Respiratory Physiology

Here is the summary:

• The respiratory system is the focus of the discussion, specifically respiratory physiology, excluding respiratory anatomy covered in the laboratory. • The respiratory tract structures, from the nasal cavity to the lungs, including the larynx, trachea, bronchi, and lung structures, are skipped in this discussion. • The branches of the tracheal bronchial tree are important to note, from the trachea to the main bronchi, secondary bronchi, tertiary bronchi, bronchioles, and finally, the alveolus. • The bronchial tree is differentiated from the bronchioles, with bronchial trees having hyaline cartilage as their main framework, making them non-collapsible, whereas bronchioles are made up of connective tissues and smooth muscles, making them collapsible. • At the level of the bronchioles, the smooth muscles contract, causing bronchoconstriction, which can occur during severe asthma attacks or in patients with chronic obstructive pulmonary disease. • Bronchoconstriction results in a narrower airway, and aside from smooth muscle contraction, there is also severe swelling of the airway wall. • The difference between terminal bronchioles and respiratory bronchioles lies in the fact that gas exchange takes place in the respiratory bronchioles, whereas it does not occur in the terminal bronchioles. • The alveolus is the last part of the respiratory tract, surrounded by pulmonary capillaries, where gas exchange occurs. • The layers of the respiratory membrane include alveolar fluid with surfactant, alveolar epithelium, and basement membrane of the alveolar epithelium on the side of the alveolus, and capillary endothelium and basement membrane of the capillary endothelium on the side of the pulmonary capillaries. • The surfactant decreases the surface tension of the alveolus, preventing spontaneous collapse. • The process of ventilation involves the movement of air into and out of the lungs, with two phases: inspiration and expiration. • Inspiration involves the use of principal muscles, including the diaphragm and external intercostals, whereas expiration is a passive process that does not require muscles. • During normal quiet breathing, only the external intercostals and diaphragm are used for inspiration, whereas accessory muscles such as pectoralis minor, scalins, and sternocleidomastoid are used during labored breathing. • The mechanics of ventilation can be explained by Boyle's Law, which states that pressure is inversely proportional to volume, or vice versa. • During inspiration, the volume of the thoracic cavity increases, causing the intrapulmonary pressure to decrease, and air moves from outside to inside due to the pressure difference. • At the end of inspiration, the alveolar pressure equals atmospheric pressure, and there is no air movement for a brief period. • During expiration, the volume of the thoracic cavity decreases, causing the intrapulmonary pressure to increase, and air moves out due to the pressure difference.