Flashcards in Gas Exchange and Smoking (Chapter 9) Deck (66)
What are the lungs surrounded by and what do these do?
Pleural membranes - these enclose an airtight space which contains a small quantity of fluid to allow friction-free movement as the lungs are ventilated by the movement of the diaphragm and ribs
Describe the order of the breathing system
Two bronchi (bronchus)
What do trachea and bronchi contain (but not bronchioles)?
Describe the cartilage in the trachea
A regular arrangement of C-shaped rings
Describe the cartilage in the bronchi
What is the function of cartilage in the trachea and bronchi?
- To keep these airways open and air resistance low
- Prevents them from collapsing and bursting as the air pressure changes during breathing
What are bronchioles surrounded by?
What is the function of smooth muscle in the bronchioles?
It can contract or relax to adjust the diameter of these very small airways
What happens in the bronchioles during exercise?
The smooth muscle relaxes to allow a greater flow of air to the alveoli. (The absence of cartilage makes these adjustments possible)
What is desiccation?
How are surfaces inside the lungs protected from desiccation?
As air flows through the nose and trachea, it is warmed to body temp and moistened by evaporation from the lining
How do goblet cells and ciliated epithelial cells protect the lining of the trachea (and bronchi)?
- Goblet cells secrete mucus which traps dust and bacteria
- The mucus is then removed from the trachea by ciliated epithelial cells which sweep the mucus upwards towards the throat where it is swallowed
Where are goblet cells found?
In the trachea and bronchi (and nasal airways)
What is mucus?
A slimy solution which is composed of glycoproteins with many carbohydrate chains that make them sticky and able to trap particles
Where is mucus produced/secreted?
- Mucin droplets (containing mucus) are secreted by goblet cells
- Mucous glands beneath the endothelium
How can chemical pollutants (e.g. NO2 and SO2) irritate the lining of the airways?
They dissolve in mucus to form an acidic solution
Where are the ciliated cells?
Between the goblet cells
What do ciliated cells do?
- The continual beating of their cilia carries the carpet of mucus upwards towards the throat (larynx)
- When mucus reaches the top of the trachea it is usually swallowed so that pathogens are destroyed by the acid in the stomach
What do alveolar walls contain?
What is the function of elastic fibres in alveolar walls?
- They stretch during inspiration and recoil during expiration to help force out air
- This elasticity allows alveoli to expand according to volume of air breathed in
- They prevent bursting of the alveoli
What happens to the alveoli during exercise
During exercise, the alveoli are fully expanded so the surface area available for diffusion increases, and the air is expelled efficiently when the elastic fibres recoil
How are alveoli adapted so that the diffusion pathway for O2 and CO2 is very short?
They have extremely thin walls - each consisting of a single layer of squamous epithelial cells no more than 0.5μm thick
What are the two ways that a steep concentration gradient is maintained so that gas exchange can take place rapidly?
Movement of the blood
How does breathing and constant movement of blood maintain a steep concentration gradient?
- Breathing brings fresh supplies of oxygen to the lungs with a relatively high O2 conc and low CO2 conc, increasing the O2 conc in the alveoli
- Blood is brought to the lungs with a lower O2 conc and higher CO2 conc than the air in the alveoli
- Oxygen therefore diffuses down its concentration gradient from the air in the alveoli to the blood and carbon dioxide in the opposite direction
- The blood is constantly flowing through and out of the lungs, so, as the oxygenated blood leaves, more deoxygenated blood enters to maintain the conc gradient with each new breath
What are the two types of smoke that tobacco smoke is made up of?
'mainstream' and 'sidestream' smoke
What is passive smoking?
Breathing in someone else's smoke
What are the main dangerous components in cigarette smoke and what systems do they damage in general?
Tar (containing carcinogens) - gas exchange system
Carbon monoxide and nicotine - cardiovascular system
What is tar?
A mixture of compounds that settles on the lining of the airways in the lungs and stimulates a series of changes that may lead to obstructive lung diseases and lung cancer
What are carcinogens?
Cancer-causing compounds which cause mutations in the genes that control cell division