Gas exchange in humans Flashcards
What is the order of the gas exchange system ?
- nose + mouth
- trachea
- bronchus
- bronchioles
- alveoli
What is the trachea?
Flexible airway supported by rings of cartilage to prevent collapse.
What is the bronchus?
2 divisions in trachea
produces mucus
What are the bronchioles?
Branching subdivisions of the bronchus
Muscle lined with epithelium cells so can constrict to control air flow
What are the alveoli?
Minute air sacs
Between alveoli is collagen and elastic fibres which are allowed to stretch.
Outline the process of inhalation
- internal intercostal relax
- external intercostal contract
- ribs up and out
- diaphragm contracts + flattens
- volume of thorax increases
- pressure in lungs decreases
- atmospheric pressure higher than pulmonary pressure
- air moves in to lungs
Outline the process of exhalation
- internal intercostal contract
- external intercostal relax
- ribs down and in
- diaphragm relaxes (dome shaped)
- volume of thorax decreases
- pressure in lungs increases
- atmospheric pressure lower than pulmonary pressure
- air moves out of lungs
Give 7 ways the lungs are adapted for gas exchange
- Lots of alveoli
- lots of capillaries
- rbc slowed
- rbc flattened against capillary wall
- thin alveoli walls
- constant ventilation
- constant flow of blood through pulmonary capillaries
How does lots of alveoli + lots of capillaries increase gas exchange?
Large SA
How does rbc being slowed increase gas exchange?
more time for diffusion
How does rbc being flattened against the capillary wall and thin alveoli walls increase gas exchange?
Distance between alveolar air and rbc decreased = shorter diffusion path
How does constant ventilation increase gas exchange?
Steep concn gradient between alveoli and capillary is maintained.
How does constant blood flow through pulmonary capillaries increase gas exchange?
Maintains concn gradient
