Study Notes on The Digestive System: Mouth, Tongue, and Salivary Glands

Ingestion, Secretion, & Propulsion:
- Receives food: The mouth is the entry point for food intake.
- Monitors food quality: The mouth plays a role in assessing the quality of food through taste and texture.
- Prepares food: The mouth moistens and manipulates food into a form suitable for swallowing.
Mechanical digestion:
- Teeth: Break down food into smaller pieces through tearing and crushing.
Chemical digestion:
- Salivary glands: Secrete mucus and enzymes, initiating the digestion of carbohydrates and lipids.

Oral cavity proper: The space extending from the gums and teeth to the fauces, which is the opening between the oral cavity and the oropharynx.
Bolus: A soft, flexible, easily swallowed mass manipulated by the tongue and teeth.
- Formed by: cheeks, hard and soft palates, and tongue.

Types of epithelial tissue:
- Transitional epithelium
- Simple columnar epithelium
- Stratified squamous epithelium
- Correct Answer: Stratified squamous epithelium provides protection from abrasion and high temperatures.

Role of the tongue:
- A large skeletal muscle essential for food manipulation (forming the bolus) and speech.
- Covered with a mucus membrane and lined with taste buds to assess food quality.
Deglutition: The act of swallowing involves the mouth, pharynx, and esophagus, facilitated by the secretion of saliva and mucus.

Intrinsic muscles:
- Contained entirely within the tongue, responsible for subtle movements necessary for speech.
Extrinsic muscles:
- Originates elsewhere and inserts into the tongue, responsible for stronger movements and food manipulation.
Lingual glands: Secrete lingual lipase, which begins the breakdown of triglycerides.

Dentition: Collective term for teeth.
Tooth decay:
- The mouth hosts more than 700 species of microorganisms.
- Bacteria digest trapped food, producing acids that erode enamel and lead to cavities.
- Plaque: A sticky residue formed by an invisible layer of bacteria, mucus, and sugars, promotes tooth decay.
Gingivitis:
- Inflammation of the gums, which can progress to periodontitis if untreated.
- Periodontitis: Inflammation of the soft tissues surrounding the tooth, potentially causing tooth loosening.

Function:
- Release saliva into ducts which empty into the oral cavity.
- Saliva maintains moisture and cleanliness in the mouth and pharynx.
- Secretion increases upon food entry to lubricate, dissolve and begin chemical digestion.

Functions:
- Lubrication: Facilitates smooth passage of food.
- Cleansing: Maintains oral cavity hygiene.
- Digestive enzyme: Contains salivary amylase, which initiates the breakdown of starch, a large polysaccharide.
- Bacterial growth inhibition: Utilizes lysozyme and antibodies to inhibit bacterial growth.
- Taste detection: Dissolves food molecules facilitating taste sensation.
Composition of saliva:
- 99.5% Water
- Electrolytes
- Lysozyme
- Mucus
- Salivary Amylase
- Immunoglobulin A
- Urea
- Lingual lipase

Why does your mouth suddenly “go dry”?
- Parasympathetic activity: Similar to motor activity, stimulates salivation.
- Sympathetic activity: Inhibits salivation, leading to dry mouth, especially when nervous or under stress.

Autonomic Nervous System (ANS): Controls salivation.
Parasympathetic stimulation: Promotes moderate saliva secretion.
Sympathetic stimulation:
- Constricts blood vessels in the salivary glands, decreasing saliva production, contributing to dry mouth in stressful situations.

Definition: An inflammation and enlargement of the parotid salivary glands caused by the mumps virus (myxovirus).
Symptoms:
- Fever
- Malaise
- Pain and swelling of one or both glands
- Possible sterility in post-pubescent males due to inflammation of testes.
Vaccine: Introduced in 1967 to prevent mumps infections.