3.1.1 Exchange Surfaces Flashcards
(42 cards)
Why do larger more active organisms require specialised gas exchange surfaces?
- higher demand for oxygen
- greater need to remove carbon dioxide
- have a smaller SA:VOL ratio
- diffusion distance too great to just use SA
- diffusion alone wouldn’t meet needs of organism
Why don’t smaller more active organisms require specialised gas exchange surfaces?
- lower demand for oxygen
- lesser need to remove carbon dioxide
- have a larger SA:VOL ratio
- diffusion distance small enough to just use SA
- diffusion alone meets needs of organism
What factors affect rate of diffusion?
- temperature
- concentration gradient
- stirring movement
- surface area
- diffusion distance
- size of molecule
Explain the structure of trachea
- supported by cartilage c-ring - prevents collapse during low air pressure
- elastic fibers allow stretch, preventing bursting
- smooth muscle fibres can contract to reduce the diameter of the trachea
- goblet cells release mucus - trapping pollen/bacteria
Explain the structure of bronchi
- similar structure to trachea - smaller diameter + thinner walls
- complete rings of cartilage - doesn’t lie against the oesophagus
- larger bronchioles have muscle cells
- smaller bronchioles have no muscle cells
Explain the structure of alveoli
- arranged in groups at end of small bronchioles
- walls consist of squamous epithelium cells - short diffusion distance
- elastic fibres allow for stretching - prevents bursting
- water fluid lining - produces surface tension
Explain the structure of ciliated epithelial tissue
- columnar
- have cilia
- line the trachea, bronchi and larger bronchioles
What is the rib cage?
Provides a semi-rigid case within which pressure can be lowered with respect to the air outside
Explain the different muscles used for ventilation
External Intercostal Muscle
- when these contract, the ribcage moves up + out - opposite when relaxed
Internal Intercostal Muscle
- when you exhale forcibly using energy these contract, pulling ribs down hard and fast
Diaphragm
- broad, doamed sheet of muscle which forms the floor of the thorax
Explain the mechanism of inspiration
- external intercostal muscles contract
- ribcage moves up + out
- diaphragm contracts + moves down
- thorax volume increases
- pressure in thorax decreases below atmospheric pressure - air flows in
Explain the mechanism of expiration
- external intercostal muscles relaxes
- ribcage moves down + in
- diaphragm relaxes + moves up
- thorax volume decreases
- pressure in thorax increases above atmospheric pressure - air flows out
What is pulmonary ventilation and how is it calculated?
The volume of air breathed in during 1 minute
Pulmonary ventilation = ventilation rate x tidal volume
What is tidal volume?
The volume of air inhaled or exhaled in one breath during steady/regular breathing
What is inspiratory + expiratory volume?
The additional volume of air that can be inhaled/exhaled after normal inspiration/expiration.
What is vital capacity?
The maximum volume of air inhaled or exhaled in one breath - reserve + tidal capacity = vital capacity
What is total lung capacity
The maximum volume of air that can fill the lungs
What is residual volume?
Air stuck in the lungs - thorax/ribcage cannot be completely flattened
Explain key aspects of using a spirometer
- person attached via tube to air chamber
- chamber contains oxygen, sits on top of water
- moves up during expiration, down during inspiration
- traced on graph
- contains soda lime - removes CO2
- nose clip ensures all air goes through chamber - no invalid result due to breathing out through nose
List safety precautions when using a spirometer
- use medical grade oxygen
- disinfect mouthpiece
- person is healthy/ not asthmatic
- ensure chamber can move
List features of an efficient exchange system and how they are achieved
- increased surface area (e.g. root hair cells)
- thin layer (e.g. alveoli)
- good blood supply to maintain steep concentration (e.g. gills/alveolus)
How does air enter into insects?
Through spiracles in the thorax + abdomen
How can spiracles be opened and closed?
Sphincters
Where does air flow after entering spiracles, and give key aspects
- leads into tracheae (1mm diameter)
- run into and along the insect body
- supported by circular bands of chitin (NOT C-shaped)
- impermeable to gases
Where does air flow after entering trachea, and give key aspects
- leads into tracheoles (0.6-0.8 μm diameter)
- single, greatly elongated cells
- no chitin lining
- freely permeable to gases
- run between individual cells
