As the diaphragm contracts and the intercostal muscles relax, a negative intrathoracic pressure is created which generates a pressure gradient between what is currently higher air pressure outside the respiratory airways, thus directing airflow into the nostrils towards the lungs. A molecule of oxygen near the nostril is sucked in to this moving air and enters the nasal cavity where it experiences turbulence due to the irregular path created by the nasal conchae and nasal meatuses. Here, other larger particles in the air are filtered out from the multiple contact with the sticky mucous membrane lining the interior walls of airway. The oxygen molecule is warmed and the air it is travelling is becomes more moist as it enter into the pharynx.
…show more content…
It sits posterior to the nasal and oral cavities and posterior to the larynx. It is divided into nasal, oral, and laryngeal parts. Beginning at the superior end is the nasopharynx, then the oropharynx, and inferiorly, the laryngopharynx. The anterior part of the nasopharynx may be regarded as the posterior portion of the nasal cavity, with which it has a common function as part of the respiratory system. When swallowing, the nasopharynx is blocked and closed by the soft tissue of the uvula. For defense against airborne pathogens, the lymphoid pharyngeal tonsil sits high on the posterior nasopharyngeal wall. An addition tonsil, the tubal tonsil, protects against pathogens leaving the pharynx into the auditory tube draining the middle ear. The oropharynx extends posteriorly from the oral cavity and soft palate to the superior border of the epiglottis. The entrance into is this area is termed the fauces and contains a palatine tonsil embedded on each lateral mucosal wall. The tongue itself has a lymphoid tonsil on its posterior surface- the lingual tonsil. The laryngopharynx extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage, where it becomes continuous with the esophagus. Its anterior portion has the inlet of the larynx and the
It sits posterior to the nasal and oral cavities and posterior to the larynx. It is divided into nasal, oral, and laryngeal parts. Beginning at the superior end is the nasopharynx, then the oropharynx, and inferiorly, the laryngopharynx. The anterior part of the nasopharynx may be regarded as the posterior portion of the nasal cavity, with which it has a common function as part of the respiratory system. When swallowing, the nasopharynx is blocked and closed by the soft tissue of the uvula. For defense against airborne pathogens, the lymphoid pharyngeal tonsil sits high on the posterior nasopharyngeal wall. An addition tonsil, the tubal tonsil, protects against pathogens leaving the pharynx into the auditory tube draining the middle ear. The oropharynx extends posteriorly from the oral cavity and soft palate to the superior border of the epiglottis. The entrance into is this area is termed the fauces and contains a palatine tonsil embedded on each lateral mucosal wall. The tongue itself has a lymphoid tonsil on its posterior surface- the lingual tonsil. The laryngopharynx extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage, where it becomes continuous with the esophagus. Its anterior portion has the inlet of the larynx and the