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Pharynx And Larynx Notes

Veterinary Medicine Notes > Cardiorespiratory system 1 Notes

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Pharynx and Larynx Pharynx

1. Function The pharynx is a common cavity for food and ingesta. It lies behind the mouth and continues into the oesophagus. It can be split into three parts - the nasopharynx, the oropharynx and the laryngopharynx. It is part of both the respiratory and alimentary systems. Both systems have entrances to the pharynx but they are separated from each other by the soft palate. During exercise or times of respiratory distress, the mouth may function as an additional opening of the respiratory system and then the oropharynx also becomes an airway.

2. The soft palate. The soft palate is a mass of soft tissue continuous with the palatine bone, known as the hard palate. It divides the pharynx, and is covered by respiratory and stratified squamous epithelium. The palatinus muscle can shorten the palate. At rest, the soft palate lies on the tongue. During swallowing, the soft palate is raised which divides the pharynx into dorsal and ventral sections. The dorsal compartment is the nasopharynx and the rostral compartment is the oropharynx. The laryngopharynx is separated from the oropharynx by the epiglottis. Two pairs of arches connect the soft palate to adjacent structures. The palatopharyngeal arches pass onto the lateral walls of the pharynx and meet above the entrance to the oesophagus. Together with the free margin of the soft palate they divide the pharynx into the dorsal and ventral compartments. The more rostral palatoglossal arches pass onto the sides of the tongue at its route, and mark the passage from the mouth to the oropharynx.

3. The nasopharynx The nasopharynx is located dorsally to the soft palate. It extends from the choanae (opening of nasal cavity into the nasopharynx) to the intrapharyngeal opening (formed from the free edge of the soft palate and the palatopharyngeal arches). It is lined with respiratory epithelium, and its borders are defined by the base of the skull, the soft palate and the cranial cervical vertebrae. In the dorsal region of the nasopharynx are paired openings into the auditory (Eustachian) tubes. The lining of the middle ear cavity and auditory tube is continuous with that of the nasopharynx.

4. The oropharynx The oropharynx is ventral to the soft palate. It extends from the oral cavity to the epiglottis. It is lined with stratified squamous epithelium, and its borders are defined as the tongue, palate and palatoglossal arches. Tonsils are present on the lateral walls of the oropharynx and are covered by flaps of mucosa.

5. The laryngopharynx The laryngopharynx extends from the intrapharyngeal opening to the opening of the oesophagus and larynx. The opening of the larynx is located on the floor of the pharynx. Caudal and dorsal to the laryngeal opening is the opening to the oesophagus. It contains the

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