**3.3 Tubal tonsils**

Eustachian tube (ET) tonsils, small aggregates of lymphoid tissue, form the upper lateral aspect of the ring and are located bilaterally around the pharyngeal ostium of the ET (torus tubarius) which is below and in front of the pharyngeal recess (fossa of Rosenmüller) in the posterolateral wall of the nasopharynx [6]. Because of their close relationship to the torus tubarius, they are called tubal or Gerlach's (German anatomist) tonsils. This triangular pharyngeal ostium has three prominences: anterior, posterior, and inferior. The anterior fold continues as a plica salpingopalatina descends into the soft palate. The posterior prominence is conspicuous and formed by the projecting cartilage of the auditory tube, called the torus tubarius, and also lies as plica salpingopharyngeus which is composed of the SPm. The torus tubarius can be used for ET catheterization. On the lower aspect of the ostium, the LVPm insertion forms a slightly rounded prominence [6, 7].

Tubal tonsils are covered by pseudostratified ciliated columnar epithelium with no crypts. They receive arterial supply via the ascending pharyngeal artery. Their lymphatic drainage is the same as the pharyngeal tonsil's [6, 7].

#### **3.4 Oropharynx**

The oropharynx extends from the OPI at the level of the soft palate to hyoid bone (C3 vertebra level). Anteriorly, the oropharynx communicates with the oral cavity via isthmus faucium which is limited by the PGa bilaterally, the uvula superiorly, and the posterior one third of the tongue that is in line with the sulcus terminalis inferiorly. According to the oncologic description, the oropharynx consists of four parts: the soft palate, the pharyngeal wall, the base of the tongue, and the palatine tonsillar fossa. So, a thorough understanding of the anatomy of oropharyngeal parts and adjacent structures is paramount in differential diagnosis and surgical interventions. It contains the palatine tonsils laterally and lingual tonsil in the retrolingual region anteriorly [6, 9].

#### **3.5 Lingual tonsil**

Lingual tonsils are the inferior-most of the ring and composed of numerous lymphoid nodules in the posterior third of the tongue. The stratified squamous nonkeratinized epithelium covers this lymphoid tissue aggregates forming large, irregular protrusions. Also, they have less branching shallow crypts which are covered by the reticulated epithelium and mucous salivary glands which are drained through several ducts into these crypts which appear after birth [6, 9].

**31**

*Surgical Anatomy of the Tonsils*

nodes [6, 7, 9].

*3.6.1 Poles*

*3.6.2 Borders*

borders also limit the tonsil [7].

myotomy of these muscles [3, 10].

join.

*DOI: http://dx.doi.org/10.5772/intechopen.93038*

**3.6 Anatomy of the palatine tonsils**

Vascular supply to the lingual tonsils is provided with the dorsal lingual branches of the lingual artery and vein. Efferent lymphatic vessels of the lingual tonsil passing through the pharyngeal wall drain into the deep cervical lymph

The palatine tonsils are two large, conspicuous almond-shaped mass of the lymphoid tissue forming the lower lateral aspect of the ring and localized in a triangular tonsillar fossa along the anterolateral border of the oropharynx on each side. The dimensions of the tonsils are about 10–15 mm in width and 20–25 mm in length in adults, but increase in children. The surface landmark of the tonsil corresponds to the lower part of masseter muscle in front of the angle of mandible [3, 6, 9]. The palatoglossal (anterior pillar) and palatopharyngeal (posterior pillar) mucosal folds diverge from the soft palate to form the boundaries of the tonsillar fossa, which lodges the palatine tonsils. These mucosal arches consist of the palatoglossal muscle (PGm) anteriorly and the PPm posteriorly. The palatine tonsil has two poles, upper and lower; two borders, anterior and posterior; two surfaces, medial and lateral; three mucosal folds, plica semilunaris, plica triangularis, and plica retrotonsillaris;

and two depressions, supratonsillar and anterior tonsillar fossa [3, 6, 7].

Superiorly, the tonsil is free and expands into the soft palate where both arches

Inferiorly, the suspensory ligament, a band of fibrous tissue, connects the lower pole with the posterior one third of the tongue. Most of carcinomas develop in the tonsillolingual sulcus which separates the tonsil from tongue anteroinferiorly [3, 6].

The tonsillar fossa or sinus is a triangular space between the anterior pillar in front, the posterior pillar behind, and the dorsal surface of the posterior one third of the tongue inferiorly (**Figure 2**). Because the tonsils are positioned in it, its

The anterior boundary is formed by the PGa which is composed of the PGm. A cylindrical muscle extends from the palatine aponeurosis to the posterolateral surface of the tongue and becomes continuous with the intrinsic transverse muscles [6, 7]. It acts as an antagonist of the LVPm and constricts the OPI during swallowing. All of the muscles of the tongue derive from the occipital myotomes except the PGm which is derivation of the fourth branchial arch. According to the variations of the origin of the PGm, the tongue elevator's function increases or decreases. During lateral pharyngoplasty, the relaxation of the SPCm and PGm is provided by the

The posterior boundary is formed by the PPa including the PPm which originates from the palatine aponeurosis and the median part of soft palate by two heads and consists of muscle bundles medial and lateral to the LVPm. The lateral fibers of the PPm are composed of the longitudinal and transverse parts. The transverse part inserts into the pharyngeal raphe to join with the contralateral side, whereas the longitudinal part joins with the medial fibers at the posterior border of the soft palate and afterward are merged by the SPm [7, 8, 11]. This muscle bundle is observed to course downward along the inner surface of pharyngeal wall and inserts into

#### *Surgical Anatomy of the Tonsils DOI: http://dx.doi.org/10.5772/intechopen.93038*

Vascular supply to the lingual tonsils is provided with the dorsal lingual branches of the lingual artery and vein. Efferent lymphatic vessels of the lingual tonsil passing through the pharyngeal wall drain into the deep cervical lymph nodes [6, 7, 9].

## **3.6 Anatomy of the palatine tonsils**

The palatine tonsils are two large, conspicuous almond-shaped mass of the lymphoid tissue forming the lower lateral aspect of the ring and localized in a triangular tonsillar fossa along the anterolateral border of the oropharynx on each side. The dimensions of the tonsils are about 10–15 mm in width and 20–25 mm in length in adults, but increase in children. The surface landmark of the tonsil corresponds to the lower part of masseter muscle in front of the angle of mandible [3, 6, 9]. The palatoglossal (anterior pillar) and palatopharyngeal (posterior pillar) mucosal folds diverge from the soft palate to form the boundaries of the tonsillar fossa, which lodges the palatine tonsils. These mucosal arches consist of the palatoglossal muscle (PGm) anteriorly and the PPm posteriorly. The palatine tonsil has two poles, upper and lower; two borders, anterior and posterior; two surfaces, medial and lateral; three mucosal folds, plica semilunaris, plica triangularis, and plica retrotonsillaris; and two depressions, supratonsillar and anterior tonsillar fossa [3, 6, 7].

#### *3.6.1 Poles*

*Oral and Maxillofacial Surgery*

known as adenoid [7].

**3.3 Tubal tonsils**

prominence [6, 7].

**3.4 Oropharynx**

**3.5 Lingual tonsil**

retropharyngeal lymph nodes [7].

nodules commonly enlarge and become adenoid which results in respiratory difficulties and nasal obstruction during childhood and often start to involute after 7 years of age or even atrophied in the adult. Chronic inflammation of the pharyngeal tonsil results in hyperplasia and hypertrophy of the lymphoid tissue

The arterial supply of it comes from ascending pharyngeal artery, pharyngeal branch of the maxillary artery, artery of the pterygoid canal, basisphenoid artery, ascending palatine, and tonsillar branch of the facial artery. It has a lymphatic drainage into upper deep cervical within the parapharyngeal space (PPS) and

Eustachian tube (ET) tonsils, small aggregates of lymphoid tissue, form the upper lateral aspect of the ring and are located bilaterally around the pharyngeal ostium of the ET (torus tubarius) which is below and in front of the pharyngeal recess (fossa of Rosenmüller) in the posterolateral wall of the nasopharynx [6]. Because of their close relationship to the torus tubarius, they are called tubal or Gerlach's (German anatomist) tonsils. This triangular pharyngeal ostium has three prominences: anterior, posterior, and inferior. The anterior fold continues as a plica salpingopalatina descends into the soft palate. The posterior prominence is conspicuous and formed by the projecting cartilage of the auditory tube, called the torus tubarius, and also lies as plica salpingopharyngeus which is composed of the SPm. The torus tubarius can be used for ET catheterization. On the lower aspect of the ostium, the LVPm insertion forms a slightly rounded

Tubal tonsils are covered by pseudostratified ciliated columnar epithelium with no crypts. They receive arterial supply via the ascending pharyngeal artery. Their

The oropharynx extends from the OPI at the level of the soft palate to hyoid bone (C3 vertebra level). Anteriorly, the oropharynx communicates with the oral cavity via isthmus faucium which is limited by the PGa bilaterally, the uvula superiorly, and the posterior one third of the tongue that is in line with the sulcus terminalis inferiorly. According to the oncologic description, the oropharynx consists of four parts: the soft palate, the pharyngeal wall, the base of the tongue, and the palatine tonsillar fossa. So, a thorough understanding of the anatomy of oropharyngeal parts and adjacent structures is paramount in differential diagnosis and surgical interventions. It contains the palatine tonsils laterally and lingual tonsil

Lingual tonsils are the inferior-most of the ring and composed of numerous lymphoid nodules in the posterior third of the tongue. The stratified squamous nonkeratinized epithelium covers this lymphoid tissue aggregates forming large, irregular protrusions. Also, they have less branching shallow crypts which are covered by the reticulated epithelium and mucous salivary glands which are drained through several ducts into these crypts which appear after

lymphatic drainage is the same as the pharyngeal tonsil's [6, 7].

in the retrolingual region anteriorly [6, 9].

**30**

birth [6, 9].

Superiorly, the tonsil is free and expands into the soft palate where both arches join.

Inferiorly, the suspensory ligament, a band of fibrous tissue, connects the lower pole with the posterior one third of the tongue. Most of carcinomas develop in the tonsillolingual sulcus which separates the tonsil from tongue anteroinferiorly [3, 6].

## *3.6.2 Borders*

The tonsillar fossa or sinus is a triangular space between the anterior pillar in front, the posterior pillar behind, and the dorsal surface of the posterior one third of the tongue inferiorly (**Figure 2**). Because the tonsils are positioned in it, its borders also limit the tonsil [7].

The anterior boundary is formed by the PGa which is composed of the PGm. A cylindrical muscle extends from the palatine aponeurosis to the posterolateral surface of the tongue and becomes continuous with the intrinsic transverse muscles [6, 7]. It acts as an antagonist of the LVPm and constricts the OPI during swallowing. All of the muscles of the tongue derive from the occipital myotomes except the PGm which is derivation of the fourth branchial arch. According to the variations of the origin of the PGm, the tongue elevator's function increases or decreases. During lateral pharyngoplasty, the relaxation of the SPCm and PGm is provided by the myotomy of these muscles [3, 10].

The posterior boundary is formed by the PPa including the PPm which originates from the palatine aponeurosis and the median part of soft palate by two heads and consists of muscle bundles medial and lateral to the LVPm. The lateral fibers of the PPm are composed of the longitudinal and transverse parts. The transverse part inserts into the pharyngeal raphe to join with the contralateral side, whereas the longitudinal part joins with the medial fibers at the posterior border of the soft palate and afterward are merged by the SPm [7, 8, 11]. This muscle bundle is observed to course downward along the inner surface of pharyngeal wall and inserts into

**Figure 2.** *The mucosal folds and arches of the palatine tonsil.*

the palatal tonsil to form the posterior pillar. Also, some of its fibers insert into the posterior border of the thyroid cartilage with the stylopharyngeus muscle (StPm) and into the SPCm [11].

During velopharyngeal closure, the PPm performs various functions such as a sphincter with the SPCm, a puller of the pharyngeal wall medially in collaboration with the SPCm and StPm, and an elevator with the StPm because of the fibers of the PPm running in various directions [8, 11].

## *3.6.3 Mucosal folds*

In the 14th–15th week of gestation, the primitive tonsil and tonsillar fossa develop indirectly from the endoderm part of the second pharyngeal arch. At first, the tonsil has two lobes and a plica intratonsillaris (intratonsillar cleft) between them. This plica later usually disappears, but it may infrequently transform into crypta magna [6, 12]. Because the tonsil does not completely fill this fossa, two small depressions exist at the upper and anteroinferior parts of the tonsillar fossa. They are separated from the tonsil by mucosal folds, known as the plica semilunaris and triangularis, which are remnants of the primitive tonsillar fossa (**Figure 2**) [6, 7].

Superiorly the plica semilunaris originates from the upper aspect of the PGa and extends backward toward the PPa along the upper pole of the tonsil. It encloses a small depression that is known as supratonsillar fossa which separates the tonsil from the uvula [6, 7].

Anteroinferiorly the plica triangularis, an inconstant mucosal fold, arises from the PGa and covers the anteroinferior part of the tonsil. It encloses a smaller fossa that is known as anterior tonsillar fossa, which is then obscured by its walls and forms the imbedded portion of the tonsil [6, 7].

Also, the plica infratonsillaris or retrotonsillaris may extend to the PPa at the posteroinferior part of the tonsil [7]. At first there is no lymphoid tissue in these fossae, but in childhood, they are usually transformed into lymphoid tissues, which are an exclusive hiding place for a constant lithified secretion and foreign bodies, causing an inflammation or quinsy [6, 7].

**33**

*Surgical Anatomy of the Tonsils*

*3.6.4 Surfaces*

tonsil [6, 7, 9].

follicles [9, 12].

through the trabeculae [6, 9, 12].

from within outward (**Figure 3**):

starts and increases after 25 years of age [12, 13].

*DOI: http://dx.doi.org/10.5772/intechopen.93038*

the surface area of the tonsil up to 300 cm<sup>2</sup>

Medial surface is the free mucosal part of the tonsil that faces the oropharynx and contains bulging lymphoid projects. It is lined by stratified squamous nonkeratinized epithelium which contains polygonal superficial cells with microridges and numerous tubule-like long invaginations or orifices leading into tonsillar crypts. There are about 10–30 branching (primary and secondary) and anastomosing crypts, small pores, ranging in size between 5 and 25 μm. They increase

tions between antigens and the nodular lymphoid tissue. Secondary crypts are branching part of the primary crypts and continue deeply into the lymphoid tissue and forms the lymphoid fronds. The largest and deepest crypt is called crypta magna or intratonsillar cleft which is localized near the upper part of the

The transitional type nonkeratinized stratified epithelium, reticulated lymphoepithelium, with a discontinuous basement membrane covers the crypts with fenestrated capillaries and represents pores that are filled with large oval microvillus cells (M cells or dendritic cells) or lymphocytes (T and B cells). Dendritic cells play a role in the uptake and transport of antigens to extrafollicular T cell and B cell

At about 5th month of gestation, there are no germinal centers, and the lymphocytes develop from the connective tissue cells or are relocated in the blood and lymph vessels [13]. After birth, the exogenous antigens cause immune response which is represented by the transformation of effector B cell into extrafollicular plasma cell in 2 weeks, and secondary follicles containing active germinal centers develop and rapidly expand not invade the surrounding tissue in the first decade of life [7, 12]. The tonsillar lymphoid follicles consist of the lymphoid (germinal centers) and non-lymphoid cells (reticular cells and dendritic cells/macrophages). The germinal center is composed of a central area of proliferating B cells which is surrounded by resting B and T cells. Between these follicles, high endothelial venules allow the entrance of T and B cells from the blood and the release of mature lymphocytes into blood [6, 9, 13]. So, the tonsils have efferent lymphatic vessels to connect to lymph nodes, but no afferent vessels unlike a lymph node. The lymphoid fronds are separated from the tonsillar bed by a capsule, which is firmly coherent to the lymphoid tissue by multiple septa or trabeculae that dissect the tonsillar parenchyma. The trabeculae consist of elastin fibers and reticular fibers that are composed of type III collagen and provide cytoskeletal support. So, each tonsil is in a fixed position, in contrast to other MALTs, which are distributed throughout the body, and to disconnect the tonsil from its capsule is impossible. Also, the nerves, lymphatic and blood vessels, pass

The tonsils are most immunologically active at 4–10 years of age, whereas the adenoids are at 4–6 years. Age-dependent involution of the tonsil which refers to the regression of the germinal centers and the proliferation of fibrous tissue including the capsule and trabeculae occurs by adolescence. Also, fat deposition in tonsils

Lateral surface is a base of the tonsil that is covered by well-defined fibrous capsule at the lateral wall of the tonsillar fossa, which is composed of five layers

1.Tonsillar capsule, a thin false or surgical sheet, covers the tonsillar fossa as an appendage of the pharyngobasilar fascia. The upper part of this condensed

except the anterior part for interac-

#### *3.6.4 Surfaces*

*Oral and Maxillofacial Surgery*

and into the SPCm [11].

**Figure 2.**

*3.6.3 Mucosal folds*

fossa (**Figure 2**) [6, 7].

from the uvula [6, 7].

PPm running in various directions [8, 11].

*The mucosal folds and arches of the palatine tonsil.*

forms the imbedded portion of the tonsil [6, 7].

causing an inflammation or quinsy [6, 7].

the palatal tonsil to form the posterior pillar. Also, some of its fibers insert into the posterior border of the thyroid cartilage with the stylopharyngeus muscle (StPm)

During velopharyngeal closure, the PPm performs various functions such as a sphincter with the SPCm, a puller of the pharyngeal wall medially in collaboration with the SPCm and StPm, and an elevator with the StPm because of the fibers of the

In the 14th–15th week of gestation, the primitive tonsil and tonsillar fossa develop indirectly from the endoderm part of the second pharyngeal arch. At first, the tonsil has two lobes and a plica intratonsillaris (intratonsillar cleft) between them. This plica later usually disappears, but it may infrequently transform into crypta magna [6, 12]. Because the tonsil does not completely fill this fossa, two small depressions exist at the upper and anteroinferior parts of the tonsillar fossa. They are separated from the tonsil by mucosal folds, known as the plica semilunaris and triangularis, which are remnants of the primitive tonsillar

Superiorly the plica semilunaris originates from the upper aspect of the PGa and extends backward toward the PPa along the upper pole of the tonsil. It encloses a small depression that is known as supratonsillar fossa which separates the tonsil

Anteroinferiorly the plica triangularis, an inconstant mucosal fold, arises from the PGa and covers the anteroinferior part of the tonsil. It encloses a smaller fossa that is known as anterior tonsillar fossa, which is then obscured by its walls and

Also, the plica infratonsillaris or retrotonsillaris may extend to the PPa at the posteroinferior part of the tonsil [7]. At first there is no lymphoid tissue in these fossae, but in childhood, they are usually transformed into lymphoid tissues, which are an exclusive hiding place for a constant lithified secretion and foreign bodies,

**32**

Medial surface is the free mucosal part of the tonsil that faces the oropharynx and contains bulging lymphoid projects. It is lined by stratified squamous nonkeratinized epithelium which contains polygonal superficial cells with microridges and numerous tubule-like long invaginations or orifices leading into tonsillar crypts. There are about 10–30 branching (primary and secondary) and anastomosing crypts, small pores, ranging in size between 5 and 25 μm. They increase the surface area of the tonsil up to 300 cm<sup>2</sup> except the anterior part for interactions between antigens and the nodular lymphoid tissue. Secondary crypts are branching part of the primary crypts and continue deeply into the lymphoid tissue and forms the lymphoid fronds. The largest and deepest crypt is called crypta magna or intratonsillar cleft which is localized near the upper part of the tonsil [6, 7, 9].

The transitional type nonkeratinized stratified epithelium, reticulated lymphoepithelium, with a discontinuous basement membrane covers the crypts with fenestrated capillaries and represents pores that are filled with large oval microvillus cells (M cells or dendritic cells) or lymphocytes (T and B cells). Dendritic cells play a role in the uptake and transport of antigens to extrafollicular T cell and B cell follicles [9, 12].

At about 5th month of gestation, there are no germinal centers, and the lymphocytes develop from the connective tissue cells or are relocated in the blood and lymph vessels [13]. After birth, the exogenous antigens cause immune response which is represented by the transformation of effector B cell into extrafollicular plasma cell in 2 weeks, and secondary follicles containing active germinal centers develop and rapidly expand not invade the surrounding tissue in the first decade of life [7, 12]. The tonsillar lymphoid follicles consist of the lymphoid (germinal centers) and non-lymphoid cells (reticular cells and dendritic cells/macrophages). The germinal center is composed of a central area of proliferating B cells which is surrounded by resting B and T cells. Between these follicles, high endothelial venules allow the entrance of T and B cells from the blood and the release of mature lymphocytes into blood [6, 9, 13]. So, the tonsils have efferent lymphatic vessels to connect to lymph nodes, but no afferent vessels unlike a lymph node. The lymphoid fronds are separated from the tonsillar bed by a capsule, which is firmly coherent to the lymphoid tissue by multiple septa or trabeculae that dissect the tonsillar parenchyma. The trabeculae consist of elastin fibers and reticular fibers that are composed of type III collagen and provide cytoskeletal support. So, each tonsil is in a fixed position, in contrast to other MALTs, which are distributed throughout the body, and to disconnect the tonsil from its capsule is impossible. Also, the nerves, lymphatic and blood vessels, pass through the trabeculae [6, 9, 12].

The tonsils are most immunologically active at 4–10 years of age, whereas the adenoids are at 4–6 years. Age-dependent involution of the tonsil which refers to the regression of the germinal centers and the proliferation of fibrous tissue including the capsule and trabeculae occurs by adolescence. Also, fat deposition in tonsils starts and increases after 25 years of age [12, 13].

Lateral surface is a base of the tonsil that is covered by well-defined fibrous capsule at the lateral wall of the tonsillar fossa, which is composed of five layers from within outward (**Figure 3**):

1.Tonsillar capsule, a thin false or surgical sheet, covers the tonsillar fossa as an appendage of the pharyngobasilar fascia. The upper part of this condensed

#### **Figure 3.**

*The layers of the lateral pharyngeal wall at the level of tonsillar fossa, the parapharyngeal space compartments, and the structures between external and internal carotid arteries: SPm, salpingopharyngeus muscle; SPCm, superior pharyngeal constrictor muscle; PPm, palatopharyngeus muscle; PGm, palatoglossal muscle; StPm, stylopharyngeus muscle; StHm, stylohyoid muscle; StGm, styloglossus muscle; MPm, medial pterygoid muscle; GPn, glossopharyngeal nerve; PPS, parapharyngeal space; ICA, internal carotid artery; ECA, external carotid artery; X, vagus nerve; XI, accessory nerve; XII, hypoglossal nerve.*

capsule is even and loosely fixed, whereas the lower part is irregular and intermingled with the pharyngeal muscle fibers and is firmly attached anteroinferiorly by the suspensory ligament to the posterior one third of the tongue. The tonsillar artery enters near this ligament. So, the surgical removal of the upper part of the capsule up to the lower third is very easy, but the lower part requires cautious resection [6, 7, 14].


**35**

*Surgical Anatomy of the Tonsils*

*DOI: http://dx.doi.org/10.5772/intechopen.93038*

portions depending on their origins;

mylohyoid line of the mandible.

through the buccopharyngeal fascia [7, 15].

inferior fibers of the muscle. Efferent lymphatic vessels from the tonsil pierce

SPCm and pharyngobasilar fascia superiorly, the StPm posteriorly, and the stylohyoid ligament, middle pharyngeal constrictor (MPCm), the glossopharyngeal nerve (GPn), and styloglossus (StGm) muscles anteroinferiorly [7, 14, 15].

a.The pterygopharyngeal portion originates from the posterior margin of

b.The buccopharyngeal portion arises from the pterygomandibular raphe.

c.The mylopharyngeal portion originates from the posterior end of the

All of the muscle fibers are inserted into the median pharyngeal raphe posteriorly [7, 11]. Frequently, there is a space of 1–3 cm between the SPCm and MPCm. The GPn between the stylohyoid ligament and StGm curve forward and medially and pass through this space at the level of the lower pole of the palatine tonsil. The StGm and stylohyoid ligament originate from the anterior margin of the styloid process near its apex. The StGm inserts into the inferolateral surface of the tongue and interdigitates with intrinsic longitudinal lingual muscle, whereas the stylohyoid ligament lies between the StPm and StGm and attaches to the hyoid bone medially [7, 14, 16]. The StGm functions to elevate and retract the base of the tongue. Inferolaterally the lingual artery crosses the StGm and gives the dorsal lingual branches

d.The glossopharyngeal portion arises from the side of the tongue.

medial to the attachment of the StGm to the base of tongue [16].

PPm, MPCm, and pharyngeal mucosa [14, 17].

pterygoid musculature (**Figure 3**) [4, 15].

**3.7 Anatomy of the parapharyngeal space**

palatini muscles medially,

At the junction of pharyngeal constrictor muscles beneath the tonsil, the GPn gives tonsillar branch and afterward, extends into the base of tongue between the StGm and the stylohyoid ligament posteroinferiorly. The StPm originates from the posterior margin of the styloid process and courses downward along the posterolateral part of the stylohyoid ligament. Between the SPCm and MPCm, it passes and inserts to the

5.The buccopharyngeal fascia covers the lateral aspect of the SPCm medially and the medial pterygoid muscle anterolaterally. It forms anteromedial wall of the PPS and contains the pharyngeal plexus of nerves and vessels. The PPS like an inverted pyramid is situated between the lateral pharyngeal wall and the

The base of the parapharyngeal pyramid is located at the skull base and its apex at the greater cornu of the hyoid bone. The PPS is bounded by the following structures:

a.The buccopharyngeal fascia which covers the SPCm, the LVPm, and tensor veli

4.The lateral wall of tonsillar fossa or tonsillar bed is mostly made up of the

The SPCm narrows the superior part of the pharynx and is composed of four

the medial pterygoid plate and pterygoid hamulus.

*Oral and Maxillofacial Surgery*

**34**

**Figure 3.**

cautious resection [6, 7, 14].

capsule is even and loosely fixed, whereas the lower part is irregular and intermingled with the pharyngeal muscle fibers and is firmly attached anteroinferiorly by the suspensory ligament to the posterior one third of the tongue. The tonsillar artery enters near this ligament. So, the surgical removal of the upper part of the capsule up to the lower third is very easy, but the lower part requires

*The layers of the lateral pharyngeal wall at the level of tonsillar fossa, the parapharyngeal space* 

*ECA, external carotid artery; X, vagus nerve; XI, accessory nerve; XII, hypoglossal nerve.*

*compartments, and the structures between external and internal carotid arteries: SPm, salpingopharyngeus muscle; SPCm, superior pharyngeal constrictor muscle; PPm, palatopharyngeus muscle; PGm, palatoglossal muscle; StPm, stylopharyngeus muscle; StHm, stylohyoid muscle; StGm, styloglossus muscle; MPm, medial pterygoid muscle; GPn, glossopharyngeal nerve; PPS, parapharyngeal space; ICA, internal carotid artery;* 

2.Loose areolar tissue refers to the peritonsillar space between the tonsillar capsule and the pharyngobasilar fascia and contains the paratonsillar veins. A collection of pus in this space result in peritonsillar abscess or quinsy. It allows free movement of the pharyngeal muscles in the bed and makes easy to dissect

3.Pharyngobasilar fascia or pharyngeal aponeurosis originates from the pharyngeal tubercle and covers the first layer of the SPCm and is limited with the

the tonsil with capsule during tonsillectomy [6, 7].

inferior fibers of the muscle. Efferent lymphatic vessels from the tonsil pierce through the buccopharyngeal fascia [7, 15].

4.The lateral wall of tonsillar fossa or tonsillar bed is mostly made up of the SPCm and pharyngobasilar fascia superiorly, the StPm posteriorly, and the stylohyoid ligament, middle pharyngeal constrictor (MPCm), the glossopharyngeal nerve (GPn), and styloglossus (StGm) muscles anteroinferiorly [7, 14, 15].

The SPCm narrows the superior part of the pharynx and is composed of four portions depending on their origins;


All of the muscle fibers are inserted into the median pharyngeal raphe posteriorly [7, 11]. Frequently, there is a space of 1–3 cm between the SPCm and MPCm. The GPn between the stylohyoid ligament and StGm curve forward and medially and pass through this space at the level of the lower pole of the palatine tonsil. The StGm and stylohyoid ligament originate from the anterior margin of the styloid process near its apex. The StGm inserts into the inferolateral surface of the tongue and interdigitates with intrinsic longitudinal lingual muscle, whereas the stylohyoid ligament lies between the StPm and StGm and attaches to the hyoid bone medially [7, 14, 16]. The StGm functions to elevate and retract the base of the tongue. Inferolaterally the lingual artery crosses the StGm and gives the dorsal lingual branches medial to the attachment of the StGm to the base of tongue [16].

At the junction of pharyngeal constrictor muscles beneath the tonsil, the GPn gives tonsillar branch and afterward, extends into the base of tongue between the StGm and the stylohyoid ligament posteroinferiorly. The StPm originates from the posterior margin of the styloid process and courses downward along the posterolateral part of the stylohyoid ligament. Between the SPCm and MPCm, it passes and inserts to the PPm, MPCm, and pharyngeal mucosa [14, 17].

5.The buccopharyngeal fascia covers the lateral aspect of the SPCm medially and the medial pterygoid muscle anterolaterally. It forms anteromedial wall of the PPS and contains the pharyngeal plexus of nerves and vessels. The PPS like an inverted pyramid is situated between the lateral pharyngeal wall and the pterygoid musculature (**Figure 3**) [4, 15].
