The Respiratory System Flashcards
Give 3 special features of the trachea
The presence of large C shaped plates of cartilage
A distinct band of smooth muscle bridging the open end of the C shaped cartilage at the posterior trachea.
Abundance of mixed sero- mucous glands in the connective tissue below the epithelium with ducts linking the gland lumina to the tracheal surface
These glands help humidify the air and trap particles from inspired air
Where is the opening of the C shaped cartilage in the trachea
This opposes the trachea to allow its expansion during swallowing
What is the mechanism of coughing
The contraction of smooth muscle narrows the trachea by both pulling the end of the cartilage plates together and pushing soft tissue out into the lumen
This increases expired airflow to dislodge and remove any irritant particle or mucous
What kind of cartilage is the C shaped cartilage in the trachea
What are the small cavities in the cartilage matrix
Hyaline
Chondrocytes
How can you identify a bronchus
3 distinctive features:
- The epithelium is pseudostratified and columnar but less tall and with fewer goblet cells
- serous- mucous glands become sparse
- the bronchial cartilage framework is arranged in interconnected plates rather than C shaped rings
How does the epithelium change down the bronchi
As the bronchi diameter decreases the epithelium becomes columnar with little pseudostratification
How does the cartilage framework change as the bronchi become smaller
It is reduced to irregular plates and a layer of smooth muscle which separates the lamina propria from the submucosa becomes prominent
What is the diameter of the bronchiole
<1mm
How does the epithelium of the bronchioles change
From ciliated pseudo stratified columnar in large bronchioles to simple ciliated columnar or cuboidal epithelium in terminal and respiratory bronchioles with few/ no goblet cells
What do the epithelia of terminal bronchioles contain
Non ciliated Clara cells
Describe a Clara cell
What do they do
Have a round apical surface and contain dense cytoplasmic granules
Secrete a component of sufactant to cover the surface of the bronchiolar epithelium
What is the main feature of a bronchiole
Smooth-muscle layer
What happens to the smooth muscle layer of bronchioles during pathology
It can contract excessively in asthma causing affective collapse of the bronchioles which can seriously compromise airflow
Do bronchioles have cartilage
No
What is the alveolar septum
What is it covered by on either side
The thin layer between adjacent alveoli
Long respiratory epithelium
It is penetrated by a comprehensive network of blood vessels
How can you spot the a) lung respiratory epithelium and b) blood vessels in the alveolar septum
a) look for nuclei
b) Look for spaces in the thickness of the wall or for trapped red blood cells
Most of the surface of an alveolus is covered by what kind of cell
What do these look like
Pneumocyte type 1
Flattened cells with very thin cytoplasm that is not visible with the light microscope ( must be detected by their nuclei)
What proportion of the epithelium is pneumocyte type 1 covering alveoli
What is the rest
40% but they line 90% of the alveolar surface
The other 60% is pneumocyte type 2 but these only line 10% of the alveolar surface
Describe pneumocyte type 2
Larger cells with a substantial amount of cytoplasm around the nucleus.
They secrete surfactant
Other than pneumocytes what else might be present on the alveolar surface
Scavenging macrophages (dust cells)
What does surfactant do
Reduces the surface tension of the film of fluid which lines the alveoli, without it the alveoli would collapse and considerably increase the work of breathing
It also helps stabilise alveoli of different sizes
What is the axoneme?
A central microtubular structure in cilia which is capable of generating movement independently from the rest of the cell
It consists of a peripheral rings of nine doublet microtubules and two singlet microtubules in the centre of the ring
Other than axoneme, what else in the respiratory system has a distinct microtubular arrangement
Basal bodies
They have nine triplets of microtubules forming a short cylinder with no central pair
Which pneumocyte produces surfactant
When does it begin
Type 2
24-28 weeks of gestation
It plays an important role in the rapid expansion of lungs at birth
What happens to babies with insufficient surfactant quantity
How can this be treated
The respiratory distress syndrome develops
Surfactant administration into the lungs decreases the mortality rate
What is surfactant
A mixture of lipids and protein
Its major constituent is dipalmitoyl phosphatidylcholine, a phospholipid with detergent properties
Discuss alveolar macrophages
Commonly found free within the alveoli space where they play a central role in the immune processes of the lung
They engulf inhaled particulate material in the alveoli after which they usually migrate to the airways. From the airways they move up by the mucociliary escalator
Pseudopodia (extensions of the cell membrane and cytoplasm) May be present
