The Oral Cavity
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The ear | Main Anatomy Index | The salivary glands
Last updated 30 March 2006
The Oral
Cavity
- The oral cavity (mouth) consists of two parts: the vestibule and the mouth proper.
- The vestibule is the
slit-like spaced between the cheeks and the lips and the
teeth and gingivae.
- It is the entrance of the digestive tract and is also
used for breathing.
- The vestibule communicates with the exterior through the orifice of the mouth.
- The oral cavity is bounded:
- Externally: by the cheeks and lips.
- Roof of oral cavity: formed by the palate.
- Posteriorly: the oral cavity communicates with the oropharynx.
The Lips (p. 734)
- These are mobile muscular folds that surround the mouth,
the entrance of the oral cavity.
- The lips (L. labia) are covered externally by skin
and internally by mucous membrane.
- In between these are layers of muscles, especially the orbicularis oris
muscle.
- The upper and lower lips are attached to the gingivae in
the median plane by raised folds of mucous membrane,
called the labial frenula.
Sensory
Nerves of the Lips (p. 734)
The Cheeks (pp.
735-6)
- 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 (p. 736)
- These are branches of the maxillary and mandibular nerves.
- They supply the skin of the cheeks and the mucous
membrane lining the cheeks.
The Palate
- The palate forms the arched roof of the mouth and the
floor of the nasal cavities.
- The palate consists of two regions: the anterior 2/3 or
bony part, called the hard palate,
and the mobile posterior 1/3 or fibromuscular part, known
as the soft palate.
The Hard
Palate (pp. 741, 743)
- The anterior bony part of the palate is formed by the palatine process of the maxillae and the horizontal plates of the palatine bones.
- Anteriorly and laterally, the hard palate is bounded by
the alveolar processes
and the gingivae.
- Posteriorly, the hard palate is continuous with the soft palate.
- The incisive foramen is
the mouth of the incisive canal.
- This foramen is located posterior
to the maxillary central incisor teeth.
- This foramen is the common opening for the right and left
incisive canals.
- The incisive canal and foramen transmit the nasopalatine nerve and the
terminal branches of the sphenopalatine
artery.
- Medial to the third molar tooth,
the greater palatine foramen
pierces the lateral border of the bony palate.
- The greater palatine vessels and nerve emerge from this
foramen and run anteriorly
into two grooves on the palate.
- The lesser palatine foramen
transmits the lesser palatine nerve
and vessels.
- This runs to the soft palate and adjacent structures.
The Soft
Palate (pp. 743-5)
- This is the posterior curtain-like part, and has no bony
support. It does, however, contain a membranous
aponeurosis.
- The soft palate, or velum palatinum (L. velum,
veil), is a movable, fibromuscular fold that is
attached to the posterior edge of the hard palate.
- It extends posteroinferiorly to a curved free margin from
which hangs a conical process, the uvula
(L. uva, grape).
- The soft palate separates the nasopharynx superiorly and
the oropharynx inferiorly.
- During swallowing the soft palate moves posteriorly
against the wall of the pharynx, preventing the
regurgitation of food into the nasal cavity.
- Laterally, the soft palate is continuous with the wall of
the pharynx and is joined to the tongue and pharynx by
the palatoglossal and palatopharyngeal folds.
- The soft palate is strengthened by the palatine
aponeurosis, formed by the expanded tendon of
the tensor veli palatini muscle.
- This aponeurosis attaches to the posterior margin of the hard palate.
Muscles
of the Soft Palate (pp. 743-5)
The
Levator Veli Palatini (Levator Palati) (p. 743)
- Superior attachment: cartilage of the auditory tube and
petrous part of temporal bone.
- Inferior attachment: palatine aponeurosis.
- Innervation: pharyngeal branch of vagus via pharyngeal
plexus.
- This cylindrical muscle runs
inferoanteriorly, spreading
out in the soft palate, where it attaches to
the superior surface of the palatine aponeurosis.
- It elevates the soft palate,
drawing it superiorly and posteriorly.
- It also opens the auditory tube
to equalise air pressure in the middle ear and pharynx.
The
Tensor Veli Palatini (Tensor Palati) (pp. 743-4)
- Superior attachment: scaphoid fossa of medial pterygoid
plate, spine of sphenoid bone, and cartilage of auditory
tube.
- Inferior attachment: palatine aponeurosis.
- Innervation: medial pterygoid nerve (a branch of the
mandibular nerve).
- This thin, triangular muscle passes inferiorly, and hooks around the hamulus of the medial
pterygoid plate.
- It then inserts into the palatine aponeurosis.
- This muscle tenses the
soft palate by using the hamulus as
a pulley.
- It also pulls the membranous portion of the auditory tube
open to equalise air pressure of the middle ear and
pharynx.
The
Palatoglossus Muscle (p. 744)
- Superior attachment: palatine aponeurosis.
- Inferior attachment: side of tongue.
- Innervation: cranial part of accessory nerve (CN XI)
through the pharyngeal branch of vagus (CN X) via the
pharyngeal plexus.
- This muscle, covered by mucous membrane, forms the palatoglossal arch.
- The palatoglossus elevates
the posterior part of the tongue
and draws the soft palate inferiorly onto the tongue.
The
Palatopharyngeus Muscle (p. 744)
- Superior attachment: hard palate and palatine
aponeurosis.
- Inferior attachment: lateral wall of pharynx.
- Innervation: cranial part of accessory nerve (CN XI)
through the pharyngeal branch of vagus (CN X) via the
pharyngeal plexus.
- This thin, flat muscle is covered with mucous membrane to
form the palatopharyngeal arch.
- It passes posteroinferiorly in this arch.
- This muscle tenses the soft palate and pulls the
walls of the pharynx superiorly, anteriorly and medially
during swallowing.
The Musculus
Uvulae (p. 745)
- Superior attachment: posterior nasal spine and palatine
aponeurosis.
- Inferior attachment: mucosa of uvula.
- Innervation: cranial part of accessory through the
pharyngeal branch of vagus, via the pharyngeal plexus.
- It passes posteriorly on each side of the median plane
and inserts into the mucosa of the uvula.
- When the muscle contracts, it shortens the uvula and
pulls it superiorly.
Nerves
of the Palate (p. 745)
- The sensory nerves of the palate, which are branches of
the pterygopalatine
ganglion, are the greater and lesser palatine nerves.
- They accompany the arteries through the greater and
lesser palatine foramina, respectively.
- The greater palatine nerve
supplies the gingivae, mucous membrane, and glands of the hard palate.
- Another branch of the pterygopalatine ganglion, the nasopalatine nerve, emerges
from the incisive foramen and supplies the mucous membrane of the anterior part of the hard palate.
Vessels
of the Palate (p. 745)
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 (p. 745)
- 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 (p. 745)
- 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 (p. 746)
- 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 (p. 746)
- 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.
Muscles
of the Tongue
- The tongue is divided into halves by a medial fibrous lingual septum that lies deep
to the medial groove.
- In each half of the tongue there are four extrinsic and
four intrinsic muscles.
- The lingual muscles are all supplied by the hypoglossal
nerve (CN XII).
- The only exception is palatoglossus,
which is supplied by the pharyngeal branch of the vagus
nerve, via the pharyngeal plexus.
Extrinsic
Muscles of the Tongue (p. 746)
The
Genioglossus Muscle (p. 746)
- This is a bulky, fan-shaped muscle that contributes to
most of the bulk of the tongue.
- It arises from a short tendon from the genial tubercle
(mental spine) of the mandible.
- It fans out as it enters the tongue inferiorly and its
fibres attach to the entire dorsum of the tongue.
- Its most inferior fibres insert into the body of the
hyoid bone.
- The genioglossus muscle depresses the tongue and its
posterior part protrudes it.
The
Hyoglossus Muscle (p. 746)
- This is a thin, quadrilateral muscle.
- It arises from the body
and greater horn of the hyoid bone and passes
superoanteriorly to insert into the side and inferior
aspect of the tongue.
- It depresses the tongue, pulling its sides inferiorly; it
also aids in retrusion of the tongue.
The
Styloglossus Muscle (p. 746)
- This small, short muscle arises from the anterior border
of the styloid process
near its tip and from the stylohyoid ligament.
- It passes inferoanteriorly to insert into the side and
inferior aspect of the tongue.
- The styloglossus retrudes the tongue and curls its sides
to create a trough during swallowing.
The Palatoglossus Muscle (p. 746)
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previous reference.
Intrinsic
Muscles of the Tongue (pp. 746-7)
The Superior Longitudinal Muscle of the Tongue (p.
747)
- The muscle forms a thin layer deep to the mucous membrane
on the dorsum of the tongue, running from its tip to its
root.
- It arises from the submucosal
fibrous layer and the lingual
septum and inserts mainly into the mucous membrane.
- This muscle curls the tip and sides
of the tongue superiorly, making the dorsum of
the tongue concave.
The Inferior Longitudinal Muscle of the Tongue (p.
747)
- This muscle consists of a narrow band close to the
inferior surface of the tongue.
- It extends from the tip to the root of the tongue.
- Some of its fibres attach to the hyoid bone.
- This muscle curls the tip of the
tongue inferiorly, making the dorsum of the
tongue convex.
The
Transverse Muscle of the Tongue (p. 747)
- This muscle lies deep to the superior longitudinal
muscle.
- It arises from the fibrous lingual
septum and runs lateral to its right and left
margins.
- Its fibres are inserted into the submucosal
fibrous tissue.
- The transverse muscle narrows and
increases the height of the tongue.
The
Vertical Muscle of the Tongue (p. 747)
- This muscle runs inferolaterally from the dorsum of the
tongue.
- It flattens and broadens
the tongue.
- Acting with the transverse muscle, it increases
the length of the tongue.
Nerves
of the Tongue (pp. 747-8)
|
Anterior
2/3 of tongue |
Posterior
1/3 of tongue |
|
Motor Innervation |
All muscles by hypoglossal
nerve (CN XII) except palatoglossus muscle (by the
pharyngeal plexus) |
General Sensory
Innervation |
|
Special Sensory
Innervation |
|