Respiratory System

• The left lung is physically smaller than the right because the heart occupies space left of the midline (the cardiac notch).
• Dividing the lung up into lobes helps limit the spread of infection from one part of the lung to another.
• Cartilage is present in the tracheal wall as C-shaped rings, supporting the trachea and maintaining a patent airway.
• Goblet cells produce mucus.
• The epithelial cells are pseudostratified columnar cells.
• The respiratory membrane is between 2 and 5 microns thick and comprises the alveolar wall, the capillary wall and a thin layer of basement membrane between.
• The image above shows the standard view of the epiglottis at the top of the larynx, guarding the opening into the trachea. The left shows the tip of the epiglottis seen through the widely open mouth-you can better see its leaf-shape from this view.
• The negative intrapleural pressure keeps the lung inflated against the chest wall (red arrows). However the negative pressure can suck air in if the pleural sac is punctured, which compresses and collapses the affected lung
• The dome-shaped diaphragm pulls downwards during inspiration, increasing the volume of the lungs
• Boyle's law says that pressure and volume vary inversely in a closed container. That is, as volume falls, pressure rises, and vice versa.
• At rest, tidal volume is about 500ml, but obviously increases significantly in exercise
• The pulmonary artery leaves the right ventricle, carrying deoxygenated blood to the lungs. This image shows the pulmonary trunk, a short section of blood vessel that splits into the right and left pulmonary arteries.
• Atmospheric pressure at sea level: 760mmHg, 78% nitrogen, 21% oxygen, Remaining 1% carbon dioxide, water vapour and other trace gases
• Asthma is an obstructive (not restrictive) disorder associated with episodes of inflammation of the airway wall which along with hypersensitivity of the airway smooth muscle reduces airflow. Unlike other chronic obstructive disorders, e.g. chronic bronchitis, obstruction is reversible
• Your total lung capacity is made up of the air you can shift in and out with maximal effort (vital capacity) and the air that stays in the lung no matter how hard you exhale (residual volume)
• Compliance is the ease with which the lung tissue can be stretched and the lung expanded. A tumour growing underneath the pleura of one lung, while not good news, won't affect lung expansion. Breakdown of lung elastic tissue actually increases compliance, because elastic recoil opposes stretchability. Increasing upper body strength with regular resistance exercise will improve lung expansion and compliance, because the chest and shoulder muscles expand the chest. Fibrotic changes in the lung tissue will make the lung tissue stiffer and harder to stretch, reducing its compliance.
• Intrapleural pressure FALLS when the chest wall lifts and the diaphragm contracts (green arrows). Intrapleural pressure RISES when the lungs are compressed as the chest wall sinks during expiration.
• Bronchial tree refers to the network of airways within the lungs.
• The bronchi are two tubes that branch off from the trachea into the lungs.