The Parotid Region of the Face

The parotid region is actually part of the neck but it extends into the facial region as well. It also must be studied before the infratemporal region can be examined. We will examine the parotid region from superficial to deep pointing out the gland itself and the structures running through it.

The parotid gland is a superficial structure located in the upper neck above the posterior belly of the digastric muscle. It is a salivary gland that has a large duct (pd) which crosses the masseter muscle to pierce the buccinator muscle opposite the upper 2nd molar tooth. The duct can frequently be rolled between the finger and the masseter muscle. The skin overlying the lower pole of the gland is supplied by the greater auricular nerve (ga), a branch of the cervical plexus. You have already identified the branches of the facial nerve appearing at the upper and anterior edges of the gland (yellow).

If the parotid gland is carefully removed, you can identify the structures located within it. The first plane is the venous plane and consists of the retromandibular vein (rm) and its tributaries and branches:

	st--superficial temporal
	rm--retromandibular vein
	m--maxillary vein
	ad--anterior division
	f--facial
	cf--common facial
	pd--posterior division
	pa--posterior auricular
	ej--external jugular

The common facial vein empties into the internal jugular vein and the external jugular into the subclavian vein near its junction with the internal jugular.

When the venous plane is removed we reach the important nervous plane. The importance of this plane is the presence of the facial (VII) nerve. The facial nerve leaves the skull through the stylomastoid foramen and immediately enters the deep part of the parotid gland where it gives off its branches:

	posterior auricular (pa)
	motor branch to posterior belly of digastric (db)
	temporal branch (t)
	zygomatic branch (z)
	buccal branches (b)
	mandibular branch (m)
	cervical branch (c)

Deep to the nerves lies the arterial plane which includes terminal parts of the external carotid artery and its branches:

	external carotid artery (EC)
	occipital artery (oc)
	maxillary artery (m)
	transverse facial artery (tf)
	superficial temporal artery

The deepest part of the parotid region is the parotid bed and houses the deep part of the gland which fills the small space between the neck of the condyle of the mandible (nc) and the mastoid process (m). Other structures forming the floor of this space are the :

	styloid process (sp)
	stylohyoid muscle (sh)
	stylopharyngeus muscle (sph)
	posterior belly of the digastric muscle (pbd)

The gland becomes infected and swollen in mumps. If you have had the mumps, you will realize just how difficult it is to open your mouth. Now, you can see why this is so. When you open the mouth, you narrow the parotid bed space and compress the deep parotid gland between the neck of the condyle and the mastoid process.

The Infratemporal Fossa and Muscles of Mastication

The infratemporal fossa is a small space between the ramus of the mandible and the lateral pterygoid plate of the sphenoid. On a skull, it is big enough for maybe 1 1/2 fingers but it has many things in it. Following is a tabulation of the infratemporal fossa and all of its contents.

The lateral wall of the infratemporal fossa is noted in the 1st image and consists of the

ramus (4)

	coronoid process (1)
	head of condyle (2)
	neck of condyle (3)

body (5)

angle (6)

Medial wall:
lateral pterygoid plate (1)
Roof;
greater wing of sphenoid (3)
includes foramen ovale & foramen
spinosum
Posteriorly:
styloid process (4)

There are four muscles of mastication on each side that control the movement of the mandible:

	masseter
	medial pterygoid
	lateral pterygoid
	temporalis

The lateral pterygoid is the main muscle that opens the mouth. It is helped from gravity and a couple of neck muscles. It opens the jaw by pulling forward on the neck of the mandible and causing the jaw to drop.

The artery entering the infratemporal fossa is the maxillary branch of the external carotid artery. As can be seen, it has many branches (11 in all). You will probably not be responsible for all of them but I have included them all for completeness.

Maxillary artery

	deep auricular (da)
	anterior tympanic (at)
	middle meningeal (mm)
	accessory middle meningeal (amm)
	inferior alveolar (ia)
	buccal (b)
	deep temporal (dt)
	posterior superior alveolar (psa)
	descending palatine (dp)
	infraorbital (io)
	sphenopalatine (sp)

External carotid artery (ec)

	occipital (oc)
	transverse facial (tf)
	superficial temporal (st)

The sphenopalatine and descending palatine arteries pass through a small space between the pterygoid process of the sphenoid and the maxilla, the pterygomaxillary fissure.

The mandibular nerve (V3) is the nerve of the infratemporal fossa and is responsible for supplying the muscles of mastication plus two tensor muscles: 1) tensor palati and 2) tensor tympani. The branches are as follows:

deep temporal (dt)

auriculotemporal (at)

inferior alveolar (ia)

nerve to the mylohyoid (nmh)

lingual (l)

buccal (b)

branches to lateral pterygoid (not labeled)

Not shown:

	meningeal branch
	nerve to masseter

The Temporomandibular Joint (TMJ)

The temporomandibular joint (tmj) is a synovial type joint separated by an interarticular disc. The disc splits the joint into two separate joints. The upper joint (ujc) is between the mandibular (articular) fossa of the temporal bone and the articular disk and provides a sliding motion when the lateral pterygoid contracts and pulls the condyle and disc forward.

The lower joint (ljc) is between the articular disc and the head of the condyle of the mandible. The action here is a hinge-like action, in which the mandible drops, thereby opening the mouth.

When dentition or muscle action is not in proper alignment, the joint can be secondarily affected and pain can ensue. This is TMJ disease and requires dental specialists to correct the problem.

Table of Muscles

Muscle	Origin	Insertion	Action	Nerve Supply
masseter	zygomatic arch	ramus & angle of mandible	closes mouth	muscular branch (V3)
medial pterygoid	medial surface of lateral pterygoid plate and maxillary tuberosity	medial surface of ramus and angle of mandible	closes mouth and helps protrude mandible	muscular branch (V3)
lateral pterygoid	upper head: greater wing of sphenoid lower head: lateral surface of lateral pterygoid plate	upper head: articular disc lower head: neck of condyle	open and protrudes mandible, moves mandible side to side	muscular branch (V3)
temporalis	temporal fossa	coronoid process and anterior border of ramus	closes and retracts mandible	muscular branch (V3)

Summary of Items in This Lesson

Bones

Mandible

body

angle

ramus

condyle

head

neck

coronoid process

mental foramen

Temporal bone

Mastoid process

styloid process

stylomastoid foramen

mandibular (or articular) fossa

Temporomandibular joint

articular disc

Sphenoid bone

greater wing

foramen ovale

foramen spinosum

pterygoid process

lateral pterygoid plate

Pterygomaxillary fissure

Posterior surface of maxilla

posterior superior alevolar foramina

Muscles

Masseter

Medial pterygoid

Lateral pterygoid

upper belly

lower belly

Temporalis

Nerves

Mandibular division of trigeminal (V3)

auriculotemporal

deep temporal

inferior alveolar

nerve to mylohyoid

lingual

chorda tympani

buccal

muscular branches

muscles of mastication

tensor palati

tensor tympani

Nerves (contd.)

Facial (VII)

posterior auricular

tympanic

zygomatic

buccal

mandibular

cervical

branch to posterior belly of the digastric

Arteries

external carotid

occipital

maxillary

inferior alveolar

middle meningeal

accessory middle meningeal (if present)

deep temporal

buccal

posterior superior alveolar branches

descending palatine

sphenopalatine

infraorbital

transverse facial

superficial temporal

Veins

superficial temporal

maxillary

retromandibular

anterior division

facial

common facial

posterior division

posterior auricular

external jugular

Viscera

parotid gland

parotid duct

Pharynx

Parts of the pharynx have been identified when the carotid triangle of the neck was discussed. Now that the head and cervical viscera have been separated, you can identify the pharyngeal muscles and the structures that lie lateral to them.

The muscles of the pharynx consists of three pharyngeal constrictors:

	superior
	middle
	inferior

and the stylopharyngeus and palatopharyngeus muscles.

The three constrictors are nested within each other from the top down. You might visualize the constrictors as three cone-shaped cups fitting within each other. The superior fits into the middle which fits into the inferior. The only thing wrong with this picture is that the cups are open on one side. These openings are the nasal cavity, oral cavity and the larynx. Now take a look at the pharynx from the back.

When you first observe the back of the pharynx, you will want to identify the structures that run parallel to its lateral surface:

	glossopharyngeal nerve (IX)
	vagus (X)
	spinal accessory nerve (XI)
	hypoglossal nerve (XII)
	common carotid artery (CC)
	internal jugular vein (IJ)
	carotid sheath (CS)

In this image, the carotid sheath and its contents has been removed in order to show the stylopharyngeus muscle (SP). One reason to be able to identify the stylopharyngeus muscle is that the glossopharyngeal nerve (IX) runs along its posterior surface and can always be identified at this point. The stylopharyngeus muscle also extends between the superior and middle pharyngeal constrictors and can be used to separate these two muscles.

Finally, identify the three pharyngeal constrictors. Before identifying the pharyngeal constrictors, you should first memorize their origins and then you won't have trouble picking them out during a dissection or an examination.

The superior pharyngeal constrictor (SC) arises from the hamulus of the medial pterygoid plate and the pterygomandibular raphe which extends from the hamulus to the lingula of the mandible. This origin is not easy to point out so you will usually identify the other two constrictors first.

The middle pharyngeal constrictor (MC) arises from the greater horn of the hyoid bone (GH). This structures can always be seen or felt.

The inferior pharyngeal constrictor (IC) arises from the thyroid and cartilages which are also obvious structures.

The inferior pharyngeal constrictor continues as the esophagus (ES).

The constrictors join in the mid line posteriorly as a seam (pharyngeal raphe) which is suspended form the pharyngeal tubercle on bottom of the occipital bone.

We will cover the nerve supply of the pharynx later.

Along the lateral sides of the pharynx, you will find four gaps associated with the superior, middle and inferior constrictors. Specific structures pass through each of these gaps.

Above the superior pharyngeal constrictor:

auditory tube (AT)
levator palati (LP)
ascending palatine artery (APA)

Between the superior and middle constrictors:

stylopharyngeus muscle (SP)
glossopharyngeal nerve (IX)

Between the middle and inferior constrictors:

internal laryngeal branch of the superior laryngeal nerve (IL)
superior laryngeal artery from the superior thyroid artery (SLA)

Below the inferior constrictor:

inferior laryngeal nerve ( ILN) (recurrent laryngeal branch of the vagus)
inferior laryngeal artery (ILA) (inferior thyroid)

Pharyngeal Cavity as Viewed From the Back

After the pharynx has been cleaned from the back and the pharyngeal constrictors are identified, the pharynx can be opened and the anterior relationships exposed.
What you should be able to identify are:

	nasopharynx (arrow)
	oral pharynx (where tongue is seen)
	laryngeal pharynx (larynx).

If you inserted you finger into each one of these, you would enter the nasal cavity, oral cavity and larynx from behind. To have another view of this same relationship, see the following section.

Sagittal Section of the Head and Neck

There comes a point in the anatomy laboratory when the body must be divided into strange sections in order to study its innermost parts. One of these divisions is the sagittal section of the had and neck. This will aid in the visualization of the nasal cavity, oral cavity and the larynx. Once smaller pieces of the head and neck are produced, it becomes difficult to know what is anterior, posterior, up or down. You should make it a habit to pick out a structure that you can always identify (such as the mandible, tip of nose, tip of tongue, etc.) and use this to give you the proper orientation. Every time you walk up to a cadaver, or look at an image, the first thing to do is orient yourself. Orientation is very important!!!

Once the head and neck have been separated into left and right halves, you can see relationships of the nasal cavity, oral cavity and larynx to the pharynx. These cavities function as part of the respiratory and gastrointestinal systems. You will notice in the diagram that the two systems merge. I am sure that most of you have experienced choking after inhaling fluid or food instead of swallowing it.
Air flows through both the nasal cavity and oral cavity to travel through the nasopharynx and oropharynx respectively before entering the larynx.
Food travels through the oropharynx, down the laryngopharynx and into the esophagus. The innervation to this area, both motor and sensory, is important in keeping the pathways functioning properly. We will cover the nerve supply in future sessions.

Remember to orient yourself when you look at these images.
I usually use the mandible (M) or maxilla (Mx) as a starting point. Then I look for the tip of the tongue or tip of the nose.
Once oriented with the sagittal section, identify the nasal cavity, the oral cavity with the tongue, the epiglottis and larynx.
The borders of the naso-, oro-, and laryngopharynges are arbitrary and shown as red dotted lines in the diagram. Classically, the anterior border of the opening of the auditory tube and tip of uvula for the nasopharynx, the palatoglossal fold and upper border of epiglottis for the oropharynx and the opening of the larynx for the laryngopharynx. Nasopharynx (np), oropharynx (op), and laryngopharynx (lp).
Posterior to the pharynx, you can identify the atlas (C1), axis (C2) and the remaining cervical vertebrae. You can also see the spinal cord passing through the vertebral canal (yellow).

Innervation of the Pharynx

Motor Innervation

glossopharyngeal (IX)
vagus (X) and allied spinal accessory (XI)
recurrent laryngeal

Sensory Innervation

glossopharyngeal (IX to oropharynx region
vagus (X) to remainder of pharynx

AFGALALY محمد عبد الفتاح جلال

The Parotid Region of the Face

The Infratemporal Fossa and Muscles of Mastication

The Temporomandibular Joint (TMJ)

Table of Muscles

Summary of Items in This Lesson

Pharynx

Pharyngeal Cavity as Viewed From the Back

Sagittal Section of the Head and Neck

Innervation of the Pharynx