Histology 2

• Lip (labium oris)


  Consists of three parts: the outer pars cutanea, the middle rubor labii (or vermilion border, on the top), and the inner pars mucosa
• Pars cutanea


  • Covered by: hairy skin, the stratified squamous keratinizing epithelium, the dermis and subcutis, hair follicles, sebaceous glands, and sweat glands are recognizable

  
• Rubor labii


  • The keratinization of the epithelium is thin and this part has NO glands. This is unique in the body! We may wet it with our tongue, or keep it protected by lip-stick or face cream (wet it with saliva + H2O). The connection towards the dermis is rich in connective tissue papillae (function: Absorption & Mechanical fixation) with capillary loops in them: these capillary loops and the thin epithelium give the red color. The tactile function of the lip is also important, in the papillae numerous Meissner corpuscles are present

  
• Pars mucosa


  • Epithelium is stratified squamous non keratinizing, salivary glands may be seen in the submucosa. There are some cells in the planocellulare cell layer that are paler than others. These cells store glycogen

  
• SSKE consist of: (from bottom to top) Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum (Stratum Disjunctum, Stratum Compactum)
• Sebaceous glands


  • Branching, Alveolar, Holocrine (whole cell apoptosis) secretory mechanism

  
• Sweat glands


  • Branching, Tubular, Coiled, Merocrine (vesicle mediated) secretory mechanism
• Mixed salivary (Mucous and Serous) glands

  • Mucous: Big lumen, Nuclei is peripherally placed, Mucin is the content (CH and Lipid rich). Serous: Small lumen, Round nuclei centrally located, Basophilic (Rough ER)

  
• General rule: You can look at cell nucleus to see if cell is alive (basophilic/purple) or dead (white/pale). Strong basophilic/purple color also means proliferation

  
• Popular exam questions: Find border between Rubor Labii and Pars Mucosa, Why are some cells in the SSKE pale (they are storing glycogen), What is the lip anatomically (separation between skin and oral cavity)

  
• Parotid gland


  • Lobulated organ, Consists 100% of serous alveoli, Scattered fat cells increase with age, Intercalated ducts lined with cuboidal epithelium, Striated ducts have columnar cells with rod-like mitochondria, Interlobar ducts have columnar or pseudostratified epithelial lining

  
• Submandibular gland


  • Lobulated organ, Consists of 75% serous and 25% mucous alveoli, Gianuzzi demilunes present, Intercalated ducts are shorter, Striated ducts are relatively longer

  
• Sublingual gland


  • Lobulated organ, Consists of 33% serous and 67% mucous alveoli, Mucous alveoli stain dark purple with PAS-H, Duct system is more simple than other salivary glands

  
• Gland Comparison


  • Parotid: 100% serous, Intercalated/Striated/Excretory ducts
  • Submandibular: 75% serous, 25% mucous, Intercalated/Striated/Excretory ducts
  • Sublingual: 33% serous, 67% mucous, Striated duct

  
• Sympathetic Nervous System


  Produces dense saliva
• Parasympathetic Nervous System


  Produces watery saliva
• Parakeratinized epithelium


  Keratinized epithelium with nucleus, they have "pykrotic nuclei" (highly condensed nuclei)
• Foramen cecum


  Remnant of the site from which an evagination of the floor of the embryonic pharynx occurred to form the thyroid gland
• Cell types in a taste bud

  • Neuroepithelial (sensory) cells, Supporting cells, Basal cells (stem cells)
• Taste determination


  Depending on if it's sour, sweet, bitter, salt or umami, either G-protein receptors open or Ion channels
• Teeth are a major component of the oral cavity and are essential for the beginning of the digestive process. Teeth are embedded in and attached to the alveolar processes of the maxilla and mandible
• Deciduous (primary, milk) teeth

  • 10 teeth in each jaw, on each side: Medial (central) incisor, Lateral incisor, Canine, 2 Molars
• Permanent (secondary) teeth


  • 16 teeth in each jaw, on each side: Medial (central) incisor, Lateral incisor, Canine, 2 Premolars, 3 Molars
• Tooth structure


  • Enamel: Hard, thin, translucent layer of acellular mineralized tissue covering the crown
  • Dentin: Most abundant dental tissue, lies deep to enamel and cementum
  • Cementum: Thin, pale-yellowish layer of bone-like calcified tissue covering the dentin of the root
• Tooth eruption


  1. Bud stage

  2. Cap stage

  3. Bell stage

  4. Appositional dentin and enamel stage

  5. Tooth eruption stage

  6. Functional tooth stage
• Predentin is lighter because it's unmineralized
• Ground tooth, Fuchsin


  • Longitudinal cut, low power. D: dentin, E: enamel, P: pulp cavity, the yellow line covers the cementum (acellular). At the enamel-cementum junction (neck of the tooth) a small cavity is seen (under the star). On the lower side of the dentin the dried remnant of the pulp is colored by the fuchsin (blue line)
• Most preparations are cross sections for technical reasons: the pulp cavity is very narrow, so from one tooth only 1-2 longitudinal sections could have been made
• Ground tooth cross-section


  • From left to the right: pulp cavity, dentin, cellular cementum. The deep purple, uneven surface is the dried remnant of the periodontial tissue stained with fuchsin
• Dentin


  • Radial black or purple striation: these are the dentin canaliculi that were formerly occupied by the Tomes fibers of odontoblasts
• Fuchsin


  Blue line that colors the pulp
• Most of the preparations are cross sections for technical reasons: the pulp cavity is very narrow, so from one tooth only 1-2 longitudinal sections could have been made
• Cross-section


  • Changes according to the actual level of the cut
  • You will see the pulp cavity, surrounded by dentin, and depending on the level, the enamel, the acellular cementum, or cellular cementum
• From left to the right

  • Pulp cavity
  • Dentin
  • Cellular cementum
• Periodontial tissue


  Deep purple, uneven surface is the dried remnant stained with fuchsin
• Enamel


  Borderline of enamel (top) and dentin (bottom)
• Interglobular spaces


  Purple amoeboid shapes, artefact due to the shrinkage of the drying tooth, their origin is similar to that of the granulation of Tomes
• Dentin


  • Radial black or purple striation are the dentin canaliculi that were formerly occupied by the Tomes fibers of odontoblasts
  • Close to the external surface of the dentin the organic material is less, and since the tissue in the ground preparation dries, due to shrinkage spaces will appear
  • Next to the enamel, usually larger spaces appear in the dentin, these are the interglobular spaces, next to the cementum they are smaller and called granular layer of Tomes
• What you look at, that is a dead, dried, ground tooth. In live the pulp chamber is lined by the odontoblasts that do not cease producing dentin as long as the tooth is alive
• Secondary or reparatory dentin production


  It may cure smaller defects on a tooth and is important for stable and lasting fillings