2.2 Resp histology Flashcards
respiratory tract divided into what portions ?
- conducting portion
- respiratory portion
conducting portion is what ?
nasal cavity to the terminal bronchioles
- cleansing , warming and moistening of air
respiratory portion is what ?
respiratory bronchioles, alveolar ducts and alveoli
- gas exchange
nasal cavity, sinuses & nasopharynx lined by what ?
pseudostratified ciliated columnar + goblet cells -> respiratory epithelium
small areas on roof of nasal cavity is lined by ?
olfactory epithelium
olfactory epithelium is devoid of ..1.. but has ..2… and underlying ..3.. (Bowman’s glands)
- goblet cells
- olfactory cells
- olfactory glands
larynx is covered with …1… epithelium except at the ..2… where it is covered with ..3.. epithelium
- respiratory
- true vocal cords
- stratified squamous
connective tissue of the larynx glands ?
mixed mucoserous
are there any glands in submucosa of true vocal cords ?
no glands
trachea supported by ?
C-shaped cartilage rings
trachea lined by what epithelium ?
respiratory
numerous what found in submucosa ?
seromucous glands
difference between keeping lumen of bronchus and bronchiole open ?
no cartilage in bronchiole
what do smaller, respiratory bronchioles have none of ..1… and are lined with ..2. epithleium ?
- no smooth muscle
- cuboidal
what cells are type 1 pneumocytes ? what % of alveolar cell population ?
simple squamous epithelial
40%
what cells are type 2 pneumocytes ? what % of alveolar cell population ?
cuboidal
60%
numerous …1… line alveloar surface to ..2.. foreign particles
- macrophages (dust cells)
- phagocytose
Membranes of what cells form a blood-air barrier ?
type 1 and endothelial cells
type 2 alveolar cell does what ?
secretes surfactant
type 1 alveolar cell does what ?
permits gas exchange
upper respiratory tract contains what ?
mouth / nose to larynx
* nasal cavity
* nasopharynx
* epiglottis
* larynx
* trachea
lower respiratory tract contains what ?
- trachea
- lungs ‘respiratory tree’
- bronchi
- bronchioles (terminal , respiratory)
- alveolar ducts
- alveoli
upper airways and bronchi epithelium ?
- respiratory epithelium
- pseudo-stratified, ciliated columnar epithelium
- mucus secretion until terminal bronchioles
epithelium of oropharynx, anterior epiglottis, larynx vocal cords ?
squamous epithelium
nasal passages apart from the vestibule of nose lined by what epithelium ?
respiratory
what tissue is there lots of in URT ?
lymphoid
what divides nose into 2 nasal cavities ?
nasal septum subdivides it
major function of the paranasal sinuses ?
adjust the temperature and humidity of the inspired air
what is nasal polyp ?
chronic allergic oedematous mass
trachea cartilaginous tube connect what ?
larynx to the bronchi
type of cartilage of C-shaped cartilage of trachea ?
hyaline cartilage
C-shaped circles of hyaline cartilage prevents what in trachea?
prevents the collapse of tracheal muscosa when breathing in
Gap in C-shape is bridge posteriorly by what ?
trachealis muscle
At what point do the primary/main bronchi enter the lungs, and what is this location called?
enter the lungs at the hilum, which is the point where the bronchi, blood vessels, and nerves enter the lungs.
What is the difference between primary, secondary, and tertiary bronchi?
- Primary (Main) = are the first branches from the trachea and are extra-pulmonary (located outside the lungs). They enter the lungs at the hilum.
- Secondary (Lobar) = branch from the primary bronchi, with one lobar bronchus entering each lobe of the lungs (two in the left lung and three in the right lung).
- Tertiary (Segmental) = branch from the lobar bronchi and further divide into smaller bronchi and bronchioles, ultimately distributing air to specific lung segments.
as bronchi get smaller what do they get ?
- less cartilage
- more smooth muscle
Why are the primary bronchi considered ‘extra pulmonary’?
They are located outside the lungs.
They only enter the lungs at the hilum, after which they continue to branch into secondary and tertiary bronchi within the lung tissue.
define metaplasia
one mature tissue type replaces another mature tissue type
What type of carcinoma is typically associated with the bronchial epithelium?
Bronchial squamous cell carcinoma
metaplastic progression of bronchial squamous cell carcinoma ?
- normal respiratory epithelium
- squamous metaplasia
- carcinoma in situ
- invasive carcinoma
list the 10 hallmarks of cancer
which ones are the 8 hallmarks and what are the additional 2 ?
A GREAT SIDE !
1. activating invasion & metastasis
2. genetic instability & mutation (additional)
3. resisting cell death (apoptosis)
4. evading growth suppressors
5. avoiding immune destruction
6. tumour promoting inflammation (additional)
7. sustaining proliferative signalling
8. induces angiogenesis
9. deregulated cellular metabolism
10. enabling replicate immortility
diameter of bronchioles ?
< 1mm
What type of muscle is found in the walls of bronchioles, and what is its function?
Bundles of smooth muscle are found in the walls of bronchioles.
These muscles regulate the diameter of the bronchioles, controlling airflow to the alveoli.
How does the epithelium of bronchioles change as their diameter decreases?
Changes from simple columnar epithelium to a more cuboidal shape
Are bronchioles still ciliated, and what is the significance of this?
Yes, bronchioles are still ciliated.
The cilia help to move mucus and trapped particles out of the airways, maintaining airway cleanliness.
What happens to goblet cells as bronchioles become smaller?
goblet cells disappear.
Goblet cells are responsible for producing mucus in larger airways.
Which cells replace goblet cells in bronchioles, and what are their functions?
club cells (formely ‘Clara cells’)
thinning the mucus
detoxifying harmful substances
playing a role in immune defense within the airways.
bronchioles form part of what ?
distal airways
what are club cells ?
- dome/club-shaped apical cells
- mainly found in terminal bronchiles & lesser extent in respiratory bronchioles
although club cells are ..1.. cells they feature ..2.. (non-..3…)
- non-ciliated
- short microvilli
- motile
Club cells don’t produce mucus but what do they have ?
- many large mitochondria
- abundant smooth ER
- secrete many proteins e.g. CCSP (club cell 10-kDa secretory protein)
3 main functions of club cells ? & explain each
- detoxification - cytochrome P450 activity allow detoxification of inhaled substances
- surfactant production - helps to protect bronchial epithelium
- regeneration - have stem cell properties for regenerating damaged ciliated bronchial epithelial cells
Hallmarks of the pathological changes seen in the airways of individuals with asthma ?
B THEM
1. bronchial constriction
2. thickened basement membrane
3. hyper-inflated lungs
4. eosinophil-rich luminal inflammation
5. muscle hypertrophy
What is indicated by the thickened basement membrane in the context of asthma?
It’s indicative of chronic inflammation and airway remodeling in asthma, which contributes to the persistence and severity of the disease.
How does muscle hypertrophy contribute to the symptoms of asthma?
contributes to increased airway constriction during an asthma attack, making it harder to breathe and exacerbating symptoms.
What does the presence of eosinophil-rich luminal inflammation suggest about the nature of the asthma?
suggests that the asthma is associated with an allergic or atopic response, where eosinophils contribute to the chronic inflammatory process and airway hyperreactivity.
respiratory airways include what ?
- respiratory bronchioles
- alveolar duct
- alveolar sacs
- alveoli
when do respiratory airways commence ?
after terminal bronchioles
major function of respiratory airways ?
allow fast and efficient transfer of O2 and CO2 between the blood and the air
what are alveolar ducts ?
- structurally ill-defined
- feature flattened epithelium surrounded by a spiral of smooth muscle
what is there none of in alveolar ducts or sacs ?
cilia
what are the smallest conducting portion of the respiratory tree ?
terminal branches
name of one respiratory unit (1) and plural name for it (2) ?
- acinus
- acini
what is pulmonary emphysema a type of ?
chronic obstructive airways disease (COPD)
How is pulmonary emphysema characterised ?
- abnormal, permanent enlargement of the airspaces distal to the terminal bronchiole
- accompanied by the destruction of their walls
- without obvious fibrosis.
how does having no obvious fibrosis (scar) in pulmnoary emphysema differ from other lung diseases like pulmonary fibrosis ?
damage to the lung tissue is accompanied by significant scar tissue formation, leading to stiffening of the lungs.
How does the enlargement of the airspaces in pulmonary emphysema affect lung function?
abnormal enlargement of the airspaces in pulmonary emphysema, often described as the “explosion of the acinus,” reduces the overall surface area available for gas exchange.
alveoli provide surface area of roughly how much m^2 ?
70-80
what are alveoli composed of ?
an air sac with a thin wall containing pulmonary capillaries
what are adjacent alveoli connected by ?
alveolar pores (pores of kohn)
Why do type 1 pneumocytes have very strong connections between their tight junctions ?
prevent leakage of interstitial fluid into alveolus
function of type 1 pneumocytes ?
provide the thinnes possible gas-permeable barrier
difference between the 2 pneumocytes (1)% of alveolar cell population + (2)% of surface area of alveoli ?
type 1 : 1 = 40% , 2= 95%
type 2: 1 = 60% , 2 = 5%
difference in size and content of the 2 pneumocytes (AT-I + AT-II) ?
AT-I
* very flat cells
* contain few organelles
AT-II
* rounded in shape
* mitochondria rich + electron-dense vesicles (lamellar bodies)
why do pneumocytes type 2 produce surfactant ?
to reduce alveolar surface tension
what do alveolar macrophages (dust cells) carry ?
engulfed debris to the terminal bronchioles where they can be transported upwards by the cilia to the pharynx, where they are swallowed
summary of architecture of respiratory tract epithelium ?
gradual progression:
1. large airways - pseudostratified columnar
2. small airways - cuboidal
3. in alveoli - squamous type epithelial cells
What type of lung injury is observed in SARS-CoV-2 infection (COVID-19)? & what is it characterised by ?
acute lung injury
alveolar wall inflammation and pneumocyte desquamation.
What is the significance of alveolar wall inflammation in COVID-19?
indicates a severe inflammatory response within the lungs, which can lead to impaired gas exchange and respiratory distress as the alveoli become filled with inflammatory cells and fluids.
What does pneumocyte desquamation refer to, and how does it effect lung function ?
shedding or sloughing off of pneumocytes
disrupts the integrity of the alveolar lining, contributing to the formation of hyaline membranes and further impairing the lung’s ability to exchange gases effectively.
What pathological feature results from the combination of necrosis and exudate in the lungs during COVID-19?
formation of hyaline membranes
These membranes line the alveoli and are a hallmark of diffuse alveolar damage (DAD), which severely compromises lung function.
What does the term “hyaline membrane” refer to in the context of lung pathology, and why is it significant?
“hyaline membrane” = proteinaceous and cellular debris that accumulates in the alveoli following significant inflammation and necrosis.
its presence indicates severe damage to the alveolar structure, leading to impaired gas exchange and respiratory failure in conditions like COVID-19.
