3.1.1 Exchange Surfaces Flashcards
What is the relationship between size of cube/organism and SA:V ratio?
As size increase, the SA:V ratio decreases
What is the SA:V of single celled organisms?
- Large SA:V ratio
- Sufficient diffusion across the cell membrane to meet the needs of the organism
What is the SA:V of multicellular organisms?
- Small SA:V ratio
- Not enough substances can diffuse in and out to supply the whole organism
- They have exchange surfaces (large SA to compensate) and transport systems (as distance between tissues and exchange surfaces increases)
What are the features of root hair cells?
Large surface area increases the rate of absorption of water by osmosis and minerals by active transport
What are the features of alveoli?
- Made of a single layer of flat cells (squamous epithelial cells) which provides a short diffusion distance
- A good blood supply maintains a concentration gradient by taking oxygen away
What are the features of an efficient exchange surface?
Thin - short diffusion pathway
Large surface area - lots of opportunity for exchange to occur and lots of substance can diffuse at once
Good blood supply - maintains concentration gradient
Moist - gases/soluble substances can dissolve
LAMBTV
What are the components of the mammalian gaseous exchange system?
Nasal cavity -> trachea -> bronchi -> lung -> bronchioles -> alveoli
- Pleural membrane
- Rib
- Intercostal muscles
- Diaphragm
What is the structure and function of the inside of the trachea?
- Goblet cells secrete mucus to trap microorganisms and dust
- Cilia waft mucus, trapped microorganisms and dust upwards towards the throat so that it can be swallowed and stomach acid can kill microbes
What is the structure of the trachea?
- C-shaped cartilage
- Elastic fibres
- Ciliated epithelium
- Smooth muscle
What is the structure of the bronchi?
- Small cartilage pieces interspersed with smooth muscle
- Elastic fibres
- Ciliated epithelium
What is the structure of the bronchioles?
- Smooth muscle and elastic fibres outer wall
- Ciliated epithelium (only some goblet cells
What is the structure of the alveoli?
- Elastic fibres
- Alveolar epithelium
- Next to capillaries
What is the function of cartilage?
- Strong and flexible
- Prevents collapsing when the pressure drops as you breathe in
What is the function of smooth muscle?
- Allows diameter to be controlled
- In trachea, bronchi and bronchioles
What is the function of the elastic fibres?
- Fibres are stretched when you breathe in
- They reoil to help push air out during exhalation
What is the mechanisms of inspiration?
- External intercostal muscles and the diaphragm contract
- Ribcage moves up and out, increasing the volume of the thorax
- Lung pressure decreases
- Air is forced into the lungs
Active process as it requires energy for muscle contraction
What is the mechanisms of expiration?
- External intercostal muscles and diaphragm relax
- Ribcage moves down and in, decreasing the volume o the thorax
- Lung pressure increases
- Air is forced out of the lungs
Passive process
What is the mechanism of forced expiration?
- Internal intercostal muscles contract
- Pulls ribcage down and in
- Active process
What are the components of a spirometer?
- Spirometer chamber
- Kymograph
- Water level
- Mouthpiece
- Nose clip
- Carbon dioxide absorber
- Counterpoise
What type of system is a spirometer?
Closed system
What does tidal volume mean?
Volume of air in each normal breath
What does vital capacity mean?
Maximum volume of air that can be breathed in or out
What does breathing/ventilation rate mean?
Number of breaths taken per unit of time (usually 1 minute
What does oxygen uptake mean?
The rate at which a person uses up oxygen (dm3/min)
How do you measure lung function?
- Pulmonary ventilation measures the volume of air taken into the lungs in 1 minute
- Pulmonary ventilation rate (dm3/min) = tidal volume (dm3) x breathing rate (per min)
- VR = TV x BR
What does the spirometer trace show?
Volume of the chamber and time
Why does the spirometer trace slant downwards?
- Slants down with successive cycles
- Oxygen is removed from the spirometer as you breath in
- Carbon dioxide that you breath out is absorbed
- Chamber doesn’t rise as high
What direction will an inhale and exhale go in on a spirometer trace?
Inhale - down
Exhale - up
How does the oxygen content in air differ to that in water?
Air = 20.9%
Water = approx 0.8%
- Concentration increases when temperature decreases and when flow increases
- Fish have to pass large volumes of water over their as exchange systems relative to the volumes of air ventilated by land animals
How does gas exchange occur in fish?
- When fish open their mouth, they lower the floor of the buccal cavity
- Volume inside the buccal cavity increases and pressure within the cavity decreases
- Pressure is higher outside the mouth so water flows into the buccal cavity
- Fish then raise the floor of the buccal cavity to close their mouth, which increases pressure within the buccal cavity
- Water flows from buccal cavity (high pressure) to gill cavity (low pressure)
- As water enters, pressure begins to build up in the gill cavity and causes the operculum to be forced open and water to exit fish
- Operculum is pulled shut when the floor of the buccal cavity is lowered at the start of the next cycle
How are the gills adapted for good gas exchange?
Large surface area:
- Usually have 4 gill arches on either side of fish to support gills
- Each arch has multiple gill filaments which in turn have multiple gill lamellae
Thin:
- Lamellae are very thin so blood flowing through them is only a short diffusion distance from seawater
Concentration gradient:
- Blood and water flow over the gill lamella in opposite directions
- Countercurrent system provides a relatively constant rate of diffusion
- Steep gradient is maintained along the whole length of the lamella
What does the countercurrent graph look like?
- Distance along gill plate vs oxygen concentration
- Water line on top of blood line
What is the cuticle?
- Impermeable
- Prevents water loss from the body cells to the surroundings
- Oxygen and carbon dioxide are unable to move through it
What are the spiracles?
Small holes in the cuticle
What is the structure of the tracheal system?
- Spiracle
- Trachea (reinforced with rings of chitin)
- Tracheoles
Where does most gas exchange occur in insects?
Tips of the tracheoles and cells with a very high metabolic rate to ensure an adequate oxygen supply for respiration
How does gas exchange work in insects when they are more active?
- When less active, the ends of the tracheoles contain fluid
- As activity increase, fluid is removed from the tracheoles as the muscle cells produce lactic acid
- Lactic acid lowers the water potential in cells so water moves into the cell
- Exchange of gases therefore occurs nearer the cell and there is a higher concentration gradient as air has a higher concentration of oxygen than water
How are diffusion gradients created in insects?
- When cells are actively respiring, oxygen is used up
- Concentration of oxygen towards the end of the tracheoles falls
- Creates a diffusion gradient for oxygen towards the cells
- Carbon dioxide is produced by cells, creating a diffusion gradient with the atmosphere
What is the mechanism of expiration in larger insects?
- Muscles contract and flatten the body
- Volume of the tracheal system decreases
- Air is forced out
What is the mechanism of inspiration in larger insects?
Achieved passively when the elastic nature of the body segments returns them to their original shape
What are the limitations of the tracheal system?
- Imposes a limitation on the size of insects
- As it relies on diffusion of oxygen through the body
- Diffusion occurs efficiently across small distances but is only effective up to 1cm
What is discontinuous gas exchange?
- Insects have the ability to close spiracles using valves in the cuticle
- Reduces water loss or prevents excess oxygen from entering their cells (particularly during periods of rest/ianctivity)
- No transport system is involved
What are the differences between ventilation in insects and mammals?
- Expiration in insects is active as muscles contraction
- Expiration in mammals is achieved passively as muscles relax
- Inspiration is achieved passively in insects
- Inspiration is active in mammals as muscles contract
What are the differences between the structures of insect and mammal ventilation systems?
Insects:
- Tracheae with no ciliated epithelium
- Many tracheae
- Narrower diameter
- Chitin (not cartilage)
- Spiral chitin
Mammals:
- Trachea with ciliated epithelium
- 1 trachea
- Wider diameter
- Cartilage only
- C shaped rings of cartilage
