anatomy

2. Muscles of mastication
Temporalis :
Origin: Temporal fossa and temporal fascia
Insertion: margin and deep surface of Coronoid process.
Nerve supply: deep temporal nerve.
Action : Elevation & protrusion of mandible and Side to
side grinding movement.

3. Origin:
Masseter:
Origin:
Superficial layer: anterior 2/3rd of lower border zygomatic arch
Middle layer: from anterior 2/3rd of deep surface & post. 1/3rd of
lower border of Zygomatic arch.
Deep layer: deep surface of zygomatic arch
Insertion
Superficial layer to lower part
Middle layer to middle part
Deep layer to upper part of lateral surface of mandible.
Nerve supply: masseteric nerve,
Action: Elevation of mandible during chewing.

4. Lateral pterygoid:
Origin of Upper head : Infratemporal surface and crest of greater wing of
sphenoid bone.
Origin of Lower head: Lateral surface of lateral pterygoid plate.
Insertion
I. Pterygoid fovea
II. Articular disc and capsule of TMJ
Nerve supply: Ant. division of mandibular nerve
Action: Depress and protrude the mandible, assist in grinding movement

5. Medial pterygoid:
Origin:
Superficial head from tuberosity of maxilla &
Deep head from medial surface of lateral pterygoid plate.
Insertion: medial surface of ramus of mandible.
Nerve supply: nerve to medial Pterygoid, br. Of main trunk
of mandibular nerve.
Action: elevation of mandible, grinding movement.

6. MylohyoidMylohyoid
O: Mylohyoid line on mandible
I; Body of hyoid bone and fibers from muscle on opposite
side
N: Mylohyoid nerve from inferior alveolar branch of
mandibular nerve
A: Support and elevation of floor of mouth; elevation of hyoid
Fixed mandible elevates and pulls hyoid bone forward; fixed
hyoid bone pulls mandible downward and in-ward

7. Geniohyoid
O: Inferior mental spine on inner surface of mandible
I; Anterior surface of body of hyoid bone
N: Branch from anterior ramus of C1 (carried along the hypoglossal
nerve)
A; Fixed mandible elevates and pulls hyoid bone forward; fixed hyoid
bone pulls mandible downward and in-ward

8. Sternohyoid
O; Posterior aspect of sternoclavicular joint and adjacent
manubrium of sternum
I; Body of hyoid bone medial to attachment of omohyoid
muscle
N; Anterior rami of C1 to C3 through the ansa cervicalis
A: Depresses hyoid bone after swallowing

9. Omohyoid
O; Superior border of scapula medial to suprascapular notch
I; Lower border of body of hyoid bone just lateral to
attachment of sternohyoid
N; Anterior rami of C1 to C3 through the ansa cervicalis
A; Depresses and fixes hyoid bone

11. Thyrohyoid
O; Oblique line on lamina of thyroid cartilage
I; Greater horn and adjacent aspect of body of hyoid bone
N; Fibers from anterior ramus of C1 carried along hypoglossal nerve
A; Depresses hyoid bone, but when hyoid bone is fixed raises larynx

12. Sternothyroid
O; Posterior surface of manubrium of sternum
I; Oblique line on lamina of thyroid cartilage
N: Anterior rami of C1 to C3 through the ansa cervicalis
A; Draws larynx (thyroid cartilage) downward

13. Trapezius
O ; Superior nuchal line; external occipital protuberance; ligamentum
nuchae; spinous processes of vertebrae CVII to TXII
I: Lateral one-third of clavicle; acromion; spine of scapula
N; Motor-accessory nerve [XI]; proprioception-C3 and C4
A: Assists in rotating the scapula during abduction of humerus above
horizontal; upper fibers-elevate, middle fibers-adduct, lower fibers-
depress scapula

14. Sternocleidomastoid muscle
O; Upper part of anterior surface of manubrium of sternum
I; Lateral one-half of superior nuchal line
O; Superior surface of medial one-third of clavicle
I : Lateral surface of mastoid process
N : Accessory nerve [XI] and branches from anterior rami of C2 to C3 (C4)
A: Individually-will tilt head to-wards shoulder on same side rotating head to turn face
to opposite side; acting to-gether, draw head forwards

16. Torticollis or wry neck- deformity in which the head bent to one
side and the chin points to the other side
1. Rheumatic torticollis- due to exposure to cold or draught
2. Reflex torticollis- due to inflamed or suppurating cervical
lymph nodes which irritate the spinal accessory nerve
3. Congenital torticollis- due to birth injury
4. Spasmodic torticollis- due to central irritation on CN-XI.

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