Pharynx

 

Pharynx iis usually called the throat, it is funnel-shaped tube fibromuscular tube . It carries air, food and fluid down from nose and mouth. 

Interiorly esophagus is present and anteriorly larynax is present.

Pharynx is a common pathway of both respiratory annd digestive tract. 

Food passes from oral cavity into the pharynx then to esophagus below. It is pathway for movement of food from mouth to esophagus.

Passageway carries air through pharynx to larynx and into trachea.

Parts of Pharynx

Pharynx is divided into three regions-

1. Nasopharynx; connect nasal passages.

2. Oropharynx; allows air, food and fluid to pass through.

3. Laryngopharynx or hypopharynx;  branching pathway between digestive and respiratory systems.

Layers of Pharynx

There are 5 layers of pharynx, from internal to external -

1. Mucus membrane

2. Submucosa

3. Pharyngobasilar fascia

4. Muscular layer

a. Outer circular layer

b. Inner longitudinal layer

5. Buccopharyngeal fascia

Layer of Pharynx

1. Mucus Membrane

In nasopharynx 

Lining of ciliated columnar epithelium with lining of nose.

In oropharynx and laryngopharynx

Lining of stratified squamous epithelium with lining of mouth and esophagus.

2. Pharyngobasilar fascia

Pharyngobasilar fascia is fibrous layer situated between the mucous and muscular layers.

 It attaches pharynx to the skull base.

3. Muscular layer

Muscular layer composed of inner longitudinal and outer circular layer.

Layers of pharyngeal wall muscular -

A. Outer circular layer

1. Superior constrictor

2. Middle constriction

3. Inferior constriction

Contraction superior to inferior constriction end of the pharynx.

B. Inner longitudinal layer

There are three muscle layer-

1. Stylopharyngeus

2. Palatopharyngeus

3. Salpingopharyngeus

Aids in swallowing and speaking.

5.  Buccopharyngeal fascia

Buccopharyngeal fascia composed of loose connective tissue layer. Covering Buccinator and pharyngeal muscle. It contains Pharyngeal plexus of nerve and veins.

Function of Pharynx

1. Common passageway for food and air

2. Warming and humidifying

3. Hearing

4. Control friction of air

5. Taste bud

6. Movement of food mouth to esophagus

7.  Provide drainage to nose, oral cavity, middle ear; eustachian tube

8. Speech

9. Protection

10. Prevent food entry into larynx

11. Secretion mucus; lubricate pharynx

12. Respiration

Note -

Gastrointestinal tract

1. Outer muscle arrangement; longitudinal arrangement

2. Inner muscle  arrangement; circular arrangement

Exception, in Pharynx

1. Outer muscle; circular arrangement

2. Inner muscle; longitudinal arrangement