Histo block II: oral cavities Flashcards
the vestibule of the oral cavity lies where?
between the lips and cheeks and the gums and teeth. Mouth proper is internal to the gums and teeth.
what type of epithelium lines the oral cavity?
Stratified squamous epithelium
what are the 3 components of the oral cavity epithelium?
- masticatory mucosa
- lining mucosa
- specialized mucosa
describe masticatory mucosa?
Gums (gingiva), dorsal surface of root of tongue, and hard palate are keratinized (or parakeratinized) stratified squamous epithelium.
describe lining mucosa?
Inner surface of cheeks and rest of oral cavity lined typically by a non-keratinized stratified squamous epithelium with 3 layers: a stratum basales, stratum spinosum, and a stratum superficiale
describe specialized mucosa?
Dorsal surface of body of the tongue. Characterized by lingual papillae
In most places a lamina propria and sometimes a submucosal layer of CT underlies the epithelium. Glands may be present.
what do lips represent?
represent the junction between the facial skin (thin skin) and the oral mucosa
what does the red portion of the lips contain?
stratified squamous keratinized epithelium with deep penetrations of the connective tissue papillae
what is responsible for red color and touch sensitivity of the lips?
The numerous blood capillaries and nerve endings
describe the lamina propia of the lips
has a looser CT region immediately under the epithelium & a denser CT layer (reticular layer) below this
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Lip and mucocutaneous junction showing the very deep dermal papilla in the lip with associated neural sensory elements such as Meissner’s corpuscle
how is the tooth held?
held in socket in alveolar bone by the periodontal ligament
how much teeth does adult human dentition has?
32 teeth: 2 incisors, 1 canine, 2 premolars, and 3 molars in each quadrant
how much teeth does human deciduous dentition has?
20 teeth: 2 incisors, 1 canine, and 2 “molars” (antecedents of permanent premolars) in each quadrant
describe the anatomical crown and root of tooth
- has an outer covering of enamel and an underlying dentin layer
- has an outer covering of cementum with underlying dentin layer
what lies in the center of tooth?
the dental pulp consisting of gelatinous CT with numerous blood vessels & nerves which enter at the apical foramen at tip of root of tooth
what is the hardest substance in the body?
enamel
describe the composition of enamel
Is 96 to 98% mineralized with calcium hydroxyapatite. The 4% organic component is primarily composed of glycoproteins called enamelins and tuftelins.
During enamel formation also have amelogenins and ameloblastins, which help in mineralization but are later degraded.
what is the composition of dentin
Is ~70% mineralized with calcium hydroxyapatite. The organic component is primarily collagen Type I with smaller amounts of dentin phosphoprotein & dentin sialoprotein.
what is the composition of cementum?
Is ~50% mineralized with collagen Type I as main organic component. Composition of matrix is similar to bone. At apical regions of root, cementocytes lie in lacunae connected. Canaliculi. not initially present, but may develop with age and thickness of the dentin.
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Ground section of human tooth showing enamel on surface of crown portion of tooth, underlying dentin, and cementum layer on root
how does tooth formation happen?
Dental laminae develop from oral epithelium (ectoderm) and form enamel organs. The inner enamel epithelium later forms ameloblasts The rest of the tooth, periodontal ligament etc. derives from neural crest derived mesenchyme.
tooth formation is and inductive process, explain
ameloblasts induce adjacent neural crest mesenchymal cells to become odontoblasts, which begin making dentin which induces enamel production. Crowns form first, then roots. Cementum is laid down on dentin of roots
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Diagrams and photomicrographs of a developing tooth
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Diagrams and photomicrographs of a developing tooth
what forms the enamel?
Ameloblasts and are lost upon rupture of the tooth through gums. thus enamel is not repairable in the body/
What forms the dentin?
Odontoblasts; these remain throughout life and continue to form dentin
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showing the cellular relationships during enamel formation in which dentin is laid down first by odontoblasts and enamel is laid down on the enamel by secretory ameloblastsIn (b) the actual cell layers and their products can be seen
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Photomicrograph of developing tooth showing dental pulp (DP), layer of odontoblasts (OD), adjacent predentin (PD) and dentin (D), enamel (E), secretory stage ameloblasts (AM), and enamel organ cells (EO).
ameloblasts are divided into?
secretory ameloblasts and maturation stage ameloblasts
where can we find secretory ameloblasts and describe them
lay down the entire partially mineralized enamel layer. These cells have an apical process called a Tomes process around which forms the new enamel .
where can we find maturation stage ameloblasts and describe them
which differentiate from the secretory ameloblasts are involved in removal of most of organic material and final mineralization involving transport of ions. 70% of these cells are characterized by a ruffled border adjacent to the enamel that may be involved in the ion transport necessary for the final mineralization and the removal of the amelogenins and ameloblastin proteins. 30% are characterized by a smooth surface adjacent to the enamel. In both cases the Tomes process is no longer present
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Light micrograph showing secretory ameloblasts in which Tome’s process is evident next to enamel
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Colorized scanning EM of maturation stage ameloblasts showing smooth ends adjacent to enamel.
what are enamel rods?
The forming enamel is in the form of hydroxyapatite enamel rods with a unique keyhole shape which form along the path of the receding Tomes process
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Electron micrographs showing structure of young enamel with enamel rods obliquely sectioned at both low magnification (a) and high magnification (b). The dark needle-like structures are hydroxyapatite crystals
what is the odontoblastic process?
long cellular proccess embedded on the dentin that odontoblasts leave as they lay down dentin
where does the odontoblastic process lay?
in a space called the dentinal tubule
what gives rise to the pain felt upon damage of the enamel?
Free nerve endings that enter the dentinal tubule
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Micrograph of dental pulp in center and odonoblasts and dentin on outside. Yhe insets show longitudinal sections and cross-sections through the dentinal tubules which contain the odontoblastic processes of the odontoblasts
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Electron micrograph ofodontoblasts with extensive RER and a large Golgi apparatus. The black densities are abacus bodies. The odontoblastic process which would be at the top is not visible
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Electron micrograph of Golgi apparatus in odontoblasts with large vesicles and abacus bodies (arrows) containing parallel arrays of filaments with attached dense granules. The black densities are abacus bodies
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Electron micrograph of odontoblast showing the odontoblastic process
What si the gingivia and what does it do?
(gum epithelium) forms a tight attachment to the tooth called the junctional epithelium or attachment plaque involving a basal lamina-like material attached to tooth to which hemidesmosomes attach
what ligament is below the gingivia
The periodontal ligament attaches the tooth to alveolar bone
what si the periodontal ligament composed of nd explain the arrangement of the collagen fibers
dense irregular CT; The arrangement of the collagen fibers is such as to both attach the tooth to the bone and to cushion the pressure of tooth against bone during mastication
where are collagen fibers of the ligament embedded?
into the cementum of tooth & the alveolar bone as Sharpey’s fibers
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Micrograph showing the periodontal ligament in the middle attaching to the cementum of the tooth on the left to the alveolar bone on the right. dentin
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Electron micrograph showing Sharpey fibers extending from the periodontal ligament on right into the cementum of the tooth
what is the largest organ in the mouth
tongue
what are the divisions of the tongue?
body (anterior two-thirds) & root (posterior one-third)
what does the root of the tongue contain?
lingual tonsils
the body of the tongue on the dorsal surface is covereed by what?
specialized mucosa of stratified squamous epithelium with lingual papilla involved in taste sense
describe the lamina propia of the tongue
Lamina propria with fibroelastic CT underlies epithelium. Numerous sero-mucous glands
the core of the tongue is made up of?
bundles of skeletal muscle arranged in three mutually perpendicular directions
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Photomicrograph of the anterior two-thirds of the tongue with upper surface with lingual papilla and a core of skeletal muscle
what are the types of papillae of tongue?
*Filiform papillae: the most numerous
*Foliate papillae: Present at birth on lateral surfaces of body of tongue, but rudimentary in adult
*Fungiform papillae: Mushroom shaped. Scattered across tongue surface.
*Circumvalate (Valate) papillae: 8-12 papillae arranged along sulcus terminalis
characteristics of filiform papillae
*Composed of projections of keratinized stratified squamous epithelium
*No major core of CT
*Shaped like rose thorns or shark teeth with point curved toward back of mouth
*No taste buds
*Give frictional surface to tongue for moving food
characteristics of fungiform papillae
*Mushroom shaped – narrow stalk, larger upper portion
*Large CT core
*Upper (dorsal) surface covered with thin non-keratinized stratified squamous epithelium allowing blood to be visible- thus papilla appears red
*Taste buds may be present on upper surface
characteristics of folliate papillae
- Present as series of ridges separated by grooves on lateral surfaces of tongue
- Rudimentary in adult
- Large CT core
- Taste buds present on lateral surfaces of papilla
- Von Ebner’s glands in CT under papillae- serous secreting. Ducts enter at bottom of grooves. Fluid serves to rinse surface of taste buds to allow binding of new taste producing molecules. Also contains a lipase (lingual lipase) which facilitates breakdown of fat droplets in breast milk
characteristics of circumvallate papillae
*Largest of papillae
*Present as 8-12 papillae along sulcus terminalis
*Surrounded by a deep trench (moat)
*Large CT core
*Taste buds on lateral surfaces of papilla
*Von Ebner’s glands in CT under papillae- serous secreting similar to those of folliate.
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Micrograph of filiform papillae
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Micrograph of fungiform papillae
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Micrograph of foliate papillae with von Ebner’s glands and taste buds
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Micrograph of circumvalate papilla with von Ebner’s glands (serous glands)
what are taste buds
Intraepithelial sensory organs involved in sense of taste
describe shape of taste buds
Ovoid in shape with opening to epithelial surface called taste pore. Microvilli on sensory cells sample the fluid in the taste pore
what type of cells are present in taste buds?
- neuroepithelial sensory cells : the taste receptor cells for sweet, salty, bitter, sour, & umami (aspartate & glutamate). They make intimate contact with sensory nerves of cranial nerve VII (facial), cranial nerve IX (glossopharyngeal), & cranial nerve X (vagus)
- supporting cells
- basal cells: are the stem cells for other 2 cell types
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photomicrograph of a taste bud and its component cell types
Explain the taste perception of sweet, bitter and umami
involves activation of T1R and T2R family receptors with coupled G-proteins & coupled production of 2nd messengers (inositol 1,4,5-triphosphate – IP3) which activate taste specific Na+ channels causing depolarization of the cells causing opening of calcium channels resulting in the release of neurotransmitters.
explain the taste receptor activation for salty and sour
involves direct entrance of the Na+ and H+ ions through specific amiloride-sensitive Na+ channels, depolarization of the receptor cell plasma membrane and opening of calcium channels resulting in the release of neurotransmitters.
what is the epithelium of hard palate?
lined with parakeratinized stratified squamous epithelium. Epithelium rests on dense irregular CT layer
what is the epithelium of soft palate?
lined with stratified squamous non-keratinized epithelium. Epithelium rests on dense irregular CT and skeletal muscle. Numerous underlying mucous glands.
describe the oral pharynx
connects the oral cavity & the esophagus. It is lined with nonkeratinized stratified squamous epithelium overlying dense irregular CT & the constrictor and longitudinal muscles of the pharynx
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Hard palate showing parakeratinized stratified squamous epitelium and underlying subepithelial connective tissue that connects to underlying bone
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Soft palate lined by stratified squamous non-keratinized squamous epithelium with a lamina propria connective tissue with underlying area of skeletal muscle fibers and mucous glands
