UNIT 5: Tongue + Hypoglossal Nerve Flashcards
what is considered a muscular hydrostat
tongue
what is a muscular hydrostat
a fluid filled incompressible epithelial bag - the muscles serve as the fluid
a constant volume sys
any reduction in volume in one part is associated w an equivalent inc in another part
what are the two anatomical divisions of the tongue
oral tongue
pharyngeal tongue
oral tongue includes
anterior 2/3 w/i oral cavity (tongue dorsum aka superior surface)
tip, blade, front, back
pharyngeal tongue includes
posterior 1/3 aka tongue base
w/i oropharynx
what are the general features of the anterior 2/3 of the tongue? midline depression?
thick rough, epithelial covering
midline depression = longitudinal sulcus
4 types of papillae on ant 2/3 of tongue
fungiform
filiform
folliate (simple)
vallate
papillae
microscopic projections
fungiform papillae are …. and contain …
mushroom shaped paillae
contain taste buds
where do you find fungiform papillae
scattered over tongue dorsum and sides
predominant on tip of tongue
fungiform papillae are innervated by
chorda tympani of CN VII
which type of papillae is most numerous
filiform papillae
describe filiform papillae, do they have taste buds? purpose?
very small, sharp pointed projections on tongue dorsum
no taste buds, used to grip food
what type of paillae is highly dev in cats?
filiform
which papillae accounts for the rough texture of the tongue dorsum?
filiform
how are filiform papillae arranged?
in parallel rows
describe foliate papillae
variable in humans
mucosal folds present on the lateral aspects of the tongue, anterior to the palatoglossal arch
aka simple papillae
what are foliate papillae covered by
epithelium containing taste receptors
which are the largest papillae
vallate
how are vallate paillae arranged? what shape are they?
7-12 arranged in posteriorly pointing arrowhead
cylinder-shape surrounded by a moat w taste buds on the cylinder and in the wall of the moat
what division do the vallate papillae form?
division bw anterior 2/3 and posterior 1/3 of tongue
vallate papillae are innervated by
CN XI (glosso)
describe the surface of the pharyngeal tongue (post 1/3)
smooth, thin, nodular covering due to presence of lingual tonsils in underlying submucosa
terminal sulcus is
a groove on the pharyngeal tongue that is just posterior to circumvallate papillae
foramen cecum is a
small pit w/i the terminal sulcus on the pharyngeal tongue - marks the embryological origin of the thyroid gland
median and lateral glossoepiglottic folds on the pharyngeal tongue form the
valleculae at junction w epi
describe the ventral and inferolateral tongue
thin, smooth mucous membrane
lingual frenulum is
a fold of mucosa that attaches underside of tongue to floor of mouth
on either side of the lingual frenulum you will see
lingual veins seen thru thin mucosa
sublingual papilla is
opening of duct of submandibular salivary gland (L and R on either side of mouth)
sublingual folds of mucosa overlie the ______, with openings along the
sublingual salivary glands, w openings along the sublingual fold
5 basic taste sensations
salty
sweet
sour
bitter
umami
current hypothesis of how taste is mapped is
each papilla contains receptors for each taste sensation
which areas that send taste signals are innervated by CN IX?
posterior 1/3
tastes from soft palate and lingual surface of epi
what CN innervated anterior 2/3 of the tongue?
chorda tympani of CN VII
Taste from laryngeal surface of epi and larynx is supplied by
CN X
the gustatory nucleus is in
the NTS of the medulla
the gustatory cortex is in the
lateral cortex, insula
complex tastes also involve participation of the
olfactory nerve CN I
so what 4 CNs are involved in taste?
CN IX, CN X, CN VII, CN I
all muscles of the tongue are ____, with the two sides partially separated by the _____
bilateral
median septum
median septum is
a fibrous partition that runs from tongue tip to hyoid bone (doesn’t reach surface of the tongue)
intrinsic muscles of the tongue are …… and are responsible for
contained in the hydrostat, arranged at right angles
responsible for shape
extrinsic muscles of the tongue are …. and are responsible for ….
originate outside the tongue, pass into the tongue thru root
responsible for position and shape
the 4 intrinsic muscles of the tongue are
superior longitudinal
inferior longitudinal
transverse
vertical
superior longitudinal: O, I, A, Inn
O = fibrous tissue near epi and hyoid, and the median septum
I = lateral regions of tongue and apex
A= shortens tongue; acts on tongue tip - elevating, retracting, turning tip unilaterally
Inn = hypoglossal (CN XII)
superior longitudinal forms
broad band beneath the dorsal epithelium
inferior longitudinal: O, I, A, Inn
O = tongue root and hyoid bone
I = tongue tip
A= shortens tongue; turns tip down, deviates
Inn = CN XII
inferior longitudinal occupies…
lower sides of tongue
transverse is arranged at
right-angle to the longitudinal fibres
transverse: O, I, A, Inn
O = median septum
I = fibrous tissues at lateral margins
A = narrows and elongates tongue
Inn = CN XII
vertical is perpendicular to
transverse and longitudinal
vertical: O, I, A, Inn
O = inferior and lateral margins of tongue
I = dorsal membranous cover
A = flattens and widens
Inn = CN XII
what are the 4 extrinsic muscles of the tongue
genioglossus
hyoglossus
styloglossus
palatoglossus
genioglossus: O, I, A, Inn
O = mental spine of mandible
I = mucous membrane of tongue dorsum from base to tip; inferior fibres insert into hyoid bone
A = protrudes tongue, depresses central portion
Inn = CN XII
genioglossus is a
large muscle making up bulk of the tongue
hyoglossus is a
quadrilateral sheet on side of tongue, lateral to genioglossus
hyoglossus: O, I, A, Inn
O = greater cornu and body of hyoid bone
I = mucous membrane on lateral margins of tongue
A = pulls down sides of tongue
Inn = CN XII
styloglossus is a
slender muscle, runs inferiorly/anteriorly, passing below superior constrictor of pharynx
styloglossus: O, I, A, Inn
O = styloid process of temporal bone, stylomandibular ligament
I = posterolateral portion of tongue, interdigitates w hyoglossus
A = lifts sides of tongue, pulls tongue backward
Inn = CN XII
palatoglossus forms the
anterior faucial pillars; marks junction bw oral cavity and pharynx
palatoglossus: O, I, A, Inn
O = inferior surface of palatal aponeurosis (palatine bone)
I = posterolateral portion of tongue
A = elevates and retracts tongue base; depresses soft palate (narrows the oropharyngeal isthmus)
Inn = pharyngeal branch of CN X
hypoglossal CN XII has how many fibre types
one, GSE
how does the hypoglossal nerve dev?
does not dev from a branchial arch, therefore somatic vs visceral
i.e. Developing along the neural tube, remember it comes from somites (give rise to skin and muscles of limbs and muscles of the tongue)
the hypoglossal nerve supplies ____ extrinsic muscles of the tongue and ____ intrinsic muscles of the tongue
3/4
all
describe the intracranial course of the hypoglossal nerve
cell bodies of LMNs are contained in the hypoglossal nucleus in the medulla
hypoglossal nerve exits cranium via hypoglossal foramen in the posterior cranial fossa (near foramen magnum)
there is _____ innervation of all tongue muscles except _____
bilateral
genioglossus (contralateral)
hypoglossal nerve extracranial course:
courses medial to CN IX, X, XI
runs bw arteries and veins
passes lateral to hyoglossus and genioglossus, and then supplies target muscles
cortical neurons that drive the genioglossus muscle project only to the ______ hypoglossal nuclei, therefore to test CN XII you can…
contralateral
test the action of the genioglossus - if the muscle contracts bilaterally it will protrude the tongue, if innervation is impaired it will deviate laterally on protrusion to the side of weakness
the right and left hypoglossal nuclei are located close to the midline of the _____, a nuclear lesion tends to affect ______ nuclei causing ….
medulla
both nuclei causing loss of innervation to the tongue
6 ways to test CN XII functions
symmtery of tongue at rest
symmetry on protrusion
range of motion on lateralization
range of motion on elevation
range of motion on retraction
accuracy and speech of diadochokinesis
during dev, where does the anterior 2/3 of the tongue arise from
the mounds of tissue at the fusion line bw the mandibular processes of the 1st arch
tuberculum impar and lateral lingual swellings
during dev, where does the posterior 1/3 of the tongue arise from
a swelling, hypobranchial eminence, at the midline bw the 3rd and 4th arches
anterior half of hypobranchial eminence grows forward to
fuse w the anterior tongue at sulcus terminalis
posterior half of the hypobranchial eminence becomes the
epiglottis
where do the muscles of the tongue arise from
somites - blocks of tissue in the occipital region
cells migrate and infiltrate the epithelial covering of the dev tongue formed by the 1st, 3rd, 4th arches
nerve associated w somites = CN XII
how does the epiglottis form
anterior half of hypobranchial eminence migrates to tongue base
transverse depression devs bw anterior and posterior halves of hypobranchial eminence
depression deepends w backward migration of posterior half = glossoepiglottic fossa then divided into calleculae by the median glossoepiglottic fold
they hypoglossal nerve is purely
a motor nerve
