Lesson 1: gas exchange Flashcards
(37 cards)
Why do larger multi-cellular organisms need exchange systems?
- small surface area to volume ratio
- cells in the centre of the organisms would not receive anything using only diffusion.
- higher metabolic rate
What are five characteristics of specialised exchange surfaces in animals?
- Large Surface Area
- Thin layers
- Blood supply
- Ventilation
- Moist surface
- Permeability
How is having a large surface area an adaptation for efficient gas exchange?
a large area that gas exchange can occur over.
How is having thin layers an adaptation for efficient gas exchange?
short diffusion path
How is having a good blood supply an adaptation for efficient gas exchange?
maintain a large diffusion gradient, constant diffusion
How is having a moist surface an adaptation for efficient gas exchange?
dissolves gas
How is ventilation an adaptation for efficient gas exchange?
maintains diffusion gradient
How is permeability an adaptation for efficient gas exchange?
pores and openings
What adaptations do animals have to maintain a steep concentration gradient at exchange surfaces?
- A dense network of blood vessels
- Continuous blood flow
- Ventilation
Describe the nasal cavity.
- large SA & good blood supply = warms air to body temperature
- hairy lining = secrets mucus and traps bacteria
- moist = increases humidity and reduces evaporation
Describe the trachea.
- c shape cartilage rings = prevents collapse and allows food down oesophagus
- ciliated epithelium = beat and move mucus to back of throat
- goblet cells = secrete mucus
Describe the bronchioles.
- held by smooth muscle
- small diameter slows air flow = more time for gas exchange in the alveoli.
- lined with epithelial tissues = some gas exchange possible
Describe alveoli.
- made up of collagen, elastic fibres and flattened epithelial cells.
- elastic fibers recoil removing air from alveoli
Describe surfactant.
- dissolves gasses
- reduces surface tension, preventing collapse
What are the adaptations of alveoli for efficient gas exchange?
- Large surface area: numerous + folded
- Short diffusion distance: one cell thin
- Large concentration gradient: surround by an extensive network of capillaries and regular ventilation
What is the difference between type 1 and 2 pneumocytes in structure and coverage %?
type 1:
* covers 95% of alveoli SA
* thin + flat cells
type 2:
- cuboidal cells
- 5%
What is the difference between type 1 and 2 pneumocytes in function?
type 1: gas exchange
type 2: produces surfactant + differentiate into type 1 (when damaged).
Summarise ‘inspiration’.
- Diaphragm contract – Moves Down
- External Intercostal Muscles contract – move up and out
- Thoracic Volume – Increases
- Thoracic Pressure – Decreases
- Air Flow – In to lungs (to equalise the pressure difference)
Summarise ‘expiration’.
- Diaphragm – Moves up
- External Intercostal Muscles – move down and in
- Thoracic Volume – decreases
- Thoracic Pressure – increases
- Air Flow – out the lungs (to equalise the pressure difference)
What are external intercostal muscles used for?
forced expiration
What does tidal volume mean?
the volume of air in each breath
What does vital capacity mean?
The maximum volume of air that can be breathed in and out
What does breathing rate mean?
The number of breaths per minute
What does oxygen uptake mean?
The rate at which a person uses up oxygen (dm3 min-1)
