Ciliated epithelium

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Electron micrograph

The ciliated epithelium, or respiratory epithelium, is a layer of specialized epithelial cells that lines most of the airways . It is characterized by cilia (cilia) on the lumen- side cell surface. Even if the name suggests, the respiratory epithelium is not used for gas exchange, but for cleaning the airways .

Fine tissue structure

The respiratory ciliated epithelium is a multi-row, highly prismatic epithelium that is equipped with cilia and goblet cells . Physiologically, the goblet cells within the epithelium make up between 15 and 20 percent of the epithelium. All cells are connected to the basement membrane .

The thickness of the ciliated epithelium continuously decreases along the bronchial tree in the direction of the alveoli . The bronchioles ( bronchioli terminales ) located just in front of the alveoli only have a single layer of ciliated epithelium.

Cilia-bearing cells

They make up the main part of the cells of the ciliated epithelium. Cilia are mobile protuberances of the cell membrane at the apical cell pole that are about 7-10 µm long and about 0.3 µm in diameter. Their motility is ensured by so-called microtubules . These cilia move symbolically like ears in the wind and through this movement transport mucus and unwanted substances out of the lungs and usually trigger a coughing stimulus. According to the latest research results, in addition to this purely mechanical task, they also have a sensory function. If, for example, bitter substances such as nicotine or quinine come into contact with cilia-bearing cells, the calcium concentration inside the cell increases, the cell is activated as a whole and starts the reaction to remove pollutants from the lungs.

Goblet cells

The goblet cells are unicellular, cup-shaped glands that - in addition to the serous and mucosal glands of the lamina propria  - produce bronchial mucus. The mucins secreted by them cover the epithelium and moisten the air that passes by .

Other cells

In addition to these two types of cells , the ciliated epithelium also has sensory cells that are in contact with afferent nerve fibers at their basal pole . They trigger the coughing or sneezing reflex when irritated . The basal cells represent a preliminary stage of the mature epithelial cells and provide for cell replenishment.

physiology

The ciliated epithelium has a sophisticated self-cleaning mechanism . The mobile cilia line the airways like a dense lawn. Their coordinated movement is directed towards the throat. As a result, the bronchial mucus and the smaller foreign bodies and microorganisms that have penetrated the airways are constantly transported out of the airways.

Occurrence

Respiratory ciliated epithelium is found in the following locations:

In addition, the ciliated epithelium is localized with cinema cilia in the following places:

  • Female internal genital organs:
    • Fallopian tubes ( tuba uterina ) as lining / boundary tissue

Individual evidence

  1. ↑ http://www.scienceonline.org/cgi/content/abstract/1173869v1 Alok S. Shah et al .: Motile Cilia of Human Airway Epithelia Are Chemosensory , Science, online publication, July 23, 2009, doi : 10.1126 / science.1173869 .

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