3.3.2 Gas Exchange Flashcards
Name the two major gas exchange surface adaptations
Large SA
Thin (short diffusion pathway)
Describe the counter current system
1) water (containing O2) enters fish through the mouth and passes out through the gills
2) blood flows through lamellae in one direction and water flows over in the opposite direction
(Maintains a large concentration gradient between water and blood)
Conc of O2 in water is always higher than the conc in blood, so as much oxygen diffuses from the water into the blood
Gill filaments
Make up the gills
Thin plates (give big SA)
Covered in lamellae (increase SA)
Lamellae
Have lots of blood capillaries and thin surface layer of cells to speed up diffusion
How do insects use tracheae to exchange gases?
1) air moves into trachea through pores on the surface called spiracles
2) oxygen travels down concentration gradient towards the cells
3) trachea branch off into smaller tracheoles (thin,permeable walls and go into cells) oxygen diffuses directly into the respiring cells
4) CO2 from cells move down its own concentration gradient towards the spiracles to be released into the atmosphere
(Insects use rythmitic abdominal movements to move air in and out of spiracles)
Dicotyledonous plants (dicots)
- Exchange at the surface of mesophyll cell
1) gases move in and out of pores in the epidermis called the stomata
2) stomata can open to allow exchange of gases and close if the plant is losing too much water (guard cells control opening and closing of stomata)
How do insects control water loss?
- They close spiracles if they are losing too much water/inactive
- Have a waterproof waxy cuticle all over their body and tiny hairs around spiracles, reduce evaporation
- sunken spiracles H2O build up around spiracle and reduces diffusion gradient
How do plants control water loss?
- water enters guard cells making them turgid, opens stomata, when it starts to get dehydrated the guard cells lose water and become flaccid which closes the stomata
What are xerophytes?
plants adapted to hot climates
Stomata sunk in pits
Trap moist air, reduced concentration gradient of water between leaf and the air, reduces amount of water diffusing out of the leaf and evaporating
Layer of hairs on epidermis
Trap moist air around the stomata
Curled leaves with stomata inside
Protects stomata from wind, (wind=increased rate of diffusion )
Reduced number of stomata
Fewer places for water to escape
Waxy cuticle
Protective layer, Reduce evaporation
Explain the role of the stomata
Allows water to be lost rapidly
- water evaporates from gas exchange to become water vapour and passes out through spiracle down a concentration/water potential gradient.
Thick fleshy stem
Increases in size to store more water when it rains.
Shallow roots
So it can get as much rain as possible from surface when it rains occasionally.
Deep roots
Obtain water from deep
What is the humans gas exchange organ?
Lungs
Name the different parts of the human gas exchange system?
Intercoastal muscles Bronchus (one)/ bronchi (two) Bronchiole Alveoli Diaphragm Lung Rib cage Trachea
What is inspiration?
breathing in
Process of inspiration
1) The external intercostal and diaphragm muscles contract.
2) causes the rib cage to move upwards and outwards and the diaphragm to flatten, increases volume of thorax cavity
3) as volume of thoraic cavity increases the lung pressure decreases
4) air flows down a pressure gradient (high-low) so air flows down trachea in to the lungs
Is inspiration active or passive?
Active, requires energy
What is the thoraic cavity?
The space where the lungs are
What is expiration?
breathing out
Process of expiration (relaxed)
Passive-no energy needed
1) external Intercoastal muscles and diaphragm muscles relax
2) rib cage moves downwards and inwards and the diaphragm becomes curved again.
3) volume of the thoraic cavity decreases, air pressure increases.
4) air is forced down down the pressure gradient and out of the lungs
(elastic recoil of lungs)
Expiration (forced)
1) External intercoastal muscles relax and internal intercoastal muscles contract, pulling the ribcage further down and in
(muscle movement is opposing)
Is relaxed expiration active or passive?
Passive- Doesn’t require energy
Where does gas exchange take place in the lungs?
Alveoli
Explain gas exchange in the alveoli
1) O2 diffuses out of the alveoli, across the alveolar epithelium, and the capillary endothelium and into the haemaglobin in the blood.
2) CO2 diffues into the alveoli from the blood, and is breathed out.
How is alveoli adapted for gas exchange?
- huge number of alveoli in lungs- large SA
- Thin exchange surface- one cell thick (short diffusion pathway)
- steep concentration gradientof O2 and CO2 between alveoli and capillaries (increases rate of diffusion, maintained by the blood flow and ventillation)
What is tidal volume?
volume of air in each breath
what is ventillation?
number of breaths per minute
Forced expiratory volume
maximum volume of air that can be breathed out in 1 second.
Forced vital capacity
Maximum volume of air it is possible to be breathed forcefully out of the lungs after a deep breath.
How is pulmonary tuberculosis formed?
- someone becomes infected with tuberculosis bacteria
- immune system cells build a wall around the bacteria in the lungs
- Forms small, hard lumps known as tubercles.
- tubercles dies and gaseous exchange surface is damaged so tidal volume decreases.
How is tidal volume reduced do to tuberculosis?
- tubercles dies and gaseous exchange surface is damaged so tidal volume decreases.
- causes fibrosis which further reduces tidal volume.
Effects of reduced tidal volume
- less air inhaled with each breath
- in order to take in enough oxygen, patients have to breathe faster (increased ventilation rate)
Symptoms of tuberculosis
- persistent cough
- coughing up blood and mucus
- chest pains
- shortness of breath
- fatigue
What is fibrosis?
formation of scar tissue. can be a result of an infection or exposure to substances like asbestos or dust.
Scar tissue
Thicker and less elastic than normal lung tissue
Effects of fibrosis
- lungs are less able to expand and can’t hold as much air as usual. tidal volume is reduced and so is FVC (forced vital capacity)
- reduction in the rate of gaseous exchange - diffusion is slower across a thicker scarred membrane.
- Faster ventilation rate to get enough air into lungs to oxygenate blood.
Symptoms of fibrosis
- shortness of breath
- dry cough
- chest pain
- fatigue
- weakness
What is asthma?
when airways become inflamed and irritated
Causes of asthma
- allergic reaction to pollen and dust
What happens during an asthma attack?
- smooth muscle lining the bronchioles contract and a large amount of mucus is produced
- this causes constriction of the airways, making it difficult for the sufferer to breathe properly.
- Air flow is reduced, so less oxygen enters the alveoli and into the blood.
- this means FEV (forced expiratory volume) is reduced
Symptoms of asthma
- wheezing
- tight chest
- shortness of breath
Relieved by drugs which relax the muscles in bronchioles and open up airways.
What is emphysema?
Lung disease caused by smoking and air pollution
foreign particles become trapped in the alveoli.
Effects of emphysema
- attracts phagocytes
- phagocystes produce and enzyme which break down eleastin (walls of alveoli)
- loss of elastin means alveoli can’t expell air as well (remains trapped)
- Destruction of alveolar walls, reduces SA of alveoli and decreases rate of gas exchange.
symptoms of emphysema
- shortness of breath
- wheezing
- increased ventilation rate
Ethical issues with dissecting animals
- morally wrong
- vegan
- not raised in humane way (overcrowding, lack of food, killed inhumanely)
formula for finding the pulmonary ventilation rate
PVR=tidal volume X breathing rate
