Oral Tissues and Salivary Glands Flashcards
What are the major structures of the oral cavity?
Lips
Teeth
Tongue
Oral mucosa
Associated salivary glands
What is the epithelium of the oral mucosa?
Stratified squamous with keratinisation in areas of friction e.g. the palate
What is the lamina propria that supports the mucosa made of?
Dense collagenous tissue
Where is the lamina propria connected to the underlying muscle by loose submucosal supporting tissue?
Highly mobile areas e.g. floor of the mouth and soft palate
True of False: In areas where the oral mucosa overlies bone, the lamina propria is tightly bound to the periosteum by a relatively dense fibrous submucosa.
True
List the types of oral mucosa.
- Lining
- Masticatory
- Specialised
Describe lining mucosa.
Mainly non-keratinised stratified squamous epithelium with underlying supportive lamina propria that lines the inner lips, cheeks, soft palate, floor of mouth and underside of the tongue
What type of epithelium is masticatory mucosa?
Keratinised/para-keratinised stratified squamous epithelium
Where is masticatory mucosa found?
Hard palate and the gingiva (gums around the teeth)
What is an example of specialised mucosa?
The dorsal surface of the tongue has taste buds, is keratinised and has numerous papillae
What are the surfaces of the lip?
- Outer cutaneous
- Red (vermillion) border
- Inner oral mucosa
Describe the outer cutaneous surface of the lip.
Thin skin
Epidermis with hair follicles, sebaceous gland and sweat glands
Underlying dermis
Rich sensory innervation
What is the vermillion border?
Transition zone between skin and oral mucosa
Thick stratified squamous epithelium with either no keratin or light keratin
Tall C.T. papillae under epithelium
Pink/red
Lacks hair follicles and no glands
What are the labial glands?
Small groups of minor salivary glands deep to the oral mucosa lamina propria
Is the core of the lip skeletal, smooth or cardiac muscle?
Skeletal
What is the purpose of the palate?
Forms roof of mouth and separates oral and nasal cavities
Is the hard palate anterior or posterior?
Anterior
Describe the hard palate.
Covered by masticatory mucosa with rugae
Underlying lamina propria with papillae containing many capillaries and lymphocytes
Ducts connect palatine glands to epithelial surface
What is the uvula?
A conical projection on the posterior aspect of the soft palate
What is the soft palate’s function?
To close off the nasopharynx from the oropharynx during swallowing
What is the lining of the soft palate?
Oral: Non-keratinised stratified squamous
Nasal: Ciliated pseudostratified columnar with goblet cells
Why is the soft palate red?
Rich vascular supply
What is the tongue?
Mobile muscular organ on the floor of the oral cavity, involved in mastication, swallowing, speech and taste
What is the sulcus terminalis?
A V-shaped groove on the dorsum of the tongue that demarcates the anterior 2/3 from posterior 1/3
What embryological tissue is the epithelium of the tongue made of?
Anterior: Oral ectoderm
Posterior: Foregut endoderm
What are the 4 types of lingual papillae?
- Filiform
- Fungiform
- Circumvallate
- Foliate
True or False: The posterior 1/3 of the dorsal tongue has numerous lingual papillae.
False, instead studded by 35-100 irregular mucosal bulges that correspond to lingual tonsils creating a cobblestone appearance
What is the composition of the body of the tongue?
A mass of interlacing bundles of skeletal muscle (allowing a wide range of movements) bound to the mucous membrane by a dense collagenous lamina propria which is continuous with the epimysium of the muscle
What papillae type are very numerous and a keratin-tipped elongated conical shape?
Filiform papillae
What is the role of filiform papillae?
Provide a rough surface that facilitates food movement during chewing
Describe fungiform papillae.
Less numerous than filiform
Keratinised mushroom shape with scattered taste buds on the upper surface
Where are the majority of fungiform papillae located?
Near the tip of the tongue
What is the structure of foliate papillae?
Parallel ridges and furrows on the side of the tongue and have taste buds
Describe circumvallate papillae.
Least numerous
Largest lingual papillae
One row of 8-12 circumvallate papillae lies just anterior to the sulcus terminalis
Contain over half of the taste buds on the human tongue
What are taste buds?
Small, ovoid intraepithelial organ
Taste pore on the apical surface
Embedded on lateral surfaces of fungiform and circumvallate papillae
What is the name of the serous salivary glands that empty into the deep groove that surrounds each circumvallate papilla?
von Ebner’s glands
What is the purpose of von Ebner’s glands?
Washes food particulates from the vicinity by providing a continuous flow of fluid over the taste buds
What enzyme do von Ebner’s glands secrete and why?
Lipase
Prevents the formation of a hydrophobic film over the taste buds
What number of tastes buds are on the listed areas:
a) Tongue
b) Soft palate
c) Epiglottis
d) Larynx and pharynx
a) 5000
b) 2500
c) 900
d) 600
What are the 3 types of cells recognised in a taste bud?
- Sensory/taste receptor cells (lightly stained)
- Supporting/sustentacular cells (darkly staining)
- Basal cells
What is the lifespan of the sensory and support cells of taste buds?
10-14 days
What is the compostion of the posterior surface of the tongue?
Relatively smooth stratified squamous epithelium with underlying lymphoid tissue called the lingual tonsil
What is Waldeyer’s ring of lymphoid tissue?
Lingual tonsil, palatine tonsils and adenoids that guard the entrance to the gastrointestinal and respiratory tracts
What are salivary glands?
Exocrine glands of the oral cavity that produce saliva
What is saliva?
Hypotonic watery secretion
Contains mucous, enzymes, antibodies and inorganic ions
What is the pH of saliva?
6.7-6.9
What are the principle enzymes in saliva?
Amylase and lysosyme
True or False: 500-1000 mL of saliva is produced daily.
False, 700-1200 mL
List the basic functions of saliva.
- Protection
- Antimicrobial activity
- Digestion
- Taste
- Buffering
- Tooth integrity
What percentage of saliva is produced by the major salivary glands?
90%
What are the major salivary glands?
Parotid
Submandibular
Sublingual
Name the minor salivary glands.
Palatine
Lingual
What type of gland are major salivary glands?
Compound tubulo-acinar gland
What are the components of the salivary parenchyma?
Serous acini
Mucous acini
Duct system
True or False: Salivary glands are covered by a tough C.T. capsule with septa subdividing the gland into lobes.
True
What is the difference between simple and compound ducts?
Simple are unbranched while compound are branched
Salivary glands use a merocrine mechanism of secretion. Define merocrine secretion.
Occurs by exocytosis
What are the secretions of serous cells like?
Thin and watery
Contains proteins and ions
Is a serous cell more likely to be an acinus or a tubular element?
More likely to form the rounded acinus
What is the duct system for major salivary glands?
Intercalated ducts into striated ducts and then empty into main excretory duct
Describe serous cells.
Polarised, protein-secreting cells
Pyramidal with a prominent basal nucleus and extensive RER
Connected by junctional complexes
Describe mucous cells.
Cuboidal-columnar cells with basal nuclei and large numbers of secretory granules
Stain lighter than serous cells
What is a serous demilune?
A cap-like/cresent shaped arrangement of serous cells at the end of a secretory unit in mixed acini
Why are convention preparations of mixed acini not as accurate as other methods such as rapid freezing?
Mucous cells swell and push serous cells aside, creating an artifact
What are myoepithelial cells?
Specialised epithelial cells
Contract to help expel secretions from the acini
Where are myoepithelial cells found?
Inside the basal lamina of secretory units as well the initial duct system to a lesser extent
What is the epithelium of intercalated ducts?
Simple cuboidal
What is the epithelium of striated ducts?
Simple columnar
What is the epithelium of excretory/interlobular ducts?
Pseudostratified/stratified cuboidal to stratified columnar in distal parts
Why are striated ducts striated?
Membrane infoldings of the basal lamina with mitochondria
What classification of gland is the parotid gland?
Compound acinar gland with secretory portions with exclusively serous cells
Describe the structure of the parotid gland.
Divided into several lobules
Outer capsule with radiating septa carrying vessels and excretory ducts
What type of gland is the submandibular gland?
Mixed gland with secretory units often being seromucous (but pure versions of each also present)
How do mucigen and zymogen (enzyme-containing) granules appear in H&E staining?
Mucigen stain poorly while zymogen stains strongly
Compare the nuclei of mucous vs serous cells.
Mucous: flattened and condensed on the basement membrane
Serous: rounded and central
True or False: Serous cells predominate within the sublingual gland with only a small number of mucous cells.
False, mucous cells are more numerous
What are the amount of serous vs mucous in each major salivary gland?
Parotid: entirely serous
Submandibular: 2/3 serous
Sublingual: about 1/3 serous
What are the minor salivary glands and their location?
- Lingual - posterior dorsum of the tongue
- Minor sublingual - lower surface of tongue
- Labial - inner lip
- Palatine - soft and post. hard palate submucosa
- Buccal - cheek submucosa lining
What type of secretion is typical in minor salivary glands?
Mucous
