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3.1 EXCHANGE AND TRANSPORT - Coggle Diagram
3.1 EXCHANGE AND TRANSPORT
3.1.1 Exchange surfaces
Organisms must exchange substances with their environment, for example taking in oxygen and water and giving out carbon dioxide and urea.
The smaller the animal the higher the SA:V ratio. This means substances can diffuse directly across cell membranes due to a small diffusion distance.
In larger organisms direct diffusion is too slow because...
cells are deep withing the body creating a large distance
low SA:V ratio
there is a higher metabolic rate
Features of a good exchange surface include...
large surface area
thin barrier
good blood supply/ventilation
3.1.3 Tissues in the gaseous exchange system
Goblet cells - secrete mucus which traos mircroorganisms and dust particles in the air
Cilia - beat the mucus moving it upwards away from the alveoli, helping to prevent lung infection
Elastic fibres - help the process of breathing out , they recoil pushing the air out.
Smooth muscle - enables diameter of structures to be controlled
Rings of cartilage - provide support in the trachea and bronchi
3.1.2 Mammalian gaseous exchange surfaces
When you breathe in air enters the trachea
The trachea splits into two bronchi leading to one lung
The bronchus splits off into bronchioles
The bronchioles end in alveoli
Gaseous exchange
Gases diffuse through the alveoli. Oxygen moves from the air in the alveoli to the blood in the capillaries. The same goes for carbon dioxide in the opposite direction.
Large surface area provides more space for molecules to pass through
Barrier is permeable to carbon dioxide and oxygen
Thin barrier to reduce diffusion distance is achieved by...
one cell thick alveolus
one cell thick capillary
squamous cells
close contact
The blood supply helps maintain a steep concentration gradient
Breathing in and out ventilates the lungs
Inspiration
Diaphragm contracts to move down and flatten
External intercostal muscles contract to raise the rib cage
Chest cavity volume increases
Pressure in chest cavity drops
Air moves into lungs
Expiration
Diaphragm relaxes to move up
External intercostal muscles relax to lower the rib cage
Chest cavity volume decreases
Pressure in chest cavity rises
Air moves out of lungs
3.1.4 Measuring lung volumes
Spirometers give readings of tidal volume, vital capacity, breathing rate and oxygen uptake
1) There's an oxygen filled chamber with a moveable lid
2) The subject breathes into a tube
3) The lid of the chamber moves up and down
4) The movements are recorded by a pen attached writing on a rotating drum
5) There is soda lime in the tube to prevent carbon dioxide build up
Tidal volume is the volume of air in a normal breathe
Vital capacity is the maximum volume of air that can be breathed in or out
Breathing rate is how many breaths are taken
Oxygen intake is the amount of oxygen an organism consumes in a given period of time
3.1.5 Gas exchange in other organisms
Fish use a counter-current system for gas exchange
1) Water enters the fish's mouth and passes out the gills 2) Each gill is made out of gill filaments (primary lamellae), which give a large surface area for gas exchange. The filaments are covered in gill plates (secondary lamellae), which further increase the surface area.
3) Gill plates have lots of capillaries and a thin surface layer of cells to speed up diffusion
4) Blood flows through gill plates in one direction and water the other, maintaining a large concentration gradient.
Fish gills are ventilated via the following...
1) The fish opens its mouth lowering the buccal cavity. This increases the capacity and lowers the pressure so water flows in.
2) The buccal cavity is raised, closing the fish's mouth. Decreasing volume and increasing the pressure meaning the water is forced out across the gill filaments
3) Each gill is covered by a bony flap called the operculum. The increase in pressure forces it open allowing water to leave the gills.
Insects have an open circulatory system and use tracheae for gas exchange
In insects...
1) Air moves into the trahcea via the spiracles.
2) The tracheae brances off into tracheoles which have thin, permeable walls leading to individual cells.