LO4: Respiratory system Flashcards
Structure
When you breathe, air enters your body through your mouth and nasal cavity.
It passes through your pharynx, past your epiglottis, and down your trachea.
The trachea branches into two bronchi (left and right); each bronchi breaks down further into smaller bronchioles (like a tree’s roots branching out).
At the end of each bronchiole lies a group of alveoli.
The alveoli is the place where the O2 diffuses into the blood and CO2 back to the lungs.
Inspire at rest
The external intercostal muscles of the ribs must contract, as does the diaphragm in the abdomen.
The contraction increases the volume of the lungs, which reduces the pressure of the air inside the lungs.
The pressure of air is higher outside the body, so it rushes in through the mouth and nose to fill the lungs until the pressure is equalised.
Expire at rest
The intercostal muscles and diaphragm must relax. As lungs are not now being stretched, they return to original size.
This in turn increases the pressure of air inside the lungs compared to outside. The air is forced out.
Breathing during exercise (Inspire)
The same process when at rest, but additional muscles help to increase the volume of the lungs. Sternocleidomastoid, scalene and pectoralis major help to pull the clavicle upwards & outwards. Clavicle is the bone that internal intercostals pull against.
Breathing during exercise (Expire)
Breathing out during physical activity is much more involved. Rather than passively relaxing, the ribcage is forced downwards and inwards by the internal intercostal muscles. The rectus abdominus helps to force the diaphragm upwards. These actions reduce the volume of the lungs, increasing the pressure inside them and therefore forcing air out quicker.
Gaseous exchange at the alveoli
The exchange of oxygen and carbon dioxide in the lungs is described as external respiration because gases exchanged within the atmosphere. The air we breathe in is made up of 21% oxygen, 78% nitrogen & 0.04% carbon dioxide. The remainder is other gases and pollution.
Tidal Volume (TV)
The volume of air inspired or expired per breath- approx 500ml during breathing at rest
Frequency (f)
Also known as the ‘rate’, the number of breaths taken in 1 minute- you take approx 12-15 breaths when you breathe at rest.
Minute Ventilation (VE)
The volume of air inspired or expired in 1 minute
Formula for Minute ventilation (VE)
VE = TV x f
Inspiratory reserve volume (IRV)
The volume of air available that could be inspireed after tidal volume.
Expiratory reserve volume (ERV)
The volume of air available that could be expired after tidal volume
Residual volume (RV)
The volume of air that is left in the lungs after total forced expiration.
Vital Capacity (VC)
The total volume of air that can be inspired and expired
Total Lung Capacity (TLC)
The total volume of lungs at maximum inflation