Gaseous exchange in the lungs Flashcards
Why do single celled organisms not need a specialised exchange surface whereas multicellular organisms do?
Metabolic activity of a single celled organism is relatively low compared to a multicellular organism, therefore oxygen demands and CO2 production is low
SA:V ratio of the organism is larger therefore all gases can be exchanged through the cell surface
What are the features of a good exchange system?
1- Increased surface area
2- Thin layers
3- Good blood supply
4- Ventilation
What are the features of the nasal cavity?
Large surface area with good blood supply to warm the incoming air
A hairy lining which secretes mucus to trap dust and bacteria
Moist surfaces to increase the humidity of incoming air- to reduce evaporation
Good blood supply and moist surfaces to produce air at a similar temperature and humidity to air already in the lungs
What are the features of the trachea?
Main airway carrying air from the nose into the chest
Supported by incomplete rings of strong, flexible cartilage (incomplete rings so that food can move easily down the oesophagus)
What are the features of the ciliated epithelial cells?
Line the trachea
Goblet cells secret mucus onto the lining of the trachea to trap dust and microorganisms
Cilia beat and move the mucus away from the lungs
What are the features of the alveoli?
Tiny air sacs which are the main gas exchange system of the body
Ability to carry out elastic recoil- to help stretch as air comes in and recoil to force air out
Large surface area
Good blood supply- surrounded by a network of capillaries to maintain a steep concentration gradient
Thin layers- both the alveoli and the capillaries are one cell thick so there is a short diffusion distance
Good ventilation
What is the order of air travel in the body?
Trachea- Bronchus- Bronchioles- Alveoli
Describe the process of inspiration (inhalation)
The diaphragm contracts and lowers
The external intercostal muscle contracts, moving the ribs upwards and outwards
The volume of the thorax increases so the pressure in the thorax is less than atmospheric air
Air is drawn in
Describe the process of expiration (exhalation)
The diaphragm relaxes and moves up
The internal intercostal muscle contracts, moving the ribs downwards and inwards
The volume of the thorax decreases so the pressure in the thorax is less than atmospheric air
Air is moved out
Components of lung volume
Tidal volume- volume of air that moves into and out of the lungs with each resting breath
Vital capacity- volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath- max volume of air that can be breathed in/ out in one breath
Inspiratory/ expiratory reserve volume- volume of air above and below tidal volume (- residual volume )
Can be calculated using a spirometer
What is ventilation rate and how is it calculated?
The total volume of air inhaled in one minute
Tidal volume x breathing rate
