Oral histology and embryology Mgr. Jan Křivánek, Ph.D. jan.krivanek@med.muni.cz 24. 2. 2022 Lecture 1 Objectives of the course • Microscopic structure of the organs of the orofacial system • Connections of structure and function • Detailed understanding of developmental processes • Understanding the background of congenital malformations Lectures (7): Even week Thursday 9:00 – 10:40 Practicals (6+1): Odd week Thursday 9:00 – 10:40 Lecturer: Mgr. Jan Křivánek, Ph.D. Practicals: 100% attendance Successfully completed credit test (26 May 2022) ROPOTS Exam: Successfully completed practicals Written test (minimally 60 % of correct answers) New: Successful completion of Histology I + II is no longer a prerequisite for admission to the OHE examination The exam may include questions from presentations in practicals and lectures (written and orally communicated information), from ROPOTS and from discussions during practicals and lectures. Literature For a more detailed understanding of the presented information, the study of comprehensive literature is recommended, for example: Ten Cate's Oral Histology: Development, Structure, and Function. Antonio Nanci Essentials of Oral Histology and Embryology: A clinical Approach Illustrated Dental Embryology, Histology and Anatomy, Fehrenbach and Popowics Oral Anatomy, histology and Embryology, Berkovitz, Holland, Moxham Conditions to successfully pass the course Ten Cate's Oral Histology: Development, Structure, and Function. Antonio Nanci Essentials of Oral Histology and Embryology: A Clinical Approach Daniel J. Chiego ROPOTS • Every 14 days, one ROPOT • The ROPOT will be published in the "lecture" week • It has to be completed by the end of the week in which practicals are held • Each answer sheet consists of about 10-15 questions to be answered in your own words • The answer sheets should enable to practice the knowledge acquired • Some questions from the ROPOTS may appear on the exam Timetableoflessons Orofacial system Structures of the head and neck which: o Are essential for intake, grinding and processing of food o Maintain taste and tactile sensations o Forms an interface for social interactions (phonetic, aesthetic-physiognomic function, mimics, speak) (Helms et al. 2005) Development from pharyngeal arches, frontonasal prominence and maxillary and mandibular prominences Orofacial system Orofacial system is composed of: • Skeleton faciei - (facial skeleton) mandible, maxilla, ossa zygomatica, os ethmoides, ossa nasalia et lacrimalia, vomer, ossa palatina, os hyoides) + art. temporomandibularis) • Cavitas oris - lingua (tongue), dentes, periodontium, salivary glands (glandulae salivariae) • Art. temporomandibularis • Mimic muscles and muscles of mastication • Soft tissues of the face – lips, cheeks • Hard and soft palate – (palatum durum a palatum molle) • Isthmus of the fauces – (isthmus faucium) • Palatinal and tongue tonsils Orofacial system • Basic anatomy • Oral mucosa and microscopic structure • Lining mucosa • Masticatory mucosa • Specialized mucosa • Lips • Microscopic structure of tongue • Taste buds Oral cavity (cavitas oris) vestibulum oris / cavitas oris propria Borders Lips, cheeks, hard and soft palates, caudally floor of cavity, faucial isthmus (connection to oropharynx) Inside Tongue, teeth, gums, tonsilla palatina Major salivary glands: gl. submandibulatis gl. sublingualis gl. parotis (positioned outside) https://bonebroke.org/ https://inside.ucumberlands.edu Oral cavity (cavitas oris) Cook, Sarah et al. A food perspective. Food Hydrocolloids. 2017. Oral mucosa Except of teeth it covers all surfaces inside the oral cavity Oral mucosa has 2 layers (epithelium + lamina propria mucosae) At some places is between mucosa and the base (bone/muscles) located connective tissue - tela submucosa Functions of oral mucosa: • Protective - resistant to mechanical and chemical forces or effects of the bacterial flora • Secretory - saliva - a product of small and large salivary glands • Sensory - contains receptors for perception of temperature, pain, touch and taste • Thermoregulatory - in animals - (protruding tongue) • Food processing Features of the oral mucosa : • Forms special transitory zone inserted between the skin and the mucosa of the alimentary canal (starts in the pharynx) • The oral mucosa differs from mucosa of the alimentary canal or mucosa other tubular organs by the origin - it was developed from the ectoderm and head mesenchyme of ectodermal origin (ectomesenchyme – neural crest), while elsewhere from the entoderm or mesoderm and mesenchyme of mesodermal origin. • Thanks to these circumstances the oral mucosa shows some characteristics of the skin: keratinization of the epithelium, presence of lamina propria protrusions against the epithelium (papillae) Oral mucosa (Soukup et al., Nature 2005) Lining (65 %) Inner part of lips, cheeks soft palate, inferior aspect of the tongue, floor of the mouth and alveolar process (except of the gingiva) Tela submucosa located under mucosa Soft and slightly movable (submucous coat) Lamina propria from loose connective tissue Masticatory (25 %) Hard palate and gingiva Keratinized epithelium Tela submucosa is usually missing Lamina propria is composed from dense collagenous of irregular type and firmly connected with periosteum (mucoperiosteum) Specialized (10 %) Dorsal surface of the tongue Mucosa protrudes into papillae Tela submucosa is missing Lamina propria connected with aponeurosis linguae Classification of oral mucosa B, In histologic sections, the gingival epithelium is seen to be tightly bound to bone by a dense fibrous connective tissue (CT), whereas the epithelium of the lip (C) is supported by a much looser connective tissue. Gingiva Lip • Lamina propria from dense collagenous connective tissue of irregular type • Firmly connected to periosteum (mucoperiosteum) • Lamina propria from loose collagenous tissue • Tela submucosa under mucosa • Mucosa is slightly movable Orální sliznice krycího typuOrální sliznice mastikačního typu Epithelium Lamina propria Mucosa Tela submucosa ( ) epithelium stratified squamous • Masticatory mucusa • Specialized mucosa* Oral mucosa nonkeratinized keratinized • Lining mucosa Lamina propria mucosae • Contains numerous of melanocytes or melanophages; Merkel cells • Multiple papilae projected against the epithelium. Their shape and density are spatially different • (depends on different mechanical needs of oral mucosa) • Differences between: Melanophages, melanocytes, (melanophores), melanosomes a melanin !! Lamina epithelialis: tlustý vrstevnatý dlaždicový epitel Squid skin https://youtu.be/0wtLrlIKvJE?t=12 (Yadav et al., 2012) Nonkeratinized Stratum basale - melanin Stratum spinosum Stratum intermedium Stratum superficiale Keratinized Stratum basale - melanin Stratum spinosum Stratum granulosum - keratohyalin Stratum corneum - keratin Classification of cell layers in the epithelium - similar as in the epidermis lamina propria tela submucosa Lining mucosa mucoperiosteum gingiva Masticatory mucosa palatum durum palatum mole Palate Adipose zone Glandular zone raphe palati (in the middle line) Hard palate (palatum durum) Masticatory mucosa: • Epithelium stratified squamous keratinizing • Tela submucosa is usually missing High regional variability: Raphe palati • Midline area from papilla incisiva to soft palate, mucosa of raphe palati is without glands and adipocytes • Formed by fusion of the maxillary processes (origin of clefts) Foramen incisivum • Location on the papilla incisiva • In the fetal period, forms opening between the nasal and oral cavities • Before or shortly after birth, the connection is closed Adipose zone • Paired structure • Medially divided by papilla incisiva and raphe palati, Laterally bordered by gingiva and premolars • Mucosa is thickened into 3-5 transversal plicae - plicae palatinae transversae, core of plicae is formed by stripes of dense colagenous connective tissue interlaced with adipocytes Glandular zone • Paired structure • Mucosa is smooth and contains mucous glands – gll. palatinae Local differences in hard palate structure Hard palate – glandular zone glandulae palatinae Lips Sagitally: • ventral aspect of the lip (skin) • dorsal aspect of the lip (mucosa) • Structural support: m. orbicularis oris • Vermilion zone Vermilion zone glandulae labiales (mixed glands) Tongue Lingua (lat.) Glossa (gr.) radix Base: intra- and extraglossal striated muscles Evolutionary: developed in terrestrial vertebrates and amphibians (tetrapods) from muscles of oral floor Surface Dorsum linguae Specialized oral mucosa Inferior aspect Lining mucosa Fibrous parts Aponeurosis linguae - very stiff fibrous membrane Septum linguae - composed by dense collagenous tissue Glands of tongue mucous serous mixed Glandula apicis linguae (gl. Blandini) mixed gland Ebner‘s serous glands (SŽ) with secretory parts of tubular character (VS – septum of connective tissue) Ebner‘s glands - gll. gustatoriae serous Duct (V) of Ebner´s gland (SŽ) Weber‘s mucinous glands MT – mucinous tubules, V – duct. Weber‘s glands - gll. linguales post mucinous Weber‘s glands - gll. linguales post mucinous Ebner‘s glands - gll. gustatoriae serous Specialized oral mucosa • Firmly connected with aponeurosis linguae • Rough surface • Mucosal outgrowths - lingual papillae • Covered by nonkeratinized squamous stratified epithelium (except of papillae filiformes) Dorsum linguae Papillae fungiformes Apex; Mushroom-shape (0.5 - 1.5 in height, 0.5 - 1.0 mm in width) Taste buds in epithelium Papillae filiformes The most abundant and distributed over the entire dorsal surface of the tongue; Brush-like appearance (0.5 - 1 mm in height, 0.2 - 0.3 mm in width); The stratified squamous epithelium is often keratinized Papillae filiformes vs. Papillae fungiformes Taste bud Differences in keratinization Papillae foliatae • Count: 3 - 8 • Vertically-oriented • Rudimental • Laterally on the edge of the main body and root of tongue • Taste buds Papillae vallatae Largest (1-4 mm in height, 1-3 mm in width), 7–12 just in front of sulcus terminalis, submerged into mucosa. Deep circumpapillary furrow. Taste buds Papilla vallata Ebner‘s glandsCircumpapillary furrow (caliculi gustatorii) Intraepithelial structures Localization: • In epithelium of vallate papillae + circumpapillar furrows • In epithelium of fungiform papillae and foliate papillae • Rarely in other places Amount: around 2000 – 2500 in young individual, reduction with age up to 1/3 Every taste bud is composed of 50-150 cells Taste buds Porus gustatorius Support cells Taste cells Basic tastes: Sweet Salty Sour Bitter Umami Suggested (still discussed): Fatty Metalic ? Three types of taste bud cells Support cells / type I (bright) - cells are characterized by bright cytoplasm (on electron-microscopy images) and presence of microvilli at apex Taste bud cells / type II (dark) - have numerous synaptic vesicles in the cytoplasm and they have nerve fibres on their bodies Type I and II cells go through the entire height of the taste bud Basal cells / type III - are lower than the previous and less differentiated serve as precursors for cells I and II (stem cells) Number of taste bud cells: 50 - 150 Life span of taste cells: about 10 - 14 days (renewal from basal cells) Inervation of taste buds • Taste buds on fungigorm papillae – n. facialis - chorda tympani (through lingual nerve) • Taste buds on foliate papillae and vallate papillae - n. glossopharyngeus • Taste buds in other locations (radix of the tongue, the isthmus faucium - n. vagus Signal transmission Thank you for your attention!