Lecture 15: LOWER RESPIRATORY TRACT Flashcards
What are the components of the LRT?
Larynx, trachea, bronchi, bronchioles and alveoli
What are the functions of the LRT?
Conduct, complete and provide
What does the LRT conduct?
Air to/from site of gas exchange
What does the LRT complete?
Cleaning, warming and humidifying of air
What does the LRT provide?
A barrier between the air and blood, and a large surface area for gas exchange
What is the larynx a passage for?
Air only so has respiratory epithelium
Where is the larynx positioned?
Anterior to the esophagus
Where does the larynx go from?
The hyoid bone to the trachea
What does cartilage in the larynx do?
Protect and maintain open airway (remains potent)
What does the epiglottis do?
Closes over the airway when swallowing to prevent food entering the larynx
What are the cartilage in the larynx?
Cricoid cartilage, thyroid cartilage (with laryngeal prominence) and epiglottis
What does glottis mean?
Voicebox
What do the folds attach to?
Cartilages
What are the folds?
Vocal folds and vestibular folds
What are the true vocal cords?
Vocal folds
What does air passing the vocal folds do?
Cause vibrations = sound waves
What are the vocal folds used for?
Normal phonation
What affects cartilage and muscle?
Testosterone, resulting in longer, thicker folds which means a deeper voice
What are the false vocal cords?
Vestibular folds
Where are the vestibular folds found?
Superior to the vocal folds
What do vestibular folds do?
Prevent foreign object entry to glottis if it gets past the epiglottis
What sound can the vestibular folds produce?
Very deep sounds
Where is the trachea found?
Anterior to the esophagus
Where is the trachea between?
The larynx and primary bronchi
What is the function of the trachea?
To maintain a potent airway. Clean, warm and humidify air.
What epithelium does the trachea have?
Respiratory
What is the cartilage in the trachea?
C shaped cartilage rings. They aren’t completes so that oesophagus space isn taken up and muscle can run down the posterior
What are the ends of the cartilage in the trachea connected by?
A band of smooth muscle (trachealis) which contracts for coughing
What is in the lamina propria and submucosa layer of the trachea?
Many elastin fibres and all submucosal glands for producing extra mucus
What does the mucocillary escalator do?
Removes debris against gravity to the pharynx to be swallowed and digested
What coats the epithelium in the trachea?
Mucus from goblet cells and mucous glands
What happens with debris in the trachea?
It becomes trapped
What do cilia do in the trachea?
Moves mucus up to the pharynx
How many lungs are there?
2
How many lung lobes are there?
5
How many lobes are there in the right lung?
3 (superior, middle and inferior)
How many lobes are there in the left lung?
2 (as the heart takes up more space on the left)
What is the hilum?
Where bronchi and blood vessels enter
What is the apex of the lungs?
The superior region
What is the costal surface of the lungs?
The outer surface against the ribs
What is the base of the lungs?
The inferior region which sits on the diaphragm
What is the start of the bronchial tree?
Trachea
What comes after the trachea?
2 primary bronchi which enter the lungs at the hilum
What comes after the primary bronchi?
Secondary (lobar) bronchi - 3 on right and 2 on left
What comes after secondary (lobar) bronchi?
Tertiary segmental bronchi
what comes after tertiary segmental bronchi?
Bronchioles
What comes after the bronchioles?
A lot more branching leads to the terminal bronchioles
What is the epithelium of primary bronchi?
Respiratory
How is the cartilage and smooth muscle of primary bronchi?
Complete rings as there is no esophagus
What is the epithelium of the secondary and tertiary bronchi?
Respiratory epithelium which is starting to decrease in height and less goblet cells
How is the cartilage in secondary and tertiary bronchi?
Cartilage plates (not full rings as the air pressure holds them open)
What is the size of bronchioles?
Less than 1mm
what is the epithelium of the bronchioles?
Cuboidal
How is the cartilage and smooth muscle in bronchioles?
No cartilage but thick smooth muscle for bronchoconstriction/dilation
What is the size of terminal bronchioles?
Less than 0.5mm
What does each terminal bronchiole supply?
A pulmonary lobule
What is the respiratory zone made up of?
Pulmonary lobules made of many alveoli (air sacs)
How are the alveoli arranged in the pulmonary lobules?
Like bunches of grapes
How many alveoli per lung?
Approximately 150 million
What makes up most of the lung volume?
Alveoli
What does having many alveoli do?
Give an enormous surface area for gas exchange
How are the alveolar walls?
Very thin - simple squamous epithelium on a thin basement membrane
What is the external surface of alveoli covered in?
A fine network of pulmonary capillaries
How is an alveolus described?
Pocket-like (open at one side)
What is an alveolus covered by?
A dense capillary network
What are the cells of the alveolus?
Pneumocytes (lung epithelial cells)
What are the types of pneumocytes?
Type 1 squamous and Type 2 cuboidal
What does the type 1 squamous cells form?
The respiratory membrane/bood-air barrier with the capillary wall and shared basement membrane
Where are type 2 cuboidal cells found?
Scattered amongst type 1
What do type 2 cuboidal cells do?
Secrete surfactant, a complex lipoprotein (phospholipid) that reduces the surface tension. of alveolar fluid (no deformation)
What do roaming macrophages in the alveoli do?
Remove any debris which makes it to the alveoli
What does each alveolus connect to?
Neighbouring alveoli so that air can flow through
What is the respiratory membrane made of?
The alveolar cell layer, fused basement membrane of alveolar and capillary endothelium and also the capillary endothelium
What way does oxygen flow from?
Alveoli to capillaries
What way does carbon dioxide flow?
From capillaries to alveoli
What is the respiratory membrane the site of?
Gas exchange
