Salivary Glands and Saliva

Functions of Saliva

• Lubricates and cleans the mouth
• Dissolves food chemicals for taste via taste buds on the tongue
• Moistens food
  • Assists in forming a bolus (ball of food with help from the tongue)
• Contains enzymes that start the breakdown of polysaccharides (e.g., starch) into smaller sugars

Types of Salivary Glands

Major Salivary Glands

• Produce the majority of the saliva
• Located outside the oral cavity
• Three main glands:
  • Parotid gland:
    • Located anterior to the ear, triangular shape
    • Lies between the masseter muscle and the skin
    • Associated with the facial cranial nerve (surgical impact can cause facial paralysis)
    • Duct deposits into the oral vestibule
    • Associated condition: MS virus causes inflammation
  • Submandibular gland:
    • Located below the mandible, medial to its body
    • Duct deposits at the base of the lingual frenulum
  • Sublingual gland:
    • Located under the tongue
    • 10-12 ducts depositing into the floor of the mouth

Minor Salivary Glands

• Enhance saliva secretion
• Located within the oral cavity (e.g., buccal glands)

Secretory Cells in Salivary Glands

• Serous cells: Secrete watery saliva with enzymes, ions, and some mucin
• Mucus cells: Produce mucus
• Gland activity:
  • Parotid and submandibular glands: Mostly serous cells
  • Sublingual gland: Mostly mucus cells

Composition of Saliva

• Mostly water
• pH: Slightly acidic (around 6.5)
• Electrolytes:
  • Sodium, potassium, phosphate, bicarbonate ions
• Enzymes:
  • Salivary amylase: Breaks down complex carbohydrates
  • Lingual lipase: Begins lipid breakdown
  • Enzymes become more active in the stomach's lower pH
• Metabolic wastes: Urea
• Antimicrobial elements:
  • IgA: Promotes adaptive immune response
  • Lysozyme: Targets gram-positive bacteria, weakens cell walls
  • Defensins and cyanide compounds: Destroy microbes
  • Over 500 bacterial species present, e.g., Streptococcus mutans and Lactobacillus (tartar and tooth decay)

Salivation Details

• Volume: Approx. 1.5 liters per day
• Function: Keeps the mouth moist
• Control System: Nervous system, primarily parasympathetic
  • Parasympathetic: Active during rest, controls salivary glands
  • Sympathetic: Overstimulation leads to dry mouth
• Stimulation triggers:
  • Ingested food items activating chemoreceptors and mechanoreceptors
  • Signals sent by neurons in the brain stem via cranial nerves
    • Cranial nerve VII (Facial): Near parotid glands
    • Cranial nerve IX (Glossopharyngeal): Controls salivation