Osteology of Head & Neck - Mandible

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Mandible - It forms the lower jaw.
Only movable bone in the facial skeleton.
It has a horse shoe shaped body & rami
Each halves is L shaped, presents two surfaces - External & Internal
two borders - superior or alveolar, Inferior or base
External surface near the symphysis menti presents mental protuberance and two mental tubercles on either side.
Along the alveolar border presents incisive fossa, gives attachment to mentalist muscle.
close to alveolar border gives attachment to orbiculares oris muscle
An oblique line extends from mental tubercle to the anterior border of rams of mandible.
Anterior part of oblique line gives attachment to depressor labii inferioris in front and depressor anguli oris behind
Posterior part extends behind the 3rd molar tooth, and opposite to three molar teeth the line gives attachment to buccinator muscle.
Internal surface shows an oblique line - mylohyoid line - gives attachment to mylohyoid muscle
This line separates sublingual fossa & submandibular fossa
Posterior to symphysis meant it presents two pairs of genial tubercles
Superior genial tubercle gives attachment to genioglossus muscle.
Inferior genial tubercle gives attachment to geniohyoid muscle
Below the mylohyoid line presents mylohyoid groove, transmitting mylohyoid nerve & vessels
Upper border presents sockets for lower teeth.
Lower border is rounded, presents digastric fossa gives attachment to anterior belly of digastric muscle.
Entire base give attachment to superficial lamella of investing layer of deep cervical fascia, deep lamella covers the submandibular gland and attaches to mylohyoid line.
in front of the attachment of investing layer, the base gives attachment to platysma muscle.
Ramus - an oblong flattened plate, extending upwards from the posterior aspect of body of mandible.
It presents two surfaces - medial & lateral
Four borders - superior, inferior, anterior & posterior
2 processes - coronoid & condylar process
Lateral surface - gives attachment to master muscle
Medial surface presents mandibular foramen transmitting inferior alveolar nerves & vessels. Anteromedial margin of the foramen presents a tongue shaped projection - lingua, gives attachment to sphenomandibular ligament.
Below the mlyohyoid groove gives attachment to medial pterygoid muscle.
Upper border presents mandibular notch transmitting masseteric nerve & vessels
Coronoid process gives attachment to temporals muscle.
Condylar process is convex in all sides, transversely elliptical. Articulates with anterior part of mandibular fossa of temporal bone forming temporomandibilar joint.
below the head presents a constricted part - the neck has a depression called pterygoid fovea, gives attachment to lateral pterygoid muscle. The head and neck gives attachment to capsule of temporo mandibular joint. Posterior border and lateral surface of neck gives attachment to lateral temporo mandibular ligament.
Below the capsular attachment the neck is related to auriculotemporal nerve.
The junction of lower and posterior borders forms the angle of the mandible which is 110 -115˚in adult mandible.
Posterior border is rounded related to parotid gland.
Age related changes of mandible :
In new born - the angle is 140˚, the mental foramen is close to the lower border. The coronoid process is higher than the condylar process
In adults - The angle is 110 -115˚, the mental foramen is midway between the superior and inferior border. The condylar process is higher than coronoid process.
In old age - the angle is 140˚, the mental foramen close to upper border due to absorption of alveolar border after the falling of teeth. The coronoid process is higher than the condylar process. Follow me in blogspot - human-anatomylessons.blogspot... _________________________________________________________________________________________________________________ Visit my blogs - humananatomyonline.in/
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