The Tongue

• The tongue (L. lingua; G. glossa) is a highly mobile muscular organ that can vary greatly in shape.
• It consists of three parts, a root, body, and tip.

• The tongue is concerned with mastication, taste, deglutition (swallowing), articulation (speech), and oral cleansing.
• Its main functions are squeezing food into the pharynx when swallowing, and forming words during speech.

Gross Features of the Tongue

• The dorsum of the tongue is divided by a V-shaped sulcus terminalis into anterior oral (presulcal) and posterior pharyngeal (postsulcal) parts.
• The apex of the V is posterior and the two limbs diverge anteriorly.
• The oral part forms about 2/3 of the tongue and the pharyngeal part forms about 1/3.

Oral Part of the Tongue

• This part is freely movable, but it is loosely attached to the floor of the mouth by the lingual frenulum.

• On each side of the frenulum is a deep lingual vein, visible as a blue line.
• It begins at the tip of the tongue and runs posteriorly.
• All the veins on one side of the tongue unite at the posterior border of the hyoglossus muscle to form the lingual vein, which joins the facial vein or the internal jugular vein.

• On the dorsum of the oral part of the tongue is a median groove.
• This groove represents the site of fusion of the distal tongue buds during embryonic development.

The Lingual Papillae and Taste Buds

• The filiform papillae (L. filum, thread) are numerous, rough, and thread-like.
• They are arranged in rows parallel to the sulcus terminalis.

• The fungiform papillae are small and mushroom-shaped.
• They usually appear are pink or red spots.

• The vallate (circumvallate) papillae are surrounded by a deep, circular trench (trough), the walls of which are studded with taste buds.

• The foliate papillae are small lateral folds of lingual mucosa that are poorly formed in humans.

• The vallate, foliate and most of the fungiform papillae contain taste receptors, which are located in the taste buds.

The Pharyngeal Part of the Tongue

• This part lies posterior to the sulcus terminalis and palatoglossal arches.
• Its mucous membrane has no papillae.

• The underlying nodules of lymphoid tissue give this part of the tongue a cobblestone appearance.
• The lymphoid nodules (lingual follicles) are collectively known as the lingual tonsil.

Innervation of the Pharynx

• The motor and most of the sensory supply of the pharynx is derived from the pharyngeal plexus of nerves on the surface of the pharynx.
• The plexus is formed by pharyngeal branches of the vagus (CN X) and glossopharyngeal (CN IX) nerves, and by sympathetic branches for the superior cervical ganglion.

• The motor fibres in the pharyngeal plexus are derived from the cranial root of accessory nerve (CN XI), and are carried by the vagus nerve to all muscles of the pharynx and soft palate.
• The exceptions are stylopharyngeus (supplied by CN IX) and the tensor veli palatini (supplied by CN V3).

The Temporomandibular Joint

• This articulation is a modified hinge type of synovial joint.
• The articular surfaces are: (1) the head or condyle of the mandible inferiorly and (2) the articular tubercle and the mandibular fossa of the squamous part of the temporal bone.

• An oval fibrocartilaginous articular disc divides the joint cavity into superior and inferior compartments. The disc is fused to the articular capsule surrounding the joint.

• The articular disc is more firmly bound to the mandible than to the temporal bone.

• Thus, when the head of the mandible slides anterior on the articular tubercle as the mouth is opened, the articular disc slides anteriorly against the posterior surface of the articular tubercle

The Cheeks

• The cheeks (L. buccae) form the lateral wall of the vestibule of the oral cavity.
• They have essentially the same structure as the lips with which they are continuous.

• The principal muscular component of the cheeks is the buccinator muscle.
• Superficial to the fascia covering this muscle is the buccal fatpad that gives cheeks their rounded contour, especially in infants.

• The lips and cheeks act as a functional unit (e.g. during sucking, blowing, eating, etc.).
• They act as an oral sphincter in pushing food from the vestibule to the oral cavity proper.
• The tongue and buccinator muscle keep the food between the molar teeth during chewing.

Sensory Nerves of the Cheeks

• These are branches of the maxillary and mandibular nerves.
• They supply the skin of the cheeks and the mucous membrane lining the cheeks.

The Temporalis Muscle

• This is an extensive fan-shaped muscle that covers the temporal region.
• It is a powerful masticatory muscle that can easily be seen and felt during closure of the mandible.

• Origin: floor of temporal fossa and deep surface of temporal fascia.
• Insertion: tip and medial surface of coronoid process and anterior border of ramus of mandible.
• Innervation: deep temporal branches of mandibular nerve (CN V³).

• The temporalis elevates the mandible, closing the jaws; and its posterior fibres retrude the mandible after protrusion.

The Inferior Wall of the Orbit

• The thin inferior wall of the orbit or the floor is formed mainly by the orbital surface of the maxilla and partly by the zygomatic bone, and orbital process of the palatine bone.

• The floor of the orbit forms the roof of the maxillary sinus.

• The floor is partly separated from the lateral wall of the orbit by the inferior orbital fissure.