Head and Neck Flashcards
Bony Orbit: Gross Anatomy
The orbit is a feature of the face and contains the globe
Has a roof, floor, medial and lateral wall - four sided pyramid with the apex posterior and the base forming the orbital margin
Orbit open anterior, but bound by the orbital septum
Communicates with the intracranial compartment via the optic canal and superior orbital fissure
Bones of the orbit
The bony orbit is made up of:
- Maxillary bone
- Lacrimal bone
- Ethmoid bone
- Zygomatic bone
- Frontal bone
- Orbital process of the palatine bone
- Greater and lesser wings of the sphenoid
Spaces of the Orbit
- Globe
- divided into anterior and posterior chambers by the lens
- parts: lens, iris, sclera, choroid, retina, vitreous humour
- Extraconal space contents
- fat
- lacrimal gland and sac
- inferior opthalmic vein and portion of the superior ophthalmic vein
- extraconal branches of the opthalmic artery (eg. lacrimal artery) - initially intraconal then becomes extraconal
- Conal space contents
- extraocular muscles (LR, MR, SR, IR, SO, IO)
- interconnecting fascia
- Intraconal space
- formed by the posterior half of the globe and the sides are formed by the extraocular muscles which pass posteriorly and converge on the tendinous ring at the orbital apex
- contents
- orbital fat
- intraconal branches of the ophthalmic artery
- superior ophthalmic vein
- cranial nerves III, IV, V1, VI
- Optic nerve-sheath complex
- optic nerve
- ophthalmic artery
- central retinal artery (branch of opthalmic artery) and vein
- surrounding sheath of meninges as an extension of the cerebral meninges
Communication with the orbit
- Optic canal to intracranial cavity
- Superior orbital fissure also to the intracranial cavity
- Inferior orbital fissure to infratemporal fossa
- Anterior ethmoidal foramen
- Posterior ethmoidal foramen
- Supra and infra orbital foramen
- Nasolacrimal foramen
Ethmoid Sinus: Description
The ethmoid air cells form one of the four pairs of paranasal sinuses.
Location: within the midline ethmoid bone between the orbits
Ethmoid Sinus: Gross Anatomy
- 3-18 air cells separated by bony septa within each lateral mass of the ethmoid bone
- The air cells are separated into anterior and posterior by the basal lamella, the lateral attachment of the middle concha
- The anterior ethmoid air cells drain the hiatus semilunaris and middle meatus
- The posterior ethmoid air cells drain the superior meatus and sphenoethmoidal recess
Ethmoid Sinus neurovasculature
- Blood supply: Ophthalmic, anterior and posterior ethmoidal arteries
- Lymphatic drainage: submandibular and retropharyngeal nodes
- Innervation: anterior and posterior ethmoid nerve from the nasociliary nerve, a branch of the ophthalmic division of the trigeminal nerve.
Ethmoid Sinus Variants
- Agger nasi cells – anterior most air cells located inferior to the frontal recess 90% of patients, actually located in the lacrimal bones
- Ethmoid bulla – largest and most consistently found air cell located in the roof of the middle meatus
- Haller cells – infraorbital air cells found in 20 percent of patients
- Onodi cells – posterior most ethmoid air cell, that lies superior to the sphenoid sinus ~30%
- Concha bullosa – middle turbinate pneumatisation
Maxillary Sinus: Description
- Paired pyramid shaped sinuses in the maxillary bone
- Function: lighten the head, vocal resonance
- Location: body of the maxilla
Maxillary Sinus: Gross anatomy
- They are the largest of the paranasal sinuses.
- Pyramid with base in the lateral boarder of the nose with apex pointing toward the zygomatic process of the maxilla. The floor is formed by the alveolar section of the maxilla, the roof forms the floor of the orbit.
Maxillary Sinus: Drainage
Via the maxillary ostium medial superior point of the pyramid, into the infundibulum, draining into the hiatus semilunaris, then into the middle meatus.
Maxillary Sinus: Neurovasculature
Blood supply:
- Supplied by branches of the facial, maxillary, infraorbital and greater palatine arteries.
- Venous drainage is via the sphenopalatine veins and the pterygoid plexus
Lymphatic drainage:
- Submandibular group
Innervation:
- Superior alveolar nerves
- Greater palatine nerves
- Infraorbital nerves
Maxillary Sinus: Variants
- Concha bullosa
- Haller cells – infraorbital air cells
- Agger nasi cells – most anterior ethmoidal air cells
- Silent sinus syndrome
Ostiomeatal Complex: Description
Is the common drainage pathway for the frontal, maxillary and anterior ethmoid air cells. Drains to the middle meatus in lateral nasal wall allowing airflow and mucocillary drainage. Important unit for the ENT surgeons.
Ostiomeatal Complex: Gross Anatomy
5 parts:
- Maxillary Os.: opening within the medial superior maxillary sinus and drainage channel for maxillary sinus.
- Infundibulum: Common channel that drains the maxillary os. and anterior ethmoid cells to hiatus semilunaris.
- Ethmoid Bulla: Single ethmoid air cell that sits over the hiatus
- Uncinate Process: hook like bony projection of arising from the nasolacrimal duct that leads to the anterior boundary of hiatus
- Hiatus Semilunaris: Final drainage passage; a region between the ethmoid bulla superiorly and free-edge of the uncinate process
Ostiomeatal Complex: Neurovasculature
Artery:
anterior and posterior ethmoid artery
Sphenopalatine artery
Nerve:
Greater and lesser palatine N
Vein:
Inferior ophthalmic V and facial V
Ostiomeatal Complex: Variants
- concha bullosa: aerated middle turbinate
- intralamellar cell: air cell within vertical portion of middle turbinate
- oversized ethmoid bulla (Agger nasi cells)
- Haller cells (infraorbital cells)
- uncinate process bullae
- deviation of uncinate process
- deviated nasal septum
- paradoxical middle turbinate: convexity of turbinate directed toward lateral nasal wall
- ethmoidal bulla may not be pneumatised, and be a bony prominence
Frontal Sinuses: Description
The frontal sinuses are the paranasal sinuses of the frontal bone
Function: lighten the head, vocal resonance
Frontal Sinuses: Gross Anatomy
- Lined with mucosa
- Highly variable however there are typically bilateral sinuses extending within the frontal bone between the inner and outer table from the gleballa to the mid to upper forehead
- Three or more chambers may be present
- Divided by a thin bony intrasinus septa
- Drainage: Drains via the frontal recess into either:
- Ethmoidal infundibulum, through the hiatus semilunaris and into the middle meatus
- Directly into the middle meatus
Frontal Sinuses: Neurovasculature
Blood supply:
Supratrochlear
Anterior ethmoidal
Supraorbital arteries
Venous drainage:
Superior ophthalmic veins
Lymphatic drainage:
- Submandibular nodes
- Skin overlying to the pre-auricular nodes
Frontal Sinuses: Relations
- Anterior: Outer table of the frontal bone, frontalis muscle
- Posterior: Inner table of the frontal bone, the frontal lobe
- Lateral: Supraorbital foramen
- Medial: Intersinus septa
- Inferior: Nasal cavity
- Superior: Frontal eminance
Frontal Sinuses: Variants
- Aggar nasi air cells
- Complete absence
- Silent Sinus syndrome
- Mucosal polyps
Mandible: Description
The mandible is a large single midline bone of the lower face
Function: respiration, verbalisation, mastication
Location: Jaw
Mandible: Gross Anatomy
Irregular bone. It consists of a curved horizontal portion the body and two perpendicular portions, the rami. The rami and the body unite at almost right angles (the angle of the jaw).
Mandible: Features
Body:
- Mandibular symphysis – midline point of fusion
- Mental foramen - inferior to the second pre-molar (mental vessels and nerve, the terminal branches of the inferior alveolar vessels and nerves)
- Fossae for the sublinguinal and submandibular glands
- Alveolar process of the teeth
- Groove for the facial artery of the inferior boarder
Ramus:
- Mandibular foramen – opening of the mandibular canal, which transmits the inferior alveolar vessels and nerves
- Coronoid process – anteriorly
- Condylar process – posterior
- Mandibular notch – space between the above two
- Mandibular canal – between the mandibular foramen and the mental foramen
Coronoid Process
- Separated from the condylar process by the mandibular notch
- Temporalis muscle insert into its medial and lateral surfaces
- Masseter muscle also inserts to its lateral surface
Condylar Process
- Consists of two portions - condyle and neck
- Articulates with the articular disk of the TMJ, in the mandibular fossa of the temporal bone
- Lateral pterygoid muscle inserts into condylar neck
Mandible: Articulation
- Gomphosis joints with the lower row of teeth
- Temporomandibular joint – between the condylar process of the mandible and the mandibular fossa and the articular eminence of the temporal bone. Atypical synovial joint with a fibrocartilage articular disc
Mandible: Ligaments
Temporomandibular ligaments
Stylomandibular ligaments
Sphenomandibular ligaments
Mandible: Neurovasculature:
Blood supply:
Facial, lingual and inferior alveolar arteries and nerves
Lymphatics:
Submandibular
Ossicular Chain: Description
There are three ossicles (from lateral to medial):
- malleus
- Incus
- Stapes
Their role is to mechanically amplify the vibrations of the tympanic membrane and transmit them to the cochlea where they can be interpreted as sound. They are located in the middle ear cavity and articulate with each other via tiny synovial joints.
Interestingly, they are the only bones in the body that do not grow after birth.
Malleus
- Most lateral, latin for hammer
- Head, neck, handle, anterior and lateral processes
- Lateral process is connected to the tympanic membrane
- Anterior process small anchoring fibres
- Handle – attachment of the tensor typani (origin cartilaginous part of the eustachian tube, supplied by the mandibular nerve)
- Head – articulates with the incus
Incus
- Body, long crus and short crus
- Latin for anvil
- Body articulates with the head of the Malleus
- Short crus posterior ligament of the incus
- Long crus articulates with the stapes
Stapes
- Likes like a stirrup, is latin for stirrup
- Base plate sits on oval window
- Anterior and posterior arches
- Neck in the union of the anterior and posterior arch
- Neck articulates with the incus
- Stapedius attaches to the neck (innervated by the facial nerve)
Temporal Bone: Description
The temporal bone is an important calvarial and skull base bone and is highly complex with multiple articulations
Temporal Bones: Gross Anatomy
- Squamous – This flat portion is the external to the temporal lobe and is the lateral part of the skull.
- Petrous – Pyramidal in shape, forms the posterior part of the middle cranial fossa, inner ear organ are located within
- Mastoid – pneumatised by the mastoid air cells, posterior to the ear, serves as an attachment point for SCM
- Tympanic – Bony of the external acoustic canal, inferior surface forms the mandibular fossa for TMJ, zygomatic process for formation of the zygomatic arch
- Styloid- Slender pointed process form the inferior anterior temporal bone which is an anchor point for muscles of tongue and larynx: Styloglossus, stylohyoid muscle and ligament, stylomandibular lig, stylopharyngeus m
Temporal Bone: Articulation
- Occipital bone
- Sphenoid
- Zygomatic
- Parietal
- Mandible via TMJ
Temporal Bone: Variants
Short and long styloid process
Calcified stlylohyoid ligament – eagles syndrome compression cranial nerve or ICA
Temperomandibular joint: Description
Bilateral joint of the jaw. Modified hinge joint.
Function: Mastication, verbalisation, respiration
TMJ: Anatomy
The temporomandibular joint (TMJ) is an atypical synovial joint located between the condylar process of the mandible and the mandibular fossa and articular eminence of the temporal bone.
It is divided into a superior discotemporal space and inferior discomandibular space by the TMJ disc (or meniscus).
TMJ: Movement
- upper compartment: protraction, retraction and gliding side-to-side
- lower compartment: opening and closing
TMJ: Ligaments
- temporomandibular
- stylomandibular
- sphenomandibular
TMJ: Muscles
- Medial and lateral pterygoids
- Masseter
- Temporalis
TMJ: Neurovasculature
Arterial:
Superficial temporal
Vein:
Retromandibular
Innervation:
- auriculotemporal nerve
- masseteric nerve
Extra-ocular muscles: Description
The extra-ocular muscles are the six muscles that insert onto the eye and hence control eye
Extraocular muscles: Gross Anatomy
- superior rectus: elevation, annulus of Zinn to the superior globe
- superior oblique: intorsion, sphenoid bone via catelaginous trochlear to superior lateral globe
- medial rectus: adduction, annulus of Zinn to the medial globe
- lateral rectus: abduction, annulus of Zinn to the lateral globe
- inferior oblique: extorsion, Maxillary bone to inferior lateral globe
- inferior rectus: depression, annulus of Zinn to the inferior globe
Extra-ocular muscles: innervation
oculomotor nerve:
- superior, medial, and inferior rectus
- inferior oblique
trochlear nerve:
- superior oblique
abducens nerve:
- lateral rectus
Extra-ocular muscles: vasculature
Arterial supply:
- Primarily form opthalmic artery and branches
- Lacrimal artery (branch of opthalmic artery) supplies lateral rectus
- Inferior oblique and interior rectus receive branches of the infraorbital artery
Venous
- Sup opthalmic vein -> cavernous sinus
- Inf opthalmic vein -> pterygoid plexus -> Emmisary veins to cavernous sinus AND joint superficial temporal vein to become retromandoibular vein
Muscles of Mastication: Description
The primary muscles of mastication are: the temporalis, massester, medial and lateral pterygoids. The suprahyoid muscles assist with mastication.
Temporalis
- Origin : Infratemporal fossa
- Insertion: coronoid process and ramus of mandible, tendon passes deep to the zygomatic arch.
- Action: Elevate and retract the mandible, as well as lateral translation
- Blood: Maxillary artery
- Nerve: Deep temporal nerve from mandibular N (CNV3)
Masseter
- Multipennate arrangement of fibres, can be palpated when clench teeth together at side of cheeks.
- Origin: Zygomatic arch is origin
- Insertion: Inserts laterally on the ramus and angle of the mandible
- Action: elevates and protract the mandible
- Blood: Masseteric branch of maxillary artery, superficial temporal and facial
- Nerve: Mandibular nerve from anterior division of CNV3
- Has three layers
Lateral Pterygoids
- Divided into 2 parts:
- The superior part:
- Origin: greater wing of the sphenoid
- Insertion: TMJ capsule and disc
- The inferior part
- Origin: lateral surface of the lateral pterygoid plate
- Insertion: the pterygoid fovea, neck of the mandible
- The superior part:
- Innervation: nerve to the lateral pterygoid from the mandibular nerve
- Blood: pterygoids branches of the maxillary artery
- Action: Jaw opening and retraction
Medial Pterygoids
Medial Pterygoids
- Origin: 2 heads, one from the medial surface of the lateral pterygoid plate and the other head is from the palatine bone
- Insertion: medial surface of the ramus
- Nerve: medial pterygoid nerve from the mandibular nerve
- Blood: maxillary artery
- Action: closes mouth, elevates and protrude the jaw
Muscles of mastication: Variants
- Muscle hemihypertrophy/hemiatrophy
- Altered insertion of origin
Arteries of the nasal cavity
- Sphenopalatine
- Anterior ethmoidal
- Posterior ethmoidal
- Superior labial
- Greater palatine
Sphenopalatine artery
Origin: maxillary artery third part
Course: Through the sphenopalatine foramen, into the sphenopalatine recess
Supplies: Posterior walls and nasal septum
Posterior ethmoidal artery
Origin: Branch on the ophthalmic artery
Course: Through the posterior ethmoidal foramen
Supplies: Posterior wall, ethmoid and sphenoid sinuses
Anterior ethmoidal artery
Origin: Branch of the ophthalmic
Course: enters the nose through the anterior ethmoidal foramen
Supplies: anterior wall, anterior ethmoidal sinuses and frontal sinuses
Superior labial artery
Origin: branch of the facial artery
Course: Ascends up the lip enters the nose though the posterior nare
Supplies: anterior wall and septum, lip
Greater Palatine Artery
Origin: branch of the maxillary artery
Course: enters the nose via the incisive foramen
Supplies: hard palate
Anastamosis of nasal plexus
Kisselbach plexis:
- vascular region of the anteroinferior nasal septum that comprises four arterial anastomoses:
- anterior ethmoidal artery
- a branch of the ophthalmic artery
- sphenopalatine artery
- a branch of the maxillary artery
- greater palatine artery
- a branch of the maxillary artery
- superior labial artery (septal branches)
- a branch of the facial artery
- anterior ethmoidal artery
Woodruff’s plexus: posterior anastomosis of the sphenopalatine, posterior ethmoidal and ascending pharyngeal arteries, posterior nasal packing is required to stop epistaxis here
Ophthalmic artery: Gross Anatomy
Origin: From the ophthalmic (C6) division of the internal carotid artery, arises medial to the anterior clinoid process as the ICA exits the cavernous sinus
Course: Anterior through the suprasella cistern, courses below the optic nerve, enters the orbit by the optic canal. Cross over the optic nerve from medial to lateral
Termination: bifurcation as the supratrochlear and dorsal nasal arteries
Ophthalmic artery: Branches (9)
- Orbital group (ASSLIP)
- lacrimal artery
- supraorbital artery
- posterior ethmoidal artery
- anterior ethmoidal artery
- internal palpebral artery
- supratrochlear artery
- dorsal nasal artery
- Ocular group (CLAMS)
- central retinal artery
- long posterior ciliary arteries
- short posterior ciliary arteries
- anterior ciliary artery
- muscular artery
Ophthalmic artery: variants
- Communication with the middle meningeal artery via the sphenoidal artery
- Meningo-orbital foramen
- Complete orbital supply by the middle meningeal artery
- Cavernous origin of the ophthalmic artery
Extracranial Facial nerve: Description
The seventh cranial nerve carries motor for the muscles of facial expression. Also relay taste and parasympathetics in a complex manner
Extracranial facial nerve: Gross anatomy
- Exits the stylomastoid foramen and gives of the posterior auricular nerve
- Passes between the posterior belly of the digastric and the stylohyoid muscle, supplying both
- Enters the parotid gland
- Between the deep and superficial lobes it divides into its five main branches:
- Temporal
- Zygomatic
- Buccal
- Mandibular
- Cervical
These branches are in reality a complex nerve network.
CN VII: Temporal branch
The temporal branch runs over the zygomatic arch. This branch is at risk during surgery in this region.
Motor to facial muscles above the orbits
CNVII: Zygomatic branch
Motor to orbicularis oculi
CNVII: Buccal Branch
Motor to muscles around the mouth
CNVII: Mandibular branch
The mandibular branch, in 80% of cases, runs along the lower border of the mandible (thus also referred to as marginal branch). In 20% of cases however it can be up to 2 cm below the margin of the mandible.
Motor to mouth depressors
CNVII: Cervical Branch
Motor to platysma
CNVII: Variants
Corda tympani may branch after the nerve has exited the stylomastoid foramen
Nasolacrimal apparatus: Description
The nasolacrimal apparatus is the system responsible for drainage of tears. Production of tears by the lacrimal gland is included in some text under this heading.
Lacrimal gland Gross Anatomy
- Location in the superior lateral orbit in the extraconal space
- Almond shaped
Lacrimal Apparatus: Gross anatomy
Location: From the medial canthus to the inferior concha
Consists of:
- Lacrimal canaliculi which drain the lacrimal lake via the lacrimal puncta
- Lacrimal sac – the superior and inferior lacrimal canaliculi drain into the lacrimal sac which lies in the lacrimal fossa, it drains into the nasolacrimal duct via the valve of Krause, the sac is enclosed in the lacrimal fascia and the orbicularis oculi
- Nasolacrimal duct – Is the inferior continuation of the lacrimal sac, it is approximately 17mm in length, it has 2 parts: intraosseous part which lies within the nasolacrimal canal of the maxilla, the membranous part which runs in the nasal mucosa. It terminates below the inferior nasal meatus as a slit like opening where it is covered by a mucosal fold called the valve of Hasner
Nasolacrimal Apparatus: Neurovasculature
Artery: lacrimal artery from the ophthalmic artery
Vein: Superior ophthalmic vein
Nerves: greater petrosal nerve (from facial nerve) and lacrimal nerve (ophthalmic division of the trigeminal nerve)
Nasolacrimal apparatus: Relations
- Medial: the maxilla
- Lateral: Lacrimal lake
- Superior: Superior orbital rim
- Inferior: Floor of the nasal cavity
- Posterior: ethmoid labyrinth and nasal cavity
- Anterio-medial: Nasal vestibule
Nasolacrimal Gland Variants
- Incompetent valve of Hasner
- Absence
- Accessory glands
- Draining to the middle meatus
Tympanic Membrane: Description
The tympanic membrane is a thin membrane that separates the external ear from the middle ear. It acts to transmit sound waves from air in the external auditory canal (EAC) to the ossicles of the middle ear.
Tympanic membrane: Gross description
The tympanic membrane is shaped like a flat cone pointing into the middle and inner ear. At the centre of the concavity the deepest point is called the umbo.
It attaches to an incomplete ring of bone along the wall of the EAC, the tympanic annulus. It consists of three layers (from external to internal):
- cutaneum (skin)
- radiatum circulare (collagen fibres)
- mucosum (epithelium)
There are two distinct portions of the membrane:
- pars tensa: the tense portion of the membrane is the larger portion inferior to the anterior and posterior malleolar folds
- pars flaccida: the flaccid portion of the membrane is much smaller and is the portion of the membrane above the anterior and posterior malleolar folds
Quadrant separation:
It is anatomically separated into four quadrants:
- anterosuperior
- anteroinferior
- posteroinferior
- posterosuperior
Tympanic Membrane: Relations
- Anterior – TMJ
- Posterior – mastoid process
- Superior – Tegmen typani and epitympanic recess
- Inferior – Jugular bulb
- Medial – Eustachian tube, ossciles and tympanic cavity
- Lateral – EAM and ear
Tympanic membrane: Vasculature
Arterial Supply:
- Branches of the maxillary artery
Veins:
- External jugular
- Transverse sinus