Cavitas oris
- Throat – Pharynx
- Larynx – Larynx
- Trachea (approx. 20 cm) – Trachea
- Forking of the trachea – Bifurcatio tracheae
- Right main bronchus – Bronchus principalis dexter
- Left main bronchus – Bronchus principalis sinister
- Tip of the lung – Apex pulmonis
- Upper lobe – Lobus superior
- Oblique lung cleft – Fissura obliqua
- Lower lobe – Lobus inferior
- Lower edge of the lung – Margo inferior
- Middle lobe (only for the right lung) – lobus medius
- Horizontal cleft lung (between upper and middle lobe on the right) – Fissura horizontalis
Histological structure
The large bronchial tubes contain a multi-row, highly prismatic ciliated epithelium. The smaller the bronchial tubes become, the simpler the structure of the epithelium becomes. In the bronchioles, single-layer iso- or high-prismatic ciliated epithelium predominates.
Under the epithelial layer there is smooth musculature. The muscle layer increases with the smaller diameter of the bronchioles. In addition, the bronchi contain elastic fibres as well as mucosal and serous glands.
The ducts of the glands end in the bronchi and cover the mucous membrane with a protective film. On the very outside of the large bronchi there is a layer of cartilage which stabilises the bronchial wall. The gas exchange takes place in the smallest parts of the bronchial system, the alveoli.
These are bag-like extensions consisting of the small alveolar cells (pneumocytes type I) and the large alveolar cells (pneumocytes type II). Pneumocytes type I are used for epithelium formation, pneumocytes type II form surfactant. This reduces the surface tension of the alveoli and prevents their collapse. In addition, alveolar macrophages serve to clean the alveoli by phagocytising dust, or after bleeding, to break it down.
Structure of the bronchial system
The entire bronchial system is made up of different types of bronchi. It begins with the trachea and the two large main bronchi. These large main bronchi are then divided in the two lungs and branch out to the tips of the lungs. In this way, the bronchi become smaller and smaller until they are called alveoli, where the actual gas exchange takes place. The individual bronchial tubes have different structures and are described in more detail below:
