Pharynx is present behind the oral and nasal cavity. It is a part of the throat and a common passage for both the digestive and respiratory system.
Pharynx opens into the oesophagus in the digestive tract and opens into the larynx in the respiratory tract.
Pharynx is also present in some of the invertebrates. The shape and size varies in different organisms. It may be thick and muscular, rotated or turned outward.
- The pharynx can be divided into three main regions according to its location. They are
Nasal pharynx- As the name suggests, it is the part of the pharynx that is present posterior to the nasal cavity.
Oral pharynx- It is the part behind the oral cavity and continues in the throat till hyoid bone.
Laryngeal pharynx- It is the lowermost part of the pharynx from epiglottis and continues to the oesophagus.
- The wall of pharynx consists of both longitudinal and circular muscles. These muscles determine the shape of the lumen.
- Isthmus connects oropharynx to nasopharynx. It is useful for breathing through the mouth and inserting food into the oesophagus through the nasal tube if required.
- Pharyngeal adenoids or tonsils are located in the wall of nasopharynx.
- Nasopharynx is lined with pseudostratified, columnar and ciliated respiratory epithelium.
- Eustachian tubes connect middle ears to pharynx. It helps in equalizing air pressure on the eardrum.
- Palatine tonsils are present in the lateral wall of the oropharynx.
- The wall of oropharynx is made up of non-keratinized, stratified squamous epithelium.
- The opening of the pharynx to the larynx is controlled by a muscular flap known as epiglottis. It is present over the larynx opening and prevents food from entering the trachea.
- The wall of laryngopharynx consists of stratified squamous epithelium.
- Laryngopharynx regulates the movement of air to lungs and food to oesophagus.
- Pharyngeal, tubal, palatine and lingual tonsils present in different parts of the pharynx are called Waldeyer’s ring. These are lymphoid tissues present in the nasopharynx and oropharynx. It provides defence against invasion of microorganisms in the digestive and respiratory tract.
Pharynx performs dual function. It allows passage for both air and food. The main function of pharynx are:
- It makes air warm and humidifies it before reaching the lungs.
- It helps in the movement of food to oesophagus. Circular muscles help in pushing the food down and longitudinal muscles help in swallowing the food by lifting and widening the walls.
- Pharynx also helps in speech, it amplifies the sound produced by the larynx or sound box.
- Lymphoid tissues present in the pharynx are the first line of defense against foreign pathogens.
Some of the diseases associated with the pharynx are:
- Pharyngitis- inflammation of the pharynx
- Tonsillitis- inflammation of tonsils
- Pharyngeal cancer
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