Gas Exchange in Humans Flashcards
What is the organ of gaseous exchange in humans (and other mammals)?
The lungs
Why is it important for the lungs to be efficient?
To allow mammals to be very active animals
What are the main components of the human gas exchange system?
Trachea, bronchi, bronchioles, alveoli
What is the alveoli?
The site of gaseous exchange
What are the trachea and bronchi held open by, why is this beneficial?
They are held open by bands of cartilage to prevent them from collapsing and to ensure constant air flow
What is the wall of an alveolus made up of?
A single layer of squamous epithelium
What is an advantage of squamous epithelial cells being very thin?
They are freely permeable to respiratory gases
How many cells this are the blood capillaries surrounding the alveoli?
One cell thick
Where does oxygen dissolve on the epithelium and where does it diffuse into?
Oxygen dissolves in the film of water on the surface of the epithelium and diffuses across into the blood capillary
What do the alveolar epithelium secrete?
A phospholipid surfactant
What is the role of the phospholipid surfactant secreted by the alveolar epithelium?
They decrease surface tension and so prevent alveoli from collapsing as they recoil after each breath
What is ventilation?
The exchange of air in the lungs with ambient air.
What does ventilation ensure?
A steep diffusion gradient is maintained across the alveoli
How is ventilation achieved?
By changes in the volume of the thoratic cavity and associated changes in pressure in the lungs
What happens to the external intercostal muscles in inspiration?
They contract
