Divisions of the Pharynx: Naso-, Oro- and Laryngopharynx

00:01 The pharynx is anatomically divided into three parts, the nasopharynx, sometimes also called the epipharynx, the oropharynx, and the laryngopharynx, also known as the hypopharynx.

00:18 The nasopharynx, which is also sometimes referred to as the epipharynx is the superior most division of the pharynx and is located behind the nasal cavities.

00:30 It is enclosed by a rough, a posterior wall, a floor, an anterior wall, and a lateral wall.

00:38 The rough of the nasopharynx which also represents its superior limit is formed by the basiocciput.

00:45 Its posterior wall into which the rough of the nasal pharynx transitions can concavely is formed by multiple layers.

00:53 From anterior to posterior, these layers include the mucosal layer underlying for pharyngobasilar fascia, superior constrictor, pre vertebral musculature, and lastly the anterior arch of the atlas or the first cervical vertebra.

01:15 Additionally at the junction of the rough and the posterior wall, the nasopharynx can be found a pharyngeal tonsil also known as the adenoids.

01:24 We will come back to this tonsil later in our lecture when we discuss the circumferential ring of lymphoid tissue called "Waldeyer's Ring" that protects the upper respiratory tract.

01:36 Now the floor of this nasopharynx can be divided into an anterior and posterior sections.

01:43 The anterior section is formed by the soft palate and the posterior section is deficient forming the pharyngotympanic isthmus, through which the nasal pharynx communicates with the underlying oropharynx.

01:57 The anterior wall the nasopharynx corresponds to the posterior colony.

02:02 And lastly, inarguably the most relevant, the lateral wall, the lateral wall that nasopharynx is formed for the most part by the muscular layer of the pharyngeal wall.

02:12 The importance of this wall results from several noteworthy topographic features.

02:18 But the only landmark we will mention today is the triangular opening the pharyngotympanic or the Eustachian tube.

02:26 This anteromedially angled proximately 24 millimetre long tube is composed of cartilage, fibrous tissue, and some bone.

02:37 It passes through the sinus of morgagni to connect the middle ear to the nasopharynx for several physiological reasons.

02:46 The most important of which is the ventilation of the middle ear and the equalisation of air pressure on both sides of the tympanic membrane necessary for hearing.

02:58 Also, another mass of lymphoid tissue, called the tubal tonsil can be variably found near the opening of the Eustachian tube, and it contributes to the formation of the aforementioned, Waldeyer's Ring.

03:11 Lastly, I mentioned this in the beginning of the lecture, and I'd like to point it out again that the mucosal layer the nasopharynx, unlike the remaining parts of the pharynx, is lined by respiratory pseudostratified ciliated columnar epithelium.

03:30 The oropharynx is the next version of the pharynx.

03:34 The oropharynx is located posterior to the oral cavity and extends from the plane of the hard palate above to the plane of the hyoid bone and the epiglottis below.

03:47 Let us now discuss the walls of the oropharynx.

03:51 The oropharynx has four walls, anterior, posterior and two lateral walls.

03:58 The anterior wall or oropharynx is deficient above and presents as the oropharyngeal isthmus, through which it communicates with the oral cavity.

04:10 Below the anterior wall was formed by the base of the tongue, posterior to the circumvallate papillae, the lingual tonsil which are themselves located in the base of the tongue, and by the molecularly, which are cup shaped depressions between the base of the tongue and the anterior surface of the epiglottis.

04:32 The posterior wall was nothing more than the layers of the posterior pharyngeal wall separating the oropharynx from the retropharyngeal space at the level C-2 and C-3 vertebrae.

04:44 The lateral walls are made up of the: Anterior pillar, which is formed by the palatoglossal muscle, by the posterior pillar which is formed by the palatal pharyngeal muscle and by the palatine tonsil, which sets in the tonsillar fossa in between the anterior and posterior pillars.

05:05 Also keep in mind that the oropharynx lacks a rough and a floor.

05:10 Rather where these should be, there are openings through which the oropharynx communicated with the nasopharynx above and the laryngeal pharynx below.

05:20 There is one additional thing I want to mention before we conclude our discussion of the oropharynx in the oropharynx, some fibres of the palatal pharyngeus muscle, which forms the posterior pillar, travel posteriorly in the posterior wall, and along with the lower fibres of the superior constructor muscle form a ridge called Passavant Ridge.

05:42 During speaking and swallowing, this ridge participates in the closure of the nasopharynx isthmus, along with the soft palate, so that the oropharynx and nasopharynx no longer communicate.

05:55 Now let's move on to laryngopharynx.

05:59 The laryngopharynx sometimes also known as the hypopharynx, is the inferior most division of the pharynx.

06:08 It extends from the plane passing through the body of the hyoid bone to the lower border of the cricoid cartilage, or the hypopharynx becomes continuous with the oesophagus.

06:18 Additionally, laryngopharynx spans the length of the third, fourth, fifth, and six cervical vertebrae.

06:29 Lastly, laryngopharynx can be subdivided into three regions, the Pyriform fossa, also known as the Pyriform sinus, this lies on either side of the larynx and extends all the way down to the oesophagus.

06:46 The post cricoid region is located between the upper and lower borders of the cricoid lamina and then the posterior pharyngeal wall which spans the length of the entire laryngopharynx.

07:01 With this we conclude the discussion of the pharyngeal regions, but there are still a few topics left to cover with regard to the pharynx.

07:11 Let us now briefly look at the neural vasculature, the pharynx, and then conclude our lecture with the discussion of Waldeyer's Ring.

07:19 Let's first briefly discuss the sensory innervation of the pharyngeal mucosa.

07:26 The mucosa the nasopharynx will receive its sensory innervation for the maxillary division of the trigeminal nerve.

07:35 The oropharyngeal mucosa will receive its sensory innervation from the glossopharyngeal nerve.

07:42 And the mucosa laryngopharynx will receive its sensory innervation from the branches of the vagus, chiefly the internal branch of the superior laryngeal nerve and the recurrent laryngeal nerve.

07:57 And lastly, the autonomic in motor innervation, the pharynx comes from the pharyngeal plexus, which is formed by the union of the vagus nerve glossopharyngeal nerve, and the cervical sympathetic ganglia.

08:13 And again, the only exception is the stylopharyngeus muscle, which receives its motor innervation from a small motor branch of the glossopharyngeal nerve.