7.2 The Mammalian Gaseous Exchange System Flashcards
Mammals require a specialised exchange surface due to their…
low SA:V
high metabolic rate
How do mammals change the COMPOSITION of air during gas exchange?
inhale oxygen rich air
exhale carbon dioxide rich air
Structures in the Human Gaseous Exchange System:
nasal cavity,
trachea,
bronchi/bronchioles,
alveoli
Air first enters into the nasal cavity before the trachea. What is its function & its features related to each function?
WARMS air (good blood supply),
TRAPS dust & bacteria (hair + mucus),
increases HUMIDITY of air (moist),
What are the advantages linked to each function of the nasal cavity?
- warms air
- traps dust & bacteria
- humidifies air
good blood supply brings heat into large surface area,
lined with mucus & hair,
moist
Why does air need to be HEATED to body temperature in the nasal cavity before entering the lungs?
prevents damage to delicate lung tissues (squamous epithelium, ciliated epithelium)
What helps trap dust & bacteria in the nasal cavity?
mucus & hair
Why does air need to be HUMIDIFIED in the nasal cavity before entering the lungs?
prevent evaporation of LUNG SURFACTANT
What prevents the trachea from collapse due to air pressure changes?
rings of cartilage
Why are rings of cartilage incomplete?
to allow peristalsis of oesophagus behind it
Why are rings of cartilage required around the trachea?
prevent collapse from changes in air pressure
What tissue is the trachea lined with?
ciliated epithelial tissue
goblet cells»_space; mucus, ciliated epithelial cells»_space; cilia
air outside –> _____ –> _____ –> _____ –> _____ –> _____
nasal cavity, trachea, bronchi, bronchioles, alveoli
Ciliated epithelial cells waft the dust/bacteria trapped in mucus towards the…
oesophagus so that it can be digested
Rings of cartilage are found in…
trachea & bronchi
Bronchi divide into…
bronchioles
How do bronchioles direct air flow?
contain SMOOTH MUSCLE which contracts/relaxes to constrict/dilate airway
What are alveoli?
AIR SACS with elastic fibres + collagen
which increase surface area for diffusion
What are the features of alveoli and their related functions?
High SA»_space; fast rate of diffusion
1 cell thick squamous epithelium»_space; short diffusion distance
Good blood supply»_space; steep concentration gradient
Good ventilation»_space; steep concentration gradient
What are alveoli coated in and what is its function?
lung surfactant
prevents alveolar collapse
What is lung surfactant made from?
solution of water + phospholipids,
phospholipids reduce cohesion
What is found between the lungs & thorax & what does it do?
pleural fluid,
lubricates & creates vacuum preventing air escape
How does ventilation occur in the lungs?
DIAPHRAGM & EXTERNAL INTERCOSTAL muscles contract & relax
changes VOLUME & therefore PRESSURE of thorax
causes air to move in/out
EXHALATION:
Diaphragm muscle + external intercostal muscle relaxes,
Diaphragm moves up + ribs fall,
volume of thorax ￬, so pressure ￪,
pressure outside < pressure inside so air moves out
