Anatomy of the Tongue

Study Notes

Muscles of the tongue work together to depress the center of the nerve supply
Anterior 2/3 of the tongue originates from the 1st pharyngeal arch, while the posterior 1/3 originates from the 3rd pharyngeal arch
Sensory information for the anterior 2/3 of the tongue is transmitted through the lingual nerve (branch of CN V) and taste fibers are derived from the facial nerve (CN VII)
For the posterior 1/3, both general sensation and taste are transmitted through the glossopharyngeal nerve (CN IX)
Motor control of the tongue muscles is provided by the Hypoglossal nerve (CN XII), except for the palatoglossus muscle, which is innervated by the pharyngeal branch of the Vagus nerve (CN X)

Gag reflex (pharyngeal reflex) involves bilateral pharyngeal muscle contraction and elevation of the soft palate, with afferent (sensory) input from CN IX and efferent (motor) input from CN X
Paralysis of the genioglossus muscle can obstruct the airway, risking suffocation
Protection of the airway is crucial, especially during general anesthesia, when the muscle relaxes and the tongue can fall backward

There are three major salivary glands: parotid, submandibular, and lingual
Minor salivary glands are located throughout the oral cavity, including the lips, cheeks, palate, and floor of the mouth
These glands contribute about 10% of the total salivary volume

Sialography is a radiographic examination of the major ducts and secretory units of the parotid and submandibular glands
Blockage of the submandibular duct by calculi (stones) can occur
Most salivary gland tumors occur in the parotid gland, and most are benign

Gums (gingivae) are composed of fibrous tissue covered with mucosa
Improper oral hygiene can lead to food and bacterial deposits in gum crevices, causing gum inflammation (gingivitis) and eventually periodontitis
Teeth are used in mastication and assist in speech, with children having 20 deciduous teeth and adults having 32 permanent teeth

Decay of teeth can lead to dental caries (cavities) and eventually invade the pulp cavity, causing pulpitis and intense pain
Abscesses from maxillary molar teeth can extend into the maxillary air sinus, causing sinusitis

The palate consists of a bony part (hard palate) and a muscular part (soft palate)
The hard palate is composed of four layers, including a bony skeleton, submucosa, lamina propria, and keratinized squamous epithelium
The soft palate is composed of musculoaponeurotic tissue attached to the hard palate, tongue, and pharynx

The pharynx is an expanded portion of the digestive system posterior to the oral cavity
It is divided into three parts: nasopharynx, oropharynx, and laryngopharynx
The pharynx wall is composed of voluntary muscles, including the external circular and inner longitudinal layers

The outer circular layer includes three pharyngeal constrictors: superior, middle, and inferior
The inner longitudinal layer includes three muscles: stylopharyngeus, salpingopharyngeus, and palatopharyngeus
The pharyngeal muscles are innervated by the pharyngeal branch of the Vagus nerve (CN X), except for the stylopharyngeus muscle, which is innervated by the glossopharyngeal nerve (CN IX)

The esophagus is a muscular tube that connects the pharynx to the stomach
It has two sphincters: the upper esophageal sphincter and the lower esophageal sphincter
Factors that prevent reflux of gastric contents into the esophagus include the angle of entry of the esophagus into the stomach, the right crus of the diaphragm, the location of the fundus, and the mucosal flap in the cardiac region of the stomach

The esophagus receives blood from three arterial sources: the inferior thyroid artery, the aorta, and the left gastric artery
Venous drainage is through the inferior thyroid vein, azygos system, and the left gastric vein into the portal system

Narrowing at three points: at its commencement, where it is crossed by the left bronchus, and at its entry into the stomach
Portal hypertension can cause esophageal varices, which may rupture and cause hemoptysis
Metaplasia in the esophageal mucosa can occur due to continual gastric reflux (GORD)
Dysphagia, or swallowing difficulties, can occur due to various conditions, including achalasia, a motor disorder characterized by failure of the lower esophageal sphincter to relax and abnormal function of the smooth muscle in the lower esophagus.