E&T: Gas Exchange in Humans COPY Flashcards
1
Q
Describe the key components of the human gas exchange system:
A
- Trachea
- Splits into bronchi - one enters each lung
- Each branches off into bronchioles
- End in alveoli
- Ribcage, intercostal muscles and diaphragm work together to move air in and out
2
Q
What are the two layers of intercostal muscle called?
A
Internal and external
3
Q
What are the two stages of ventilation?
A
Inspiration and expiration
4
Q
Describe inspiration:
A
- External IM and diaphragm contract (internal relaxes)
- Ribcage moves upwards and outwards
- Diaphragm flattens
- Increases volume of thoracic cavity
- This decrease lung pressure below atmospheric pressure
- Air flows down trachea and into lungs
Active process!
5
Q
Is inspiration active or passive?
A
Active
6
Q
Describe normal expiration
A
- External IM and diaphragm relax
- Ribcage moves downwards adn inwards
- Diaphragm curves
- Decreases thoracic cavity
- Lung pressure increases above atmospheric
- Air forced down pressure gradient and out of lungs
Passive!!
7
Q
Describe forced expiration
A
- External intercostal muscles relax
- Internal muscles contract
- Pulls ribcage further down and in
- This is antagonistic - opposite
8
Q
Where does gas exchange happen in humans?
A
Alveoli
9
Q
What is each alveoli made from?
A
Single layer of thin, flat cells called alveolar epithelium
10
Q
Describe gas exchange in alveoli:
A
- Alveoli increase SA and are surrounded by capillaries
- O2 diffuses out of alveoli, across alveolar epithelium and capillary endothelium into haemoglobin.
- CO2 diffuses into alveoli from blood and is breathed out.
11
Q
Briefly summarise gas exchange in humans:
A
- O2 moves down trachea, bronchi and bronchioles in to alveoli.
- Happens down a pressure gradient.
- In alveoli, O2 diffuses across alveolar epithelium, capillary endothelium and into capillary.
- Happens down a diffusion gradient.
12
Q
How are the alveoli adapted for gas exchange?
A
- Thin exchange surface - alveolar epithelium is one cell thick - short diffusion pathway.
- Large surface area - due to large number of alveoli.
- Steep concentration of O2 and CO2 between alveoli and capillaries - increase rate of diffusion.
