Corpus: Ciliated respiratory epithelium

The respiratory epithelium is a layer of specialised epithelial cells that lines most of the airways. It is characterised by cilia (kinocilia) on the lumen-side cell surface (apical cell pole).

The respiratory epithelium is a multi-row, highly prismatic epithelium, which is equipped with kinocilia and goblet cells. The goblet cells within the epithelium physiologically make up between 15 and 20 % of the epithelium. All cells are connected to the relatively pronounced basal lamina.

The thickness of the ciliated epithelium decreases continuously along the bronchial tree towards the alveoli. The bronchioli terminales only have a single-layered ciliated epithelium.

Cinocilia-bearing cells[Bearbeiten]

They make up the main part of the cells of the ciliated epithelium. Their kinocilia at the apical cell pole are mobile protrusions of the cell membrane, which are about 7 to 10 µm long and have a diameter of about 0.3 µm. Their motility is ensured by so-called microtubules.

Goblet cells[Bearbeiten]

The goblet cells are unicellular, goblet-shaped, intraepithelial glands that produce bronchial mucus in addition to the serous and mucous glands of the lamina propria. The mucins secreted by these glands cover the epithelium and moisturise the air passing through.

Cleft lobe cells[Bearbeiten]

The club cells, formerly Clara cells, are secretory cells that are mainly found in the distal part of the airways. They are found, for example, in the bronchioli and in the alveolar ducts. They produce a glycoprotein-containing secretion.

Pulmonary neuroendocrine cells[Bearbeiten]

Pulmonary neuroendocrine cells (PNEC) are rare and act as sensors in the airways, releasing neuropeptides and neurotransmitters in response to mechanical or chemical stimulation.

Other cells[Bearbeiten]

In addition to these two cell types, the ciliated epithelium also has sensory cells that have contact with afferent nerve fibres at their basal pole. They trigger the cough or sneeze reflex when stimulated. The basal cells are a precursor of the mature epithelial cells and ensure cell replenishment.

Ciliated epithelium has a sophisticated self-cleaning mechanism known as mucociliary clearance (MCC). The mobile kinocilia line the airways like a dense lawn. Their coordinated movement is orientated towards the pharynx. As a result, bronchial mucus and smaller foreign bodies and microorganisms that have entered the airways are constantly removed from the airways.

The respiratory epithelium is not used for gas exchange - even if the name suggests it.

Respiratory epithelium is found in the following places:

• Upper airways
  • Paranasal sinuses (e.g. frontal sinus, maxillary sinus)
  • Nasal cavity (Regio respiratoria nasi)
  • Epiglottis (laryngeal side)
  • Palatum molle (nasal side)
  • Epipharynx (upper part)
  • Larynx
  • Tuba auditiva
  • Tonsilla pharyngea
• Lower respiratory tract
  • Trachea
  • Bronchi (except at bifurcations)
  • Bronchioles