Pharynx

Pharynx, commonly known as throat, is a cone-shaped hollow tube that emerges from the back of the nose, extends to the neck and ends in the trachea and oesophagus. Depending on the body size, a pharynx can be upto 5 inches long. It is connected laterally with the middle ear and serves as the passageway for both digestive and respiratory tract.

Muscles of Pharynx

It is a musculomembranous structure that performs several vital functions related to digestion and respiration. The pharynx is attached to the base of the skull with thick fibres of muscles and connective tissues. Both circular and longitudinal muscles are present in the walls of pharynx. The circular muscles of pharynx form constrictions that help in the swallowing of food and prevents the entry of air.

The longitudinal muscles of pharynx help in lifting the walls of the pharynx during the process of swallowing.

Pharynx Anatomy

• It is a funnel shaped structure that is broad at the upper end and is situated just below the lower surface of the skull.
• It tapers at the lower end and is present at the level of sixth cervical vertebrae.
• The pharyngeal wall is composed of muscle fibres, lymphoid tissue, mucosal and submucosal membranes.
• The nasopharynx is composed of columnar and ciliated epithelial cells that are interspersed with goblet cells. The other pharynx structures are covered with non keratinised stratified squamous epithelium.
• At the roof of the pharynx where no muscle fibres are present, there is a thick layer of the submucosal membrane.

Divisions of the Pharynx

The pharynx structure is divided into three main regions. Let us look at each of them separately.

1. Nasopharynx

Nasopharynx or nasal pharynx lies in the anterior portion of the nasal cavity. The nasal pharynx is the site of air passage for the respiratory tract. On the lateral surfaces of the nasopharynx are present tube-like structures on either side called the eustachian tubes.

The tubes are surrounded by elevated mucus membranes called tubal elevations. These tubes are connected to the middle ear and function to equalise the pressure and facilitate the drainage of middle ear secretions. The nasopharynx also houses lymphoid tissues called adenoids or pharyngeal tonsils that function as the first line of defence against pathogens entering the oral cavity.

2. Oropharynx

Oropharynx or oral pharynx is connected with the nasopharynx by a passage-like structure called isthmus. It is located behind the opening of the oral cavity and continues till the epiglottis (a flap-like structure that directs the food to the oesophagus).

3. Laryngopharynx

Laryngopharynx, hypopharynx or laryngeal pharynx is the third pharynx structure that begins at the epiglottis and extends till the oesophagus. The laryngeal pharynx receives the bolus (soft mass of food) from the oral pharynx and directs it to the oesophagus for digestion purposes. It also receives air from the above two regions and directs it towards the inlet of larynx to the trachea for respiration.

Function

The pharynx serves as a site for both digestion and respiratory purposes. It helps in directing food and air to the oesophagus and larynx, respectively. Below, is a well labelled pharynx diagram for your understanding.

Development of Pharynx

All the vertebrates possess pharynx. It is developed during the fourth and fifth week of gestation. Pharyngeal apparatus are present on either side of the head in a developing embryo. These apparatus consist of clefts, pouches and membranes that help in the development of head and neck. The pharynx arises from the arches of the pharyngeal apparatus.

Pharynx and Larynx

Pharynx and larynx are two distinctive structures present in the neck region. The pharynx is a muscular tube that extends from the base of the skull to the oesophagus. Larynx on the other hand is a hollow tube-like cartilaginous structure that facilitates the passage of air from pharynx into the trachea (windpipe).

Read more: Difference Between Pharynx and Larynx

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