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Trachea

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Mucosa

The trachea is lined by pseudostratified ciliated columnar epithelium with mucus cells scattered among the columnar cells.  The mucosa of the trachea is underlain by a connective tissue called the submucosa.  

Microscopic view of trachea mucosa, showcasing a pseudostratified ciliated columnar epithelium layer adjacent to the submucosal connective tissue. The columnar cells are stained pink, and have blue nuclei. Cilia are visible on the apical surface. Scattered mucus cells can be seen among the columnar cells. The connective tissue appears as a matrix of fibrils and cells.
Figure 2: Trachea mucosa histology showing ciliated columnar epithelium and mucus cells.
Anatomical vector illustration of the respiratory system. The trachea vertically descends, branching into left and right bronchi. Each bronchus diverges into numbered bronchopulmonary segments. Color is a blue hue throughout the image. The background is white.
Figure 1: Illustration of the trachea, bronchi, and numbered bronchopulmonary segments.
Microscopic image of trachea tissue displaying a violet stained section of hyaline cartilage on the left side, and pink stained submucosal glands, with red stained tissue interspersed in-between, and a darker pink tissue at the apex along the right side. The pseudostratified ciliated columnar epithelium is arranged horizontally at the right. The overall composition allows examination of the tracheal layers and their cellular structures.
Figure 3: Trachea tissue: Pseudostratified ciliated columnar epithelium, submucosal glands, and hyaline cartilage.

Submucosa

This submucosa houses blood vessels, lymph vessels, and nerves.  It also houses coiled seromucous glands. These glands are lined with simple and stratified cuboidal epithelium. They open onto the surface of the trachea epithelium.  These seromucous glands create a more watery secretion compared to the mucus cells in the epithelium.

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Hyaline Cartilage Rings

Deep to the submucosa in the trachea are the C-shaped hyaline cartilage rings. They add structure to the wall of the airway. They also prevent its collapse.  Note how these open part of the C faces the esophagus.  As large balls of food descend the esophagus, the C shape refuses to collapse completely.  Superficial to the cartilage is an outer layer of connective tissue called the adventitia, a modified serosa.  Collagen fibers from the adventitia secure the trachea in place among the other organs of the thoracic cavity.

View the Slide Yourself

Access this slide from the Histology Guide:
https://www.histologyguide.com/slideview/MHS-222-trachea/17-slide-1.html
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Figures 1-3 Trachea and esophagus, H&E, 40X Slide 126
Multi-Slide Presentation: Trachea H&E, 40X  Slide 40
All by University of Michigan Histology, licensed under CC BY-NC-SA 3.0.

Explore More on Respiratory Histology

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Pharynx
Trachea
Bronchi
Bronchioles
Alveoli

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