3.1 Exchange surfaces Flashcards
why do animals need a specialised exchange system?
- larger = small SA:V ratio
- short diffusion distance
- high metabolic demand
what are the features of the alveoli that assist in gas exchange - 5 marks
- alveolus = large SA = greater diffusion of O2 in blood and CO2 out of blood
- thin walls- one cell thick, shortens diffusion distance
- good blood supply - maintain conc. gradient
- moist- dissolve gases
function of ciliated epithelium cells?
- trachea, bronchi, bronchioles
- move mucus to remove dust or pathogens
function of goblet cells?
- trachea and bronchi
- produce mucus
function and structure of cartilage?
- trachea - c-shaped
- bronchi - full rings
- prevent it from collapsing, structural support
function of smooth muscle?
- bronchi and bronchioles
- dilates and constricts to control airflow
function of elastic fibres?
- bronchioles and alveoli
- stretch and recoil
function of squamous epithelium?
- alveoli
- short diffusion pathway
function of capillaries?
- alveoli
- one cell thick - short diffusion pathway
Describe inspiration
. external intercostal muscles contract
. ribcage moves upwards and outwards
. diaphram contracts and flattens
. volume of thorax increases
. pressure inside thorax decreases
. air is drawn in
Describe expiration
. external intercostal muscle relax
. ribcage moves downwards and inwards
. diaphram relaxes and becomes dome-shaped
. volume of thorax decreases
. pressure inside thorax increases
. air is forced out
define vital capacity
The maximum vol of air that can be breathed in and out .
define residual volume
the air that cant be expelled (remaining air left after max expiration)
define tidal volume
the vol of air in each breath
define breathing rate
how many breaths taken usually in a min
define O2 uptake
the rate at which and org. uses up O2
what is the key features of bony fish?
Filaments thin folded into primary secondary lamellae for a large SA.
describe gas exchange in water for fish
- mouth open, floor of the buccal cavity is lowered, volume increases, pressure decreases, water is taken in
- mouth closes, floor of the buccal cavity is raised, volume decreases and pressure increases
- water leaves gills and opperculum opens
describe the countercurrent system in fish. (describe with a written diagram aswell)
- Water flows over the gills in one direction.
- Blood flows in the opposite direction.
- maintains a steep oxygen concentration gradient along the entire length of the gill.
what are the key features in insects?
- Spiracles → Small openings where air enters/exits.
- Trachea → Tubes carrying air to cells.
- Tracheoles → Thin tubes for gas exchange.
- Tracheal Fluid → O₂ dissolves in it → diffuses into cells.
- Thoracic/Abdominal Movements → Change body volume to push air in/out.
how does gas exchange happen in insects? ( 6 marks)
At rest
- Oxygen diffuses through the spiracles → tracheae → tracheoles → into cells.
- COâ‚‚ follows the reverse route out of the body.
During activity (e.g., flying):
- Insects use thoracic & abdominal movements increasing ventilation.
- Tracheal fluid is drawn into muscle cells to speed up oxygen diffusion.
How are insects adapted to reduce water loss?
- waxy cuticle all over their body = waterproof = reduce evaporation.
- hairs around spiracles = reduces evaporation.
- small SA:V = less water lost
