HUMAN ANATOMY – VOLUME 1

Proper muscles of the tongue. The s u p e r i o r l o n g i t u d i n a l m u s c l e (m. l o n g i t u d i n á l i s s u p é r i o r) is situated along the sides of the median lingual groove, beneath the mucosa. It originates from the region of the root of the tongue and ends in its tip. During contraction this muscle shortens the tongue and raises its tip. The i n f e r i o r l o n g i t u - d i n a l m u s c l e (m. l o n g i t u d i n á l i s i n f é r i o r) lies in the lower part of the tongue. It originates from the root of the tongue and ends in the apex. During contraction it shortens the tongue and lowers its tip. The t r a n s v e r s e m u s c l e (m. t r a n s v é r s u s l í n g u a e) lies between the superior and inferior longitudinal muscles. It is formed by fascicles, which originate in the fibrous septa of the tongue and end in its sides. This muscle narrows the tongue, raising the dorsum. The v e r t i c a l m u s c l e (m. v e r t i c á l i s l í n g u a e) is present primarily in its side regions. Its fascicles stretch between the mucosa of the dorsum of the tongue and its underside. By contracting it flattens the tongue.

Skeletal muscles of the tongue. The g e n i o g l o s s u s muscle (m. g e n i o g l ó s s u s) originates on the mental spine of the mandible, spreads out upward and to the back, and ends inside the tongue. During contraction it pulls the tongue downward and to the front. The h y o g l o s - s u s (m. h y o g l ó s s u s) originates from the greater horn of the hyoid bone and ends in the lateral section of the tongue. This muscle shifts the tongue downward and to the back. The s t y l o g l o s s u s (m. s t y l o g l ó s s u s) originates from the styloid process, stretches forward, medially and downwards, and is inserted into the tongue from the side. During bilateral contractions it pulls the tongue up and to the back. During unilateral contraction it shifts the tongue to the side (table 16).

Table 16. Skeletal muscles of the tongue.

!

M o t o r i n n e r v a t i o n of the tongue — hypoglossal nerve; s e n - s i t i v e i n n e r v a t i o n — lingual nerve (anterior two thirds of the tongue) and glossopharyngeal nerve (posterior third); gu s t a t o r y i n n e r v a - t i o n — tympanic cord (anterior two thirds) and glossopharyngeal nerve (posterior third).

B l o o d s u p p l y: lingual artery; Ve n o u s o u t f l o w: lingual vein.

Ly m p h o u t f l o w: mental, submandibular and deep cervical lymph nodes.

Salivary glands

Glands of the mouth include the minor and major salivary glands. The m i n o r s a l i v a r y g l a n d s are found in the mucosa and submucosa of the oral cavity. Their size varies between 1 and 5 mm. According to their topography glands can be called labial, buccal, molar (situated next to the molar teeth), palatine or lingual. The m a j o r s a l i v a r y g l a n d s are situated outside the walls of the oral cavity, and are connected to it by excretory ducts. Independent of topography or size, all large salivary glands are similar in structure. They are compound alveolar or tubuloalveolar glands, derived from the ectoderm. These glands have a body (main section) and an excretory duct. The body consists of the parenchyma and the stroma of the gland. The beginning (secretory) sections are subdivided, according to the composition of their secretion, into the protein-producing (serous), mucus-producing (mucosal) and mixed types. According to a mechanism of secretion all salivary glands are of the merocrine type. The serous glands produce thin secretion, which is rich in enzymes. The mucosal glands produce a thicker, more viscous secretion, rich in mucin, which contains glycosaminoglycans.

The excretory ducts of the glands are subdivided into the intralobular and interlobular ducts and the common excretory duct. The intralobular ducts have two parts called the intercalary ducts (the beginning of the duct apparatus) and the striated ducts. The striated ducts continue into the interlobular ducts, which are connected to form the common duct. The intercalary ducts are usually lined by cuboidal and prismatic epithelium. The striated ducts are lined by columnar epitheliocytes, which are characterized by folds of the basal membrane. Between these folds there are a lot of mitochondria, which give these cells the appearance of striation. The interlobular ducts are lined with bistratified epithelium, which gradually passes into squamous. The common excretory duct is usually lined with stratified cuboidal epithelium, and in the region of it’s opening — by striated squamous epithelium.

!

Excretory ducts of different salivary glands have certain individual characteristics. In the submandibular gland the intercalary ducts are shorter and less branched than in the parotid gland. In the sublingual gland the intercalary and striated ducts are almost undeveloped.

According to the type of secretion the lingual salivary glands are primarily serous. There are some mucosal glands on the root of the tongue and its sides. The glands of the anterior section of the tongue produce mixed secretion. The palatine glands are mucosal. The buccal, molar and labial glands are also mixed.

The salivary glands regularly secrete saliva into the oral cavity, thus carrying out an exocrine function. The composition of saliva is water (approximately 99 percent), mucus (mucin), enzymes (amylase, maltase), inorganic substances and immunoglobulins. Saliva moistens the food and the mucosa inside the oral cavity. Its enzymes break down polysaccharides into disaccharides and monosaccharides (glucose).

Major salivary glands (Fig. 123, 124). The parotid gland (glándula parotídea) is paired; it produces serous secretion. It is irregular in shape and is covered by a thin capsule. Its mass is 20–30 g. The gland is situated in front of and below the auricular concha, on the side surface of the ramus of mandible. At the top it adjoins to the zygomatic arch; at the bottom it extends to the angle of mandible; and in the back it reaches the mastoid process and the anterior edge of the sternocleidomastoid muscle. The deep part of the gland adjoins the styloid process and the stylohyoid, styloglossal and stylopharyngeal muscles. The gland is perforated by the external carotid artery, the retromandibular vein and the facial and auriculotemporal nerves. Inside the gland lie the parotid lymph nodes. The excretory duct of the parotid gland (p a r o t i d, or Stensen’s d u c t) comes out from beneath its anterior edge, passes to the front 1– 2 cm below the zygomatic arch, along the outer surface of the masseter muscle. It rounds the anterior edge of this muscle, perforates the buccinator muscle and opens into the vestibule of mouth at the level of the second upper molar.

S e n s i t i v e i n n e r v a t i o n — parotid branches of the auriculotemporal nerve; s e c r e t o r y (p a r a s y m p a t h e t i c) i n n e r v a t i o n — fibers of the auriculotemporal nerve (from the auricular node); s y m p a - t h e t i c — the external carotid plexus.

B l o o d s u p p l y: parotid branches of the superficial temporal artery;

Ve n o u s o u t f l o w: retromandibular vein.

Ly m p h o u t f l o w: superficial and deep parotid lymph nodes.

!

Fig. 123. Major salivary glands (left half of mandible is removed).

1 — parotid gland; 2 — parotid duct; 3 — masseter; 4 — submandibular gland; 5 — submandibular duct; 6 — mylohyoid; 7 — mandible; 8 — sublingual gland; 9 — tongue; 10 — buccinator.

The submandibular gland (glánudula submandibuláris) is paired, produces mixed secretion and has a well-developed capsule. It is situated in the region of the submandibular triangle of the neck. On the outside the gland is covered by the superficial lamina of the cervical fascia and the skin. The inner surface of the gland adjoins the hyoglossal and styloglossal muscles. At the top it reaches the inner surface of the body of the mandible. The anterior part of the gland protrudes to the back edge of the mylohyoid muscle. Its lateral surface adjoins the facial artery and vein, and the nearby lymph nodes. The s u b m a n d i b u l a r (Wharton’s) duct passes forward, adjoining the sublingual gland. It opens on the sublingual papilla, next to the lingual frenulum.

! !

Fig. 124. Structure of major salivary glands (scheme).

A — serous secretory units. B — mucous secretory units. 1 — secretory units; 2 — intercalary duct; 3 — striated duct; 4 — gland duct; 5 — interlobular ducts; 6 — glanduloocytes.

S e c r e t o r y (p a r a s y m p a t h e t i c) i n n e r v a t i o n — fibers of the facial nerve (through the tympanic cord and submandibular node); s y m - p a t h e t i c — external carotid plexus.

B l o o d s u p p l y: glandular branches of the facial artery. Ve n o u s o u t f l o w: submandibular vein.

Ly m p h o u t f l o w: submandibular lymph nodes.

The sublingual gland (glándula sublinguális) is paired; produces primarily mucosal secretion. It is situated on the superior surface of the mylohyoid muscle, directly beneath the mucosa of the oral cavity floor. Its lateral surface adjoins the internal surface of the body of the mandible in the region of the sublingual fossa. Medially it adjoins the genioglossal, geniohyoid and hyoglossal muscles.

The m a j o r s u b l i n g u a l d u c t (main excretory duct) opens on the sublingual papilla. Several minor (additional) sublingual ducts open on the surface of the s u b l i n g u a l f o l d.

S e c r e t o r y (p a r a s y m p a t h e t i c) i n n e r v a t i o n — fibers of the facial nerve (through the tympanic cord and submandibular node); s y m - p a t h e t i c — external carotid plexus.

B l o o d s u p p l y: sublingual and mental arteries. Ve n o u s o u t f l o w: sublingual vein.

Ly m p h o u t f l o w: submandibular and mental lymph nodes.

! "

Questions for revision and examination

1.What structures form the walls of the oral cavity?

2.Name the muscles of the soft palate and their points of origin and insertion.

3.Describe the structure of a tooth. What differences are there between different types of the teeth?

4.Name the periods of eruption of deciduous and permanent teeth.

5.What papillae are found on the surface of the tongue? Which of them contain taste

buds?

6.Name the anatomical groups of muscles of the tongue. What is the function of each muscle?

7.Name different groups of small salivary glands.

8.Where in the oral cavity do the ducts of the large salivary glands open? How are these glands classified according to their structure and type of secretion?

PHARYNX

The pharynx is an unpaired organ, situated in the region of the head and neck (Fig.125, 126). It is part of both the digestive and the respiratory systems. It is shaped like an infundibular tube, which is fixed on the base of the skull. Its upper part (v a u l t o f p h a r y n x) attaches to the pharyngeal tubercle of the occipital bone, sides of pyramids of the temporal bones (in front of the external carotid opening), and to the medial laminae of the pterygoid processes. At the bottom it continues into the esophagus at the level of C4 vertebra. In an adult the pharynx is 12–15 cm long. Behind the pharynx lie the prevertebral muscles, the prevertebral lamina of the cervical fascia, and the cervical part of the spine. Between the pharynx and the fascia is the r e t r o p h a r y n g e a l s p a c e , filled with loose fibrous connective tissue. Within this space lie the retropharyngeal lymph nodes.

On both sides the pharynx is adjoined by the common and internal carotid arteries, the internal jugular vein, the vagus nerve, the greater horn of the hyoid bone and the thyroid cartilage of the larynx.

On the anterior wall of the pharynx are openings of the choanae. Below them is the fauces, and lower than that—the entrance into the larynx. The pharynx is divided into the n a s o p h a r y n x, situated behind the choanae; the o r o p h a r y n x, situated between the palatine velum and the entrance into the larynx; and the l a r y n g o p h a r y n x, situated between the entrance into the larynx and the transition into the esophagus. The nasopharynx is part of the respiratory system, while the oropharynx pertains to the digestive tract.

In the region of the vault of the pharynx, in the transitional region between its superior and posterior walls, there is an accumulation of lymphoid tissue (the p h a r y n g e a l t o n s i l). On the lateral walls, next to the back edge of the inferior nasal concha, is the p h a r y n g e a l o p e n - i n g o f t h e a u d i t o r y t u b e. The auditory (Eustachian) tube con-

! #

Fig. 125. Oral cavity and pharyngeal cavity (sagittal section of head).

1 — oral cavity proper; 2 — vestibulum oris; 3 — inferior nasal concha; 4 — nasal vestibulum; 5 — frontal sinus; 6-middle nasal concha; 7 — inferior nasal concha; 8 — superior nasal concha; 9 — sphenoidal sinus; 10 — pharyngeal tonsil; 11 — pharyngeal opening of auditory tube; 12 — torus tubarius; 13 — soft palate (velum palatinus); 14 — oropharynx; 15 — palatine tonsill; 16 — isthmus of fauces; 17 — root of tongue (lingual tonsil); 18 — epiglottis; 19 — aryepiglottic fold; 20 — laryngopharynx; 21 — cricoid cartilage; 22 — oesophagus; 23 — trachea; 24 — thyroid cartilage;

25 — hyoid bone; 26 — mylohyoid; 27 — genioglossus; 28 — mandible.

nects with the tympanic cavity, equalizing the pressure inside the middle ear with the atmospheric pressure. Above and behind the pharyngeal opening is limited by the tubal torus. At the bottom this torus continues into a thin salpingopharyngeal fold. The pharyngeal recess is behind the torus tubarius. Next to each opening of the auditory tube lies the tubal tonsil, which is an organ of the immune system.

The entrance into the larynx is bordered on the top by the epiglottis, at the sides — by the aryepiglottic folds, and at the bottom — by the arytenoid cartilage. Between the inner surface of the larynx and the aryepiglottic cartilage, on each side, there is a recess called the p i r i f o r m recess.

! $

Fig. 126. Muscles of pharynx; Posterior aspect. Frontal cut. Posterior part of cranium is removed.

1 — basilar part of occipital bone; 2 — styloid process; 3 — superior constrictor; 4 — stylopharyngeus; 5 — middle constrictor; 6 — greater horn of hyoid bone; 7 — pharyngeal raphe; 8 — inferior constrictor; 9 — oesophagus; 10 — left lobe of thyroid gland; 11 — submandibular gland (salivary); 12 — stylohyoid muscle; 13 — medial pterygoid; 14 — posterior belly of digastric; 15 — parotid (salivary) gland.

The wall of the pharynx consists of the mucosa, a thick submucosa, the muscularis and the adventitia. The mucosa is lined with pseudostratified ciliary epithelium. In the regions of the oropharynx and laryngopharynx the mucosa has striated squamous epithelium, situated on the lamina propria with a high content of elastic fibers. The submucosa of the nasopharynx and oropharynx is thickened and forms a fibrous plate called the p h a r y n g o b a s i l a r f a s c i a (fáscia pharyngobasiláris). At the level of the laryngopharynx the submucosa consists of loose fibrous connective tissue and contains a large number of glands.

! %

The mucosa of the pharynx consists of five striated muscles, which include three pharyngeal constrictors and two longitudinal elevator muscles.

The s u p e r i o r c o n s t r i c t o r muscle of the pharynx (m. c o n s t r í c - t o r p h á r y n g i s s u p é r i o r) originates on the medial lamina of the pterygoid process of sphenoid bone and the pterygomandibular raphe of the fibrous plate, stretched between the sphenoid bone and the mandible. Its fibers stretch downward and to the back, and connect with the muscle fibers of the opposite side (table 17).

Table 17. Muscles of the Pharynx.

of the hyoid bone. Its muscle fibers spread out upward and downwards, connecting with muscle fibers of the opposite side on the posterior wall of the pharynx. The upper edge of the middle constrictor overlaps the superior constrictor.

The i n f e r i o r c o n s t r i c t o r muscle of the pharynx (m. c o n - s t r í c t o r p h á r y n g i s i n f é r i o r) originates from the lateral surface of the thyroid cartilage plate and from the cricoid cartilage. Its fascicles

! &

spread out upwards, downwards and horizontally, covering the lower edge of the middle constrictor, and are connected to analogous fascicles of the opposite side. The lower fascicles of this muscle pass onto the esophagus. The accretion of the left and right fascicles of the constrictor muscles on the posterior wall forms the p h a r y n g e a l r a p h e. The constrictor muscles narrow the lumen of the pharynx.

The longitudinal group of muscles of the pharynx includes two muscles. The s t y l o p h a r y n g e u s muscle (m. s t y l o p h a r ý n g e u s) originates from the styloid process of temporal bone. It stretches downward and medially and enters the wall of the pharynx approximately between the superior and middle constrictors. During contraction it raises the pharynx together with the larynx. The p a l a t o p h a r y n g e u s muscle (m. p a l a t o p h a r ý n g e u s) originates inside the posterior wall of the pharynx and from the posterior edge of the thyroid cartilage plate. It stretches upward and is inserted into the palatine aponeurosis. Part of its fascicles attach on the hook of the sphenoid bone, and another part — to the internal cartilage plate of the auditory tube, forming the s a l p i n g o p h a r y n g e u s muscle. The palatopharyngeus muscle brings the palatopharyngeal arches toward each other and raises the lower part of the pharynx and larynx.

Swallowing (deglutition). When the food bolus touches the palate, the root of the tongue and the posterior wall of the pharynx, it triggers receptors of these regions. A nerve impulse travels along the glossopharyngeal nerves to the deglutition center of the medulla oblongata. Neurons of this center send impulses along the trigeminal, glossopharyngeal, vagus and hypoglossal nerves to the muscles of the oral cavity, tongue, pharynx, oesophagus and larynx. Coordinated contraction of these muscles promotes the swallowing of food. The act of swallowing consists of a voluntary phase (0.7– 1.0 seconds) and an involuntary phase (4–6 seconds). Deglutition is conducted through the following consecutive phases:

1.The muscles of the soft palate contract, raising the palatine velum, and the apertures of the auditory tubes become open.

2.The palatine velum pushes against the vault of the pharynx, secluding the nasopharynx.

3.During contraction of the muscles of the diaphragm of the mouth the larynx is shifted up and forwards, such that the epiglottis closes off its entrance.

4.Contraction of the styloglossus and hyoglossus muscles shifts the root of the tongue back, and the food bolus gets pushed through the fauces. Contraction of the palatoglossal muscles breaks off the part of the bolus, which is in the oropharynx, from the part, which remains in the mouth.

! '