💙 3.3.2 Gas Exchange In Humans Flashcards
What does the ultra structure of the lungs include?
- the trachea (supported by rings of cartilage)
- bronchi (pl)
- bronchioles
- alveoli (pl)
Explain how the human gas exchange system maintains a high rate of diffusion for gas exchange?
1) concentration gradient is maintained by the replacement of air with a lower concentration of oxygen with a high concentration – by breathing out, then in. Also, the blood moves so equilibrium of oxygen is not reached.
2) many Alveoli (millions of) so that there is a large surface area for gaseous exchange
3) the walls of an alveolus (epithelial cell) are one cell thick, as are the walls of the capillaries endothelial tissue so there is a short diffusion pathway for oxygen and carbon dioxide to diffuse across.
What does the ventilation rate mean?
The number of breaths per minute
What does tidal volume mean?
The volume of air in each breath
What does pulmonary ventilation rate mean?
The total amount of air entering the lungs in one minute
What is the equation to work out pulmonary ventilation rate?
Tidal volume x ventilation rate
What is another word for breathing in?
Inspiration
What is another word for breathing out?
Expiration
What are the two types of expiration?
Forced and normal
What is the mechanism of inspiration (breathing in) ?
- The diaphragm muscle contracts and flattens
- external intercostal muscle contract, and internal intercostal muscles relax (antagonistic muscle action)
- so the rib cage moves upwards and outwards
- this increases the volume of the thorax and decreases the pressure to below atmospheric pressure
- therefore air moves into the lungs from a high-pressure in the atmosphere to a low pressure in the lungs (down a pressure gradient)
What is the mechanism of forced expiration (breathing out) ?
- The diaphragm muscle relaxes (returns to dome shape)
- internal intercostal muscles contract and external intercostal muscles relax (antagonistic muscle action)
- The rib cage moved inwards and downwards
- This decreases the volume of the thorax and increases the pressure to above atmospheric pressure
- therefore air moves out of the lungs from a high pressure in the lungs to a low pressure in the atmosphere (down a pressure gradient)
What is the difference between forced expiration and normal expiration?
- In normal expiration the rib cage moves downwards and inwards passively.
- in normal expiration both sets of muscles relax and it is elastic recoil which returns the ribs down and in
Create a simplified flow diagram to show how oxygen moves through the gas exchange system.
Trachea - bronchi - bronchioles - alveoli - Alveolar epithelium - capillary endothelium - blood
