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Physiology of Saliva, Medinna Rasha - 2506557816 - Coggle Diagram
Physiology of Saliva
Vascularization and Innervation of Major Salivary Glands
Blood supply mostly from branches of external carotid artery (e.g., superficial temporal, maxillary, facial, lingual arteries).
Venous drainage into retromandibular and facial veins.
Parasympathetic innervation
Parotid gland: Glossopharyngeal nerve (CN IX) → otic ganglion → auriculotemporal nerve (CN V3).
Submandibular and sublingual glands: Facial nerve (CN VII) → chorda tympani → submandibular ganglion → lingual nerve (CN V3).
Sympathetic innervation from superior cervical ganglion impacting saliva consistency.
Sensory innervation primarily via trigeminal nerve branches (CN V3).
Microscopic Structure of Major and Minor Salivary Glands
Secretory units
Serous acini: pyramidal cells producing watery, enzyme-rich saliva.
Mucous acini: columnar cells producing thick mucous saliva.
Mixed acini: mucous cells with serous demilunes.
Myoepithelial cells: contract to expel saliva into ducts.
Duct system
Intercalated ducts (small, cuboidal epithelium).
Striated ducts (columnar epithelium, modify saliva composition).
Excretory ducts (large, open into oral cavity).
Parotid: mostly serous acini, well-developed ducts; Submandibular: mixed but mostly serous; Sublingual: mostly mucous with fewer striated ducts.
Minor glands distributed in oral mucosa, mainly mucous type with some serous mixed glands
Mechanisms of Saliva Production in Salivary Reflexes
Reflexes triggered by sensory stimuli: taste (gustatory reflex), chewing (masticatory reflex), smell (olfactory reflex), temperature/chemical irritation.
Parasympathetic pathway: uses acetylcholine activating Ca2+ signaling, promotes abundant watery secretion.
Sympathetic pathway: uses noradrenaline stimulating cAMP, promotes thicker proteinaceous saliva.
Dual stimulation produces mixed saliva types adapting to physiological needs.
Anatomy of Major Salivary Glands and Their Ducts
Parotid gland: largest, serous secretion, located by masseter muscle, Stensen’s duct opens near upper second molar.
Submandibular gland: second largest, mixed serous and mucous secretion, lies beneath mandible, Wharton’s duct opens at sublingual caruncle.
Sublingual gland: smallest, mostly mucous secretion, located in anterior floor of mouth, multiple small ducts (Bartholin’s ducts) open along sublingual fold.
Physical, Chemical, Biochemical Properties and Functions of Saliva Components
Physical: clear, slightly viscous due to mucins, hypotonic with near-neutral pH.
Chemical: electrolytes (Na+, K+, Cl−, HCO3−, Ca2+, phosphate), enzymes (amylase, lipase), proteins, immunoglobulins (IgA).
Functions
Water: solvent and lubricant.
Mucins: lubrication, tissue protection.
Amylase: carbohydrate digestion.
Antimicrobial enzymes and proteins: defense against pathogens.
Bicarbonate: neutralizes acids, protects enamel.
IgA: immune protection in oral cavity.
Medinna Rasha - 2506557816
Process of Salivary Secretion and Influencing Factors
nitiation by stimulation of taste, chewing, smell, or touch receptors.
Primary saliva secreted by acinar cells is isotonic, containing enzymes and electrolytes.
Ductal modification adjusts ion content (reabsorbs sodium, secretes potassium and bicarbonate).
Parasympathetic stimulation produces large amounts of watery saliva; sympathetic produces thicker mucus-rich saliva.
Salivary production influenced by taste (most important), chewing, smell, circadian rhythm, diet, hormones, and nature/duration of stimuli.
Salivary Index, Flow Rate, and Normal Reference Values
Salivary index includes flow rate, viscosity, pH, buffering capacity, and biochemical composition.
Flow rate
Unstimulated flow (mainly submandibular and sublingual glands) ~0.3–0.4 mL/min (low <0.1 mL/min).
Stimulated flow (mainly parotid gland) ~1.0–3.0 mL/min (low <0.5 mL/min).
Daily saliva volume approx. 0.5–1.5 liters in healthy adults.
Normal saliva maintains lubrication, enzymatic digestion, antimicrobial action, and enamel protection.