Respiratory Physiology Flashcards
What are the four major functions of the respiratory system?
pulmonary ventilation, gas exchange, transport of O2 and CO2 in blood and bodily fluids, and regulation of ventilation.
What is ventilation, respiration and pulmonary ventilation in terms of the flow of pulmonary circulation?
ventilation is the specific movement of air in and out of lungs when breathing.
respiration is the gas exchange that occurs during ventilation and is in close coordination with the circulatory system.
pulmonary ventilation is the movement of air in and out of lungs, where inspiration is breathing air in and expiration is breathing air out. it maintains the equilibrium of pressure gradients and requires the coordination of muscles and pressure gradients.
Explain the process of inspiration.
inspiration enlarges the thoracic cavity. at rest, the contraction of the diaphragm increases thoracic cavity volume. forced inspiration causes the sternum, and the 1st and 2nd ribs to raise to further enlarge thoracic cavity volume, and engages the external intercostal muscles, the sternocleidomastid muscles, and the scalene muscles.
Explain the process of inspiration.
at rest it is usually a passive activity, which is a return to the resting state due to decreasing thoracic cavity volume, which occurs due to the elastic recoil of the lungs, forced expiration is the further reduction of volume of the thoracic cavity, and engages the abdominal muscles and the internal intercoastal muscles.
What is Boyle’s law?
p1v1 = p2v2
the movement of respiratory muscles changes the volume of the thoracic cavity so that pressure will increase and decrease to stimulate air movement through the lungs.
How are pressure gradients formed in the respiratory system?
air moves from high to low pressure
inspiration causes the chest to expand, causing inc vol, dec pressure, and air is sucked in.
expiration causes the chest to recoil, causing dec vol, inc pressure, and air is pushed out
What Patm, intra-alveolar pressure and intra-pleural pressure?
Patm is the pressure within the atmosphere.
Palv is the pressure within the alveoli, which varies as the lungs expand and recoil. it equilibrates with Patm and determines the direction of air flow. inspiration = Palv < 760mmHg, expiration = Palv > 760mmHg
Pip is the pressure within the pleural sac, which is the area between the lungs and the thoracic cavity. it keeps the lungs attached to the thoracic cavity due to negative pressure, and does not equilibrate toe Patm as the pleural sac is enclosed in the body cavity. at rest = 756mmHg or -4mmHg, inspiration = 754mmHg or -6mmHg, always keeping negative pressure.
What is the transpulmonary pressure gradient?
it is the difference between Palv and Pip, and is usually 4mmHg. Pip is always more -ve than Palv, which creates a relative vacuum, allowing the lungs to stick to the pleural sac and the pleural sac to the thoracic cavity. a loss of pressure in the pleural cavity causes lung collapse.
What are the different types of lung volume?
tidal volume (Vt) is the volume of inspired or expired air with each normal breath.
inspiratory reserve volume (IRV) is the volume that can be inspired above the tidal volume.
expiratory reserve volume (ERV) is the volume that can be expired after the expiration of tidal volume.
residual volume (RV) is the volume that remains within the alveolar space after a maximal exhalation.
What are the different types of lung capacity?
inspiratory capacity = Vt + IRV
functional reserve capacity (FRC) = ERV + RV, it is the volume remaining in the lungs after tidal volume is expired.
vital capacity (VC) = Vt + IRV + ERV, it is the volume of air that can be forcibly expired after a maximal inspiration.
total lung capacity (TLC) = Vt + IRV + ERV + RV, and is the sum of all four lung volumes, the volume in the lungs after a maximal inspiration.
How is lung disease related to lung volume and capacity?
it is dependent on vital capacity (FVC and FEV1). FEV1 is the forced expiratory volume, which is the volume of air that can be forcefully expired from a maximal expiration in 1 second.
obstructive lung disease results in FEV1 and FVC reduced, but FEV1 reduced greater.
restrictive lung disease results in FEV1 and FVC reduced, but FVC reduced greater. this can be a result of fibrosis.
What is airway resistance and how is it controlled?
airway resistance Q = deltaP/R (pousille’s law). airflow is inversly proportional to airway resistance, and directly proportional to the pressure difference between the mouth/nose and alveoli. airway resistance can affect ventilation.
parasympathetic control exhibits bronchoconstriction which decreases the radius of bronchioles and increases resistance, which reduces airflow.
sympathetic control exhibits bronchodilator which increases the radius of bronchioles and decreases resistance, which increases airflow.
What is lung compliance?
it is the change in lung volume / change in transpulmonary pressure. it is the ability for the lungs to stretch and distend during ventilation, managed by elastin fibres in lung connective tissue.
Why does water line the alveoli?
it reduces the alveoli’s ability to expand, along with increasing surface tension.
What is surfactant and what happens if there is no surfactant?
surfactant lines the alveoli and prevents it from collapsing. it reduces surface tension and disrupts the IMF between the liquid molecules of the alveoli. it increases compliance and recoil and is necessary for balancing the effect of water lining the alveoli. it is synthesised by cells within the lung (type 2 alveolar cells).
if there is no surfactant, we see the collapse of the alveoli. this can occur due to a condition called the neonatal respiratory distress syndrome. it occurs in premature infants and they don’t have the ability to produce surfactant. this results in lung collapse and decreased compliance. it is treated with antenatal corticosteriods, resuscitation at birth, mechanical ventilation, and mechanical input of surfactant and oxygen.
