6 Lung Cell Biology Flashcards
(44 cards)
Q: What is the structure of the lung is optimised for? How does its cross sectional area change?
A: gas exchange
increases peripherally
Q: How many generations of gas exchange units are there?
A: around 23
Q: What are gas exchange units lined with?
A: fluid called surfactant
Q: What’s the role of epithelium in the lungs? (4)
A: -form a continuous barrier, isolating external environment from host
- metabolise foreign and host-derived compounds
- release mediators (controls the number of inflammatory mediators that reach the lungs)
- triggers lung repair processes
Q: What do the lungs produce? to? (3)
A: secretions to facilitate clearance, via mucociliary escalator, and protect underlying cells as well as maintain reduced surface tension (in the alveoli)
Q: How does airway epithelium vary between those that are healthy and those with COPD (//smokers) in terms of goblet cells? (3,3)
A: Normally:
- present in large, central and small airways
- make about 1/5 of epithelial cells
- synthesise and secrete mucus
Smokers:
- Goblet cell number at least doubles (hyperplasia)
- Secretions increase in quantity
- Secretions are thicker
Q: What does mucus contain that gives it viscoelasticity? (3) Also released from?
A: -mucin proteins
- proteoglycans
- glycosaminoglycans
seromucous glands
Q: What else does mucus contain? (5)
A: Serum-derive proteins:
- albumin
- alpha 1-antitrypsin (AKA alpha 1-proteinase inhibitor)
- Antiproteases synthesised by epithelial cells
- Antioxidants from the blood- uric acid and ascorbic acid (blood), glutathione (cells).
Q: What is alpha 1-antitrypsin? Role?
A: inhibitor of polymorphonuclear neutrophil proteases -> combats microorganism and phagocyte proteases
Q: Give an example of an antiprotease synthesised by epithelial cells. Role?
A: secretory leucoprotease inhibitor -> combats microorganism and phagocyte proteases
Q: What produces antioxidants? Role? (2)
A: epithelial cells and phagocytes
Combats inhaled oxidants e.g. cigarette smoke, ozone. Also counteracts excessive oxidants released by activated phagocytes
Q: Describe the 2 phases of mucus. Role of one? enhances?
A: very thin sol phase overlays cells, thick gel phase at the air interface
Modified gel phase traps cigarette smoke particles but also traps and harbours microorganisms, enhancing chances of infection
Q: How does airway epithelium vary between those that are healthy and those with COPD (//smokers) in terms of ciliated cells? (3,4)
A: Normally:
- present in large, central and small airways
- make 80% of epithelial cells
- cilia have metachronous beating
Smokers:
- cells are severely depleted
- beat asynchronously
- ciliated cells found in bronchioles (even though reduced in airways)
- cilia unable to transport thickened mucus - reduced mucus clearance
Q: How do ciliated cells function? (2)
A: Tips of the cilia are in the sol phase of mucus and pushes the mucus towards the epiglottis. The mucus is usually swallowed or expectorated (coughed/spit out)
Q: How does airway epithelium vary between those that are healthy and those with COPD (//smokers) in terms of mucus clearance? leading to? (2)
A: Smokers have reduced mucus clearance leading to respiratory infection and bronchitis. Airways obstructed by mucus secretions
Q: Describe small airways (2). Specifically in COPD? (3)
A: -<2 mm in diameter
-Not cartilagenous
- Mucus becomes trapped
- Airway narrow
- Broken down by enzymes and inflammatory cells-> this reduced peripheral gas exchange
Q: What are Clara cells? found? (5) Where are many found? (2)
A: non-ciliated secretory epithelial cells found in large, central, and small airways and bronchi and bronchioles
found in most conducting and transitional airways but they increase proportionally distally - the bronchi and bronchioles are enriched in these cells
Q: What’s the major role of clara cells?
A: XENOBIOTIC METABOLISM (metabolism of foreign compounds deposited by inhalation)
Q: What do clara cells contain that help with their role? What do they produce? (2)
A: phase I and phase II enzymes
- make and release high levels of antiproteases
- synthesise and secrete lysozyme (can lyse microorganisms)
Q: Where are phase I enzymes found? Give an example. What is their role and downside?
A: in clara cells
cytochrome p450 oxidases
designed to metabolise foreign compounds into a format that enables phase II enzymes to react and neutralise the toxic agent, they often activate a precarcinogen to a carcinogen
Q: Where are phase II enzymes found? Give an example and describe its role.
A: clara cells
glutathione S-transferase
enables conjugation of BPDE to a small molecule that neutralises its activity
Q: How can a phase II enzyme make someone 40 times more likely to get lung cancer?
A: Some individuals are null for glutathione S-transferase i.e. do not synthesise glutathione transferase and cannot neutralise BDPE
Consequently, if an individual who smokes has CYPIRA1 extensive metaboliser gene and the null glutathione gene they are 40 times more likely to get lung cancer
Q: What is COPD? (3)
A: bronchitis + emphysema + small airways disease
Q: Describe alveoli in susceptible smokers. (5)
A: -holes in the alveoli may appear and the alveoli may become larger
- > leads to a reduction in the surface area available for gas exchange
- > can be seen as elastic tissue loss
- > therefore, expansion during breathing is reduced
- > increases the amount of dead space
