Parotid Region and Gland Anatomy

Parotid Region

• A posterolateral part of the facial region
• Contains the parotid gland and duct, parotid plexus of the facial nerve (CN VII), retromandibular vein, external carotid artery, and masseter muscle
• Limited superiorly by the zygomatic arch
• Limited anteriorly by the anterior border of the masseter muscle
• Limited posteriorly by the external ear and anterior border of the sternocleidomastoid muscle
• Limited medially by the mandibular ramus
• Limited inferiorly by the angle and inferior border of the mandible

Parotid Gland

• The largest of the three paired salivary glands
• Prismatic and triangular in shape since it occupies the parotid bed
• Antero-inferior to the external acoustic meatus where it forms like a wedge between the mandibular ramus and mastoid process
• Adipose tissue between the lobes provides flexibility for mandibular movement
• The lateral subcutaneous surface of the parotid is almost flat
• Described by Rouvière as an inverted pyramid filling a deep, anfractuous excavation called the parotid bed, conforming to its walls
• Configuration includes three surfaces (anterior, posterior, and lateral), two extremes (superior and inferior), and three borders (anterior, posterior, and medial)
• The apex is posterior to the angle of the mandible
• The base relates to the zygomatic arch
• The parotid fascia (sheath or capsule) is strong and resistant, surrounding the parotid; it derives from the superficial layer of the deep cervical fascia
• The parotid duct runs horizontally from the anterior border of the gland, turns medially at the anterior border of the masseter, pierces the buccinator, and enters the oral cavity via a small opening opposite the 2nd maxillary molar
• Embedded structures include the parotid plexus of the facial nerve (CN VII) and its branches, retromandibular vein, and external carotid artery
• Parotid lymph nodes are located on the parotid fascia and within the gland
• The submandibular gland is primarily located during dissection of the submandibular triangle of the neck
• Sublingual glands are found when dissecting the inferior wall of the mouth
• Innervation does not directly innervate to the gland, even though the parotid plexus of CN VII is immersed within the gland
• Auriculotemporal nerve (branch of NC V3) closely associated with the parotid gland, running superiorly to it along with the temporal and superficial vessels; along with the greater auricular nerve, it innervates the parotid fascia and overlying skin
• The Glossopharyngeal nerve (NC IX) carries pre-synaptic secretory fibers to the otic ganglion
• Postsynaptic parasympathetic fibers run from the otic ganglion to the gland via the auriculotemporal nerve
• Stimulation of parasympathetic fibers leads to watery and light salivary secretion
• Sympathetic fibers derive from the cervical ganglia via the external carotid nerve plexus, which can reduce gland secretion through vasomotor activity
• Sensory nerve fibers reach the gland via the greater auricular and auriculotemporal nerves

Pterygopalatine Fossa

• A small, pyramidal space inferior to the orbital apex and medial to the infratemporal fossa
• Situated between the pterygoid process of the sphenoid posteriorly and the rounded posterior face of the maxilla anteriorly
• Connects various pathways to main compartments of the viscerocranium
• Consists of a medial wall formed by the perpendicular lamina of the palatine bone
• Superior wall is incomplete, formed by the medial continuation of the infratemporal surface of the greater wing of the sphenoid
• The inferior wall is formed by the pyramidal process of the palatine bone
• Posterior wall is traversed by the maxillary nerve (NC V2) via the foramen rotundum, providing two branches to the pterygopalatine ganglion inside the fossa
• The wide, superior extreme opens anterosuperiorly into the inferior orbital fissure
• Narrow, the inferior extreme continues into the greater and lesser palatine canals
• Composition involves the terminal portion (pterygopalatine or third) of the maxillary artery, satellite veins, maxillary nerve (NC V2), vascular nerve sheaths, and adipose matrix filling the remaining space
• The anterior wall is formed by the medial part of the maxillary tuberosity
• The posterior wall is composed of the anterior aspect of the pterygoid apophysis, with the pterygoid canal opening in the upper portion
• The medial wall is formed by the perpendicular lamina of the palatine bone, which connects the pterygopalatine fossa with the nasal cavities
• The base is superiorly oriented relative to the orbit through the inferior orbital fissure
• Vertex is located inferiorly, connecting the pterygoid apophysis of the sphenoid bone and the pyramidal apophysis of the palatine bone with the maxillary tuberosity, and the entry of the greater and lesser palatine canals
• No Lateral Wall: The communication is called pterygomaxillary fissure, and it may be partially masked by the anterior end of the infratemporal crest; it goes to the infratemporal fossa
• The pterygopalatine portion is the third part of the maxillary artery, located anteriorly to the lateral pterygoid muscle, located medially via the pterygomaxillary fissure, and gives off branches accompanying all nerves entering and exiting the fossa

Maxillary Nerve

• Passes anteriorly through the foramen rotundum and penetrates the pterygopalatine fossa via its posterior wall giving rise to the zygomatic nerve, which divides into zygomaticofacial and zygomaticotemporal branches that provide general sensation to the lateral cheek and temple
• Also gives off ganglionic branches for the pterygopalatine ganglion and has sensory fibers to the maxillary nerve that cross the Pterigopalatine ganglion without synapsing and innervate the nose, palate, and pharynx
• Leaves the pterygopalatine fossa through the orbital fissure and becomes the infraorbital nerve
• Furthermore, parasympathetic fibers of the pterygopalatine ganglion originate from the facial nerve, and continue through the lesser petrosal nerve
• The pterygoid canal nerve runs anteriorly through the lacerated foramen to the pterygopalatine fossa; it carries parasympathetic fibers from the facial nerve to the pterygopalatine ganglion and sympathetic fibers from the internal carotid plexus to the ganglion
• The greater petrosal nerve and the lesser form the pterygoid canal nerve
• The sympathetic post-synaptic fibers innervate the palatine glands, the nasal cavity mucous membranes, and the superior part of the pharynx

Nose

• Is a structure containing the peripheral olfactory organ and is part of the upper respiratory tract superior to the hard palate
• Consists of the nasal cavity and external nose separated by the nasal septum
• Responsible for olfaction, respiration, filtering of dust, humidifying inhaled air, and the removal of secretions from paranasal sinuses and nasolacrimal ducts
• The external nose is composed of bone and hyaline cartilage varying in size and shape across individuals
• Dorsum: extends from the root to apex (tip) of the nose
• The nares (anterior nasal apertures) are two piriform openings through the inferior surface of the nose and between the alae laterally
• The superior bony part of the nose is covered by thin skin, while the cartilaginous part is covered by thicker skin with sebaceous glands
• The nasal vestibule contains vibrissae (rigid hairs) that filter the incoming air
• The nasal skeleton is composed of bone and hyaline cartilage
• The bony part of the nose is formed by the nasal bones, frontal processes of the maxillae, the nasal part of the frontal bone, and the bony part of the nasal septum
• Compised: the cartilaginous part has five primary cartilages: two lateral, two alar (U-shaped, free, and mobile; dilate or contract the nares when the muscles acting on the nose contract) and one cartilage of the nasal septum
• The nasal septum separates the nose into two nasal cavities, has a bony and pliable cartilaginous part
• Components of the nasal septum include the perpendicular plate of the ethmoid, vomer, and the septal cartilage
• The perpendicular plate of the ethmoid forms the superior aspect of the nasal septum
• Vomer forms the posteroinferior part of the nasal septum with contribution to nasal crests of the maxillary and palatine bones
• Septal cartilage articulates with bony septal edges
• The nasal cavity is a whole, or either of its halves that communicate anteriorly through the nostrils, and posteriorly through the choanae to become the nasopharynx; lined by mucous membrane, except for the nasal vestibule, which is lined by skin
• The nasal mucous Is bound firmly to the periosteum and perichondrium of the nasal cavity's supporting bones and cartilages
• Is continuous: also continues with the lining of the nasopharynx, paranasal sinuses, and the lacrimal sac and conjuntiva
• The respiratory area makes up the lower two-thirds of the nasal cavity and warms/humidifies the air prior to lung entry
• The Olfactory area: sensory area for olfaction
• Limits: superior, inferior, medial and lateral
• The superior wall is curved and narrow, but widens posteriorly where it joins the body of the sphenoid
• The floor, inferior wall, is wider than the walls above it and is formed by the palatine processes of the maxilla and the horizontal plates of the palatine bone
• The medial wall is formed by the nasal septum
• The lateral wall are highly irregular, as they contain three bony projections called the nasal conchae that protrude inferiorly towards the floor

Nasal Cavity Characteristics

• Nasal conchae (supreme, superior, middle, and inferior) protrude inferomedially
• The supreme and middle conchae are part of the ethmoid bone, the inferior concha is the largest and is formed by an independent bone that contain large vascular spaces in the mucosa
• Nasal meatuses are recesses under each conchae where nasal cavity is divided into five passages
• Sphenoethmoidal Recess: drains air cells of the sphenoidal sinus
• Three meatuses: The narrow passage is between the superior and middle nasal conchae in which posterior ethmoidal cells drain and the mid. The anterior superior part leads to the Ethmoidal Infundibulum so the channel communicates with the frontal sinus
• One Common Nasal Meatus: is the medial aspect of nasal cavity between conchae & nasal septum with the 4 lateral drainages
• The Frontonasal Duct: runs along the frontal sinus
• Semilunar hiatus is a semicircular groove where the frontal sinus drains
• The ethmoidal bulla is a rounded elevation above the semilunar hiatus that is formed from middle ethmoidal air cells

Vasculatization & Innervation of the Nose

• Arterial irrigation comes from five sources to both the septal and lateral walls; ethmoidal (ant. & post) , sphenopalatine, greater palatine, and branches from facial arteries
• The first three arteries branch into Medial (septal) and lateral arteries
• Plexus of Kiesselbach: arterial anastomoses on anterior nasal septum
• The nose Receives Arterial Supply: from listed arteries and nasal branches of facial artery
• Venous Supply: from submucosal venous plexus draining Ethmoidal, Facial, and Opthalmic Veins The nose: this is the reason the heat exchange takes place in warm air of the lungs. Facial Vein: most of venous blood is transported by this vein through the angular and lateral nasal veins