Lecture 15 LRT Flashcards
what does the lower respiratory tract (LRT) consist of?
- Trachea
- Bronchi
- Bronchioles
- Alveoli
whats the functions of the LRT?
conducts air to/from site of gas exchange
completes cleaning, warming, humidification of inhaled air
where does gas exchange occur?
Alveolus (pl Alveoli)
LRT: Trachea
where is it located?
- anterior to esophagus
* larynx to primary bronchus
LRT: Trachea
whats it lined with?
respiratory mucosa
LRT: Trachea
whats its functions?
Maintain patent (open) airway
Cleans, warms and humidifies inhaled air
Cilia -> mucociliary escalator (‘tracheal elevator’)
LRT: Trachea
how does it Maintain patent (open) airway?
– “C”-shaped cartilage rings
– trachealis muscle
– CT with elastic fibres
trachealis muscle
Trachea
Band of smooth muscle connect ends of a rings
• Contracts on coughing
LRT: Trachea
how does it Cleans, warms and humidifies inhaled air?
– RS epithelium
• Mucous cells, ciliated cells
• Mucociliary escalator
– Glands
Left bronchus
Narrower
Steeper angle
- blockages
LRT: Bronchial Tree
what does it consist of?
- Trachea
- 1° bronchi
- 2° (lobar) bronchi
- 3° tertiary bronchus
- branching (tree like)
- alveolus
LRT: Bronchial Tree
How many lobes does the right side have?
3
LRT: Bronchial Tree
How many lobes does the left side have?
2
1° Bronchi histology
– extra and intrapulmonary
– cartilaginous plates
– complete layer of smooth muscle
3° bronchi histology
bronchopulmonary segments
branch
bronchioles histology
<1mm, no cartilage
ring of smooth muscle
As the bronchi decrease in diameter
– Cartilage – decreases
– Height of epithelium decreases
– Number of mucous secreting cells decrease
bronchioles – No cartilage
If airborne debris gets to alveoli
– macrophages
End of airway is the air sacs
alveoli
alveoli
Arranged like bunches of grapes
Each lung around 150 million
- has large SA
- most of lung volume
The walls of the alveoli are composed of
single layer of thin, flattened epithelial cells with a thin basement membrane (aka basal laminae).
basal laminae
alveoli
single layer of thin, flattened epithelial cells with a thin basement membrane
what are the external surfaces of the alveoli covered in?
pulmonary capillaries.
LRT: Alveolus
whats the structure?
- pocket like - open at one side
- dense capillary network covering (cobweb basket)
- pneumocytes (lung epithelial cells)
what are Type 1 pneumocytes?
squamous epithelial cells
gas exchange
scattered amongst type 1 are type 2 cells
what are type 2 pneumocytes?
cuboidal surfactant secreting cells
mix of phospholipids and proteins to decrease surface tension of alveolus
LRT: Alveolus
whats surfactant?
complex glycolipid / phospholipid that acts to reduce the surface tension of the alveolar fluid
macrophage (dust cells)
release elastase
enzyme destroys elastin
what makes up the blood air barrier?
surfactant coating alveolar surface
alveolar cell layer
fused basement membranes of alveolar epithelium and capillary endothelium
capillary endothelium
endothelial cell
fused basement membrane
type 1 epithelial cell
lungs in thoracic cavity
breathing / ventilation
pleural cavity
whats pleura?
serous membrane
- parietal pleura
- visceral pleura
thoracic contents
Mediastinum (heart vessels, pericardium) Pleural cavities (lungs separate, if 1 not function got another 1)
where does 1° bronchius vessels enter?
Hilum of lung
LRT:
Difference between right and left lung
Right lung
- 3 lobes (sup, middle, inf)
- 2 fissures (horiz, oblique)
Left lung
- 2 lobes (sup, inf)
- 1 fissure (oblique)
- cardiac notch
what makes up the left and right lungs?
medial view
Apex groove for aorta root of lung hilum base inferior surface on diaphragm = domed
apex of lung is
superior region of lung
coastal surface
outer surface against ribs
base of lung is
inferior sits on diaphragm
How are the trachea and primary bronchi held open so that they do not collapse?
by cartilage
Which of the following structures does not have cartilage in its wall A. Intrapulmonary bronchus B. 2 ̊ bronchus C. trachea D. bronchiole E. Nasal septum
D. bronchiole
Name the features of the mucous membrane that are very important in the gas exchange barrier
flattened type 1 pneumocytes sharing basement membrane. type 2 pneumocytes provide surfactant to keep the gas barrier moist and prevent sticking to the surface of other alveoli, strong basement membrane, elastic fibres near to help inspiratory recoil.
