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
identify
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.
identify
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
identify
Diagrams and photomicrographs of a developing tooth
identify
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
identify
identify
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
identify
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).