Respiratory physiology W9 Flashcards
What is the main function of the respiratory system
To supply body with O2 and dispose of CO2
The respiratory system consists of two distinct processes
- Pulmonary ventilation: movement of air in and out of the lungs
- Gas exchange: exchange of O2 and CO2 between blood and alveolar air (respiration) by diffusion
The respiratory system can be anatomically divided into upper and lower. What structures are present in each divison?
Upper: nose, nasal cavity, pharynx
Lower: Larynx, trachea, bronchi, lungs
The respiratory system can be functionally divided into 2 zones, conducting and respiratory. Describe the difference
Conducting: all passageways from the nose to respiratory bronchioles - rigid. allow air to reach the site of gas exchange and warm, clean and humidfy incoming air.
Respiratory: respiratory bronchioles, alveolar ducts and aleoli. site of gas exchange
What is the function of the conducting zone?
Allows easy transfer of air to and from respiratory zone & warms, cleans and humidifies incoming air.
For efficient air exchange - maximal surface area and minimal distance between alveolar air and capillaries is needed. Solution = fractal branching tree
Trachea divides into left and right bronchi -> airways continue to divide dichotomously (24 generations) into smaller tubes until alveoli
What does airway patency refer to
Problem in respiratory system: need to keep respiratory passageways open to allow easy passage of air.
In a normal situation how is airway patency achieved
Trachea have cartilage rings (keep trachea open) = unlikely to collapse
Bronchi: cartilage plates aid to keep bronchi open
Bronchioles: kept open by air pressure in airway + support from surrounding lung tissue (radial traction)
Alveolar kept open by surfactant secreated by type 2 alveolar cells
Air movement in and out of the lungs is dependent on pressure gradients between…
- Atmospheric pressure (P atm)
- Intra-alveolar pressure (P alv)
- Intraplural pressure (P ip)
What is Boyle’s Law
Inverse relationship between volume and pressure
pressure x volume = constant (k)
P atm < or >?
Gas molecules move down pressure gradients from region of high pressure to low pressure. This pressure gradient drives pulmonary ventilation (breathing).
For air to move into and out of our lungs…
Into P alv < P atm
Out P alv > P atm
How are pressure changes achieved (in order to create pressure gradients)
By varying the volume of the thorax
Bigger volume = lower pressure
Smaller volume = higher pressure
What does inspiration involve
Increasing volume of the thorax (enlarging lungs)
How do we change (increase) the volume of the thorax during inspiration?
Inspiration is an active process
Involves contracting and relaxing muscles
What muscles are involved in quiet inspiration/breathing?
Diaphragm and external intercostals contract
= thoracic cavity and lung volume expands
= pressure decreases
What muscles are involved in active inspiration/breathing?
Diaphragm, external intercostals and accessory muscles (sternocleidomastoid and scalenes) are activated
Why does changing the volume of the thorax change the volume of the lungs
intrapleural pressure
cavity filled with fluid between visceral and parietal pleura = adhesive force
Keeps lungs vacuum sealed to thorax wall, therefore when volume of thorax increases, lungs also expand.
Expiration is primarily a passive process but can be active based on the level of respiratory activity. What muscles are involved in quiet expiration/breathing?
Diaphragm and external intercostals relax - elastic recoil
= thoracic cavity and lung volume reduced
= increase in pressure (Palv > Patm)
= air flows out
What muscles are involved in active expiration/breathing?
Diaphragm + Accessory muscles activated (internal intercostals and abdominals)
Healthy lungs are stretchy and elastic = easy expansion and recoil
What are some factors that impair lung compliance (resilence/elasticity)
Fibrosis
What does tidal volume (TV) refer to?*
Air you move in and out during quiet breathing
* 0.5L of air moves in and out per breath
* 12-18 breaths per minute in adults (respiratory rate)
What does inspiratory reserve volume (IRV) refer to?*
Air that can be inspired beyond the tidal volume ie. amount of air you can inhale after a normal tidal inhalation
* 2.1-3.2L
What does expiratory reserve volume (ERV) refer to?*
Air that can be expelled after a tidal expiration ie. air you can expel after a tidal expiration - forceful
* 1-1.2L
What does residual volume refer to?*
Air that is left in the lungs if you exhale as much air as possible. Residual air keeps airways open ie. alveoli from collapsing
What does dead space refer to?*
The volume of ventilated air that does not participate in gas exchange (does not go to respiratory zone)
What does respiratory capacities refer to
Combination of two or more selected volumes