lecture 15 - lower respiratory tract Flashcards
What are the components of the lower respiratory tract (5)?
Larynx, trachea, bronchi, bronchioles, alveoli
What are the 3 key functions of the lower respiratory tract?
Conducts air to/from the site of gas exchange, completes cleaning, warming and humidifying of air, provides a barrier between air and blood with a large surface area for gas exchange
What travels through the larynx?
Air - no food
Where does the larynx sit in relation to the oesophagus?
Anteriorly
Where are the boundaries of the larynx?
From hyoid bone to the top of the trachea
What is the key function of the cartilages of the larynx?
To protect/maintain and open/patent airway
What structure closes over the airway when swallowing to prevent food entering the LRT?
The epiglottis
What is the common name for the glottis?
Voicebox
What are the 2 types of folds found in the larynx?
Vocal folds and vestibular folds
What folds are the ‘true’ vocal cords?
Vocal folds
What folds are the ‘false’ vocal folds?
Vestibular folds
What determines the opening and closing of the glottis?
The vocal cords, which are attached to cartilage
What causes the vocal folds to produce sound?
Air passing over them causes vibrations and sound waves
Why do men have deeper voices?
Testosterone affects cartilage and muscle of the glottis, resulting in longer, thicker vocal folds that produce deeper sounds
Where do the vestibular folds sit in relation to the vocal folds?
They sit superiorly
What is the main function of the vestibular folds?
Prevent foreign object (e.g. food) from entering the glottis
What type of sounds can (rarely) be produced by the vestibular folds?
Very deep sounds
Where is the trachea located?
Anterior to the oesophagus, between the larynx and primary bronchi
What are the 2 main functions of the trachea?
Maintain a patent airway and clean, warm and humidify air
How does the trachea maintain a patent airway?
Has C-shaped cartilage rings that keep it open, ends connected to by band of smooth muscle (trachealis), lamina propria and sub-mucosa contains many elastin fibres
What lines the trachea?
Respiratory epithelia
Where is the musociliary escalator found?
In the trachea
What is the function of the musociliary escalator?
Removes debris to the pharynx to be swallowed and digested.
What generates the mucus for the musociliary escalator?
Goblet cells and mucous glands.
How many lobes does the right lung have?
3
How many lobes does the left lung have?
2
What is the shape of the base of the lungs, and why?
Dome shaped that sits of the diaphragm
Where do the bronchi and blood vessels enter the lungs?
The hilum
Where do the apexes of the lungs sit?
Below the clavicle
What is the name for the lateral surface of the lungs?
The costal surface
Where does the base of the lungs sit?
On the diaphragm
What are the components, from top to bottom, of the bronchial tree?
Trachea, primary bronchi,l secondary bronchi, tertiary bronchi, bronchioles, terminal bronchioles
Where are the trachealis muscles found on the trachea?
At the posterior of the trachea, connecting the C shaped cartilage rings
Are the cartilage rings surrounding the trachea C-shaped or complete?
C-shaped
Are the cartilage rings surrounding the primary bronchi C-shaped or complete?
complete
What is the cartilage structure found in the secondary and tertiary bronchi?
Cartilage plates
How does the epithelium change in the secondary and tertiary bronchi?
Respiratory epithelium decreases in height and concentration of goblet cells decreases.
What is the diameter of bronchioles?
<1mm
What is the epithelium of the bronchioles, and why?
Cuboidal - no space for columnar cells
What is the structure of the bronchioles?
No cartilage, but thick smooth muscle for bronchoconstriction and dilation. Cuboidal epithelium
What is the diameter of a terminal bronchiole?
<0.5mm
What does each terminal bronchiole supply?
A pulmonary lobule
What is the structure of a pulmonary lobule?
Made of many alveoli arranged like a ‘bunch of grapes’
What is the structure of an alveolus?
Very thinned wall, covered in a fine network of pulmonary capillaries, open on one side
What is the epithelium of an alveolus?
Simple squamous epithelium on a thin basement membrane
What cells make up alveoli?
Pneumocytes
What are pneumocytes?
Lung epithelial cells that make up the alveoli
What are the 2 types of pneumocytes?
Type I (squamous), type II (cuboidal)
What is the function of type I pneumocytes?
Forms the respiratory membrane/blood air barrier with capillary wall and shared basement membrane
What is the function of the type II pneumocytes?
Scattered amongst type I. Secrete surfactant, a complex lipoprotein (phospholipid) that reduces the surface tension of alveolar fluid
What is secreted by type II pneumocytes?
Surfactant
What is surfactant?
A complex lipoprotein (phospholipid) that reduces the surface tension of alveolar fluid
What removes the debris that makes its way into the alveoli?
Roaming macrophages
What type of epithelial cell type are type I pneumocytes?
Squamous
What type of cell make up type II pneumocytes?
cuboidal
What is the alternative name for the respiratory membrane?
Blood-air barrier
What is the structure of the blood-air barrier/respiratory membrane?
Layer of alveolar epithelium and capillary endothelial cells, with the alveolar and capillary basement membranes fused together between them
What sits between the alveolar epithelium and capillary endothelium in the respiratory membrane?
Alveolar and capillary basement membranes fused together
