CH7 the mammalian gaseous exchange system Flashcards
1
Q
Why are gaseous exchange surfaces moist
A
So that oxygen can dissolve in water before diffusing into body tissues
2
Q
Where does gas exchange occur in humans
A
The lungs
3
Q
What is the order of air flow in the lungs
A
Nasal cavity, trachea, bronchus, bronchioles, alveoli
4
Q
What are the features of the nasal cavity
A
- large surface area with a good blood supply that warms air to body temperature
- a hairy lining that secretes mucus to trap dust and bacteria
- moist surfaces to increase humidity of incoming air, reducing evaporation
5
Q
Trachea
A
- wide tube supported by c rings of cartilage to prevent collapsing
- rings incomplete so food can move easily down oesophagus
- lined with a ciliated epithelium with goblet cells between and below
6
Q
Bronchus
A
- supporting rings of cartilage but smaller than trachea
7
Q
Bronchioles
A
- walls contain smooth muscle
- when smooth muscle contracts, bronchioles close up changing the amount of air entering the lungs
- lined with a thin layer of flattened epithelium
8
Q
Alveoli
A
- tiny air sacs
- consists of a layer of thin, flattened epithelial cells, along with collagen and elastic fibres
- elastic tissues allow alveoli to stretch as air drawn in (elastic recoil)
9
Q
What are the main adaptations of the alveoli
A
- large surface area
- thin layers
- good blood supply
- good ventilation
- inner surface covered in a thin layer of water, salts and lung surfactant (remain inflated)
10
Q
What is the process of inspiration
A
- diaphragm contracts, flattening and lowering
- external intercostal muscles contract, moving ribs upwards and outwards
- volume of thorax increases so pressure of thorax decreases
- air drawn into lungs to equalise pressure
11
Q
What is the process of expiration
A
- muscles of diaphragm relax
- elastic fibres of alveoli relax
- ribcage moves inwards
- decreases volume of thorax
- pressure inside greater than outside so air drawn out
