Chapter 7 - Exchange Surfaces And Breathing Flashcards
Why do multicellular organisms need exchange surfaces
- diffusion across cell surface membrane is too slow because large distance between cells and outside environment
- can’t exchange enough substance through small SA:V
- high metabolic rate
Characteristic features of good exchange surface
Increased SA
- overcome limitations of SA:V ratio of large organisms
Thin layers
- decrease diffusion distance
Good blood supply/ ventilation
- maintain steep concentration gradient for diffusion
Goblet cells
Secrete mucus
Traps microorganisms and dust in air
Cilia
Beats the mucus
Moving it away from alveoli
Towards the throat - swallowed and digested
Prevents lung infections
Elastic fibres
Help the process of breathing
Provide flexibility to walls
Fibres stretch when lungs inflate
Recoil to push air out
Smooth muscle
Contracts or relaxes to change the size of lumen
Allow diameter to be controlled
Collagen
Provides structural support
Maintain the shape and volume of vessel
Cartilage
Provide support
Strop trachea and bronchi collapsing
Adaptations of alveoli
Large surface area
- 75m2
Thin layers
- squamous épithélial cell
Good blood supply
- 280 million capillaries
Good ventilation
- constantly replaced
Inspiration
- diaphragm contracts , flattening and lowering
- external intercostal muscles contract , moving upwards and inwards
- increased thorax volume, lowered pressure
- air is drawn in
- to equalise pressures inside and outside chest
Expiration
- diaphragm relaxes , back to dome shape
- external intercostal muscles relax , downwards and inwards
- volume decreases
- pressure increases
- air forces out
Calculate ventilation rate
Breathing rate
X
Tidal volume
How do insects use tracheae to exchange gas
- air moves into tracheae through spirales
- oxygen travels down concentration gradient towards cells through tracheae
- carbon dioxide moves down concentration gradient into atmosphere
- tracheae branch into tracheoles
- oxygen dissolves in fluid in tracheoles and diffuses into surroundings
How can insects increase the amount of gaseous exchange taking place in their bodies
- when lactic acid builds, fluid at the end of tracheole moves out by osmosis
- exposing more SA for gaseous exchange
- can be mechanically ventilated
- Muscular pumping movements of the thorax changes volume and pressure of the body
- air is drawn in or out
- collapsible enlarge trachea
- reservoirs of air to increase air movement in gaseous exchange
- inflated and deflated by ventilation
How are fish gills ventilated
- fish opens mouth , lowers floor of buccal cavity
- increases volume , lowers pressure
- water sucked into cavity
- fish mouth closed , buccal cavity floor rises
- decreases volume , increases pressure
- water forced out of cavity over the gills
- operculum opens and the sides of the opercular cavity move inwards
- increasing pressure in opercular cavity
- forces water over gills and out of cavity
