Module 18: The Digestive System: Tongue, Saliva, Esophagus Functions

vallate papillae

Also known as circumvallate papillae. 7-12 taste buds; form a V-shaped row along the posterior tongue.

deglutition

Also known as swallowing. Moving food from the oral cavity to the stomach; bypasses the nasopharynx and trachea.

bolus

Chewed food and saliva at the time it passes the palate.

taste buds

Clusters of gustatory receptor cells scattered over the surface of the oral cavity. 3 groups: fungiform, foliate and vallate (circumvallate).

elongated papillae

Condition caused by inflammation: enlarges papillae up to 15 times their normal size.

black hairy tongue

Condition of stained, elongated papillae. Can be corrected by brushing the tongue.

voluntary

Consciously controlled stage of swallowing.

dysphagia

Difficulty swallowing caused by some issue between the oral cavity and stomach.

lingual lipase

Enzyme secreted by the lingual glands; helps break down fatty foods in the mouth.

sublingual salivary gland

Gland located beneath the tongue. Contains both serous and mucous acini; makes water, mucous and enzymes.

submandibular salivary gland

Gland located on the floor of the mouth medial and inferior to the mandible. Contains mostly mucous acini; makes mucous with few enzymes.

lingual glands

Gland that secretes mucus and lingual lipase.

pharyngeal

Involuntary; stage of swallowing controlled by the brainstem. Occurs when the food bolus is in the oro-and laryngopharynx. Stage where food and water is kept out of the trachea.

esophageal

Involuntary; stage of swallowing controlled by the brainstem. Occurs when the upper esophageal sphincter opens and autonomic process of peristalsis begins.

parotid salivary gland

Largest of the salivary glands; located inferior and anterior to the ears. Contains more serous acini; makes water + enzymes.

circular muscle layer

Layer of the esophagus muscularis; closes off the lumen when contracted.

longitudinal muscle layer

Layer of the esophagus muscularis; contracts in waves during peristalsis.

foliate papillae

Leaf-shaped taste buds; found along the lateral surface of the posterior tongue.

functions of saliva

Moistens, forms food bolus; softens, lubricates oral cavity and food, initiates digestion, facilitates taste, cleanses oral cavity and teeth, bacteriocidal.

esophagus

Muscular tube located in the mediastinum. Consists of 4 layers; mucosa, submucosa muscularis, serosa. Responsible for moving food from the pharynx to the stomach; lacks an absorptive surface. Upper 1/3 is voluntary, striated muscle, lower 2/3 is involuntary smooth muscle.

fungiform papillae

Mushroom shaped taste buds; scattered on lower tongue.

filiform papillae

Non-taste structures that cover most of the tongue surface; give the tongue a rough texture.

gastro-esophageal reflux disease (GERD)

Occurs when lower esophageal sphincter fails to close completely; allows stomach acid to flow back into esophagus. Can be caused by obesity or pregnancy.

mucus acini

Oral structures that make mucus.

serous acini

Oral structures that make water + enzymes.

pharynx

Point of transition between the oral cavity and the esophagus. Divided into 3 parts; nasopharynx, oropharynx, and laryngopharynx.

peristalsis

Process that moves food, chyme and feces through the GI tract.

salivary amylase

Saliva enzyme that begins the breakdown of starchy foods into sugars; the reason potatoes taste sweet even though have little free sugar.

lysozyme

Saliva enzyme that breaks down invading microbes.

immunoglobulin A (IgA)

Saliva enzyme; plays an immunological function in mucous membranes.

salivary glands

Secrete saliva. 3 major glands: parotid, sublingual and submandibular; many minor glands; located throughout the lower head and neck.

laryngopharynx

Structure adjacent to the larynx. Epiglottis covers the trachea when swallowing food or drink and esophagus when breathing.

oropharynx

Structure that connects the nasal and oral cavities to the gut tube and trachea.

nasopharynx

Structure that connects the paranasal sinuses to the pharynx. Allows air to pass from the nose to the trachea.

saliva

Substance secreted by salivary glands. Plays an important role in digestion; ensures food is pre-digested and soft before swallowing. Defends the GI tract from microbial invaders.

branches of the facial nerve

Temporal; zygomatic, buccal, mandibular, cervical.

lower esophageal sphincter

Valve that allow substances to pass from the esophagus to the stomach.

upper esophageal sphincter

Valve that allows substances to pass from the pharynx to the esophagus.

tongue

Voluntary skeletal muscle covered with a mucous membrane; forms the floor of the oral cavity.