3.1 EXCHANGE SURFACES Flashcards
State the SA:V of single celled organisms
- High surface area to volume ratio
State and explain how single celled organisms obtain nutrients/gases
- Via simple diffusion
- Because they have large SA:V ratios
- So short diffusion distance for maxiumum absorbtion
State the SA:V of large organisms
- Low surface area to volume ratio
State the formula for surface area:volume ratio
SA:V = Surface area(cm2) ÷ Volume(cm3)
State what more metabolic organisms require
- ENERGY from food and oxygen to release energy in the form of ATP in aerobic respiration
- Energy to keep them warm
State and explain three features of a good exchange surface
1) Large surface area to enhance the space molecules can pas through
2) A thin barrier to reduce the diffusion distance
3) A good blood supply to maintain a concentration gradient and bring in molecules
Define alveoli
- Tiny folds in the lung epithelium to increase surface area
Describe bronchioles
- Smaller, smooth muscle airways leading to the lungs
- Has no cartilage
- Made of smooth muscle sp can contrict and dilate to controll airway airflow
- Narrow with thin walls so some exchange may occur
Describe bronchi/bronchus
- Smaller than trachea but larger than bronchioles
- Thin walls with a smaller diameter than the trachea
- Have a full ring of cartilage
Define diaphram
- A layer of muscle between the lungs
Define intercoastal muscles
- Muscles between the ribs
- Contraction of the intercoastal muscles raise the ribcage
Describe trachea
- The main airway leading from the back of the mouth to the lungs
- Has C-shaped cartillage rings to prevent friction with the asophagus behind
- Has cillitaed epithelial cells to waft microbes to filter airways
- C-shaped cartillage also prevents collapse
- Has goblet cells that produce mucus to capture dust and microbes
Define ventilation
- The refreshing of air in the lungs so that there is a higher oxygen concentration than in the blood and a lower carbon dioxide concentration than in the blood
- (Thus, gaseous exchange occurs)
Draw the structure of the lungs
Describe inhalation
1) External intercoastal muscles contract so that the ribs move up and out
2) The diaphram contracts to move down and flatten
3) Therefore, the volume of the chorax/chest cavity increases
4) The pressure in the thorax drops down below atmospheric pressure
5) So, air is drawn in
6) ACTIVE PROCESS
Describe exhilation
1) External intercoastal muscles relax so that the ribs move down and inwards
2) The diaphram relaxes also and becomes dome shaped
3) Therefore, volume in the thorax/chest cavity decreases
4) Pressure inside the thorax/lungs increases above atmospheric pressure
5) So, air is drawn out
6) PASSIVE PROCESS
State five features of the alveoli
1) Large surface area
2) Exchange barrier is permeable to oxygen and carbon dioxide
3) Thin barrier to reduce diffusion distance
4) A good blood supply
5) Elastic fibres
Explain the large surface area of the alveoli
- Provides more space for molecules to pass through
- Also lined with a layer of moisture so gases can dissolve for more efficient diffusion
- Internal layer of the alveoli is coated in a surficant that reduces cohesion between water molecules
Explain the exchange barrier permeability of the alveoli
- The cells of the alveoli/capillaries and their plasma cell surface membranes are permeable to oxygen and carbon dioxide
- Because they are small and non polar molecules
Explain the thin barrier of the alveoli
- Reduces the diffusion distance
- Alveoli and capillaries are one cell thick
- Both walls are squamous
- Alveoli and capillaries are in close contact
Explain the good blood supply of the alveoli
- Helps maintain a steep concentration gradient so carbon dioxide diffuses out and oxygen diffuses in
Explain the elastic fibres of the alveoli
- Allows dilation of the alveoli as air is drawn in to maximise space
Define cilliated epithelium
- A layer of cells that have many hair like cilia
Define elastic fibres
- Protein fibres that can deform and recoil to dilate the alveoli
Define goblet cells
- Cells that secrete mucus
Define smooth muscle
- Involuntary muscle that contracts without the need of conscious thought
Define buccal cavity
- A fish mouth
Define fillament
- Branches of tissue that make up the gill (aka primary lamellea)
Define lamellea
- (Aka secondary lamellea or gill plates)
- Are folds in the fillament to increase surface area and is the site of gas exchange
Define operculum
- A bony flap that covers and protects the gills
Define counter current flow
- Where blood and water flow in opposite directions
Describe the counter current exchange of bony fish
- Blood flows along the gill arch and out along the fillament to the lamellea
- The blood then flows through capillaries in opposite direction to the flow of water over the lamellea
- The countercurrent flow absorbs the maximum amount of water
Describe ventillation in bony fish
- The buccal cavity can change volume
- The floor of the mouth moves downwards which decreases the pressure and draws in more water
- The mouth closes and the floor is raised again, pushing water through the gills
- As water is pushed from the buccal cavity, the operculum moves outwards
- This movement decreases pressure in the opercular cavity, helping water flow to the gills
State the three ways large insects can ventilate
1) Movement of the wings - (alters thorax volume)
2) Expansion of tracheal system - (expand air sacs)
3) Locusts specialised breathing movements (air control via valves)
Draw the structure of an insect
Draw the structure of insect tracheoles
State the circulatory system of insects
- Open circulatory system
- Slow circulation and can be affected by body movements
Describe the exchange of insects
- Air enters via spirical pores through to the tracheae tubes
- Then through to smaller tracheoles which are open ended and filled with tracheal fluid
- Gaseous exchange occurs between the air in the tracheoles and the tracheal fluid
Describe exchange in insects with high metabolic activity
- Tracheal fluid gets withdrawn into the body fluid in order to increase the surface area of the tracheole wall that is exposed to air
- This means that more oxygen can be absorbed when the insect is active
Describe the movement of insect wings on ventillation
- Alters the thorax volume
- As the thorax volume decreases, air in the tracheal system is put under pressure
- Therefore, its pushed out of the tracheal system
- When the thorax volume increases, the pressure inside the thorax decreases
- Therefore, air is pushed into the tracheal system from outside
Describe the expansion of insect tracheal system on ventilation
- Tracheal expansion occurs to increase flexibility of the walls
- These act as air sacs which can be squeezed by the action of flight muscles
- Repetative expansion and contraction of these sacs ventilate the tracheal system
Describe the abdomine volume alteration of insects on ventillation
- Abdomine volume alteration is co-ordinated by opening and closing valves in the spiricals
- As the abdomine expands, spiricals at the front end of the body open and air enters the tracheal system
- As the abdomine reduces in volume, the spiricals near the end of the body open and air leaves the tracheal system
Define breathing rate
- The number of breaths per minute
Define oxygen uptake
- The volume of oxygen absorbed by the lungs in one minute
Define spirometer
- A device that can measure the movement of air into and out the lungs
Define vital capacity
- The maximum volume of air that can be expelled from the lungs after taking deepest possible breath
Define tidal volume
- The volume of air inhaled or exhaled in one breath, usually measured at rest
Define residual volume
- The volume of air that remains in the lungs after forced exhilation
- (Remains in the airways and alveoli)
- (Aprox. 1.5dm3)
Draw a labled spirometer
State precautions to take with spirometers
- The subject should be healthy/asmtha free
- The soda lime should be fresh/functioning
- There should be no air leaks in the apparatus (invalid/inaccurate result)
- The mouthpeice steralised
- The water chamber must not be overfilled (or water may enter air tubes)
State three factors that vital capacity depends on
1) The size of the person (particularly height)
2) Their age/gender
3) Their level of exercise
State the average vital capacity
- 2.5dm3 to 5.0dm3
State the average tidal volume
- 0.5dm3
Draw a labled spirometer trace
State an assumption about oxygen uptake/CO2 removal
- That the volume of carbon dioxide absorbed by the soda lime is equal to the oxygen uptake into the blood
Describe how to calculate oxygen uptake from a spirometer trace
State how to measure breathing rate from a spirometer trace
- Count the number of peaks in each minute
State two factors explain increased oxygen uptake
- Increased breathing rate (excercise)
- Deeper breaths (excercise)
