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