Ramus mandibulae
Encyclopedia
The ramus of the mandible (perpendicular portion) is quadrilateral
in shape
, and has two surfaces, four borders, and two processes.
.
The medial surface presents about its center the oblique mandibular foramen
, for the entrance of the inferior alveolar vessels and nerve
.
The margin of this opening is irregular; it presents in front a prominent ridge, surmounted by a sharp spine, the lingula mandibulae
, which gives attachment to the sphenomandibular ligament
; at its lower and back part is a notch from which the mylohyoid groove
runs obliquely downward and forward, and lodges the mylohyoid vessels and nerve.
Behind this groove is a rough surface, for the insertion of the internal pterygoid muscle (Pterygoideus internus). The mandibular canal
runs obliquely downward and forward in the ramus, and then horizontally forward in the body, where it is placed under the alveoli
and communicates with them by small openings.
On arriving at the incisor teeth
, it turns back to communicate with the mental foramen
, giving off two small canals which run to the cavities containing the incisor teeth.
In the posterior two-thirds of the bone the canal is situated nearer the internal surface of the mandible; and in the anterior third, nearer its external surface.
It contains the inferior alveolar vessels and nerve, from which branches are distributed to the teeth.
is attached to the angle between these muscles. The anterior border is thin above, thicker below, and continuous with the oblique line.
The posterior border is thick, smooth, rounded, and covered by the parotid gland
. The upper border is thin, and is surmounted by two processes, the coronoid in front and the condyloid behind, separated by a deep concavity, the mandibular notch.
is a thin, triangular eminence, which is flattened from side to side and varies in shape and size.
The condyloid process
is thicker than the coronoid, and consists of two portions: the condyle, and the constricted portion which supports it, the neck.
The mandibular notch, separating the two processes, is a deep semilunar depression, and is crossed by the masseteric
vessels and nerve.
Quadrilateral
In Euclidean plane geometry, a quadrilateral is a polygon with four sides and four vertices or corners. Sometimes, the term quadrangle is used, by analogy with triangle, and sometimes tetragon for consistency with pentagon , hexagon and so on...
in shape
Shape
The shape of an object located in some space is a geometrical description of the part of that space occupied by the object, as determined by its external boundary – abstracting from location and orientation in space, size, and other properties such as colour, content, and material...
, and has two surfaces, four borders, and two processes.
Surfaces
The lateral surface is flat and marked by oblique ridges at its lower part; it gives attachment throughout nearly the whole of its extent to the masseterMasseter muscle
In human anatomy, the masseter is one of the muscles of mastication.In the animal kingdom, it is particularly powerful in herbivores to facilitate chewing of plant matter.-Origin and insertion of the two heads:...
.
The medial surface presents about its center the oblique mandibular foramen
Mandibular foramen
The Mandibular foramen is an opening on the internal surface of the ramus for divisions of the mandibular vessels and nerve to pass.-Contents:...
, for the entrance of the inferior alveolar vessels and nerve
Inferior alveolar nerve
The inferior alveolar nerve is a branch of the mandibular nerve, which is itself the third branch of the trigeminal nerve .-Path:...
.
The margin of this opening is irregular; it presents in front a prominent ridge, surmounted by a sharp spine, the lingula mandibulae
Lingula of mandible
The margin of the mandibular foramen is irregular; it presents in front a prominent ridge, surmounted by a sharp spine, the lingula of the mandible which gives attachment to the sphenomandibular ligament; at its lower and back part is a notch from which the mylohyoid groove runs obliquely downward...
, which gives attachment to the sphenomandibular ligament
Sphenomandibular ligament
The sphenomandibular ligament is a flat, thin band which is attached above to the spina angularis of the sphenoid bone, and, becoming broader as it descends, is fixed to the lingula of the mandibular foramen...
; at its lower and back part is a notch from which the mylohyoid groove
Mylohyoid groove
The margin of the mandibular foramen is irregular; it presents in front a prominent ridge, surmounted by a sharp spine, the lingula mandibulæ, which gives attachment to the sphenomandibular ligament; at its lower and back part is a notch from which the mylohyoid groove runs obliquely downward and...
runs obliquely downward and forward, and lodges the mylohyoid vessels and nerve.
Behind this groove is a rough surface, for the insertion of the internal pterygoid muscle (Pterygoideus internus). The mandibular canal
Mandibular canal
The mandibular canal is a canal within the mandible that contains the inferior alveolar nerve, inferior alveolar artery, and inferior alveolar vein...
runs obliquely downward and forward in the ramus, and then horizontally forward in the body, where it is placed under the alveoli
Dental alveolus
Dental alveolus are sockets in the jaws in which the roots of teeth are held in the alveolar process of maxilla with the periodontal ligament. The lay term for dental alveoli is tooth sockets...
and communicates with them by small openings.
On arriving at the incisor teeth
Incisor
Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...
, it turns back to communicate with the mental foramen
Mental foramen
The mental foramen is one of two holes located on the anterior surface of the mandible. It permits passage of the mental nerve and vessels. The mental foramen descends slightly in edentulous individuals.- Variations :...
, giving off two small canals which run to the cavities containing the incisor teeth.
In the posterior two-thirds of the bone the canal is situated nearer the internal surface of the mandible; and in the anterior third, nearer its external surface.
It contains the inferior alveolar vessels and nerve, from which branches are distributed to the teeth.
Borders
The lower border of the ramus is thick, straight, and continuous with the inferior border of the body of the bone. At its junction with the posterior border is the angle of the mandible, which may be either inverted or everted and is marked by rough, oblique ridges on each side, for the attachment of the Masseter laterally, and the Pterygoideus internus medially; the stylomandibular ligamentStylomandibular ligament
The stylomandibular ligament is a specialized band of the cervical fascia, which extends from near the apex of the styloid process of the temporal bone to the angle and posterior border of the angle of the mandible, between the Masseter and Pterygoideus internus.This ligament separates the parotid...
is attached to the angle between these muscles. The anterior border is thin above, thicker below, and continuous with the oblique line.
The posterior border is thick, smooth, rounded, and covered by the parotid gland
Parotid gland
The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands...
. The upper border is thin, and is surmounted by two processes, the coronoid in front and the condyloid behind, separated by a deep concavity, the mandibular notch.
Processes
The coronoid processCoronoid process of the mandible
The mandible's coronoid process is a thin, triangular eminence, which is flattened from side to side and varies in shape and size....
is a thin, triangular eminence, which is flattened from side to side and varies in shape and size.
The condyloid process
Condyloid process
The condyloid process is part of the mandible and is thicker than the coronoid, and consists of two portions: the condyle, and the constricted portion which supports it, the neck.-Condyle :...
is thicker than the coronoid, and consists of two portions: the condyle, and the constricted portion which supports it, the neck.
The mandibular notch, separating the two processes, is a deep semilunar depression, and is crossed by the masseteric
Masseteric
Masseteric can refer to:* Masseteric artery* Masseteric nerve* Masseter muscle...
vessels and nerve.