Structure of the mandibular body (Corpus mandibulae)
The basis of the bone is its body, designated in Latin as Corpus mandibulae. Anatomically, the body has two main borders, each with specific features. The lower border is distinguished by its massiveness and thickness — this is the base of the mandible (Basis mandibulae).
On the external surface of the body, visible from the front strictly along the midline, projects the mental protuberance (Protuberantia mentalis). On either side of this protuberance are the paired mental tubercles (Tuberculum mentale). Moving laterally along the external surface of the body, one can find the important mental foramen (Foramen mentale). It is the terminal point of the mandibular canal (Canalis mandibulae), which runs through the thickness of the bone itself.
Internal surface of the body
The internal surface of the bone body has a pronounced relief. Right along the midline, two mental spines protrude here — superior and inferior (Spinae mentales superior et inferior). Lateral to these spines lies the digastric fossa (Fossa digastrica).
Special attention should be paid to the fossae when studying the internal surface. Slightly superior and posterior to the digastric fossa is the sublingual fossa (Fovea sublingualis). Inferior and further posterior lies the larger submandibular fossa (Fovea submandibularis). The visual and anatomical boundary reliably separating these two fossae is a bony ridge — the mylohyoid line (Linea mylohyoidea).
Alveolar part and dental structures
The upper margin of the bone body is more complex in structure, as it is designed for tooth fixation, and is called the alveolar part (Pars alveolaris). In terms of its function and structure, it is the analogue of the alveolar process of the maxilla. Together, this part forms a curved alveolar arch (Arcus alveolaris).
Within this arch are depressions for tooth roots — dental alveoli (Alveoli dentales). Adjacent alveoli are separated from each other by bony interalveolar septa (Septa interalveolaria). If a tooth has multiple roots, then within a single alveolus there are also interradicular septa (Septa interradicularia). The external surface of the bone in this zone is uneven: tooth roots form characteristic alveolar juga (Juga alveolaria).
Immediately posterior to the last molar is a flat area — the retromolar triangle (Trigonum retromolare), which is posteriorly complemented by the retromolar fossa (Fossa retromolaris).
Mandibular ramus (Ramus mandibulae)
Paired structures extend upward from the posterior part of the bone body — the mandibular rami (Ramus mandibulae). On the external surface of the ramus runs the oblique line (Linea obliqua). On the internal surface, the buccinator line (Linea buccinatoria) is sometimes distinguished, although this term is generally not used in modern anatomical terminology.
The point where the lower border of the body transitions into the posterior border of the ramus forms the angle of the mandible (Angulus mandibulae). This angle has rough surfaces on both sides: externally lies the masseteric tuberosity (Tuberositas masseterica), and internally — the pterygoid tuberosity (Tuberositas pterygoidea).
Processes and foramina of the ramus
The upper part of the ramus ends in two prominent processes. Between them is the deep mandibular notch (Incisura mandibulae).
- Condylar process (Processus condylaris) — the posterior process. It consists of the thickened head of the mandible (Caput mandibulae) and the narrowed neck (Collum mandibulae). On the medial side of the neck is the pterygoid fovea (Fovea pterygoidea).
- Coronoid process (Processus coronoideus) — the anterior process. It has a pointed shape and anteriorly transitions smoothly into the temporal crest (Crista temporalis).
On the medial (internal) surface of the ramus, slightly below the notch, opens the mandibular foramen (Foramen mandibulae). Inferiorly, this foramen is bounded by a bony prominence, the lingual of the mandible (Lingula mandibulae). It is from this foramen that the mandibular canal (Canalis mandibulae) originates, which runs within the body of the bone toward the mental foramen. From the lingula, the mylohyoid groove (Sulcus mylohyoideus) extends downwards and forwards along the inner surface of the bone.
Briefly: answers to topical questions
Which nerves and vessels pass through the mandibular canal?
- Inferior alveolar vessels and nerve (a. et n. alveolares inferiores) — pass through the mandibular canal (canalis mandibulae).
- Veins — also course within the canal along with the artery and nerve.
Which tuberosities are located in the region of the mandibular angle and which muscles attach to them?
- Masseteric tuberosity (tuberositas masseterica) — located on the external surface of the mandibular angle; the masseter muscle (m. masseter) attaches to it.
- Pterygoid tuberosity (tuberositas pterygoidea) — located on the inner side of the mandibular angle; the medial pterygoid muscle (m. pterygoideus medialis) attaches to it.
Which muscle attaches to the pterygoid fovea on the neck of the condylar process?
- The lateral pterygoid muscle (m. pterygoideus lateralis) attaches to the pterygoid fovea on the neck of the condylar process.
Which anatomical structures exit onto the face through the mental foramen?
- Mental nerve (n. mentalis) — terminal branch of the inferior alveolar nerve.
- Mental artery (a. mentalis) — branch of the inferior alveolar artery.
- Corresponding vein — origin of the inferior alveolar vein.
To memorize the fossae on the internal surface of the body, use this spatial landmark: the sublingual fossa (Fovea sublingualis) lies superior to the mylohyoid line, while the larger submandibular fossa (Fovea submandibularis) lies inferior and posterior.
Class and exam questions
What bounds the mandibular foramen from below?
The mandibular foramen (Foramen mandibulae) is covered and bounded inferiorly by a bony projection called the lingula of the mandible (Lingula mandibulae).
Which structures separate tooth roots within the alveoli?
The dental alveoli themselves are separated from each other by interalveolar septa (Septa interalveolaria), and the roots of a multi-rooted tooth within a single alveolus are separated by interradicular septa (Septa interradicularia).
Where is the digastric fossa located?
The digastric fossa (Fossa digastrica) is located on the internal surface of the mandibular body, laterally from the mental spines.
Which process terminates the ramus anteriorly?
Anteriorly, the mandibular ramus ends in the pointed coronoid process (Processus coronoideus), which continues inferiorly into the temporal crest.
What else to study on this topic
- Course of the mandibular canal: from the entrance foramen on the ramus to the mental foramen on the body.
- Topography and boundaries of the retromolar triangle and retromolar fossa.
- Differences between interalveolar and interradicular septa of the alveolar arch.
- Relative positions of the pterygoid and masseteric tuberosities in the region of the mandibular angle.
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