Gas exchange Flashcards
Features of exchange systems
Large surface area : volume
Thin cell walls for a short diffusion gradient
Good blood supply
Good ventilation- for a good diffusion gradient
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The lungs structure
Alveoli:
With epithelium which have a thin cell wall to increase the rate of diffusion’s as the distance to travel is decreased.
Have capillaries running over the surface to increase the volume of gas exchange taking place.
Diaphragm and intercostal muscles act passively.
How the intercostal muscles work
External and internal intercostal muscles are antagonistic (as 1 contracts the other relaxes).
The internal intercostal muscles contract when exhaling and relax when inhaling - this becomes conscious as exercise occurs.
How the diaphragm works
The diaphragm is smooth muscle, during inhalation it contract and flatten - in exhalation it relaxes and forms a dome, pushing the air out of the lungs
Air pressure in the lungs
Inhalation:
The external intercostal muscles contract and raise the rib cage up and out - the diaphragm also contracts and flattens , which creates a pressure gradient which allows air in via the trachea which equalises the pressure difference.
The volume of the thorax increases which lowers the air pressure inside (to become lower than the pressure of air outside of the lungs).
Active inhalation
During exercise:
The rate and depth of breathing increases as the internal intercostals contract more forcefully which pushes out more air whilst your abdominals begin to contract which forces up the diaphragm move.
Kymographs
Record the lungs volume:
- Inspiration capacity
- Vital capacity (male 5.5 dm^3, female 4.5 dm ^3)
- residual volume (never 0)
- inspiration reserve
- expiration capacity
- expiration reserve
- tidal volume
Inspiration
- diaphragm muscle contracts and flattens - increasing the volume of the thorax - this makes the air pressure in the thoracic cavity fall below the airs atmospheric pressure - air then rushes into the longs to equalise the fallen pressure gradient
Expiration
- diaphragm muscle relaxes and becomes a dome shape - the volume of the thorax decreases - therefore the air pressure in the thoracic cavity rises above the airs atmospheric pressure - air then rushes out of the lungs in order to follow and equalise the pressure gradient
Bony Fish: Gas exchange
- have to exchange gases with water (which is 1000x denser than air- and has a lower concentration of oxygen ) - to conserve energy water is pushed in one direction, through the gills where the oxygen dissolved in the water diffuses into the blood of the fish. (As scales prevent surface gas exchange)
- Bony fish have 5 pairs of gills which are covered by a plate called the Operculum
- Gill Filaments (attached to the bony arch) maintain a constant flow of water
- Gill Lamellae have a supply of capillaries giving a short diffusion pathway and large SA:Vol so are the main site of gas exchange
Bony fish: ventilation
- water is constantly flowing over the gills due to the buccal-operculum pump
- the volume is changed as the mouth of the fish raises pushing the water through the gills as the pressure in the opercular cavity is reduced
Bony fish: countercurrent flow
- blood flowed along the Gill arch and along the filaments to the secondary lamellae, the blood then flows through the capillaries in the opposite direction then the water flow through the lamellae
- this creates a countercurrent flow that absorbs the maximum amount of oxygen from the water
- the oxygen concentration then reaches almost equilibrium as there’s no net diffusion occurring
Insects: exchange systems
- insects have exoskeleton which are impermeable
- insects blood doesn’t have pigments of haemoglobin so cant carry oxygen
- Oxygen is therefore delivered directly to cells and Carbon Dioxide is taken directly from cells(as well as water). This occurs through the Spiracles (small openings) in the thorax and abdomen
- the Spiracles can be opened and closed by Sphincters (rings of muscle)
- tracheae are also used to carry air into the body , these are lined by chitin to help maintain their structure, this makes the tracheae impermeable. These tracheae then divide into trachioles which are permeable so allow gas exchange (as they have an open circulate system)
Insects: ventilation
- sections of the tracheal system can expand as they have expandable walls - acting’s s air sacs which’s re squeezed by flight muscles, the repetition of Thai ventilates the tracheal system
- as the thorax volume decreases, air in the tracheal system is put under pressure and pushes out. - as the thorax volume increases the pressure decreases which pushed air into the tracheal system.
