5. The anatomy of the oral cavity and salivary glands. The histology of the tongue and salivary glands. The development of the oral and nasal cavities.

Anatomy of the oral cavity and salivary glands.

General Info:

Borders:

• roof = palate (hard, soft)
• floor = tongue, mucosa, geniohyoid and mylohyoid m
• Lat/ant
  • Outer fleshy wall = cheeks, gums
  • Inner bony wall = teeth and inner aspect of gums
• communicates posteriorly with oropharynx

Divided into 2 areas: the oral vestibule, anterior to the teeth and buccal side of gingiva (gums) & oral cavity proper, which is the space behind the teeth and gums

Oral Vestibule = Cheeks, Lips, Gingivae

Lips

• Lips contain the orbicularis oris m, and sup/inf labial m, a/v/n.
• Covered externally by skin externally, and mucosa internally.
• Epithelium of skin transitions from normal skin –> red vermillion portion –> to inner mucosal layer. The border line b/w skin and red portion = transition zone.

Structures to identify in relation to the lips:

• upper lip = b/w nose & opening of oral cavity
• nasolabial grooves = seperate lips from cheeks, 1 cm lat to angle of mouth
• philtrum = a shallow depression below the nose, bordered by 2 lateral crests – not everyone has one
• lower lip = b/w opening of oral cavity and labiomental groove, separating lower lip from chin.
• labial frenula = a mucosal membrane fold that attaches the lips to the ant surface of the vestibular gingiva (gums facing the oral vestibule) — NOTE diff from lingual frenula, that attaches the tongue to the floor of the mouth

Blood supply = sup/inf labial a (facial a)

• upper lip = br of facial/ infraorbital = sup labial br
• lower lip = br of facial/mental a = inf labial br

Innervation

• upper lip = sup labial br of V2
• lower lip = inf labial br of mental n from V3 (mental n comes from inf alveloar n)

Lymph Drainage = submandibular/submental lymph nodes

Cheeks

over lie the zygomatic process
contain the buccinator m – that holds cheeks taught when exhaling forcefully
contains the buccal fat pad (of Bichat)
Blood Supply = buccal br of maxillary a (terminal br of ext carotid), n = buccal br of mandibular n (V3)

Gums

are fibrous tissue covered with mucosa
hold teeth in place
supplied by many a/v/n

Blood Supply

• upper (maxillary) lingual gingiva of incisors, canines = nasopalatine n,a/v – most ant, this makes sense because nasopalatine structures go through incisive foramen at most ant part of hard palate
• upper (maxillary) lingual gingiva of premolars, molars = gr. palatine n, a/v – post, makes sense b/c gr. palatine structures go through gr palatine foramen at post/lat part of hard palate
• lower(mandibular) labial buccal gingiva of incisors, canines, premolars = inf alveolar n/a/v
• lower(mandibular) labial buccal gingiva of molars = buccal n
• lower(mandibular) lingual gingiva = lingual n/a/v

*Teeth is another topic, please refer to that

Palate

Made up of hard and soft palate

Hard palate
is bony and makes up the ant 4/5 of the palate = palatine process of the maxilla, and horizontal plate of palatine bone
border b/w nasal and oral cavity
@ midline of hard palate, running back from incisive foramen = palatine raphe – where the 2 palatine shelves fused in embryonic life

3 foramina:
Incisive foramen (ant/med) = nasopalatine n/a/v

• In the netter, it looks like sphenopalatine a goes through there, but do not say this in a test, it will be considered incorrect.
• NOTE – makes the location of the fusion b/w primary/secondary palate in embryonic life

Greater and Lesser Palatine foramen (post/lat) – right next to 3rd molar (wisdom tooth) = the gr/lsr palatine n/a/v go through them.

• Gr palatine structures run ant and supply hard palate
• Lsr palatine stuctures run post and supply soft palate
• The a comes from desc palatine a, a br of maxillary a

Soft Palate

• is fibromuscular fold that makes up post 1/5 of palate
• moves agains the pharyngeal wall to close oropharynx while swallowing or speaking
• as mentioned earlier, supplied a/v/n by lesser palatine structures.
• Laterally, is continuous with palatoglossal and palato pharyngeal folds
  • These folds are form the lateral border to the exit of oral cavity = Isthmus of Fauces, that leads to Oropharynx (More on that in pharynx)
  • b/w them is the tonsillar bed = palatine tonsils
  • CLINCAL NOTE – are frequently inflamed and removed, along with pharyngeal tonsils (see pharyn) aka adenoids

• CLINCAL NOTE = Since lingual gingiva is connected to mucosa of soft palate, can inject anasthetic there to numb soft palate
• Has numerous palatine glands, that secrete mucus

Blood Supply: Gr and Lsr palatine a (more the 2nd one), Asc palatine a (Facial a), Palantine br of Asc Pharyngeal a

Innervation : SS = lsr palatine n, SM = CN X

Venous Drainage: hard and soft palate v drain in pterygoid venous plexus

NOTE that Hard palate has no SM innervation – no musc there.

Muscles of Palate: all innervated by CN X via pharyngeal plexus – except Tensor Veli Palatini (V3)

• Tensor Veli Palatini – tenses soft palate, has a large tendon that strengthens the soft palate = palatine aponeurosis
• Levator Veli Palatini – elevate soft palate
• Palatoglossus – elevates tongus (Just uses palate as an origin site, doesn’t do anything to palate itself)
• Palatopharyngeus – elevates pharynx, to help close off nasopharynx from oropharynx in swallowing
• Uvulus – @ termination of soft palate, no real function, but helps to identify issues with CN X, b/c if this doesn’t move when saying, “Ahhh”, then poss malfunction w. CN X

Tongue

• is almost purely made of muscle
• the ant 2/3 is called the oral part = originates from 1st pharyngeal arch
• post 1/3 = pharyngeal part, orginates from 3rd arch, behind terminal sulcus of tongue
• @ midline of terminal sulcus is foramen cecum, the remnant of thyroglossal duct
• root = from 4th arch
• Has midline sulcus on dosal surface = location of fusion of 1 lateral swellings of ant tongue over tuberculum impar.

Function: aid in speaking, allow for movement of food toward oropharynx and within oral cavity
Parts:
Body – most of the tongue
Apex – pointed ant part
root – part fixed to hyoid bone and mandible, is located behind palatoglossal fold, location of lingual tonsils.

Taste Buds: SEE HISTO

The inferior surface of tongue has a very thin mucus membrane, so can see many veins, and is attached to floor of mouth via another mucus membrane fold = lingual frenulum. – Basically keeps tongue in mouth while allowing apex to move about

Muscle of Tongue = all innervated by CN XII, except palatoglossus, which we already said is innervated by Pharyngeal plexus, via CN X

Intrinsic m – change the shape of tongue itself
Sup/Inf Longitudinal, Transverse, Vertical

Extrinsic m – change position of tongue

• Genioglossus – protrudes and depresses tongue
• Hyoglossus – depresses and retracts tongue
• Styloglossus – retracts and elevate tongue
• Palatoglossus – elevates tongue

How to remember them? Gay Hats STYLe Perfectly

Basic Taste sensations:
Sweetness = apex
Saltiness = lateral side
Sourness & bitterness = posterior part
Umami = used to taste the unusual tastes in cheese, meat, asparagus, & tomatoes

Blood Supply:

• Lingual a from Ext carotid a, emerges @ lever of gr. horn of hyoid bone in carotid triangle
• Pathway: runs deep to hyoglossis (lateral lingual groove), and lies on middle pharyngeal constrictorm
• Br = dorsal lingual, suprahyoid,sublingual a, terminates as deep lingual a ( on top of genioglossus m)

Lymph Drainage:

• Post 1/3 = deep cervical lymph nodes
• Medial ant 2/3 = inf deep cervical lymph nodes
• lat ant 2/3 = submandibular l.n
• apex = submental l.n

Innervation of Tongue:

• Ant 2/3:  SS = CN V3 via Lingual n, VS = CN VII via Chorda Tympani
• Post 1/3: SS/VS = CN IX
• Root: SS = CN X, no taste buds here, so no VS

Salivary Glands:

For contents of saliva and function = See HISTO

Parotid

Location: Retromandibular Space = Parotid Bed
Borders:

• ant = Masseter m, Ramus of mandible
• post = SCM, post digastric m
• sup = zygomatic arch
• inf = fascia b/w SCM and mandible
• Lat = open

General Info:
covered by dense fibrous capsule from investing fascia of neck
secretes serous saliva
largest of the glands

Duct Pathway:
From widest part of gland –> across masseter and deep to it –> lat/ant to Buccal fat pad –> peirces Buccinator m, and opens @ 2nd maxillary (upper) molar

Structures Passing through It:
Ext Carotid a – giving 2 terminal branches = Maxillary a, Superficial temporal a
Superficial Temporal v & Maxillary v combine to give Retromandibular v
Facial n peirces it and gives 5 terminal branches  – DOES NOT innervate the gland
Auriculo temporal n – carries PNS post synaptic fibers with it to increase secretion of gland

Blood supply:
from branches of external carotid and superficial temporal a = Transverse facial a
Veins follow a and drain into Retromandibular v

Lymph Drainage:
superficial and deep cervical lymph nodes

Innervation:

• Tympanic n arises from CN IX and emerges from jugular foramen
• n enters the middle ear via the tympanic canaliculus in petrous part of  temporal bone
• tympanic n forms the tympanic plexus — and lesser petrosal n emerges from this plexus
• lesser petrosal leaves skull via foramen ovale
  
• PNS fibers from it synapse in otic ganglion
• post ggl fibers from ggl RUN W/ auriculotemporal n (from V3) to supply parotid gland

*Parotid and Submandibular gland separated by stylomandibular lig b/w styloid process & angle of mandible

Submandibular Gland
Located:  below mylohyoid & mandible

General Info:
Has Superficial and Deep part (deep part located b/w mylohyoid and styloglossus)
secretes a mix of serous and mucus saliva

Duct Pathway:
ducts runs thru lat space of tongue w/ Hypoglossal n and lingual n = lateral lingual groove —> then eventually goes to and open lat to frenulum, b/w mylohyoid and styloglosses
lingual n loops under duct in the lateral lingual groove

Blood Supply: sunmental a (Facial a), V run with a.

Lymph Drainage: deep cervical l.n. –> jugulo-omohyoid nodes

Innervation:
Pre ggl PNS fibers from CN VII by chordatympani –> submandibular ggl –> post ggl fibers run w/ lingual n
SNS post ggl fibers come from sup cervical ggl

Sublingual Glands
Location: b/w mandible and genioglossus m

General info:
smallest of the 3 glands
secretes both mucus and serous, but more mucus

Duct Pathway: duct opens @ floor of oral cavity w/ submandibular duct, just below mucus membrane of tongue, lat to frenulum

Blood Supply : Submental and sublingual a (from facial and lingual a)

Innervation:
Pre ggl PNS fibers from CN VII by chordatympani –> submandibular ggl –> post ggl fibers run w/ lingual n

SNS post ggl fibers come from sup cervical ggl

Histology of the tongue and salivary glands.

Slide #38-39 Tongue * H&E

Structures to Identify:
#38

• circumvallate papillae
• serous gland (Von Ebner’s)
• CT
• Taste bud (also visible in palate, pharynx, esoph)
• ducts
• str. musc bodies
• lingual

#39

• lingual papillae
• fungiform papillae
• filliform papillae
• bundle of nerves
• sk m fibers
• adipose tissue

General info:
muscular organ in oral cavity
core = CT and bundles of sk musc fibers
distribution and random orientation of sk musc in tongue
allows inc movement during chewing, swallowing, speaking

Surface:
epith on ventral surface is smooth
epith on dorsal surface is irregular b/c of papillae – which are folds of mucosa pushed up by mounds of LP underneath
covered by str. squamous epith – partial keratinized – very fire-like

Filiform papillae

• most numerous & smallest papillae
• conical shaped
• cover entire dorsal surface of tongue
• NO taste buds

Fungiform papillae

• less in #
• larger & broader than the filiform papillae
• mushroom like shape
• ant region of tongue
• b/w filiform

Circumvallate papillae

• much larger than any of others
• about 8-12 located in post region of tongue, just next to sulcus terminalis
• have deep furrow’s next to each papillae = where von Ebner’s glands open
• Von Ebner’s glands = serous lingual glands

Foliate papillae

• not many, lateral side of tongue
• not picture on either slide

Taste buds
located in epith of foliate & fungiform papillae, lateral side of circumvallate papillae
have an apical opening = taste pore

3 types of cells:

1. have neuroepithelial taste cells w afferent n. fibers coming from them (VS)
   • VS innervation:
     • ant 2/3 = facial n (CN VII)
     • post 1/3 = CN IX
     • epiglottic region = CN X
   • most in #
   • elongated w/ light cytoplasm
   • oval and light nucleus
   • apical surface extended w/ microvilli that protrude thru taste pore
   • base forms synapses w/ processes off sensory neurons
2. also in taste bud = sustenacular (support) cells
   • elongated w/ darker cytoplasm
   • slender & darker nucleus
   • also have microvilli, but no synapse @ base
   • connected w/ tight jxns
3. base of taste bud = basal cells, thought to be stem cells for taste cells
   • small cells in basal portion of taste buds
   • near basal lamina

5 types of tastes :
sweet, bitter, umami  = G protein
salty, sour = ion channel

Core of Tongue: musc + CT
Extrinsic m: – changes position of tongue

• genioglossus m
• styloglossus m
• hyoglossus m
• palatoglossus m
• * all innervated by CN XII all except palatoglossus (pharyngeal br of CN X = pharyngeal plexus)

Intrinsic m: – changes shape of the tongue

• longitudinal
• transverse
• vertical

Connective Tissue Septa

• CT b/w musc = a/v , nerve fibers
• lower half of tongue & b/w musc fibers = seromucous lingual glands
• ant/ post seromucous glands exist – each have interlobular ducts
• interlobular ducts combine to form one lingual excretory duct

Histology of Salivary Glands:

Function of saliva:

• source of Ca2+ & PO4 for tooth development
• moisten oral mucosa
• moisten dry foods to aid swallowing
• release IgA
• controls bacterial flora by releasing lysozymes
• buffer contents of oral cavity – b/c of its inc HCO3 concentration
• digest carbs by releasing alpha amylase

Slide #40 Parotid gland *H&E

Structures to Identify:

• serous glands
• intercalated ducts
• striated ducts
• adipose cells
• excretory ducts
• CT
• n. bundles (br of Cn VII)

Easy to identify:
loads of adipose
only serous acini
looks like bubble bath

General Info:
located ant/inf to ext ear
largest of salivary glands
only serous

Lobules
entire gland surrounded by CT capsule
from CT capsule, comes CT septa that splits the gland into lobules
located w/in CT septa = arteriole, venule, interlobular excretory ducts, & adipose cells
occasional plasma cells may be seen in CT surrounding ducts = produce Igs taken up & resecreted by acinar cells

Serous acini = Secretory part

• made up of only serous acini = secretory cells
• pyramid shaped cells are arranged around a lumen
• spherical lumen located @ base of basophillic cytoplasm
• small lumen
• surrounded by thin, contractile myoepithelial cells – branches of CN VII found here
• secretory protein rich substance stored in zymogen granules
• stains in H&E better

Conducting system = Duct system

1. acini empty into intercalated duct
   • (squamous/ low cuboidal epith)
   • posses carbon anhydrase activity
   • secrete HCO3-
   • absorb Cl-
2. striated ducts
   • (larger lumina, lined by simple columnar epith w/ basal striations)
   • basal striations formed by deep infoldings of basal cell membranes
   • absorb Na+
   • secrete K+ HCO3-
3. interlobular excretory ducts
   • (pseudostratified epith)

Slide #41 Submandibular gland *H&E

Structures to Identify:

• mucus acini
• serous acini, demilunes
• adipose cells
• duct system = intercalated, striated, excretory ducts
• myoepith cells
• adipose
• a/v

General Info:

• compound tubuloacinar gland
• mixed gland = serous (2/3), mucus acini (1/3)
• duct opens lat to frenulum in oral cavity
• find adipose cells w/in lobule
• find a/v in CT septa

Conducting system:
same as parotid gland

Secretory portion:
Serous acini:

• pyramid shaped cells are arranged around a lumen
• spherical lumen located @ base of basophillic cytoplasm
• small lumen
• surrounded by thin, contractile myoepithelial cells – branches of CN VII found here
• secretory protein rich substance stored in zymogen granules
• stains in H&E better

Mucus acini:

• lightly stained w/ H&E, stained pink w/ PAS
• larger lumen
• cytoplasm is pale b/c loss of mucin during slide prep
• columnar cells, w/. flattened nuclei @ periphery
• may have serous semilunes
• surrounded by myoepithelial cells that help secretory units drain content

Slide #42 Sublingual gland *PAS w/ H background

Structures to identify:
mucus acini
ductal system

General info:
mixed tubuloacinar gland – more MUCUS (2/3) than serous (1/3)
b/c Mucin is made of carbs, stains well w/ PAS staining
cannot see serous very well

PAS reaction:
periodic acid = breaks carbs –> aldehydes
aldehydes react w/ Schiff base = magenta color

Ductal system a bit different:

• not very many intercalated and striated ducts, b/c the high amount of mucus can cause the ducts to be blocked
• and the saliva is modified minimally
• many more interlobular septa (and ducts) than in parotid or submandibular
• numerous lymphocytes & plasma cells

Embryology: Development of the oral and nasal cavities.

Nasal Cavities:

• On both sides of frontonasal prominences, there are forming 2 lateral thickenings of surface ectoderm = nasal placodes
• @ 5th wk = nasal cavity and nasal projection begins to form (nose)
  • nasal placodes fold inwards (”invaginate”) to form nasal pits
  • around nasal pit, there is a ridge of tissue = nasal prominences.
  • Picture a bowl – the actual bowl is nasal pit, and the rim of the bowl is the nasal prominences
  • The nasal prominences are split into lat & medial nasal prominences
• @ 6th wk = nasal pits deepen and penetrate into mesenchyme below
• Oronasal membrane – separate pits from oral cavity, via choanae,
  
• swelling on lat wall = sup/mid/lat conchae
• Paranasal sinuses = are pockets off nasal cavity, grow into neighboring bones – grow through puberty
• Ectoderm @ nasal placode = olfactory epith = make the sustenacular, basal, ciliated cells

Oral Cavity

• Lip formation  = see previous topic

Palate:

• Primary palate
  • formed from medial growth of maxillary prominences
  • the medial nasal prominences also merges deeper to form intermaxillary segment
  • forms philtrum of upper lip, 4 upper incisors, palate ant to foramen incisive
• Secondary palate
  • formed by 2 palatine shellves, a downward growth from maxillary segment
  • turns horizontal  @ 7th wk to fuse at midline, and then fuses ant with primary palate @ location of incisive foramen
• Primary & ant Secondary palate together form hard palate
• post secondary palate forms soft palate and uvula

Mouth:

• from surface depression called the stomodeum (ectoderm)
  
• meets foregut (endoderm)  post = oropharyngeal membrane

Tongue:

• Ant 2/3 = oral part of tongue
  • Originates from most 1st pharyngeal arch
  • there are 2 lat swelling, and 1 medial swelling (tuberculum impar)
  • lat swellings grow over the medial one and meet in midline = median sulcus
  • has the filiform, fungiform, circumvallate papillae
  • b/c from 1st arch – SS = CN V = mandibular n
• Ant 1/3 = pharyngeal part of tongue
  • behind foramen cecum & linea terminalis
  • from originally 2nd, 3rd arches – 3rd overgrows the 2nd.
  • from 2 medial swellings = copula (2nd arch), hypobranchial eminence (3rd/4th arch)
  • has lingual tonsil w/ it
  • b/c from 3rd arch – SS = CN IX
• Root of tongue
  • epiglottis & very back of the tongue
  • from post part of the hypobranchial eminence
  • from 4th arch, so SS = CN X
• Muscle of Tongue develop from occipital somites,  so innervating by CN XII, except palatoglossus (CN X)