KB

Study Guide – Salivary Glands & Oral Mucosa (Vocabulary Flashcards)

Salivary Glands

  • Functions of saliva: referenced as a five function role in the guide (5) but the five specific functions are not enumerated in the transcript provided.

  • Major glands

    • Parotid (serous) – discharges into the oral cavity through Stensen’s duct

    • Submandibular – mixed, mostly serous – secretion via Wharton’s duct

    • Sublingual – mixed, mostly mucous

  • Minor glands

    • Located in hard and soft palate, tongue, lips

    • All mucous, except von Ebner’s glands in the tongue which are serous

  • Structure of salivary glands

    • Acini consist of two main types

    • Serous acini

    • 8–12 pyramidal cells surrounding a central lumen

    • Cells have a broad base facing the stroma and a narrow apex that forms part of the lumen

    • May have myoepithelial cells at the basal aspect which are contractile and help propel saliva into the duct system

    • Nucleus is round; mitochondria and rough ER abundant

    • Secretory granules accumulate toward the apex

    • Microvilli on the luminal surface

    • Intercellular canaliculi present between cells

    • Mucous acini

    • Tubular configuration; appear round in cross-section

    • Lumen larger than serous acini

    • Large amounts of mucus accumulate toward the apical region; nucleus appears flattened

    • May have serous cells associated as demilunes covering the mucous cells at the end of the tubule

    • Secretions from these demilunes reach the lumen via intercellular canaliculi

  • Note on mucous acini

    • Some mucous acini may have serous demilunes associated with them

Salivary Gland Ducts and Secretory Pathways

  • Salivary gland ducts

    • Connective tissue fibers subdivide the gland into lobules containing secretory units and their excretory ducts

  • Intercalated ducts

    • Collect the initial secretions; the smallest ducts

    • Lumina lined by low cuboidal epithelium

    • Myoepithelial cells surround some portions

  • Striated ducts

    • Formed from merging of several intercalated ducts

    • Lined by columnar epithelium

    • Basal striations visible due to numerous elongated mitochondria in basal in-foldings

  • Excretory intralobular ducts

    • Striated ducts join to form larger intralobular ducts

    • Surrounded by increasing layers of connective tissue fibers

  • Interlobular and interlobar ducts

    • Intralobular ducts join to form larger interlobular and interlobar ducts

    • Lined with pseudostratified columnar epithelium

    • Terminal portions convey saliva from the gland to the oral cavity

    • Larger interlobar ducts may be lined with stratified epithelium (low cuboidal or columnar)

Tooth Supporting Tissues

  • Cementum, periodontal ligament, and alveolar bone proper

  • Cementum

    • Mineralized connective tissue that covers the root dentin

    • Avascular and aneural

    • Predominantly type I collagen (organic)

    • Cementum types (bolded information focus)

    • Cementoblasts: cells located in the PDL space responsible for cementogenesis

    • Cementoclasts: cells responsible for restoring or breaking down cementum

    • Cementocytes: regulation of cellular cementum formation and resorption

    • Acellular, extrinsic fibrous cementum AEFC / Primary cementum

    • Forms slowly and covers cervical 2/3 of the root

    • Function: anchorage

    • No embedded cells

    • Initial cementum fibers are perpendicular to the CEJ (fibrous fringe FF)

    • Extrinsic collagen fibers (Sharpey’s fibers) attach to the fibrous fringe

    • No well defined cementoid layer

    • Cellular, Intrinsic Fibrous cementum CIFC / Secondary cementum

    • Function: adaptation, repair, attachment

    • Confined to the apical and interradicular regions

    • Forms rapidly; cementoblasts become entrapped within the matrix (cementocytes)

    • Layer of cementoid evident

    • Extrinsic PDL fibers exist but are not continuous with intrinsic fibers

    • Acellular Afibrillar cementum

    • No collagen fibers; no known function in tooth attachment

    • Well mineralized ground substance

    • Deposited over enamel and dentin along the CEJ

  • Cementoenamel junction types

    • Most common type: Cementum overlaps enamel – ~60%

    • Edge to edge type: ~30%

    • Gap type: ~10%; exposed dentin leads to root sensitivity

  • Alveolar bone

    • Alveolar bone proper

    • Part of the alveolar bone immediately surrounding the root; fibers of the PDL embed here

    • Mainly compact bone; also called bundle bone or lamina dura

    • Supporting alveolar bone

    • Cortical/compact plates (buccal/labial and palatal/lingual) and trabecular/cancellous bone between cortical plates and alveolar bone proper

    • Alveolar crest

    • Outer cortical plate and bone lining the socket wall meet at the alveolar crest (~1–2 mm below CEJ)

    • Cortical plate thickness

    • Thinner in maxilla and anterior teeth

    • Thickest on buccal aspect of mandibular posterior teeth (molars and premolars)

  • Periodontal ligament (PDL)

    • Characteristics and functions

    • Soft, specialized connective tissue located between cementum and alveolar bone proper

    • Suspends tooth in its bony socket

    • Supplies cementum with nutrients

    • Cells form, maintain, and repair alveolar bone and cementum

    • Sensory function (proprioception)

    • Maintains a constant PDL width

    • Principal cells

    • Most abundant: fibroblasts; high protein turnover

    • Proteins and ankylosis prevention

    • MSX2 is a protein PDL can produce to prevent ankylosis

    • Innervation of PDL

    • Two types: sensory and autonomic

    • Sensory: nociception and mechanoreception

      • Myelinated fibers mediate pain

      • Ruffini-like endings are low threshold stretch receptors; essential mechanoreceptors in PDL

    • Autonomic: sympathetic and parasympathetic

    • PDL principal fiber groups (location and function)

    • Alveolar crestal group

      • Location: extends obliquely from cementum below CEJ and just beneath the junctional epithelium to the alveolar crest

      • Function: prevents tooth extrusion and resists lateral movement

    • Horizontal group

      • Location: extends at right angles to tooth long axis from cementum to alveolar bone just below the alveolar crest

      • Function: resists horizontal and tipping forces

    • Oblique group

      • Location: extends from cementum obliquely to insert into the alveolar bone coronally

      • Function: resists vertical and intrusive forces; largest and most numerous

    • Apical group

      • Location: cementum to bone at the apical region of the socket

      • Function: resists vertical force

    • Interradicular group

      • Location: between roots of multirooted teeth and running from cementum into the bone at the crest of the interradicular septum

      • Function: resists vertical and lateral forces

    • PDL gingival fibers (location and groups)

    • Trans-septal group: extends interdentally from cementum over the alveolar bone crest and is embedded in cementum of the adjacent tooth

    • Dento-gingival group: from cervical cementum to lamina propria of free and attached gingiva

    • Alveolo-gingival group: from the alveolar crest to the lamina propria of free and attached gingiva

    • Circular group: forms a band around the neck of the tooth, interlacing with other fiber groups in the free gingiva

    • Dento-periosteal group: from cementum to the periosteum of the outer plate of the alveolar process

    • Overall functions: act to resist tooth separation and gingival displacement

  • Clinical implications

    • Hypercementosis: abnormally thickened cementum, often at root apex and interradicular region or over entire root surface

    • Cementicle: small globular masses of cementum within the PDL; may be free or attached to cementum; linked to microtrauma

    • Cementoblastoma: benign neoplasm consisting of cementum-like tissue attached to the root apex, commonly in mandibular first molar region

    • Hypophosphatasia: reduced activity of tissue nonspecific alkaline phosphatase leading to reduced cementum formation

Oral Mucosa and Its Organization

  • Functions of oral mucosa in humans

    • Protection, sensation (temperature, touch, pain, taste), secretion (saliva, sebaceous glands)

  • Permeability and absorption

    • Absorption: no; permeability: yes

    • Greatest permeability in non-keratinized layers; exceptions: dentogingival junction

  • Compare oral mucosa with skin

    • Oral mucosa is generally more deeply colored due to CT vascularity, less keratinization variance, moist, and lacks skin appendages such as sweat glands and hair follicles

  • Fordyce’s spot

    • Sebaceous glands on upper lip and buccal mucosa; no stratum lucidum in these areas

  • Epithelium type

    • Stratified squamous; keratinized or non keratinized

    • Parakeratinization

    • Normal in oral mucosa; not normal in skin

  • Lamina propria and submucosa

    • Lamina propria may be just connective tissue; submucosa present in some regions

  • Mucoperiosteum vs mucosa

    • Mucosa has a submucosa; mucoperiosteum has thick bone and periosteum present

  • Epithelium maturation and terminal differentiation

    • Keratinized oral epithelium has 4 layers: surface corneum, granulosum, spinosum, basale

  • Proteins expressed during differentiation and their roles

    • Desmogleins/desmocollin: desmosome formation

    • Transglutaminases (TGs): crosslink proteins to form cornified envelope

    • Filaggrin: profilaggrin release from keratohyaline granules; promotes aggregation of keratin intermediate filaments and cell flattening

    • Lipids from membrane-coating granules in the upper spinous layer contribute to impermeability of the cornified envelope

  • Basal layer proteins involved in basement membrane attachment and disease relevance

    • Melanosomes and premelanosomes: abnormal pigmentation

  • Comparison of keratinized vs non keratinized oral epithelium

    • Keratinized: s corneum, s granulosum, s spinosum, s basale

    • Non keratinized: superficial layer, intermediate layer, prickle cell layer, basal layer

  • Where keratinization occurs and why

    • Dorsal tongue surface, hard palate, gingiva; areas subjected to higher mechanical stress or trauma

  • Non-epithelial cells in oral mucosa

    • Melanocytes in basal layer produce melanin

    • Merkel cells in basal layer function as tactile receptors

    • Langerhans cells in suprabasal layers trap antigens; antigen-presenting cells

    • Lymphocytes; location varies; participate in inflammatory responses

  • Basement membrane structure

    • Located between epithelium and lamina propria; continuous

    • Layers: Lamina lucida, Lamina densa, Lamina fibroreticularis

    • Attachment to basal epithelial cells via hemidesmosomes and integrins (alpha6 and beta4)

    • Key proteins: laminins, integrins, BP180 (collagen XVII), BP230 (plectin)

  • Lamina propria

    • Connective tissue that supports epithelium; two major layers: papillary layer and reticular layer

    • Cells: fibroblasts, macrophages (including melanophages and siderophages), mast cells, lymphocytes, plasma cells, polymorphonuclear leukocytes

    • Fibers: collagen (types I and III are typical in LP; type IV and VII associate with the basal lamina); elastin more abundant in lining mucosa

    • Ground substance: proteoglycans and glycoproteins

    • Blood supply: multiple sources; arteries running parallel to surface; present in submucosa or deep reticular layer

    • Nerve supply: primarily sensory; autonomic supply to blood vessels and minor salivary glands; mediates mastication, salivation, swallowing, gag reflex and speech

    • Sensation types: temperature, touch, pain, taste; anterior tongue temperature perception is greater; touch receptors in soft palate and oropharynx important for swallowing and gagging

Tongue and Taste Structures

  • Tongue anatomy

    • Anterior 2/3 and posterior 1/3 divided by sulcus terminalis

    • Dorsal surface: keratinized and gustatory epithelium; ventral surface: non keratinized

  • Papillae on the dorsal surface

    • Foliate papillae: located on the lateral borders of the tongue

    • Filiform papillae: most numerous; covered by non gustatory epithelium

    • Vallate (circumvallate) papillae: located at the posterior aspect; contain numerous taste buds; taste buds present but fewest on this type

    • Fungiform papillae: located mostly on the anterior portion; taste buds present in some

  • Taste buds and receptor cells

    • Taste bud contains 50–150 taste receptor cells per bud

    • Three cell types

    • Gustatory cells (taste receptor cells)

    • Sustentacular cells (supporting cells)

    • Basal cells (divide to produce gustatory and sustentacular cells)

    • Apical ends terminate in a taste pore with microvilli projecting toward the surface

  • Posterior 1/3 of the tongue

    • Characterized by mucosal folds; few or no papillae

    • Lingual tonsil present; mucous minor salivary glands discharge into tonsillar crypts or directly onto the tongue surface

  • Lingual tonsil and lymphatic tissue

    • Lymphatic tissue present in the posterior tongue (lingual tonsil)

Mucocutaneous Junctions and Dentogingival Junction

  • Mucocutaneous junction and mucogingival junction

    • Mucocutaneous junction: transition between skin and oral mucosa

    • Mucogingival junction: transition between alveolar mucosa and attached gingiva

    • Structure and color differences reflect vascularity; mucosa near the mucogingival junction is less keratinized and more vascular

  • Dentogingival junction

    • Relationship between gingiva and tooth

    • Organization overview: gingival sulcus, sulcular epithelium, gingival epithelium, and junctional epithelium

    • Junctional epithelium details

    • 12–18 cells thick

    • Fewer tonofilaments and desmosomal junctions; relatively weaker adhesion

    • Epithelium migrates to the surface but does not differentiate into a keratinized surface

    • High turnover rate; cells move coronally toward the surface and shed into the gingival sulcus

    • Readily regenerates from adjacent oral sulcular or oral epithelium if damaged

    • Important in periodontal surgery and therapy due to regenerative capacity

Skin Anatomy and Appendages (Epidermis, Dermis, and Associated Structures)

  • Skin overview

    • Epidermis + Dermis; largest organ of the body

    • Functions: protection, sensation, thermoregulation, metabolism, and communication

  • Epidermis structure

    • Keratinocytes undergo terminal differentiation called keratinization

    • Strata (from basal to surface):

    • S. basale — mitotically active; attached to basement membrane by hemidesmosomes

    • S. spinosum — multiple layers; polyhedral cells connected by desmosomes

    • S. granulosum — thinner, flatter layer; contains keratohyalin granules

    • S. lucidum — present only in thick skin; flat, enucleate, eosinophilic cells

    • S. corneum — outermost; protective against water loss and friction

    • Melanocytes in the basal layer produce melanin and contribute to UV protection

    • Albinism results from defective tyrosinase; other pigmentation disorders include nevi and melanoma

    • Langerhans cells — antigen-presenting cells, located mainly in the stratum spinosum

    • Merkel cells — mechanoreceptors, linked to nerve endings in thick skin

  • Dermis structure

    • Two major layers

    • Papillary dermis — superficial, loose connective tissue with microvasculature

    • Reticular dermis — deeper, denser connective tissue

  • Cutaneous sensory receptors

    • Free nerve endings (pain)

    • Meissner corpuscles (light touch)

    • Pacinian (Lamellated) corpuscles — large, deep in dermis and subcutaneous tissue; detect pressure

    • Krause end bulbs — low frequency vibration

    • Ruffini endings — detect tissue distortion

  • Subcutaneous tissue (hypodermis)

    • Loose connective tissue with adipocytes; binds skin to underlying tissues

    • Rich vascular supply

  • Epidermal appendages

    • Hair — keratinocyte proliferation in the hair matrix forms medulla, cortex, and cuticle; hair follicle with dermal papilla; internal/external root sheaths; basement membrane contributions

    • Nails — keratinization process similar to hair; nail root matrix forms growing nail plate

    • Sebaceous glands — holocrine secretion of sebum into pilosebaceous units

    • Sweat glands

    • Eccrine — in the dermis; produce watery sweat onto skin surface; essential for thermoregulation

    • Apocrine — confined to axillae and perineum; wider lumens; become functional after puberty; secrete protein-rich sweat into hair follicles

Connections and Implications

  • Structure-function relationships

    • Acinar cell protein synthesis and secretory granule storage enable regulated saliva production

    • Duct system (intercalated, striated, intralobular/excretory) progressively modifies saliva composition

    • Myoepithelial cells facilitate saliva expulsion into ducts

    • PDL fiber organization allows distribution of occlusal and functional forces to prevent tooth loss and support periodontal health

    • Junctional epithelium permeability is critical for periodontal health and regeneration after surgery

  • Clinical relevance

    • Cementum types impact tooth attachment and sensitivity risks at CEJ

    • Hypercementosis and cementicles can affect tooth vitality and periodontal health

    • Hypophosphatasia leads to diminished cementum formation and dental defects

    • Dentogingival junction health is essential for periodontal stability and successful therapy

    • Keratinization patterns influence health of oral mucosa under mechanical stress

  • Real-world relevance

    • Understanding glandular secretory pathways aids in pharmacology and dental therapeutics

    • Knowledge of salivary gland ducts informs pathology of salivary gland diseases and surgical approaches

    • Oral mucosa properties explain susceptibility to trauma, infection, and how mucosal healing occurs after procedures

    • Skin anatomy and appendages underpin dermatological diagnostics and treatments, including wound healing and sensory disorders