Digestive System Anatomy: Oral Cavity, Teeth, Pharynx, and Oesophagus

Vocabulary practice cards covering the macro- and micro-anatomy of the oral cavity, teeth, tongue, salivary glands, pharynx, and oesophagus, including vertebral levels, constrictions, and histological layers.

Oral cavity

The beginning of the digestive system; bounded ventrally by the lips, laterally by the cheeks, with its floor formed by the oral diaphragm, its roof formed by the palate, and opening dorsally into the pharynx via the isthmus of fauces.

Isthmus of fauces (isthmus faucium)

The posterior aperture or oropharyngeal isthmus that marks the boundary and communication between the oral cavity and the pharynx.

Oral vestibule (vestibulum oris)

The space of the oral cavity situated externally to the dental arches, bounded externally by the lips (labia oris) and cheeks (bucca).

Oral cavity proper (cavitas oris propria)

The space located internal to the dental arches, containing the teeth, gums, tongue, hard and soft palate, palatine tonsils, and salivary gland openings.

Bichat's fat pad (buccal fat pad)

A fat pad located beneath the subcutaneous connective tissue of the cheek that, together with subcutaneous fat, gives the cheek its definitive shape.

Gingiva (gum)

A specialised mucous membrane that covers the alveolar processes of the maxilla and mandible and surrounds the necks of the teeth.

Hard palate (palatum durum)

The bony anterior portion of the roof of the oral cavity formed by the palatine process of the maxilla and horizontal plate of the palatine bone, covered with stratified squamous epithelium and palatal glands.

Soft palate (palatum molle)

A mobile fibromuscular plate acting as the velum of the oral cavity; functions in swallowing and prevents food from passing into the nasopharynx.

Muscles of the soft palate

Five paired muscles comprising the tensor veli palatini, levator veli palatini, musculus uvulae, palatoglossus, and palatopharyngeus.

Gomphosis

A specialised fibrous joint (a type of syndesmosis) that anchors the root of each tooth into its corresponding bony dental alveolus.

Deciduous teeth (milk teeth)

The primary dentition numbering $20$ teeth in total; eruption begins at the $6\text{th}$ month of life and is completed by the $24\text{th}$ month.

Permanent teeth

The secondary dentition numbering $32$ teeth in total; eruption begins in the $6\text{th}$ year of life and is typically complete by the $30\text{th}$ year.

Crown of tooth (corona dentis)

The visible part of the tooth projecting above the gumline, covered externally by enamel.

Pulp cavity (cavitas dentis)

The internal chamber of the tooth containing dental pulp (pulpa dentis), composed of connective tissue with a rich neurovascular supply.

Dentine (dentinum)

The calcified tissue that constitutes the primary structural bulk and basic substance of the tooth.

Enamel (enamelum)

The highly mineralized, hard outer substance that covers the dentine of the anatomical crown of the tooth.

Cementum (cement)

A layer of modified fibrillar bone covering the dentine of the neck and root of the tooth.

Parodontium

The complex of supportive structures anchoring the tooth, consisting of the dental alveolus, periodontium, cementum, and gingiva.

Permanent dental formula (per quadrant)

The arrangement of permanent teeth in each quadrant consisting of $2$ incisors, $1$ canine, $2$ premolars, and $3$ molars ($8$ teeth per quadrant; $32$ total).

Deciduous dental formula (per quadrant)

The arrangement of milk teeth in each quadrant consisting of $2$ incisors, $1$ canine, $0$ premolars, and $2$ molars ($5$ teeth per quadrant; $20$ total).

Lingual aponeurosis (aponeurosis linguae)

A fibrous layer located directly beneath the mucous membrane of the dorsum of the tongue into which tongue muscles insert.

Sublingual caruncle (caruncula sublingualis)

A small papilla on either side of the frenulum linguae where the submandibular duct (Wharton's duct) and major sublingual duct (duct of Bartholin) open into the oral cavity.

Sublingual fold (plica sublingualis)

An mucosal fold overlying the sublingual gland on the floor of the mouth along which $8$ to $20$ minor sublingual ducts open.

Intrinsic muscles of the tongue

Four pairs of muscles contained entirely within the tongue: superior longitudinal, inferior longitudinal, transverse, and vertical muscles.

Extrinsic muscles of the tongue

Four muscles that originate from structures outside the tongue and insert into it: genioglossus, hyoglossus, styloglossus, and palatoglossus.

Parotid duct (Stensen's duct)

The excretory duct of the parotid gland that passes across the masseter and opens on the inner surface of the cheek opposite the upper second molar tooth.

Submandibular duct (Wharton's duct)

The primary excretory duct of the submandibular gland that terminates by opening on the sublingual caruncle alongside the major sublingual duct.

Major sublingual duct (duct of Bartholin)

The primary duct draining the anterior seromucous part of the sublingual gland, opening at the sublingual caruncle.

Pharynx

A funnel-shaped muscular tube situated beneath the cranial base that narrows craniocaudally and continues as the oesophagus at the vertebral level of $\text{C6}$.

Waldeyer's lymphoid ring (pharyngeal lymphoid ring)

A circular arrangement of lymphoid tissue comprising $4$ types ($6$ tonsils in total): $1$ single pharyngeal tonsil (adenoid), $2$ tubal tonsils, $2$ palatine tonsils, and $1$ single lingual tonsil.

Pharyngeal constrictor muscles

Three overlapping circular muscles (superior, middle, and inferior pharyngeal constrictors) that insert posteriorly into the median pharyngeal raphe.

Pharyngeal levators (musculi levatores pharyngis)

Three longitudinal muscles that elevate the pharynx: stylopharyngeus, salpingopharyngeus, and palatopharyngeus.

Oesophagus

An approximately $25\text{ cm}$ long muscular tube that conveys food from the pharynx ($\text{C6}$) to the stomach ($\text{T11}$).

Muscular layer of the oesophagus

The muscular tunic consisting of striated muscle fibres in the upper third, a combination of striated and smooth fibres in the middle third, and purely smooth muscle fibres in the lower third.

Pharyngo-oesophageal constriction of Killian

The first anatomical constriction of the oesophagus located at the pharyngo-oesophageal junction at the vertebral level of $\text{C6}$.

Thoracic constriction (constrictio bronchoaortica)

The second anatomical constriction of the oesophagus produced by contact with the aortic arch and the left main bronchus at the vertebral level of $\text{T4-T5}$.

Diaphragmatic constriction (constrictio phrenica)

The third anatomical constriction of the oesophagus situated where it pierces the diaphragm through the oesophageal hiatus at the level of $\text{T10-T11}$.

Histological layers of the oesophagus

The four concentric wall layers: internal mucous layer (mucosa), submucous layer (submucosa), muscular layer (circular and longitudinal), and external adventitia.