3.1.1 - Exchange surfaces Flashcards
What are the features of an efficient gas exchange system?
- large surface area to volume ratio
- thin (short diffusion distance)
- good blood supply (maintains conc gradient)
- good ventilation
Why are gas exchange surfaces moist?
it aids diffusion -oxygen dissolves in it more easily
Describe the pleural cavity
- each of the lungs is enclosed in a double membrane (known as the pleural cavity)
- space between the membranes is filled by pleural fluid
What does pleural fluid do?
- lubricates the lungs
- adheres to the outer walls of the thorax by water cohesion, meaning that the lungs expand with the chest when breathing
Describe the nasal cavity (and the functions of the parts)
- has large SA
- has good blood supply
- has a hairy lining (traps dust and bacteria in mucus to prevent them getting into the lungs)
- has moist surfaces (increases humidity of air to reduce evaporation of water in lungs)
Describe the trachea (and the functions of the parts)
- pipe supported by a ring of cartilage (holds it open + prevents it collapsing) -rings are incomplete (to allow it to bend when swallowing food down the oesophagus behind it)
- lined with ciliated epithelium and goblet cells (prevent dust and bacteria from entering by goblet cells producing mucus that cilia beat away)
Describe the bronchus
- extension of trachea (split in two -one for each lung)
- smaller version of the trachea
Describe the bronchioles (and the functions of the parts)
- very small (<1mm thick)
- have no cartilage, held open by smooth muscle (when muscle contracts, bronchioles contract depending on air flow)
- lined with layer of epithelial tissues
Describe the alveoli (and the functions of the parts)
- small air sacs where most gas exchange occurs
- have a very large SA:V
- made from thin, flattened epithelial cells and some collagen and elastic fibres (elastic fibres cause recoil to help move air out)
- lung surfactant coats surfaces of lungs (prevents alveoli from collapsing due to surface tension)
What is ventilation in gaseous exchange systems?
pressure changes in thoracic cavity
rip cage provides a cage where pressure changes facilitate breathing
What happens in inspiration?
- diaphragm moves down
- intercostal muscles contract (moves ribs up and out)
- thoracic volume increases
- pressure decreases
- air flows into lungs
What happens in expiration?
- diaphragm relaxes (curves and moves up)
- intercostal muscles relax (moves ribs down and in)
- thoracic volume decreases
- pressure increases
- air flows out of lungs
What is a spirometer?
a device that measures the volume of gas breathed in and out
How does a spirometer work?
- lower half of tank is full of water and upper half is mobile and full of oxygen
- subject has nose clip on and breathes in and out into spirometer (breathing in making the mobile half fall and breathing out makes it rise)
- trace marker is attached to mobile upper half and draws as they breathe
What is a peak flow meter?
a device that measures the rate at which air can be moved in and out of lungs
What is vital capacity?
maximum volume of air that can be inhaled/exhaled in one breath
(strongest exhale followed by strongest inhale)
What is tidal volume?
the volume of air moving in and out of lungs (inhaled/exhaled) with each resting breath (during regular breathing)
What is inspiratory reserve volume?
the maximum volume of air you can breathe in
above normal inhalation
What is expiratory reserve volume?
the maximum volume of air you can force out of lungs
above normal tidal volume of air you can breathe out
What is residual volume?
the volume of air left in your lungs when you have exhaled as hard as possibe
What is total lung capacity?
the total potential amount of air in the lungs at any given point
total lung capacity =
vital capacity + residual volume
What are spiracles?
openings in insects’ waxy exoskeleten which allow gases through to go into the trachea
What are the differences between gas exchange systems in insects and humans?
Insects:
-trachea held open by chitin
-trachea splits into tracheoles
-no blood in system, just gases -tracheoles penetrate directly into body cells
Humans:
-trachea held open by cartilage
-trachea splits into bronchi (and then bronchioles)
-blood in system carries gases to body cells
How do insects ventilate their tracheal system?
by using air sacs, flight muscles or specialised breathing systems
What is the operculum and what does it do? (in a fish)
a bony flap that covers the gills
What is the function of the bony gill arch?
supports the structure of the gills
What is the function of the gill lamella?
are the main site of gaseous exchange in fish
-increase SA of gills
What are gill filaments and what do they do?
occur in large stacks called gill plates
site of gas exchange
How do fish have efficient gas exchange at all times?
by maintaining a constant flow of water over their gills
-either by moving or opening/closing mouth and closing/opening opercular valves in order to expand/constrict buccal cavity
What is ram ventilation? (in fish)
where fish need to constantly move to ventilate the gills
-only happens in some fish like sharks
What are the adaptions of gills?
- good blood supply
- large SA
- thin layers
- tips of adjacent gills overlap (increases resistance of water flow so there’s more time for gas exchange)
- countercurrent exchange system (maintains steep concentration gradient)
What is a countercurrent exchange system?
a system where blood and water flow in opposite directions
maintains concentration gradient
Describe how fish ventilate the gills when they are not moving.
- mouth opens (operculum valve is closed)
- buccal cavity expands and its floor lowers
- this increases the volume and decreases the pressure of the buccal cavity
- water moves into buccal cavity
- opercular cavity expands
- buccal cavity constricts and floor raises
- pressure increases inside the buccal cavity
- water moves from buccal cavity over the gills into the opercular cavity
- mouth closes and operculum opens
- sides of the opercular cavity move inwards, increasing the pressure
- water leaves the fish through the operculum
