Recognising Structures in the Gas Exchange System
Trachea
- A tracheal cross-section shows the large lumen which air has to travel through
- The innermost cells of the trachea are the ciliated epithelia with projections called cilia
Cross section of a trachea diagram
Trachea cross-section as shown under a light microscope
- The cells of the ciliated epithelium are shown here – the cells are tightly packed and interspersed with goblet cells, which are shown in light grey
Tissues of the trachea diagram
A light micrograph image showing tissue of the trachea
- The density of the cilia are shown in this electron micrograph
- The cilia are essential for sweeping bacteria and dust-filled mucus away from the lungs and up the trachea into the back of the mouth
- This mucus is then swallowed, with any pathogens hopefully destroyed by the acidic conditions in the stomach
Trachea electron micrograph diagram
An electron micrograph of the tissues that can be found inside the trachea
Bronchi
- Bronchi are distinctive from the trachea because their lumen is narrower; 8.7mm instead of 18mm
- However, like the trachea, they are lined by ciliated epithelium
Cross section of a bronchi diagram
A light micrograph image showing tissue of the bronchi in cross section
Bronchioles
- Bronchioles are approximately 1mm or less in diameter
- Smooth muscle and cuboidal epithelium are found in their walls
Cross section of a bronchiole diagram
A photomicrograph showing bronchiole tissues in the gas exchange system
Alveoli
- Alveoli have a sponge-like appearance under a microscope due to their air spaces.
- They are surrounded by an extensive capillary network and are lined by squamous epithelium
Light micrograph of an alveolus diagram
The cells surrounding the alveolus air sac as viewed by a light microscope
Alveoli damaged by emphysema diagram
Several alveoli are damaged due to the medical condition emphysema
Walls of the trachea & bronchus
Trachea
- The tracheal lumen is around 15 to 20 mm and is lined by ciliated epithelia
- The tracheal wall is surrounded by strong and flexible cartilage which flexes during breathing
- The smooth muscle of the trachea constricts and allows air to be expelled with more force
Parts of the trachea wall diagram
Labelled diagram of a cross section of the trachea
Bronchus
- Like the trachea, the bronchus is lined with ciliated epithelium
- The cartilage hoops provide structural support to the bronchi and the gland ducts secrete mucus in the bronchial tubes
Parts of a bronchus wall diagram
Parts of the cross section of a bronchus. This would be the same in both bronchi