3.1.1 Exchange surfaces Flashcards
Method of gas exchange in single called organisms?
Simple diffusion
Why do single celled organisms not need specialised exchange surfaces?
- Short diffusion distance due to high SA:V ratio
- Low metabolic activity
Why do multi celled organisms need specialised exchange surfaces?
- Long diffusion distance due to low SA:V ratio
- High metabolic activity
How is increased SA a feature of efficient gas exchange?
Overcomes limitations of low SA:V ratio
How are thin layers a feature of efficient gas exchange?
Allows for shorter diffusion distances
How is a good blood supply a feature of efficient gas exchange?
Maintains steep concentration gradient so faster diffusion
How is ventilation a feature of efficient gas exchange?
For gases it maintains a steep concentration gradient so faster diffusion
Pathway of air in mammalian gas exchange system?
Nasal cavity -> trachea -> bronchus -> bronchioles -> alveoli
Why does the nasal cavity have a good blood supply and moist surfaces?
To warm incoming air and create a humid environment (reduced water loss)
Why are the trachea rings incomplete?
To allow it to bend when food travels down the oesophagus
What is the trachea supported by?
Incomplete rings of cartilage
What is the trachea lined with?
Ciliated epithelial and goblet cells
What component is similar in structure to the trachea, but is smaller?
Bronchus
What is the structure of bronchioles?
No cartilage rings, have smooth muscle and elastic fibres instead
Diameter of alveoli?
200-300 µm
What are alveoli made up of?
Thin layer of flattened epithelial cells, collagen and elastic fibres
Function of elastic fibres in alveoli?
Can stretch when air is drawn in and then return to original size (elastic recoil)
Adaptations of alveoli?
- Large SA
- Thin walls
- Good blood supply
- Good ventilation
- Liquid surfactant
Function of liquid surfactant on alveoli?
Prevent water loss
There is a _______ concentration of oxygen in the alveoli
There is a _______ concentration of oxygen in the blood
High
Low
Inspiration is an _________ process
Active
Exhalation is a _________ process
Passive
INHALATION
External intercostal muscles __________
Contract
INHALATION
Rib cage moves ____ and _____
Up and out (expands)
INHALATION
Diaphragm __________ and __________
Contracts (moves down)
Flattens
INHALATION
Volume of thorax __________
Increases
INHALATION
Pressure inside thorax _________ until slightly _______ than atmospheric pressure
Decrease
Lower
What is the mechanism of inhalation during exercising?
Same mechanism as without exercise
EXHALATION
External intercostal muscles _______
Relax
EXHALATION
Rib cage moves ____ and _____
Down and in
EXHALATION
Diaphragm __________ and becomes __________
Relaxes (moves up)
Dome shaped
EXHALATION
Volume of thorax __________
Decreases
EXHALATION
Pressure inside thorax _________
Increases
FORCED EXHALATION (exercising)
________ intercostal muscles ________
Internal
Contract
FORCED EXHALATION (exercising)
Ribcage pulled _______ and ______
Down
Back
What do the abdominal muscles do during forced exhalation?
Contract to push organs upwards against the diaphragm, increasing the internal pressure
What happens in asthma?
- Epithelial cells become inflamed
- Goblet cells secret excess mucus
- Smooth muscle in bronchioles contract
- Airways narrowed
What is tidal volume?
Volume of air that moves into and out of the lungs with each resting breath
What is vital capacity?
Maximum volume of air that can be breathed in or out in one breath
What is inspiratory reserve volume?
Maximum volume of air you can breathe in above a normal inhalation
What is expiratory reserve volume?
Extra amount of air you can force out above the normal tidal volume of air you breathe out
What is residual volume?
Volume of air left in lungs when you have exhaled as hard as possible
What is total lung capacity?
Sum of the vital capacity and residual volume
What is breathing rate?
Number of breaths (in and out) taken in one minute
How to calculate ventilation rate?
Tidal volume x breathing rate (per min)
What happens to tidal volume during exercise?
Increases
What is the normal breathing rate?
12-18 breaths per minute
What does a spirometer show?
- Vital capacity
- Tidal volume
- Breathing rate
What does each curve on a spirometer represent?
Breathing rate
What does the vertical size of each curve on a spirometer represent?
Tidal volume
How does gas exchange occur in insects?
Tracheal system
What is a spiracle?
Opening in the exoskeleton which has valves and allows air to enter
What are the valves in a spiracle called?
Sphincters
Why does a spiracle need valves?
- To control the opening and closing of it
- Closed most of the time to prevent water loss
Structure of trachea in insects?
Lined by spirals of chitin which provide support
Function of tracheoles in insects?
Site of gas exchange
Function of tracheal fluid?
- Provides barrier that prevents oxygen from moving
- When insect is moving then fluid is stopped to create more space for gas exchange
Mechanism of ventilation in insects?
- Air sacs inflating and deflating
- Abdominal muscles creating pumping movement
Gas exchange system in fish?
Gills
Why do fish gills have stacks of filaments that overlap?
To slow movement of water so there us more time for gas exchange
Why do the filaments on fish gills have rows of lamellae?
To increase SA
What do lamellae contain?
A rich blood supply of capillaries
What is a counter current system?
Blood flow is in the opposite direction to water flow with a constant gradient between them
Why is the counter current system needed?
To ensure concentration gradient is maintained
In fish gills the water with ________ oxygen concentration is found adjacent to the __________ blood
Lowest
Deoxygenated
INHALATION IN FISH
- Fish _______ mouth
- Buccal cavity floor ________
- Volume ________
- Pressure _______
- Pressure is higher outside of mouth so water flows in
- Open
- Lowers
- Increases
- Decreases
EXHALATION IN FISH
- Fish _____ mouth
- Buccal cavity floor ______
- Pressure ________ in buccal cavity
- Water flows from buccal cavity to _________ (high to low pressure)
- Pressure increases in ________
- _________ forced open and water exists
- Closes
- Rises
- Increases
- Gill cavity (x2)
- Operculum
What is operculum?
Flap of tissue covering gills
