3.1 Exchange surfaces Flashcards
How is surface area to volume ratio calculated?
Ratio= surface area/volume
Name 3 features of an efficient gas exchange surface
-Large surface area e.g root hair cells for max amount of diffusion
-Thin short distance e.g. alveoli
-Steep concentration gradient, maintained by blood supply or ventilation e.g. gills
Describe the trachea and its function in the mammalian gaseous exchange system
-Wide tube supported by C shaped cartilage to keep the air passage open during pressure changes
-Lined by ciliated epithelium cells which move mucus, produced by goblet cells, towards the throat to be swallowed, preventing lung infections
-Carries air to bronchi
Describe the bronchi and their function in the mammalian gaseous exchange system
-Like the trachea they are supported by rings of cartilage and are lined by ciliated epithelium cells and goblet cells
-However there are two of them, one for each lung
-Allow passage of air into the brochioles
Describe the alveoli and their function in the mammalian gaseous exchange system
-Mini air sacs lined with epithelium cells, site of gas exchange
-Walls only one cell thick, covered in a network of capillaries, 300 million in each lung all of which facilliates gas diffusion
Describe the bronchioles and their function in the mammalian gaseous exchange system
-Narrower than the bronchi
-Do not need to be kept open by cartilage rings, therefore only have smooth muscle and elastic fibres so that they can contract and relax easily during ventilation
-Allow passage of air into the alveoli
what is the role of cartilage ?
involved in supporting the trachea and bronchi, plays an important role in preventing the lungs from collapsing in the event of pressure drop during exhalation
what is the role of epithelium cells?
present in bronchi, bronchioles and trachea, involved in
moving mucus along to prevent lung infection by moving it towards the throat
what is the role of goblet cells?
cells present in the trachea, bronchi and bronchioles involved in mucus
secretion to trap bacteria and dust to reduce the risk of infection with the help of
lysozyme which digests bacteria
what is the role of elastic fibres?
stretch when we inhale and recoil when we exhale thus controlling
the flow of air
What is ventilation?
What are the two stages?
The flow of air in and out of the alveoli, inspiration and expiration
What muscles aid in ventilation?
two sets of muscles,
the intercostal muscles and diaphragm
What happens during inspiration
-the external intercostal muscles contract whereas the internal ones
relax, causing the ribs to raise upwards
-the diaphragm contracts and flattens
-the intercostal muscles and diaphragm cause the volume inside the thorax to
increase, lowering the pressure
–>the difference between the pressure inside the lungs
and atmospheric pressure creates a gradient, causing the air to enter the lungs
What happens during expiration?
-the internal intercostal muscles contract whereas the external ones relax –>lowering the rib cage
-the diaphragm relaxes and rises upwards–>this in
combination decrease the volume inside the thorax, increasing the pressure, forcing
the air out of the lungs
What is a spirometer? How does it work?
A spirometer is a device used to measure lung volume.
-A person using a spirometer
breathes in and out of the airtight chamber, causing it to move up and down, leaving a
trace on a graph which can then be interpreted
What is the vital capacity?
the maximum volume of air that can be inhaled or exhaled in a single breath–> Varies depending on gender, age, size and height
What is the tidal volume?
the volume of air we breathe in and out at each breath at rest
What is breathing rate?
– the number of breaths per minute, can be calculated from the spirometer
trace by counting the number of peaks or troughs in a minute
What is the residual volume?
The volume of air which is always present in the lungs
gas exchange in bony fish
-fish have a small surface area to volume ratio for gas exchange
-have an impermeable membrane so gases can’t diffuse through their skin therefore fish need a
specialised exchange surface
- bony fish have four pairs of gills, each gill supported by an
arch
- Along each arch there are multiple projections called gill filaments, with lamellae on
them which participate in gas exchange
-blood and water flow across the lamellae in a counter current direction meaning they flow in opposite direction
How are the projections held apart?
by water flow, in the absence of water they stick
together, meaning fish cannot survive very long out of water
Ventilation in bony fish and insects
Ventilation is required to maintain a continuous unidirectional flow —Ventilation begins with the fish opening its mouth followed by lowering the floor of buccal cavity,
enabling water to flow into it
- fish closes its mouth, causing the buccal cavity floor to raise, increasing the pressure
The water is forced over the gill filaments by the difference in pressure between the mouth cavity and opercular cavity. The operculum
acts as a valve and pump and lets water out and pumps it in
Because insects do not possess a transport system, what does it mean?
Insects do not possess a transport system therefore oxygen needs to be transported directly
to tissues undergoing respiration. This is achieved with the help of spiracles, small
openings of tubes, either bigger trachea or smaller tracheoles, which run into the body of an
insect and supply it with the required gases. At the end of each tracheole is a small amount of
tracheal fluid which allows gasses to dissolve and then diffuse into the cells.
Spiracles can be opened and closed to avoid excessive water loss
What is counter-current flow?
An adaptation for gaseous exchange in bony fish. Blood in the gill
filaments and water moving over the gills flow in opposite directions, maintaining a steep
oxygen concentration gradient.
