Tongue Anatomy and Function

Study Notes

Tongue

The tongue has numerous lingual papillae on the upper surface (dorsum), which house taste buds.
The tongue is essential for cleaning teeth.
The eight muscles of the tongue are classified as either intrinsic or extrinsic.
Intrinsic muscles: change the shape of the tongue and are not attached to any bone.
Extrinsic muscles: change the position of the tongue and are anchored to bone.
The four extrinsic muscles originate from bone and extend to the tongue:
Genioglossus: arises from the mandible and protrudes the tongue. It is known as the tongue's "safety muscle" since it is the only muscle that propels the tongue forward.
Hyoglossus: arises from the hyoid bone and retracts and depresses the tongue. The chondroglossus is often included with this muscle.
Styloglossus: arises from the styloid process of the temporal bone and draws the sides of the tongue up to create a trough for swallowing.
Palatoglossus: arises from the palatine aponeurosis, depresses the soft palate, moves the palatoglossal fold towards the midline, and elevates the back of the tongue during swallowing.
The four paired intrinsic muscles originate and insert within the tongue, running along its length:
Superior longitudinal muscle: runs along the upper surface of the tongue under the mucous membrane, and elevates, assists in retraction of, or deviates the tip of the tongue. It originates near the epiglottis, at the hyoid bone, from the median fibrous septum.
Inferior longitudinal muscle: lines the sides of the tongue and is joined to the styloglossus muscle.
Vertical muscle: located in the middle of the tongue and joins the superior and inferior longitudinal muscles.
Transverse muscle: divides the tongue at the middle, and is attached to the mucous membranes that run along the sides.

Digestive System

The digestive system breaks down food through mechanical and chemical processes; absorbs nutrients; and excretes undigested remnants.
The human digestive system consists of the gastrointestinal tract and the accessory organs of digestion (the tongue, salivary glands, pancreas, liver, and gallbladder).
The gastrointestinal tract includes:
Oral cavity
Pharynx
Esophagus
Stomach
Small intestine
Large intestine

Oral Cavity

The oral cavity (mouth) is the initial part of the gastrointestinal tract.
It is located inferior to the nasal cavities and has a roof, floor, and lateral walls.
It opens onto the face through the oral fissure and is continuous posteriorly with the cavity of the pharynx at the oropharyngeal isthmus.
The oral cavity is subdivided into two main parts:
Outer oral vestibule: between the dental arches and the deep surface of the cheeks and lips.
Inner oral cavity proper: enclosed by the dental arches, located behind the dental arches.
The walls of the oral cavity are:
Superior wall or roof: palate, consisting of the hard palate and soft palate.
Inferior wall or floor: diaphragm of the mouth, including mylohyoid and geniohyoid muscles, and the tongue.
Lateral walls: cheeks.
The oral cavity has multiple functions:
Inlet for the digestive system, involved in the initial processing of food.
Aids in sound manipulation produced by the larynx, leading to speech.
Used for breathing because it opens into the pharynx, which is a common pathway for food and air.

Salivary Glands

The salivary glands produce saliva through a system of ducts.
There are three paired major salivary glands (parotid, submandibular, and sublingual), as well as hundreds of minor salivary glands.
Salivary glands can be classified as serous, mucous, or seromucous (mixed).
Serous secretions contain ptyalin (alpha-amylase), an enzyme that breaks down starch into maltose and glucose.
Mucous secretions contain mucin, which acts as a lubricant.

Waldeyer's - Pirogov's Tonsillar Ring

Waldeyer's - Pirogov's tonsillar ring (pharyngeal lymphoid ring or Waldeyer's lymphatic ring) is a ringed arrangement of lymphoid tissue in the pharynx.
The ring surrounds the naso- and oropharynx, with some of its tonsillar tissue located above and some below the soft palate.
The ring consists of (from top to bottom):
Pharyngeal tonsils: (or "adenoids") located on the roof of the nasopharynx, under the sphenoid bone.
Tubal tonsil: on each side, where each auditory tube opens into the nasopharynx.
Palatine tonsils: (commonly called "the tonsils") located in the oropharynx.
Lingual tonsils located on the back part of the tongue.

Pharynx

The pharynx is a musculofascial half-cylinder that links the oral and nasal cavities in the head to the larynx and esophagus in the neck.
The pharyngeal cavity is a common pathway for air and food.
The pharyngeal muscles determine the shape of the pharynx's lumen and affect its sound properties.
They contract to push food into the esophagus.
There are two muscular layers of the pharynx:
Outer circular layer: includes the inferior, middle, and superior constrictor muscles.
Inner longitudinal layer:
During swallowing, the circular muscles constrict to propel the bolus downwards (an involuntary process).