Oral Cavity and Teeth Flashcards Preview

Histology / Embryology Unit 2 > Oral Cavity and Teeth > Flashcards

Flashcards in Oral Cavity and Teeth Deck (74):

What are the two divisions of the oral cavity?

1. Vestibule - space between lips, cheeks, and teeth
2. Oral cavity proper - space behind teeth and bounded superiorly by hard and soft palates, inferiorly by floor of mouth, posteriorly by entrance to oropharynx


What is the oral mucosa and what underlies it?

A moist epithelium (stratified squamous) that has an underlying lamina propria (loose connective tissue)


What is the lamina propria analogous to in the skin?

Papillary layer of dermis - it is loose connective tissue. Has blood vessels and nerves


What are the layers of the stratified squamous epithelium of the oral mucosa?

1. Stratum basale
2. Stratum spinosum
3. Stratum superficiale (flattened cells on surface, analogous to stratum corneum but still nucleated)


What are the three types of oral mucosa? Where are they found?

1. Masticatory - gums and hard palate
2. Lining - lips, cheeks, floor of mouth, inferior surfaces of tongue, soft palate
3. Specialized - dorsal surface of tongue only


What is masticatory mucosa?

Keratinized oral mucosa, mostly for protection (gums, hard palate). It is parakeratinized when the stratum superficiale cells do not lose their nuclei and they remain pyknotic.


What is lining mucosa?

Nonkeratinized oral mucosa, is rarely parakeratinized. Found everywhere but dorsal surface of tongue, gums, and hard palate


What is specialized mucosa?

Keratinized oral mucosa with lingual papillae and taste buds


What is oral submucosa?

Dense irregular CT underlying mucosa - analogous to reticular layer of dermis.

Provides attachment to muscle or bone.


Where can minor salivary glands be found, and what are they named for?

They are found in the submucosal layer of dense CT. They are compound tubuloalveolar exocrine glands which may be mucous, serous, or mixed.

Named for their location: labial, buccal, lingual, palatine


What is the mucocutaneous junction?

Spot on lips where thin keratinized epidermis of facial skin changes to the thick nonkeratinized lining mucosa.


What are the three distinct zones of the lip?

1. Outer cutaneous surface - thin skin of stratified squamous keratinized epithelium
2. Vermilion (red) border - transition zone, keratinized but no hair follicles
3. Inner oral mucosal surface - moist lining mucosa with underlying submucosa attached to orbicularis oris muscle. Contains labial salivary glands


Why is the vermilion border red?

It has stromal papillae from the lamina propria which brings capillaries near the surface of the keratinized epithelium


What are the three planes that skeletal muscle of tongue runs and why is this important?

1. Longitudinal (superior and inferior)
2. Vertical
3. Horizontal

Each is arranged at right angles to eachother (orthogonally) - allows for fine control, flexibility, and precise movements for speech


Where are the minor salivary glands of the tongue?

Called lingual glands, they can be mucous, serous, or mixed. Usually embedded in the muscle of the tongue.


How do the dorsal and ventral surfaces of the tongue differ with respect to mucosa?

Ventral: Lining mucosa
Dorsal: Specialized mucosa that is keratinized and has lingual papillae with taste buds. Divided into anterior 2/3 and posterior 1/3 by V shaped terminal sulcus


Where does the apex of V of terminal sulcus point? What does it point to?

Points posteriorly, at location of foramen cecum.


What are the four types of lingual papillae covering the dorsal surface of anterior 2/3 of tongue?

1. Filiform
2. Fungiform
3. Circumvallate (vallate)
4. Foliate


What are filiform papillae?

Pointed mucosal projections all over the anterior dorsal surface with tips pointing backwards. They are smallest and most numerous papillae in humans, and serve to increase friction between food and tongue.

They have NO taste buds. Connective tissue core (lamina propria) with keratinized epithelium on top


What are fungiform papillae? Where are they?

Mushroom-shaped mucosal projections scattered among filiform papillae. There are about 200 of them, mainly concentrated around tip and lateral margins of tongue. They are visible to eye as small red spots because of vascularity of lamina propria


How often do fungiform papillae have taste buds, and how many are there?

They have taste buds 90-99% of the time, and have 1-25 of them on superior surface, with an average of about 4 per papilla


What are circumvallate papillae?

There are 10-12 dome-shaped papillae surrounded by moat-like invaginations, located just anterior to terminal sulcus.


Where are the taste buds of vallate papillae?

On lateral surface of papillae which faces the moat. There are few on the upper surface.


What are von Ebner glands and what do they do?

Posterior lingual glands which secrete serous product into the moats of vallate papillae as well as foliate papillae
1. Flush material from moat to enable new taste sensations
2. Secrete lingual lipase - begins process of lipid hydrolysis in the mouth


What are foliate papillae?

Deep mucosal folds on lateral surface of tongue which are rudimentary by adulthood and rarely seen. There are tastebuds on lateral surface of folds. Less prominent in humans than other species.


What are taste buds?

Oval groups of sensory cells found primarily within epithelium of papillae. They open to surface via taste pores


What are the three types of cells in taste buds?

1. Neuro-epithelial cells
2. Supporting cells
3. Basal cells (stem-cells)


What are the characteristics of neuroepithelial cells of taste buds?

They are the sensory portion. They have microvilli on apical surface (taste hairs) which can protrude into taste pores. They synapse on afferent nerve terminals and transduce taste impules


What are the characteristics of supporting cells of taste buds?

Contain secretory granules with apical microvilli, and function to hold the bud together. Less numerous than neuroepithelial cells.


What is the characteristics of basal stem-type cells?

They are the small cell located at base of taste bud which function to differentiate into neuroepithelial and supporting cells. They replace other cell types ever 10-14 days


What are the three large paired multicellular exocrine glands of the oral cavity? Where do their ducts drain?

1. Parotid glands - largest, located below and in front of ear, duct drains opposite 2nd upper molar
2. Submandibular glands - Floor of mouth - duct empties just lateral to frenulum of tongue
3. Sublingual glands - smallest, floor of mouth anterior to submandibular. Duct drains into submandibular duct and also directly to floor of mouth.


What type of glands are the parotid, submandibular, and sublingual glands?

Compound tubuloalveolar exocrine glands


What makes us salivate and how much saliva do we produce per day?

Mechanical, chemical, or psychic stimuli (i.e. thinking about food)

1 L of saliva / day


What makes up a lobule of the salivary secretory glands?

Multiple secretory units, with intercalated ducts draining into striated ducts, make up a lobule.


What is the smallest secretory unit?

The acini, which drain into an intercalated duct. Multiple intercalated ducts will drain into a striated duct.


What is the interlobular duct?

The duct that drains the saliva from each lobule. Collects multiple striated ducts into it. Each lobe will ultimately be drained by a lobar duct. There are multiple lobes


What are serous cells and what do they produce?

They are protein-producing cells with prominent ER and Golgi.

1. Alpha-amylase - breaking 1-4 glycosidic bonds
2. Peroxidase
3. Antimicrobials - lysozyme, cystatin, and hystatin


What are mucus cells and what do they produce?

They are mucus-secreting cells which produce mucinogen granules, which, when mixed with water, will produce two glycoprotein mucuses.
1. Sialomucin
2. Sulfomucin


What are myoepithelial cells of secretory acini? How do they stain?

Contractile cells surrounding the base of acini and intercalated ducts to move secretory product towards striated duct. They are enclosed within basal lamina of epithelial cells, and have lots of actin. Thus they stain eosinophilically.


How do serous acini appear and what is the shape of their acini?

They appear darkly stained due to secretory granules and rough ER.

Acini are generally spherical


How do mucous acini appear and what is the shape of their acini?

They appear washed out due to loss of mucinogen granules during tissue preparation.

Acini are more tubular


How do mixed acini appear?

Serous cells are darkly stained serous demilunes (Crescent-shaped) surrounding mucous acini. It in unclear whether there are intercellular canaliculi draining the serous product into the intercalated duct, or if both cell types lie on its lumen


What is the stroma of secretory lobules?

The loose connective tissue the surrounds the acinia and ducts


What is the major cell type of the stroma and what is its function?

Plasma cell (in loose connective tissue)
Function: produce IgA, which will be modified by serious acinar cells to form secretory IgA (more stable than normal IgA)


What are the two types of intralobular ducts?

1. Intercalated ducts
2. Striated (salivary) ducts


What are intercalated ducts and what do they do?

Smallest duct type, made of simple low cuboidal epithelium. They use carbonic anhydrase to make HCO3- which will be pumped into the saliva via anion exchanger. Thus, Cl- is also reabsorbed


What are striated ducts and what do they do?

They are simple cuboidal to columnar epithelium with basal infoldings of plasma membrane. They drain the intercalated ducts and drain into the interlobular ducts. They also secrete HCO3- and reabsorb Cl-, but also have Na+/K+ ATPase to reabsorb Na+ and secrete K+.


Why are striated ducts striated? How do they appear in histological stains?

Striated due to basilar infoldings containing mitochondria which power the Na+/K+ ATPase. They appear eosinophilic because of the many mitochondria.


What are excretory ducts?

Interlobar ducts and larger. They are surrounded by connective tissue and drain to primary or main ducts which enter the oral cavity. They have some type of columnar epithelium which tends to stack larger as the ducts get larger.


How can you distinguish the parotid gland histologically?

All serous - serous acini only, often with some adipose tissue among secretory acina in lobules. It has long intercalated ducts


How can you distinguish the submandibular gland histologically?

Mixed secretion with mostly serous acini. Some mixed acinia but very few purely mucous acini.

Intercalated ducts are shorter


How can you distinguish the sublingual gland histologically?

Mostly mucous acini! Some mixed, but rarely pure serous acina. Poorly developed intralobular ducts which are not are prominent


What is the difference between the anatomical and clinical crown?

Anatomical - part of tooth covered by enamel
Clinical - part of tooth extending above the gingiva


What is the root of the tooth?

Part of the tooth that is embedded in an alveolus in the alveolar bone and is covered with cementum


What is the dental pulp and what does it contain?

Loose connective tissue inside pulp cavity, contains nerves and blood vessels. The outer edge is lined by odontoblasts which produce dentin


What is the apical foramen?

The opening at the bottom of the tooth where the nerves and blood vessels enter the tooth. This area is not covered by dentin.


What is dentin?

yellowish, semi-transparent material which surrounds the pulp cavity and forms the bulk of the tooth. It is harder than bone ~70% inorganic, and most organic material is type 1 collagen fibers surrounded by ground substance


What are odontoblasts?

Cells lining the pulp cavity which lay down dentin


What are dentinal tubules? Where do they extend to?

Processes embedded in spaces in dentin, which are laid down by odontoblasts as they lay down dentin and retreat into pulp cavity.

They extend to the junction of dentin with enamel or cementum


Why does the volume of the pulp cavity decrease with age?

Since dentin is produced by odontoblasts throughout the life of the tooth, and they grow inward


What is enamel?

The material covering the anatomic crown, it is the hardest substance in the body (98% inorganic). It is acellular


What is the organic portion of enamel?

unique glycoprotein called enamelin - there is no type 1 collagen


What are enamel rods and how do they grow?

They are calcium hydroxyapatite crystallite prisms that run perpendicular to the plane of the tooth surface and produced by the ameloblasts. They are large in diameter (4 microns) and are surrounded by interprismatic substance.


What are lines of Retzius?

Lines formed by staggered ameloblasts since the enamel is produced in daily increments (like tree rings). They tend to vary in appearance depending on your diet for that day and are thus distinguishable.


When do ameloblasts generate?

They degenerate after enamel is fully formed, about the time of tooth eruption.


What is cementum and its composition?

Covers the dentin in the root of the tooth. Similar composition to bone - 50-65% inorganic and the rest type 1 collagen. However, it is avascular and aneural unlike bone! It can be laid down throughout life.


What are cementoblasts and what is their fate?

They produce the cementum via appositional growth, which covers the root of the tooth.
1. They become trapped in lacunae of cementum, to become cementocytes (like osteocytes).
2. They line up along surface at length of periodontal ligament.


What is acellular vs cellular cementum?

Acellular - found at junction with enamel
Cellular - found in lower part near apical foramen, contains cementocytes in lacunae which communicate via canaliculi, but NO haversian systems. (avascular + aneural)


What is the gingiva and what are its components?

Masticatory mucosa surrounding the teeth. It is stratified squamous keratinized epithelium + underlying lamina propria (LCT).


How does the gingiva attach to enamel?

Via hemidesmosomes


What is the function of the gingiva?

Holds onto enamel, and functions as seal to prevent entrance of foreign materials into region between root and periodontal membrane


What is the periodontal membrane / ligament?

Dense irregular connective tissue between cementum of tooth and alveolar bone.


What are the two functions of the periodontal membrane / ligament?

1. Helps attach tooth to bone via Type 1 collagen fibers (Sharpey's fibers) to cementum and alveolar bone
2. Serves as a suspensory ligament to prevent crushing of soft tissue near apex of tooth (apical foramen). It a cushion here


What does the periodontal membrane / ligament contain?

Blood vessels, lymphatics, nerves, and especially proprioceptive nerves (pressure sensors)