S7 Oral Cavity - LabLink
Click here for a condensed, step-by-step dissection summary.
Locate and identify the relevant osteological features
Find these structures:
- Greater horn
- Alveolar arch
- Submandibular fossa
- Mental spines
- Sublingual fossa
- Mylohyoid line
- Digastric fossa
- Buccal shelf
- Mylohyoid groove
Determine which side will be utilized for superficial and deep dissection
Note: Description of areas of dissection:
Relocate structures in the submandibular triangle to follow into oral cavity - BOTH
Find these structures:
- Hypoglossal n. (CN XII)
- Lingual a.
1.) Locate the hypoglossal n. (CN XII), as it passes deep to the mylohyoid m.
Note: The hypoglossal n. (CN XII) provides efferent innervation to nearly all extrinsic and intrinsic muscles of the tongue, excluding palatoglossus m. (innervated by the vagus n., CN X).
Photo 1. Hypoglossal n., facial a., mylohyoid m.
2.) Follow the lingual a. from its origin, the external carotid a., to where it dives deep to the hyoglossus m.
Note: The lingual a. is an anterior branch of the external carotid a. (ECA) and often shares a common trunk with the facial a. If not, it commonly branches from the ECA proximal to the facial a. It can be seen in this area passing deep to the hyoglossus m. to supply the majority of the floor of the mouth and tongue. This artery will be dissected in more detail shortly.
Photo 2. Lingual a.
Examine the oral cavity proper - SUPERFICIAL SIDE
Find these structures:
- Oral cavity proper
- Oral vestibule
- Incisors (central & lateral)
- Premolars (first & second)
- Molars (first, second, & third)
3.) Identify the oral cavity proper, oral vestibule, gingiva, and the different types of teeth.
Note: The oral cavity can be divided into the oral cavity proper and the oral vestibule. The occlusal plane of the teeth divides these areas: oral cavity proper is internal to teeth, and the oral vestibule is external.
Note: The gingivae are masticatory mucosae that cover the roots of teeth and portions of the alveolar processes of the maxilla and mandible. It appears light pink and is closer to the teeth than the darker pink alveolar mucosa.
Note: There are four types of adult teeth: incisors (8), canines (4), premolars (8), and molars (12). The actual numbers of these types may vary among individuals.
Photo 3. Oral vestibule, teeth and gingiva, & oral cavity proper
Investigate the tongue, structures of the tongue, and associated structures of the tongue - DEEP SIDE
Find these structures:
- Tongue & Associated Structures
- External tongue
- Body (presulcal part)
- Root (postsulcal part)
- Median sulcus (of tongue)
- Filiform papillae
- Fungiform papillae
- Vallate papillae
- Terminal sulcus (of tongue)
- Foramen caecum (of tongue)
- Lingual tonsil
- Suprahyoid mm.
- Digastric m., anterior belly
- Mylohyoid m.
- Geniohyoid m.
- Extrinsic tongue mm.
- Intrinsic tongue mm.
- Superior longitudinal m.
- Inferior longitudinal m.
- Transverse m.
- Vertical m.
- Associated Structures
- Lingual frenulum (frenulum of tongue)
- Sublingual fold
- Openings of sublingual ducts
- Sublingual caruncle
- Fimbriated folds
- Epiglottic valleculae
- Median glosso-epiglottic fold
- Lateral glosso-epiglottic folds
- External tongue
4.) Turn the hemisected head so that a medial view of the tongue is possible. Identify the extrinsic and intrinsic tongue mm and associated muscles.
Note: When observing a medial view of the bisected tongue, the muscles are organized from inferior to superior: suprahyoid mm. (anterior belly of digastric m., mylohyoid m., geniohyoid m.), and tongue mm. (genioglossus m., and intrinsic muscles of the tongue).
Note: The mylohyoid m. forms the bulk of the floor of the oral cavity and can be identified superior to the digastric m. Like the anterior belly of digastric m., it is innervated by the nerve to mylohyoid (a branch of inferior alveolar n.,V3). When contracted, the mylohyoid m. elevates the tongue and hyoid, and can also depress the mandible.
Note: Geniohyoid m. attaches the mandible (inferior mental/genial spine) to the hyoid; thus, when it contracts, it will elevate the hyoid bone. When the hyoid is fixed, geniohyoid m. can play a role in depression of the mandible. Recall that geniohyoid is not a tongue muscle, and is innervated by branches from the VPR of C1 that travel with the hypoglossal n. (CN XII).
Note: Genioglossus m. is the most expansive extrinsic tongue muscle, and in sagittal section appears roughly triangular in shape. Its attachment to the mandible is on the superior mental/genial spines; thus, it is located superior to the geniohyoid m. These muscles when contracting bilaterally will depress and protrude the tongue. Acting unilaterally, genioglossus m. will deviate to the contralateral side.
Note: There are four types of intrinsic muscles of the tongue: superior longitudinal, inferior longitudinal, transverse, and vertical. These muscles independently (and in unison) alter tongue shape and perform smaller, more precise movements.
Photo 4. Medial view of tongue
5.) Using blunt dissection (scissors), carefully remove the oral mucosa superior to the sublingual space. A safe place to incise the mucosa is along the mucogingival junction adjacent to the mandible. Also using blunt dissection, remove the mental spine attachments of the geniohyoid m. and genioglossus m., and reflect the tongue posteromedially to open the sublingual space.
Photo 5. Procedural: removing mucosa
6.) Locate the remaining extrinsic tongue muscles: styloglossus m. and hyoglossus m.
Note: Styloglossus m. attaches the styloid process of the temporal with the posterolateral tongue. Innervated by the hypoglossal n. (CN XII), the styloglossus m. retracts and elevates the tongue.
Note: Hyoglossus m. attaches the greater horn of the hyoid bone to the intrinsic muscles of the tongue. Innervated by the hypoglossal n. (CN XII), the hyoglossus m. retracts the tongue and depresses the ipsilateral side of the tongue.
Photo 6. Hyoglossus m. and styloglossus m.
7.) Locate the following tongue structures from a superior view of the dorsum of the tongue: medial lingual sulcus, filiform papillae, fungiform papillae, vallate papillae, sulcus terminalis, foramen caecum, and lingual tonsil.
Note: The lingual papillae consist of four types (from anterior to posterior): filiform, fungiform, foliate, and vallate. All lingual papillae are associated with taste buds, except filiform.
Note: Filiform papillae are small, conical eruptions covering the dorsal anterior two-thirds of the tongue.
Note: Fungiform papillae are moderately sized, mushroom-shaped eruptions interspersed throughout the filiform papillae. Fungiform papillae host taste buds innervated by the axons from chorda tympani (facial n.) by way of the lingual n. (V3).
Note: Vallate papillae (sometimes referred to as circumvallate papillae) are located on the posteriormost border of the oral part of the dorsal tongue, just anterior to the terminal sulcus and foramen caecum. These papillae are the largest of the lingual papillae. Vallate papillae host taste buds innervated by the axons from the glossopharyngeal n. (CN IX), even though they lie on the presulcal side of the tongue.
Photo 7. Dorsum of tongue
Note: The median sulcus runs from the tip of the tongue to the foramen caecum, and divides the dorsum of the tongue into two halves. Deep to the median sulcus is a fibrous septum, which divides the length of the tongue.
Note: Foramen caecum is an indention located in the midline of the terminal sulcus of the tongue. This is an embryonic remnant of the thyroid diverticulum and thyroglossal duct.
The terminal sulcus is the midline junction of the body and root of the tongue.
Note: Paired terminal sulci run from the foramen caecum anterolaterally to the palatoglossal arch to form a V-shape. The terminal sulci divide the dorsum of the tongue into the body (presulcal) and root (postsulcal). The terminal sulci run parallel to the vallate papillae.
Note: The lingual tonsil is located on the root of the tongue. This tonsil is composed of groups of lymphoid follicles covered with mucosa.
Photo 8. Dorsum of tongue
Note: The root of the tongue connects to the epiglottis via three folds of mucosa: a single, median glosso-epiglottic fold, and paired lateral glosso-epiglottic folds. Between the median and lateral glosso-epiglottic folds are the epiglottic valleculae. These shallow depressions help to prevent saliva from being aspirated during breathing.
Photo 9. Glosso-epiglottic folds and epiglottic valleculae
8.) On one side of the donor, remove the mucous membrane of the tongue on the dorsal and inferior surfaces to locate the intrinsic muscles of the tongue.
Note: The intrinsic musculature of the tongue originates and inserts within the tongue, and thus controls the tongue’s shape for speech and mastication. All intrinsic tongue muscles are innervated by the hypoglossal n. (CN XII). Intrinsic tongue muscles include: superior longitudinal m., inferior longitudinal m., transverse m., and vertical m.
Note: Superior longitudinal m. consists of thin wisps of fibers running just deep to the dorsal mucosa from the root of the tongue, (adjacent to the epiglottis) to the apex.
Note: Inferior longitudinal m. consists of thin wisps of fibers running between the genioglossus m. and the hyoglossus m. from the root of the tongue (adjacent to the hyoid bone) to the apex.
Note: Transverse m. connect the median fibrous septum to the margins of the tongue.
Note: Vertical m. are robust fibers connecting the dorsal and inferior aspects of the body of the tongue.
Photo 10. Intrinsic muscles of tongue
9.) Identify the gross features of the oral cavity proper: lingual frenulum, sublingual fold (& openings of the sublingual ducts), sublingual caruncle, and fimbriated folds.
Note: The lingual frenulum connects the inferior midline of the tongue to the mucosa of the floor of the oral cavity. It may be highly variable in size and attachment. In some individuals a shortened and thickened lingual frenulum may limit the mobility of the tongue, a condition known as ankyloglossia (‘tongue-tie’). Ablation of the lingual frenulum (frenulotomy) is less frequently performed to aid in difficulties with speech, but it may increase success of latching for breast feeding. The lingual frenulum may not be present if the head was exactly sectioned in the midline, but should be present if slightly off midline. If unavailable on the donor, the frenulum of the tongue can be identified on your lab partners.
Note: The sublingual folds are formed by the sublingual glands and ducts of the submandibular glands shaping the mucosa. Along these folds are the bilateral openings of the sublingual ducts.
Note: The sublingual caruncle is situated at the confluence of the sublingual folds and the lingual frenulum. The sublingual caruncle is the location where the submandibular (Wharton’s) ducts secrete saliva into the oral cavity.
Note: Fimbriated folds flank the lingual frenulum on the inferior surface of the tongue. Typically, the lingual veins are visible deep to the inferior surface mucosa between the lingual frenulum and the fimbriated folds.
Photo 11. Lingual frenulum and sublingual: fold and caruncle
Examine the oral cavity proper and dissect the sublingual space - SUPERFICIAL SIDE
Find these structures:
- Sublingual gland
- Submandibular gland, deep portion
- Submandibular (Wharton’s) duct
- Lingual n. (V3)
- Submandibular ganglion
- Hypoglossal n. (CN XII)
- Vena comitans of hypoglossal n.
- Lingual a.
10.) Reflect the tongue posteromedially to expose the floor of the mouth in the oral cavity proper.
Note: The floor of the mouth, deep to the oral mucosa is the sublingual space. The sublingual space is a potential space, superior to the mylohyoid mm., bounded laterally by the mandible, and posteriorly by the attachments of muscles to the hyoid bone. The sublingual space is continuous with the submental, submandibular, and buccal spaces.
11.) Clean and identify structures: sublingual gland, deep portion of submandibular gland, submandibular (Wharton’s) duct, lingual a. (& brs), lingual n. (& brs), submandibular ganglion, hypoglossal n. (CN XII), and vena comitans of hypoglossal n.
Note: Of the three major salivary glands, the sublingual gland is the smallest. It is located superior to the mylohyoid m. and when covered with mucosa, it forms the sublingual fold. These glands drain via numerous small ducts along the sublingual folds. The deep, smaller part of the submandibular gland is also located in this area and is closely associated with the posterior end of the sublingual gland.
Note: The mylohyoid line of the mandible is formed by the attachment of the mylohyoid m. The two salivary glands in this region are associated with this line: sublingual gland superior, and submandibular gland inferior.
Note: The lingual a. is typically the second branch of the external carotid a. that leaves the external carotid anteriorly. Passing between the hyoglossus m. and the middle pharyngeal constrictor m., the lingual a. supplies the floor of the oral cavity and the tongue. The lingual a. produces several branches, chiefly:
- Dorsal lingual brs. - arise medially to the hyoglossus m., supply the posterior tongue, soft palate, and palatine tonsil,
- Sublingual a. - arise anteriorly to the hyoglossus m., supplies the sublingual gland, and muscles and tissues of the floor of the oral cavity, and
- Deep lingual a. - the terminal br. of the lingual a., lies along the inferior margin to the tip of the tongue, supplies the anterior tongue.
Nearly all of the lingual a. branches anastomose with their contralateral paired artery along the midline.
Note: Deep to the mucosa in the oral cavity proper, the lingual n. and submandibular duct cross. The lingual n. descends into the oral cavity and loops under the submandibular duct to provide general sensory innervation to the anterior 2/3rds of the tongue.
Note: The submandibular (Wharton’s) duct traverses the space between the submandibular gland and sublingual caruncle. The duct is located between the hypoglossal n. and lingual n. in association with the hyoglossus m. The lingual n. passes deep to the duct about midway in the oral cavity.
Note: The lingual n. is an afferent branch of the posterior trunk of V3. It traverses the infratemporal fossa medial to the inferior alveolar n., where it is joined by the chorda tympani n. (branch of facial n., CN VII). Chorda tympani carries presynaptic parasympathetic fibers to the submandibular gland and taste to the body of the tongue (excluding the vallate papillae). The lingual n. enters the oral cavity superior to the mylohyoid m., and enters the tongue to provide sensory innervation to the body of the tongue and the floor of the oral cavity.
Note: In regards to innervation of the tongue, often the tongue is described in 2 sections: the anterior 2/3rds (innervated by facial n.) and the posterior 1/3rd (innervated by glossopharyngeal n.). The division between these sections is approximately the terminal sulcus; however, the area supporting the vallate papillae is innervated by the glossopharyngeal n. (CN IX).
Note: The submandibular ganglion is delicately associated with the lingual n. and is superior to the deep portion of the submandibular gland. This ganglion is one of four named peripheral parasympathetic ganglia (ciliary, pterygopalatine, submandibular, and otic). The submandibular ganglion receives preganglionic parasympathetic fibers from the chorda tympani, a branch of the facial n. (CN VII). Postganglionic parasympathetic fibers leave the ganglion to innervate the submandibular and sublingual glands, among other smaller glands (e.g. anterior lingual) by means of the lingual n., a branch of V3.
Note: The vena comitans of hypoglossal n. is a tributary of the lingual v. This vein accompanies the hypoglossal n. (CN XII) inferiorly along the hyoglossus m.