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Trachea, Bronchi, and Esophagus


  • A: C-rings in the trachea are one of the most telling characteristics of the trachea. The c-rings are hyaline cartilage and hold the trachea open to better facilitate respiration. Hyaline cartilage can also be found in the bronchi, but in cartilagenous plates instead of c-rings.
    B: Respiratory epithelium in the trachea is ciliated pseudostratified columnar epithelium. The cilia act as a mucous elevator to move mucous with the particles it traps out of the respiratory tract.
    C: The sub-tracheal or seromucous glands in the trachea are found just beneath the epithelium.
  • A: Large c-ring. Notice the structure of the hyaline cartilage. It looks as if there are thousands of tiny little bubbles inside the purple matrix. This is very characteristic of this type of cartilage
    B: The respiratory epithelium upon closer inspection shows tall columnar cells and if you zoom in close you can see the cilia that work to move the mucous.
    C: The subtracheal gland has a characteristic similar to most glands. They stain darker and usually look like circles of tightly packed cells Many time a lumen can be seen in the middle of these circles.
  • A: The respiratory epithelium is ciliated pseudostratified columnar epithelium. This is not easily determined upon sight, but can be deduced by looking at other structures unique to the trachea like the subtracheal glands, and the c-rings.

    B: Goblet cells are also something we can find in the trachea. These secrete the mucous that lines the trachea and acts as a trap for foreign particles. They are found in between the epithelial cells.

    C: The subtracheal gland ducts are lined by simple cuboidal epithelium


  • A: Ciliated Pseudostratified epithelium lines the bronchus

    B: Hyaline cartilage makes up the cartilagenous plates that surround the bronchi
  • A: Ciliated pseudostratfied epithelium lines the length of the respiratory tract from the trachea all the way till the bronchioles
    B: Cilia are very visible here
    C: Hyaline cartilage is present in the cartilagenous plates of the bronchi until it hits the lung.

    Notice there is very little submucosa which usually holds the glands in the trachea
  • A: Hyaline Cartilage on the periphery is part of the cartilagenous plates that do not enter into the lung.

    B: Bronchioles carry air from the bronchi to the terminal bronchioles and are line by ciliated pseudostratified columnar epithelium

    C: Terminal bronchioles are lined by ciliated simple columnar epithelium. The epithelium in the terminal bronchioles slowly transitions from ciliated pseudostratified columnar to ciliated simple columnar and finally into simple squamous of the alveoli

    D: Alveolar sacs lined with simple squamous epithelium
  • A: Bronchiole is lined with ciliated pseudostratified columnar epithlium and it does not end opening up into alveoli as does the terminal bronchiole.

    B: Terminal Bronchioles open up into alveoli allowing the air to pass directly into the alveolar spaces and diffuse across the simple squamous epitheliums of the alveoli and capillaries

    C: Alveolus is lined by a thin layer of simple squamous to facilitate diffusion of O2 and CO2
  • A: Ciliated somple columnar epithelium. You will notice that all the cells are about the same height with no pseudostratified characteristic to them.They also are getting smaller and becoming more cuboidal like

    B: The alveolar walls are lined with simple squamous epithelium


  • A: Stratified squamous epithelium lines the inside of the esophagus. NOTE: This can be confused with the epidermis and the vagina, but it differs from the epidermis by not having an layers, and from the vagina by not having light stained glycogen saturated epithelium

    B: Subesophageal glands are seromucous glands that are located in the submucosa of the esophagus. These also helps differentiate the esophagus from the skin and the vagina who have the same epithelium histologically

    C: The submucosa of the GI tract usually houses glands and vasculature

    D: Muscularis externa is smooth muscle that helps in moving the bolus.
  • A: Stratified squamous epithelium

    B: Submucosa