7 Mouth, Tongue, Oral Cavity

The Mouth and Oral Cavity:

Digestion begins in the mouth via two processes: mechanical digestion involving chewing (mastication) with the teeth to tear and crush food, and chemical digestion involving saliva. The mouth is also the site of chemical digestion as saliva helps break down food using enzymes. The mouth houses 3 major pairs of salivary glands as depicted in the figure below:

• The parotid glands are located inferior and anterior to the ears.
• The submandibular glands are located within the floor of the mouth.
• The sublingual glands are located beneath the tongue.

fix x. Sagittal view: Salivary glands

Salivary Gland Contents:

Each gland produces saliva which is 99.5% water and 0.5% solutes, including ions, dissolved gasses, and various inorganic substances. Additionally, there are a number of enzymes including salivary amylase (which breaks down polysaccharides), lingual lipase (which becomes active in the stomach to process dietary triglycerides), and bacteriolytic lysozymes (destroys bacteria).

Pharynx:

Swallowing allows food to enter the pharynx; a muscular funnel-shaped structure behind the oral cavity extending towards the larynx and esophagus. The pharynx has 3 distinct regions, listed below from superior to inferior:

• Nasopharynx: connects nasal passages to the throat
• Oropharynx: connects oral cavity to the throat
• Laryngopharynx: directs food towards the esophagus and air toward the larynx.

fix x. Sagittal view: Pharynx