Basic Environmental Health - Thesis Example

1. a) When a person is exposed to a gas, what physical property of the gas determines where in the respiratory system the gas will be absorbed? Give an example of a gas that will tend to be absorbed in the nose or throat, and a gas that will tend to be absorbed in the deep lung. Absorption of any substance into the blood stream depends upon the plasma membrane permeability of the substance. This is however not a limiting factor where respiratory absorption of gases is concerned because: ionized molecules have very low volatility and the close contact of capillaries with the pulmonary pneumocytes. Their distribution and storage depends on the solubility quotient of the gas. Water-soluble gases tend to get absorbed in the watery mucus, which lines the upper respiratory tract, and less water-soluble gases proceed to the lungs. For example, formaldehyde, which is highly water-soluble, is absorbed by the URT and carbon monoxide, which is only slightly soluble in water, is absorbed in the lungs b) When a person is exposed to suspended (airborne) particles, what physical property determines where in the respiratory system the particles will be deposited? Give an example of a class of particles that will likely be deposited in the nose or throat, and a class of particles that will likely deposit in the deep lung. The main property determining absorption of particulate matter is the particle size. Large particles are restricted to the naso-pharyngeal region from where they are coughed out, medium particles stop at the tracheo-bronchial region and smaller particles reach the lungs from where they may be phagocytosed or absorbed. Large size: dust, pollen Medium size: asbestos, lead Small size: soot, CFC’s 2. List three defense mechanisms the respiratory system has to prevent injury from inhaled particles. The three respiratory zones serve as three defense mechanisms against inhaled particles: The upper portion of the respiratory system including the nose and upper pharynx, is susceptible to absorption and also filters coarse particles (>5 microns) . irritants in this area produce sneezing which clears many large particles.the mid-portion of th erespiratory tree which include the trachea and bronchial tubes contain cilia , which are hair like structures along the mucous membrane and trap smaller irritant particles (2-5 microns) . their upward propellation induces cough which results in either swallowing or expectoration. Th lower portion of the respiratory tree is exposed to very small sized particles ( Read More