1: The Muscles of the Scalp are the occipito-frontalis muscle and the muscles of the external ear.

The Occipito-Frontalis muscle does not act on any joint.

The posterior part of the muscle fibres, arising from the outer two-thirds of the superior curved line of the occipital bone, are inserted into the epicranial aponeurosis; the anterior part arises from the epicranial aponeurosis and blends with muscles round the orbital margins.

The epicranial aponeurosis is a thick fascial membrane attached posteriorly to the superior curved lines of the occipital bone, laterally to the temporal bone; anteriorly, it blends with the deep fascia.

Nerve-supply-facial.

2. The Muscles of Expression are a large number of small muscles in the face which generally have bony origins, but are inserted into the fascia or blend with other muscles; they are in three groups, associated with the eye, the nose, and the mouth.

Nerve supply-facial.

3. The Muscles of Mastication are those acting on the temporo-mandibular joint, causing movement of the lower jaw ; the muscles which depress the lower jaw are muscles of the neck, not true muscles of mastication.

Action.

Muscle.

Origin.

Insertion.

Nerve-supply.

Raising or closing of the jaw

Masseter

From the anterior two-thirds of the lower border of the zygoma and the inner surface in its whole length

The outer surface of the ramus and angle of the lower jaw

Inferior maxillary division of the fifth

Temporal

The whole of the temporal fossa and fascia covering it

The inner surface and apex of coronoid process and anterior border of the ramus of the lower jaw

Same as above

Internal pterygoid

From the inner surface of the external pterygoid plate and from the tuberosity of the maxilla

The inner surface of the angle of the lower jaw

Same as above

Protrusion

External pterygoid

From the under surface of the great wing of the sphenoid and the outer surface of the external pterygoid plate

The anterior border of the neck of the lower jaw, the inter-articular cartilage, and the capsule

Same as above

Internal pterygoid

See above

Protrusion

(contd.)

Temporal

(anterior fibres)

From the under surface of the great wing of the sphenoid and the outer surface of the external pterygoid plate

Retraction

Temporal

(posterior fibres)

See above

Lateral movement

External

Pterygoid of one side

Internal

The Buccinator muscle is also a muscle of mastication, but has no action on the jaw; it is the muscle of the cheek, and by its contraction prevents food from collecting on one side.

Muscle.

Origin.

Insertion.

Nerve-supply,

Buccinator

From the alveolar arches of the upper and lower jaw and from the pterigo-mandibular ligament

The fibres pass forward and blend with the muscles round the mouth

Branches from both fifth and seventh nerves