Module - Articulation and & Craniofacial skeleton

Buccal cavity

is the space between the teeth and cheeks.

Buccal cavity

varies greatly both in size and dimension. It varies greatly both in size & dimension. The space is bund by the lips and cheeks externally, and by the gums and teeth internally.

Nasal cavity

is divided sagittally by the bony & cartilaginous nasal septum .

Nasal cavity

It is bound anteriorly by the nares [openings in the nose]. It is bound posteriorly by the floor by the nasopharyngeal wall. It is bound inferiorly by the floor of the nose {roof of the mouth]. The lateral walls contain the conchae which serve to increase the surface area.

oral cavity

is bound anteriorly & laterally by the teeth & alveolar ridge.

oral cavity

It is bound superiorly by the hard & soft palate. It is bound posteriorly by the anterior faucial pillars [tonsils]. It is bound inferiorly by the floor of the mouth.

Pharynx

is a musculomembranous tube that extends from the base of the skull to the inferior portion of the cricoid cartilage.

nasopharynx

above the level of the soft palate.

oropharynx

extends from the soft palate to the hyoid bone.

Laryngoharanyx

Extends from the hyoid bone to the esphagus.

Oribicularis Oris

is the primary muscle of the lips. It is an oval ring of muscles located within the lips. It completely circles the oral opening. It is composed of short fibers that overlap in a circular fashion. It is a sphincter muscle.

Oribicularis Oris

Function

A. When active, it closes the mouth & puckers the lips.

B. When activated with other muscles, it will close the mouth in a straight line.

Buccinator

• is the primary muscle of the cheek. It is the deepest of the facial muscles. It originates on the pterygomandibular ligament (hamulus to the last molar). 

• It courses horizontally & anteriorly. 

• Its fibers decussate [cross] at the corners of the oral cavity to insert into OO.

Buccinator

Function - Draws the corners of the mouth laterally.

Risorius

Origin - Fascia covering masseter.

Risorius

course - horizontally & anteriorly. Parallel & superficial to buccinator.

Risorius

insert - skin & mucosa at corners of oral cavity.

Risorius

Function - assists in drawing corners of the mouth laterally.

Risorius

• Innervation - buccal branch of facial nerve. 

• Action - pulls the corner of the mouth laterally. 

  • Grinning and laughing 

zygomatic major

origin - surface of zygomatic bone

zygomatic major

course - inferiorly & medially

zygomatic major

insert - OO and skin at corner of oral cavity.

zygomatic major

Draws corner of mouth superiorly & laterally to form a broad smile. “The Big Smile” Muscle

Levator Labii Superior 

• Origin - lower margin of the orbit of the eye 

 Levator Labii Superior

Course - inferiorly

 Levator Labii Superior

• Insert - upper lip, lateral to levator anguli oris 

 Levator Labii Superior

• Function - elevates the uper lip. 

  • “The sneer.” “The Elvis Muscle.”

Depressor Labii Inferior 

Origin - mandible, just lateral to midline

Depressor Labii Inferior

Course - superiorly and medially

Depressor Labii Inferior

Function - draws lower lip inferiorly and laterally.

Depressor Labii Inferior 

Insert - lower lip

Levator Anguli Oris

• Origin - lateral to the nasal ala

Levator Anguli Oris

Course - inferiorly

Levator Anguli Oris

Insert - Into OO with some fibers decussating to the lower lip.

Levator Anguli Oris

Function - draws corners of the oral cavity superiorly & aids in closing the lower lip

Depressor Anguli Oris

• Origin - mandible, slightly lateral to midline 

Depressor Anguli Oris

Course - superior

Depressor Anguli Oris

• Insertion - OO with some fibers crossing to upper lip

Depressor Anguli Oris

Function - depresses the angle of the lip and draws the upper lip down.

Mentalis

• Origin - Mental tuberosity of the mandible 

Mentalis

Course - superior

Mentalis

• Insertion - some fibers insert into the chin, some into OO. 

Mentalis

Function - Contraction will evert the lower lip, wrinkle the chin, and stiffen the lower lip so that the mouth can be closed in a line.

Anterior Belly of Digastric

Recall that the anterior belly of digastric  is also an extrinsic laryngeal muscle - suprahyoid group.

Anterior Belly of Digastric

• As a group, extrinsic laryngeal muscles will have an effect on the larynx as a whole. 

Anterior Belly of Digastric

• As a suprahyoid muscle, the anterior belly of digastric will also elevate  or raise the larynx. 

Posterior belly of digastric

Recall that the posterior belly of digastric is also part of the suprahyoid class of extrinsic laryngeal muscles.

Posterior belly of digastric

It will also elevate or raise the larynx.

Mylohyoid

• forms the floor of the mouth. 

• It is believed that mylohyoid primarily functions as a laryngeal elevator (an extrinsic laryngeal muscle, suprahyoid group).

Mylohyoid

• It is believed that mylohyoid has minimal effect as a mandibular depressor. 

Geniohyoid

• is also part of the suprahyoid class of extrinsic laryngeal muscles. 

It will also raise or elevate the larynx.

Geniohyoid

It is deep into mylohyids.

Lateral or external pterygoid

• This muscle will protrude the mandible by sliding the condyle inferiorly and anteriorly.

Lateral or external pterygoid

Also assists in lowering or opening the mandible. Also moves the mandible side to side [laterally].

Platysma

• There is also a muscle that may have 2 functions - 

  • 1). Mandibular depressor 

  • 2). Muscle of facial expression (pulls lower lip down).

Platysma

Origin - fascia covering pectoralis major and deltoid muscles

Platysma

Course - superiorly

Platysma

• Insertion - lateral aspects of orbicularis oris, the inferior margin of the mandible, and some fibers inserting into masseter & risorius. 

Platysma

Function - Depress the mandible. May also aid in facial expression by drawing the lower lip & corner of the lip downward.

Mandibular elevators

• 1. Masseter 

• 2. Temporalis 

• 3. Medial or internal pterygoid 

• are more powerful because they work against gravity when they close the lower jaw.

mandible elevators

There are 3 muscles that serve as mandibular elevators, meaning that they will raise or elevate the mandible.

mandible depressors

are named because they depress or lower the mandible. The mandible is open when it is lowered.

mandible depressors

• 1. Anterior belly of digastric 

• 2. Posterior belly of digastric 

• 3. Mylohyoid 

• 4. Geniohyoid 

• 5. Lateral or external pterygoid 

• 6. Platysma

• Some of these muscles are also laryngeal muscles!

Masseter

• is a very powerful  jaw muscle. 

• Elevates the mandible. May also move the mandible laterally or side to side, as when chewing. 

Temporalis

• This muscle covers the temporal bone, one of the cranial bones. 

• It will elevate and retract the mandible.

Medial or internal pterygoid

• This muscle will form a sling with a masseter in order to elevate or close the 

mandible. 

Medial (internal) pterygoid

O: between lateral and medial pterygoid plates of sphenoid

Medial (internal) pterygoid

C- inferior, posterior, and lateral

Medial (Internal) pterygoid

I - medial surface of ramus and angle of mandible

Medial (Internal) pterygoid

F- forms a sling with masseter to elevate mandible.

Temporalis

O - entire temporal bone

Temporalis

C- fibers converse as they travel inferiorly under the zygomatic arch

Temporalis

I- anterior border or ramus and along coronoid process

Temporalis

F - elevates and retracts mandible

Masseter

very powerful jaw muscles

Masseter

O - zygomatic arch

Masseter

C - inferior and posterior

Masseter

I - angle, ramus, and coronoid process

Masseter

F - elevates jaw

Lateral (external) pterygoid

O -greater wing of sphenoid and lateral ptyergoid plate

Lateral (external) pterygoid

C- horizontally posterior

Lateral (external) pterygoid

I - condyle of mandible

Lateral (external) pterygoid

F - protudes mandible by sliding condyle down and forward.

Geniohyoid

O -lower part of mental symphysis

Geniohyoid

C- posterior and inferior

Geniohyoid

I - body of hyoid

Geniohyoid

F - depress mandible

Mylohyoid

O - inner surface on mandible near mental symphysis to last molar.

Mylohyoid

 muscular floor of the mouth

Mylohyoid

C - inferior and medial

Mylohyoid

I - meets fibers from other sides; posterior fibers insert directly into the hyoid

Mylohyoid

F - minimal help in lowering jaw

Posterior belly of digastric

O - mastoid process of temporal bone

Posterior belly of digastric

C - inferior and anterior

Posterior belly of digastric

I - meets anterior belly at intermediate tendon

Posterior belly of digastric

F - depresses mandible

Anterior belly of digastric

O - lower border of mandible 

Anterior belly of digastric

C - inferior and posterior

Anterior belly of digastric

I - intermediate tendon

Anterior belly of digastric -

F - depresses mandible