Exchange surfaces Flashcards
What is the formula for the surface area of a sphere
4pir^2
What is the formula for the volume of a sphere
V= 4/3pir^3
What is the formula for the surface area of cube
(WidthHeight/L)No.of faces
What are features of a good exchange surface
- Large surface area
- Thin layers
- Good blood supply
- Ventilation (maintain concentration gradient)
What is the function of the trachea and what is it made of?
Trachea
Function= tube which carries air into lungs, branches into bronchi
- C shaped rings of cartilage to prevent collapse
- Lined with ciliated epithelium (wafts mucus so it can be swallowed) and goblet cells (mucus)
- Smooth muscle and elastic fibres
Bronchi
Function= two tubes, carry air into lungs, branches into bronchioles
- Cartilage is in full rings
- Ciliated epithelial and goblet cells
- SM and elastic fibres
Bronchioles
Functions= many tubules carrying air, terminate in alveoli
- Larger tubes may have cartilage, smaller ones may not
- walls mostly smooth muscle and elastic fibres
- ciliated epithelial and goblet cells
Alveoli
Functions= site of gaseous exchange
- squamous epithelial, one cell thick
- elastic fibres
What happens inside the lungs during inhalation?
- External intercostal muscles contract, moving the ribcage up and out
- Diaphragm contracts and moves down
- Volume of the thorax is increased because of the previous actions
- Pressure in the chest decreases, pressure in the thorax is lower than the air pressure
- Air moves in
What happens inside the lungs during exhalation?
- Extermal intercostal muscles relax and ribcage fulls under its own weight/ gravity
- Diaphragm relaxes and moves up
- Volume of chest is decreased
- Chest pressure increases, air pressure in the thorax is greater than outside
- Air is forced out
How are the lungs specially adapted to gas exchange?
- Pulmonary vein removes oxygenated blood
- Pulmonary artery brings deoxygenated blood and maintains the concentration gradient
- Squamous epithelium
- Frequent ventilation keeps O2 high and CO2 low
How does a spirometer work?
- Breathing out makes the trace go up, vice versa
- Chamber is filled with air and floats on a tank of water
- Air breathed out passes through soda lime to remove CO2
- Total volume of chamber decreases as patient breathes in
- Decrease in volume = amount of oxygen used
- Volume goes down because CO2 is taken out
What precautions must be taken when using a spirometer?
- patient is healthy and free of asthma
- No air leaks as this can invalidate results
- Sterilised mouth piece
- Soda lime is fresh
Define tidal volume
Volume of air that moves in OR out in each resting breath. Usually aroumd 500cm^3
Define vital capacity
The volume of air that can be breathed out as hard as one possibly can/ breathed in as sharply as someone can.
What is inspiratory reserve volume?
Maximum volume breathed in over and above normal tidal volume
What is expiratory reserve volume?
The extra air that can be forced out of the lungs over the normal tidal volume breathed out
Define residual volume
Volume of air left in the lungs when you have exhaled as hard as possible.
What is breathing rate?
Number of breaths per minute
What is the formula for ventilation rate?
Tidal volume x breathing rate (min-^1)
How is air transported in insects?
- Air enters spiracles and is transported through the body through tubes called trachae
- trachae divide into smaller tubes called tracheoles which is filled with a fluid
- gaseous exchange occurs between the air and the tracheal fluid
- tracheal fluid can be withdrawn to increase the surface area of the tracheole wall
- when it is exposed to air, more oxygen is absorbed
Describe features of the insect ventilation system
- sections of the tracheal system have flexible walls
- Act as air sac which are squeezed by the action of flight muscles
What happens when an insect moves its wings?
- Alter the volume of the thorax
- Increases in volume= pressure inside drops, air is pushed in
Describe features of the gills in bony fish
- 5 pairs of gills which are covered by the operculum
- Each gill has 2 rows of filaments attached to a bony arch
- Filaments are thin and folded into lamallae which provide a large surface area
How does blood flow in bony fish?
- Blood flows along the gill arch and out along filaments to secondary lamallae
- Blood flows through capillaries in the opposite direction to flow of water
- Countercurrent flow ( asborb max volume of O2 )
Describe the ventilation mechanism in bony fish
- Buccal cavity= moves down so water is drawn in. When it closes it pushes water through the gills
- Movements of operculum and buccal cavity are coordinated
- Water pushed = operculum moves outwards
- Reduces pressure in opercular cavity helping water to flow through gills
