Exchange surfaces Flashcards
Why do multicellular organisms need specialised exchange surfaces?
Diffusion doesn’t have a fast enough rate
Why does diffusion not work in multicellular organisms?
Small surface area to volume ratio, high metabolic rate, large distance between where the oxygen and carbon dioxide is and where it needs to be
Features of efficient exchange surfaces
Increased surface area, thin layer, good blood supply or ventilation to maintain gradient
Example of thing with increased surface area
Root hair cells
Example of thing with a thin layer
Alveoli
Example of thing with good blood supply/ventilation
Gills, alveoli
Components of the mammalian gaseous exchange system (Muscles etc)
Cartilage, ciliated epithelium, goblet cells, smooth muscle, elastic fibres
Parts of the mammalian gaseous exchange system
Nasal cavity, trachea, bronchus, bronchioles, alveoli
Important features of the nasal cavity
Large surface area, good blood supply which warms the blood to body temperature, hairy lining to secrete mucus to trap dust, moist surfaces which increase the humidity to reduce evaporation from the exchange surfaces
What does the trachea do?
Main airway carrying clean, warm and moist air from the nose down into the chest
Things in the trachea
Cartilage, ciliated epithelium
What does cartilage do in the trachea?
Stops the trachea from collapsing, incomplete rings to allow food to move down the oesophagus behind the trachea
What does the ciliated epithelium do in the trachea?
Goblet cells secrete mucus on the lining of the trachea to trap dust and microorganisms, cilia waft the mucus away from the lungs towards the throat
Things in the bronchi
Cartilage, ciliated epithelium
Things in the bronchioles
Smooth muscle, thin layer of flattened epithelium
What does the smooth muscle do in the bronchioles?
When the smooth muscle contracts, the bronchioles constrict. When it relaxes, the bronchioles dilate. This changes the amount of air reaching the lungs.
What does the thin layer of flattened epithelium do in the bronchioles?
Makes some gaseous exchange possible
What does the alveoli do?
Main gas exchange surfaces of the body
Adaptations of alveoli
200-300 micrometres, large surface area so high surface area to volume ratio, good blood supply, good ventilation, thin layers, lung surfactant
Features of the alveoli
Collagen, elastin fibres
What do the elastin fibres do in the alveoli?
Allow alveoli to expand when inhaling, can recoil to original size when exhaling, helps expel air
Role of lung surfactant
It makes it possible for the alveoli to remain inflated
Parts of the body involved in mammal ventilation
Rib cage, internal and external intercostal muscles, diaphragm
What moves air in and out f the lungs?
Pressure changes in the thorax due to breathing movements
Ventilation
Movement of air
Role of rib cage in ventilation
Semi-rigid case within which pressure can be lowered with respect to the air outside it
Role of the diaphragm in ventilation
To form the floor of the thorax
Diaphragm
Broad, domed sheet of muscle
Where can you find the internal and external intercostal muscles?
Between the ribs
What lines the thorax?
Pleural membranes
Pleural cavity
Space between the pleural membranes
Role of the pleural cavity
To contain lubricating fluid to allow membranes to slide over each other as you breathe
Process of inspiration
Diaphragm contracts so it flattens and lowers, external intercostal muscles contract, ribs moved up and out, volume of thorax increases, pressure in thorax reduced so it is lower than air pressure, air drawn through the gaseous exchange system to equalise the pressure gradient
Is inspiration active?
Yes
Is expiration active?
No
Process of expiration
Diaphragm relaxes and moves up, external intercostal muscles relax, ribs move down and inwards under gravity, elastic fibres in the alveoli return to normal length, volume of thorax decreases, pressure inside thorax greater than air pressure, air moves out of lungs to even out pressure gradient
Process of forced expiration
Internal intercostal muscles contract, ribs pulled down hard and fast, abdominal muscles contract, diaphragm forced up, increased pressure in lungs
Triggers of asthma
House dust mites, cigarette smoke, pollen, stress
Process of an asthma attack
Cells lining the bronchioles release histamines, epithelial cells become inflamed and swollen, histamines stimulate goblet cells, more mucus, smooth muscle in bronchiole walls contract, airways narrow and fill with mucus
Ways to treat asthma
Relievers, preventers
How do relievers work?
Attach to active sites on the surface membrane of the smooth muscle in the bronchioles, relax and dilate the airways
How do preventers work?
Reduce the sensitivity of the lining of the airways
How to measure capacity of lungs
Peak flow meter, vitalographs, spirometer
Peak flow meter
Device that measures the rate at which air is expelled from the lungs
How do vitalographs work?
Patient breathes out as quickly as possible, instrument produces a graph of the air breathed out
What do vitalographs measure?
Expiratory volume
Components of lung volume
Tidal volume, vital capacity, inspiratory reserve volume, expiratory reserve volume, residual volume, total lung capacity
Tidal volume
Volume of air that moves in and out of the lungs with a resting breath
Average tidal volume
500cm^3
Vital capacity
Volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest possible intake of breath
Inspiratory reserve volume
Maximum volume of air you can breathe in over and above a normal inhalation
Expiratory reserve volume
Extra amount of air you can force out of your lungs over and above the normal tidal volume of air that you breath out
Residual volume
Volume of air left in your lungs after exhaling as hard as possible
Can you measure residual volume directly?
No
Total lung capacity
Sum of the vital capacity and residual volume
How expiratory reserve volume is represented on a spirometer graph
Line between troughs of tidal volume and start of the residual volume
How inspiratory reserve volume is represented on a spirometer graph
Line between peak of tidal volume and top of total lung capacity
How inspiratory capacity is represented on a spirometer graph
Line between trough of tidal volume and top of total lung capacity
How vital capacity is represented on a spirometer graph
Line between top of residual volume and top of total lung capacity
How residual volume is represented on a spirometer graph
Line beneath the lowest trough of tidal volume
Breathing rate
Number of breaths taken per minute
Ventilation rate
Total volume of air inhaled in one minute
Equation for ventilation rate
Ventilation rate = Tidal volume x Breathing rate
Relationship between tidal volume, breathing rate and oxygen uptake
As oxygen demand increases, tidal volume increases, breathing rate increases, oxygen uptake increases
Where does air enter the system in insects?
Spiracles
What can leave through the spiracles?
Air, water
How do insects prevent water loss through the spiracles?
Can be opened or closed by sphincters, closed for as long as possible,
What will cause the spiracles to open?
High carbon dioxide levels, high oxygen demand
What leads away from the spiracles?
Tracheae
Structure of the tracheae in insects
Lined with spirals of chitin
Purpose of chitin in the tracheae in insects
Keep them open if bent or pressed, makes up the cuticle
Why does little gaseous exchange occur in the tracheae?
The chitin lining it is impermeable
What comes off the tracheae in insects?
Trachioles
Where does most gaseous exchange occur in insects?
Trachioles
How does air move along the tracheae/trachioles?
Diffusion
How is a large surface area created in insects?
Lots of tiny tracheoles
How does air get into the places it needs to in an insect?
Tracheal fluid in the tracheoles limits diffusion of oxygen into cells, lactic acid build up will cause water to leave the tracheoles by osmosis, oxygen can then diffuse into surrounding cells
Role of tracheal fluid
To limit the penetration of air for diffusion
How do insects get their oxygen?
Tracheal system
What controls the extent of gas exchange in insects?
Opening and closing of spiracles
Examples of insects with high energy demands
Locusts, grasshoppers, bees, wasps, flies
Alternatives to tracheal system in insects
Mechanical ventilation of tracheal system, collapsible enlarged tracheae that act as air reservoirs
How does mechanical ventilation of the tracheal system work?
Air pumped into system by muscular pumping of thorax and abdomen, movements change volume of the body, changes pressure in tracheae and tracheoles, air drawn into tracheae and tracheoles
How do collapsible enlarged tracheae which act as air reservoirs work?
Increase the amount of air moved through the gas exchange system, inflated and deflated by ventilating movements of the thorax and abdomen
Explanation for why fish have the gas exchange system that they have
Too much energy to move dense water in and out of lung like respiratory organs
Adaptations of the gills
Large surface area, good blood supply, thin layers, tips of adjacent gill filaments overlap, water moving over the gills and the blood in the gill filaments flow in different directions
Role of the operculum
To protect the gill cavity
Parts of the gas exchange system in fish
Efferent blood vessel, afferent blood vessel, gill lamellae, gill filaments
Role of the efferent blood vessel in fish
To carry the blood leaving the gills in the opposite direction to the incoming water to maintain a steep concentration gradient
Role of the afferent blood vessel in fish
To bring blood into the system
Role of the gill lamellae
Main site of gaseous exchange
What do gill filaments need?
Flow of water to keep them apart to expose the large surface area needed for gaseous exchange
Ram ventilation
Continuous movement of water to ventilate the gills
Fish that do ram ventilation
Shark, ray
Process of gas exchange in fish
Mouth opens, floor of buccal cavity lowers, volume of the buccal cavity increases, pressure in buccal cavity drops, water moves into the buccal cavity, opercular valve shuts, opercular cavity expands, pressure in opercular cavity drops, floor of the buccal cavity moves up, pressure increases, water moves from buccal cavity over the gills, mouth closes, operculum closes, sides of the opercular cavity move inwards, pressure in the opercular cavity increases, water moved over the gills and out of the operculum, floor of buccal cavity moves up, water flowed out of the gills
Why do the tips of adjacent gill filaments overlap?
Increases resistance to the flow of water over the surfaces to slow down the movement of water so there is more time for gaseous exchange to take place
Why does water move over the gills in a different direction to blood in the gill filaments?
Countercurrent exchange system is set up to ensure that a steeper concentration gradient is maintained than if water and blood moved in the same direction
Tools needed for dissection
Sharp scissors, scalpels, tweezers, mounted needles
Why are light microscopes used to look at dissected stuff?
More detail than can be seen with the naked eye, use of stains
Why don’t single cellular organisms need specialised exchange surfaces?
High surface area to volume ratio, low metabolic activity, rate of diffusion is enough
Equation for surface area of a sphere
4pir^2
Equation for volume of a sphere
4/3pir^3
