3.1.1 - Exchange surfaces Flashcards
Why do single-called organisms not need specialised exchanges surfaces ?
- Due to their small size, they have a large surface area : volume ratio. This maximises surface area for absorbable/ removal of substances and results in a short diffusion distance so rate of diffusion is sufficient
- They have low metabolic demands so Ov2 demands/ COv2 production is low
Why do multicellular organisms require specialised exchange surfaces ?
- Due to their large size they have a small surface area : volume ratio. Diffusion distance is too large so the rate of diffusion is insufficient to supply cells with all required nutrients/ molecules ( ie. Ov2 )
- They have high metabolic demands due to large size and mobility so cells have greater Ov2 demands / COv2 production
What is the relationship between size and surface area : volume ratio ?
As the size of an object increases, tippets surface area to volume ratio decreases
Do you know how to calculate surface area : volume ratio ?
Yes
What are features of efficient exchange surfaces ?
- Increased surface area
- Thin layers
- Good blood supply
- Ventilation to maintain gradient
Explain how increased surface area is a feature of efficient exchange surfaces ?
Provides a larger surface area over which diffusion can occur increasing rate/ overcoming the limits of surface area to volume ratio
Name an example of specialised exchange surfaces with an increased surface area ?
Root hair cells lining roots of the plant
Explain how thin layers is a feature of efficient exchange surfaces ?
This results in a shorter diffusion distance increasing the rate of diffusion / making it more efficient
Name an example of specialised exchange surfaces with thin layers ?
Alveoli in the lungs
Explain how a good blood supply is a feature of efficient exchange surfaces ?
This results in a steeper concentration gradient which increases the rate of diffusion
Name an example of specialised exchange surfaces with a good blood supply ?
- Alveoli in the lungs
- Gills of fish
Explain how ventilation to maintain diffusion gradient is a feature of efficient exchange surfaces ?
Ventilation system helps maintain concentration gradient which increases the rate of diffusion
Name an example of specialised exchange surfaces with a ventilation to maintain diffusion gradient ?
- Alveoli in the lungs
- Gills of fish where ventilation means a flow of water carrying dissolved gases
What are the components of the respiratory system ?
- Nasal cavity/ passage way
- Lungs
- Trachea
- Bronchus
- Bronchioles
- Alveoli
What are the adaptations of the nasal cavity ?
- Large surface area with good blood supply ( warms air to body temperature )
- Hairy lining ( secretes mucus to trap dust and bacteria )
- Moist surfaces ( increases humidity of incoming air )
What is the role of the nasal cavity ?
It ensures air that passes through the nasal cavity is a similar temperate and humidity than air already in the body/ lungs
What is the trachea ?
The main airway carrying air from the nose down into the chest
What are features of the trachea ?
- It is a wide tube supported by incomplete rings of strong/ flexible cartilage
- Trachea and branches are lined with a ciliated epithelium with goblet cells between/ below epithelial cells
What is the function of the incomplete rings of strong/ flexible cartilage in the trachea ?
- They prevent the trachea from collapsing
- Since the rings are incomplete, this allows food to be easily moved down the oesophagus
What is the role of goblet cells in the trachea ?
Goblet cells secrete mucus onto trachea lining to trap dust and microorganisms
What is the role of cilia in the trachea ?
Cillia beat and move the mucus, along with any trapped dirt/ microorganisms away from the lungs to the throat were it is swallowed and digested
What is the bronchus/ bronchi ?
Trachea divides in the chest into a left branch in the left lung and a right branch into the right lung which are bronchi
What are the functions of bronchi ?
- Similar to trachea with rings of cartilage but they are smaller
What are bronchioles ?
In the lungs, bronchi divide into many small bronchioles
What are the features of bronchioles ?
- They have no cartilage
- Walls contain smooth muscle
- They are lined with a thin layer of flattened epithelium
What is the role of smooth muscle in bronchioles ?
- When the smooth muscle contracts, bronchioles constrict/ close
- When smooth muscle relaxes, bronchioles open
- This changes the amount of air that reaches the lungs
What are alveoli ?
They are tiny air sacs which are the main gas exchange surfaces of the body
What are the features of alveoli ?
- Small in diameter
- Layer of thin, flattened epithelial cells along with collagen + elastic fibres
- Inner surface of alveoli is covered in thin layer of a solution of water, slats and lung surfactant
What is the role of lung surfactant in the alveoli ?
Lung surfactant allows alveoli to remain inflated
What is the role of elastic fibres in the alveoli ?
- Elastic tissues allow alveoli to stretch and return to resting size as air is drawn in and out of the lungs
- Elastic recoil of the lungs
What are the main adaptations of the alveoli ?
- Large surface area
- Thin layers
- Good blood supply
- Ventilation system
Explain the effect of a large surface area on alveoli ?
- Due to the spherical shape and tiny size of alveoli, they have a very agreeable surface area
- This means there is greater surface area over which diffusion/ gas exchange can occur ( maximising gas exchange )
Explain the effect of thin layers on alveoli ?
- Alveoli have walls that are only a single epithelial cell thick decreasing the effusion distance between the air in the alveolus and blood din capillaries
- Increases the rate of diffusion maximising gas exchange
Explain the effect of a good blood supply on alveoli ?
- The constant flow of blood through capillaries carrying Ov2/ COv2 maintains steep concentration gradient for Ov2/ COv2 between air in alveolus and blood din capillaries
- This increases the rate of diffusion maximising gas exchange
Explain the effect of a ventilation system on alveoli ?
- Breathing moves air in and out of the alveoli helping maintain a steep concentration gradient for Ov2/ COv2 between blood/ air
Label the diagram ?
Label the diagram ?
What type of process is inspiration ?
Inspiration is an active process that requires/ used energy
Explain what happens during inspiration/ inhalation ?
- Dome-shaped diaphragm contracts, flattening and lowering
- External intercostal muscles contract, moving ribs outwards and upwards
- This causes the volume f the thorax to increase which causes the pressure of the thorax to decrease
- Pressure in thorax is lower than pressure of atmospheric air so air moves into the lungs until pressure equalises outside and inside the chest
What type of process in expiration ?
Expiration is a passive process that does not require/ use energy
Explain what happens during expiration/ exhalation ?
- Muscles of diaphragm relax so it moves up into its resting domed shape
- External intercostal muscles relax so ribs move down and inwards due to gravity
- Elastic fibres in alveoli return to their original length
- This causes the volume of the thorax to decrease which causes pressure in the thorax to increase
- pressure in the thorax is greater than pressure of atmospheric air so air moves out of the lungs until pressure inside and outside the chest equalises
When does expiration require energy ?
You can exhale forcibly which uses energy
Explain what happens during active expiration / exhalation ?
- Internal intercostal muscles contract, pulling ribs down hard and fast
- Abdominal muscle contract forcing diaphragm up to increase pressure in lungs rapidly
What can be used to measure the capacity of the lungs ?
- A peak flow meter
- Vitalographs
- Spirometer
What is a peak flow meter ?
A simple device that measures the rate at which air can be expelled from the lungs
What is a vitalograph ?
A more sophisticated device that produces a graph of the amount of air and how quickly a patient breathed out ( forced expiratory volume in 1 second )
What is a spirometer ?
A device used to measure different aspects of lung volume of investigate breathing patterns
Define the term ‘Tidal volume’ ?
Tidal volume : The volume of air that moves in/ out of lungs with each resting breath
Define the term ‘vital capacity’ ?
Vital capacity : Volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath
Define the term ‘Inspiratory reserve volume’ ?
Inspiratory reserve volume : Maximum volume of air you can breath in over and above normal inhalation
Define the term ‘Expiratory reserve volume’ ?
Expiratory reserve volume : The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you breathe out
Define the term ‘Residual volume’ ?
Residual volume : Volume of air that’s left in your lungs when you have exhaled as hard as possible
Define the term ‘Total lung capacity’ ?
Total lung capacity : Sum of the vital capacity and residual volume
What is the breathing rate ?
The breathing rate is the number of breaths taken per minute
What is the ventilation rate ?
The ventilation rate is the total volume of air inhaled in one minute
What is the equation to calculate the ventilation rate ?
ventilation rate = tidal volume x breathing rate ( /min )
Explain the relationship between oxygen demands and tidal volume ?
- Oxygen demands may increase due to exercise, anger or stress
- The tidal volume of air is moved in and out of lungs with each breath that increases ( eg. from 15 —> 50 % ) of vital capacity
- Breathing rate increases
- Therefore ventilation rate increases so oxygen uptake increases during gaseous exchange to meet demands of tissue and provide Ov2 for aerobic respiration
