Extracranial Head and Neck

Facial Bones

  • coronal struts (frontal, nasal, alveolar, maxillary antra, pterygoids)
  • sagittal struts (walls of orbits, nasal septum)
  • horizontal struts (orbital wall and floor, zygomatic process, hard palate)
  • upper face -> supraorbital ridge -> midface -> maxillary alveolus -> lower face

Frontal Bone

  • glabella
  • supraorbital ridge
  • supraorbital notch/foramen
  • nasion

Nasal Bone

  • grooves for anterior ethmoidal nn

Maxilla

  • frontal process
  • orbital surface
  • zygomatic/malar process
  • infraorbital foramen (a [<maxillary a] &v&n [V2])
  • infratemporal surface
  • (superior) alveolar process
  • inferior orbital fissure (post-sup)
  • anterior nasal spine
  • nasal surface (lat nasal wall)
  • anterior nasal spine
  • incisive canal/fossa (midline betw alveolar and palatine processes anteriorly)
  • palatine process

Zygoma/Zygomatic/Malar Bone

  • orbital surface
  • frontal process
  • zygomaticofacial foramen (a[<lacrimal<ophthalmic a]&v&n [<zygomatic n <V2])
  • temporal process
  • zygomaticomaxillary, zygomaticotemporal and zygomaticofrontal sutures

Mandible

  • condylar process (head and neck)
  • mandibular/condylar notch
  • coronoid process
  • ramus
  • lingula (tuberosity anterior to mandibular foramen; pterygomandibular raphe)
  • mandibular foramen
  • mandibular canal (inf alveolar a [<max a] and n [<V3])
  • angle of mandible
  • body of mandible
  • mental foramen (lat body)
  • mental tubercle and protuberance (ant)
  • symphysis menti = mental symphysis (fuses at 2yo)
  • (inferior) alveolar process/part/crest
  • mylohyoid line (post aspect)
  • genial tubercle = mental spine (post mental symphysis)

Sphenoid Bone

  • pterion (suture with parietal, frontal and temporal bones)
  • greater wing of sphenoid
  • temporal fossa
  • infratemporal fossa (under zygomatic arch)
  • infratemporal crest
  • pterygomaxillary fissure (betw maxilla and lateral pteryloid)  -> pterygopalatine fossa –> sphenopalatine foramen
  • medial and lateral plates of pterygoid process
  • pterygoid fossa (betw medial and lateral pterygoid plates)
  • hamulus (medial pterygoid; pterygomandibular raphe)
  • foramen ovale and spinosum

Temporal Bone

  • squamous part
  • temporal fossa (above zygomatic arch)
  • zygomatic process
  • articular eminence/tubercle
  • mandibular/glenoid/temporomandibular fossa
  • external acoustic meatus
  • mastoid process
  • stylomastoid foramen
  • styloid process
  • petrous part
  • carotid canal external opening
  • jugular fossa and foramen (betw temporal and occipital bones)

Ethmoid Bone

  • crista galli
  • cribriform plate
  • superior and middle nasal conchae/turbinates
  • perpendicular plate (sup nasal septum)

Vomer

  • ala (joints to medial pteryoid plates)

Palatine Bone

  • orbital process
  • horizontal plate
  • perpendicular plates (lat nasal cavity)
  • greater palatine foramen (betw maxilla and horizontal plate)
  • pyramidal process (extending to lateral pterygoid plate), contains the lesser palatine foramina
  • posterior nasal spine

Lacrimal Bone

Pterygopalatine Fossa

contents

  • 3rd part of maxillary artery and maxillary vein
  • V3 and pterygopalatine ganglion
  • fat

boundaries and relations

  • A = maxilla, maxillary sinus
  • P = lateral pterygoid, middle cranial fossa
  • S = body sphenoid, orbit
  • I = pyramidal process of palatine, lateral pterygoid plate, oral cavity
  • medial = perpendicular plate of palatine, nasal cavity
  • lateral = open as pterygomaxillary fissure, infratemporal fossa

connections

  • pterygomaxillary fissure (lat –> infratemporal fossa; maxillary a&v)
  • foramen rotundum (post -> middle cranial fossa; V2)
  • pterygoid/vidian canal (post -> middle cranial fossa; pterygoid a&n)
  • inferior orbital fissure (sup –> orbit; infraorbital a&n)
  • sphenopalatine foramen (med –> nasal cavity; sphenopalatine a, nasal n [<pterygoid ganglion])
  • greater and lesser palatine canal (inf –> oral cavity; greater and lesser palatine aa&vv&nn)

Temporomandibular Joint (TMJ)

  • fibrous articular disc (anterior and posterior bands with middle thin zone)
  • superior and inferior compartments
  • joint capsule (ant, medial and lat; disc to condyle)
  • bilaminar/translational zone (post, disc to condyle and temporal bone, fibrous-elastic)
  • rotation/hinge (between inferior disc surface and head of condyle)
  • translation/gliding (sup disc and glenoid fossa –> articular tubercle)

Facial Muscles

  • occipitalis = occipital belly of epicranius
  • epicranial aponeurosis = galea aponeurotica
  • frontalis = frontal belly of epicranius
  • temporalis (-> coronoid process)
  • masseter (deep and superficial; zygomatic arch- > angle of mandible)
  • lateral pterygoid (-> condylar process)
  • medial pterygoid (-> ramus of mandible)
  • orbicularis occuli (orbital and palpebral part)
  • zygomaticus major and minor (zygoma -> orbicularis ori)
  • orbicularis oris
  • buccinators (orbicularis ori -> pterygomandibular raphe)
  • patysma

Teeth

  • numbering: RUQ=1/5, LUQ=2/6, LLQ = 3/7, RLQ 4/8
  • deciduous/milk teeth (5×4, central/lateral incisors, canine/cuspid, 1st and 2nd milk molars)
  • permanent teeth (8×4; central/lat incisors, canine, 1st/2nd premolars, 1st/2nd/3rd molars)
  • root, neck and crown of tooth
  • gingival epithelium = gum
  • alveolus = bony socket
  • lamina dura (hard bone lining alveolus)
  • cement
  • periodontal membrane = alveolar periosteum (radiolucent)
  • dentine and enamel
  • pulp cavity
  • root/central canal(s)
  • dental nerve

Nasal Cavity

  • erectile cavernous tissue (in middle and inferior conchae, anterior nasal septum = septal swell body)
  • nasal cycle (q2-3hr)
  • nostrils = nares
  • nasal fossae/vestibule
  • alar cartilages
  • nasal septum (deviated in V25%)
  • septal cartilage (incl lateral process)
  • choanae
  • cribriform plate
  • cribriform foramina (~20, fibres of olfactory nerve, anterior ethmoidal vessels and nerve)
  • agger nasi crest (ant to mid concha in frontal process maxilla)
  • sup, mid and inferior conchae/turbinates
  • inverted turn of middle concha (V)

spheno-ethmoidal recess

  • highest nasal concha
  • sphenoid sinus ostium

superior meatus

  • posterior/superior ethmoid ostia (in spheno-ethmoidal recess and superior meatus)
  • sphenopalatine foramen (nasopalatine nerve, sphenopalatine a&v)

middle meatus

  • uncinate process (medial wall of maxillary sinus)
  • ethmoid/maxillary infundibulum (betw inf-med orbit and uncinate process) -> frontal recess = infundibulum to frontonasal canal
  • hiatus semilunaris (betw ethmoidal bulla and uncinate process)
  • anterior ethmoid ostia
  • maxillary sinus ostium
  • ethmoidal bulla
  • middle ethmoid ostia (on ethmoidal bulla)

inferior meatus

  • nasolacrimal duct/canal ostium

Arterial Supply

  • sphenopalatine artery (maxillary a; posterior nasal cavity)
  • anterior ethmoidal artery (ophthalmic a -> cribriform plate; anterior and superior nasal cavity)
  • nasal septal branches of superior labial a (facial a; anterior septum)
  • alar branches of lateral nasal a (facial a; nares)
  • greater palatine a (-> incisive canal -> anast with sphenopalatine a)
  • Little’s/Kiesselbach’s area (anastamosis in ant-inf nasal septum of anterior ethmoidal a, greater palatine a, sphenopalatine a, superior labial a)

Paranasal Sinuses

  • ostiomeatal complex/unit (ethmoid infundibulum, hiatus semilunaris, frontal recess)
  • mucociliary escalator

Frontal Sinuses (2-14yo)

  • between inner and outer tables of frontal bone, may extend into orbital plate
  • incomplete bony septa
  • dividing septum
  • drain to frontonasal canal, ethmoid bulla or anterior ethmoid cells
  • absence of frontal sinuses (V4%, associated with persistent metopic suture)

Maxillary Sinus/Antra (3/52yo- early adulthood)

  • body; (infra)orbital, zygomatic, alveolar and palatine recesses/processes
  • apex (post-lat); anterior, posterior/infratemporal, medial/nasal and superior/orbital surfaces/walls
  • groove for infraorbital canal
  • maxillary hiatus (sup-post-med)
  • anterior and posterior fontanelle± ostia (at max hiatus)
  • maxillary ostium (->infundibulum)
  • hypoplasia of one maxillary sinus (V10%)

Ethmoidal Sinuses (3-18 each side, 2-14yo)

  • ethmoid labyrinth
  • anterior, middle and posterior groups
  • aggi nasi cells = most anterior cells
  • Haller’s cells = posterior cells at orbital floor
  • pneumatisation of body and wings of sphenoid (V4-12%)
  • concha bullosa (V, aerated middle cocha)
  • sphenoethmoidal recess with uncovered ICA (V)

Sphenoid Sinuses (>3yo)

  • midline septum
  • pneumatisation of greater/lesser wings or pterygoid processes (V50%)
  • lateral recess of sphenoid sinus (V, posterior to antra)

Oral Cavity and Tongue

  • external vestibule (outside teeth)
  • buccal cavity proper
  • palatoglossal fold/arch (palatoglossus)
  • palatine tonsil
  • palatopharyngeal fold/arch (palatopharyngeus)
  • hard palate = maxilla and palatine bones
  • greater and lesser palatine foramen (a&n)
  • soft palate = palatine aponeurosis (of tensor veli palatini)
  • tensor and levator (veli) palatini (elevate palate and prevent reflux into nose)
  • uvula muscle
  • buccinator muscle -> pterygomandibular raphe (-> hamulus) -> superior pharyngeal constrictor
  • sublingual space (superior to mylohyoid)
  • diaphragma oris = mylohyoid and anterior belly digastric
  • submandibular space (inferior)
  • stylohyoid muscle and ligament
  • digastric (inf to mylohyoid; mandible -> fibrous loop for intermediate tendon (hyoid) -> mastoid process)
  • mylohyoid (mylohyoid line of mandible -> hyoid); median raphe of mylohyoid
  • geniohyoid = inferior fibres of genioglossus (sup to mylohyoid; midline body mandible -> hyoid)

extrinsic group of tongue muscles (movement of tongue)

  • genioglossus (genial tubercle –> ventral tongue; XII); lingual septum divides the muscle
  • hyoglossus (lat hyoid -> thick band posterior tongue; XII)
  • palatoglossus (-> soft palate; CNIX via X)
  • styloglossus (styloid –> side of tongue;CNXII)

lingual artery (betw genioglossus and hyoglossus)

hypoglossal n, lingual n[<V3]+v (lat to hyoglossus)

intrinsic group of tongue muscles (changes shape of tongue)

  • inferior longitudinal m of tongue
  • vertical and transverse mm of tongue
  • superior longitudinal m of tongue
  • fat planes (between muscles)
  • midline fibro-fatty septum
  • frenulum of tongue
  • apex, body (ant 2/3) and root (post 1/3) of tongue
  • papillae (on body) and lymphoid tubercles = lingual tonsil/nodules (on root)
  • terminal sulcus = V shaped post
  • foramen cecum

Salivary Glands

Parotid Gland (serous)

  • deep retromandibular portion
  • superficial lobe (large, with tail = anteroinferior extension), isthmus and deep lobe (small)
  • bifurcation of ECA and retromandibular vein run through isthmus
  • facial nerve and 5 branches run through deep, isthmus and superficial lobes
  • parotid duct (of Stenson) (50mm; lateral to masseter)
  • parotid papilla (sup posterior vestibule of mouth)
  • <branches of ECA, retromandibular v
  • lesser petrosal n -> otic ganglion -> secretomotor fibres
  • accessory glandular tissue along duct (V20%)

relations

  • A = ramus of mandible, medial pterygoid, buccinator, parotid duct
  • P = mastoid process, SCM, pinna, external auditory meatus
  • S = zygomatic arch
  • I = digastric, SCM
  • medial = styloid process and mm, carotid sheath, pharynx, masseter
  • lateral = superficial fascia, skin

Submandinular Gland (serous and mucous)

  • superficial/lower (submandibular space) and deep/upper (sublingual space) portions of gland around posterior mylohyoid
  • submandibular duct (of Wharton) (50mm, superior > deep gland > between mylohyoid and genioglossus)
  • sublingual papilla/caruncle
  • <facial a, facial v, chorda tympani, lingual n
  • connection to sublingual or parotid glands (V)
  • multiple ducts, or also received from sublingual (V)

relations

  • A = anterior digastric
  • P = posterior digastric, parotid
  • A/S/I = mylohyoid
  • I = hyoid
  • medial = hyoglossus, genioglossus
  • lateral = angle of mandible, facial v

Sublingual Gland (mucous)

  • sublingual ducts (of Rivinius) (~20 in sublingual fold posterior to sublingual papilla)
  • Bartholin’s duct (> into submandibular duct)
  • <lingual and facial a, chorda tympani, lingual n

relations

  • P/I = submandibular gland
  • lateral = mandible
  • medial = genioglossus, geniohyoid
  • I = mylohyoid

Pharynx ~14cm

  • base skull to cricoid ~C6
  • mucosa, pharyngobasilar fascia and muscular (contrictor m) layers
  • posterior pharyngeal/median raphe (> pharyngeal tubercle of occipital bone)
  • < ascending pharyngeal a, facial a (ascending palatine, tonsillar aa), maxillary a (greater palatine a, pharyngeal a), lingual a, inferior laryngeal a
  • >pharyngeal plexus (post to middle constrictor)> pterygoid plexus > IJV
  • < V2, CNIX, CNX

relations

  • A = nasal/oral cavities, base of tongue, larynx
  • P = prevertebral fascia/m (longus colli/capitis), C-spine
  • S = sphenoid sinus, basiocciput
  • I = oesophagus
  • lateral = Eustachian tube, styloid and mm, carotid sheath, ECA, parapharyngeal space

Nasopharynx (chonae -> soft palate)

  • palatopharyngeus (potion arises from base skull adj to Eustacian tube)
  • stylopharyngeus (<CNIX)
  • torus tubarius = cartilaginous opening of the tube
  • pharyngotympatic/auditory/Eustacian tube
  • salpingopharyngeus (torus tubarius -> pharynx)
  • lateral pharyngeal recess = fossa of Rosenmuller (above superior pharyngeal constrictor, post-lat to torus tubarius, continuous laterally with sinus of Morgagni)
  • superior pharyngeal constrictor (> hamulus, pterygomandibular raphe)
  • Passavant ridge (palatopharyngeal sphincter) at level of palate –> superior pharyngeal constrictor
  • adenoids = enlarged pharyngeal tonsils
  • levator (veli) palatini

Oropharynx (->epiglottis)

  • faucial pillars = palatoglossal and palatopharyngeal folds/arches
  • palatine tonsils
  • vallecula (anterior to epiglottis)separated by median glossoepiglottic fold
  • Waldeyer’s ring (pharyngeal, palatine and lingual tonsils)
  • middle pharyngeal constrictor (-> stylohyoid lig and hyoid)

Hypo/Laryngo-pharynx (->cricoid/C6)

  • piriform fossa (on either side of larynx)
  • inferior pharyngeal constrictor (upper = thyropharyngeus [oblique], lower = cricopharyngeus [horizontal; <recurrent laryngeal n])
  • upper oesophageal sphincter = cricopharyngeus
  • Killian’s dehiscence/triangle = pharyngeal aponeurosis between thyropharyngeus and cricopharyngeus)
  • cricoid venous plexus (ant)

Larynx (C3-6, base tongue -> trachea)

hyoid bone (body, lesser [sup] and greater [post-lat] cornu)

relations

  • A = hyoid, strap mm, pretracheal fascia
  • P = laryngopharynx, inferior constrictor
  • S = oropharynx, tongue
  • I = trachea
  • lateral = carotid sheath, strap mm, thyroid gland

Cartilages

  • hyaline cartilages = thyroid, cricoid, arytenoids (may irregularly calcify or ossify and contain fatty marrow); the others are yellow elastic fibrocartilage and do not calcify apart from triticeal
  • epiglottis and petiole (narrow base > inner thyroid)
  • thyroid cartilage
    • superior and inferior horns/cornu
    • superior thyroid notch
    • laryngeal prominence
    • thyroid cartilage lamina
  • triticeal cartilage (in lateral thyrohyoid ligaments)
  • cricoid cartilage (arytenoid articular surface, lamina, arch [ant])
  • arytenoid cartilage (post-sup-lat cricoid; muscular [lat] and vocal [ant] process)
  • corniculate carlilage (on arytenoids)
  • cuneiform cartilages (lat to corniculate in aryepiglottic fold)
  • cricothyroid joint (synovial; thyroid inferior horns > cricoid lamina)

Membranes, Folds and Ligaments

extrinsic

  • hyoepiglottic ligament (ant epiglottis > hyoid)
  • median (dividing vallecula) and lateral (2) glossoepiglottic folds (ant epiglottis > base of tongue)
  • pharyngeal folds (epiglottis > pharyngeal wall)
  • thyrohyoid membrane and ligament (midline thickening)
    • lateral thyrohyoid ligaments (sup horns thyroid> greater horns of hyoid)
    • aperture/foramen for superior laryngeal vessels and internal branch of recurrent/superior laryngeal nerve
  • cricotracheal membrane

intrinsic

  • aryepiglotic muscle and fold (epiglottis > artenoids)
  • thyroepiglottic ligament (epiglottic petiole > thyroid cart)
  • quadrangular membrane (submucosa between aryepiglottic and vestibular fold)
  • vestibular/ventricular folds/ligaments = false cords (ant thyroid > ant-lat arytenoids)
  • vocal ligaments (vocal process arytenoids > thyroid)
  • vocal folds = true cords (slightly medial to vocal ligaments)
    • anterior and posterior commisures (fusions of true cord)
  • cricothyroid membrane
    • median and lateral cricothyroid ligaments (ant)

Vocal Muscles

  • transverse and oblique arytenoid muscles (between posterior arytenoids; adduction of vocal lig)
  • posterior cricoarytenoid (m process -> posterior cricoid; abduction by rotation)
  • lateral cricoarytenoid ( m process > lateral cricoid; adduction by rotation)
  • thyroarytenoid and vocalis (along cords; shortening/relaxation)
  • straight and oblique cricothyroid (lat thoroid > ant-lat cricoid; lengthening/tension)

Spaces

  • vallecula (betw tongue and epiglottis)
  • pre-epiglottic space (fat between epiglottis and thyrohyoid membrane)
  • laryngeal aditus/opening/inlet
  • piriform fossa/recess (hypopharynx, between thyroid cartilage/thyrohyoid membrane and aryepiglotic fold)
  • vestibules = laryngeal sinus (between vestibular folds and aryepiglottic fold)
  • ventricles (between true and false cords) with laryngeal saccule (ant-sup pouch)
  • glottis = vocal cords + rima glottidis (space between cords)
  • paraglottic/paralaryngeal space (betw aryepiglotic fold and thyroid cartilage; anterior to piriform recess)
  • infraglottic larynx (betw true cords and trachea)

Neurovasculature

supraglottic

  • superior laryngeal a&v (<superior thyroid a <ECA)
  • upper cervical nodes
  • internal laryngeal nerve

infraglottic

  • inferior laryngeal a&v (<inferior thyroid < thyrocervical trunk)
  • lower cervical nodes
  • recurrent laryngeal n (>mucosa and all mm except cricothyroid < external laryngeal n)

Thyroid Glands

  • thyroid cartilage to 6th tracheal ring
  • right usually > left lobe (30 x 20mm)
  • upper and lower poles of the lobes
  • isthmus (2nd-4th tracheal rings @C6)

relations

  • A = sternothyroid, sternohyoid, anterior jugular v
  • P = parathyroid glands, larynx, trachea,pharynx, oesophagus
  • S = hyoid
  • I = subclavian a&v
  • medial = recurrent laryngeal n
  • lateral = external jugular v, carotid sheath (CCA,IJV,vagus n)

neurovasculature

  • superior thyroid artery < ECA
  • inferior thyroid a (passes posterior to carotid sheath) < thyrocervical trunk < SCA
  • superior and middle thyroid vv > IJV
  • inferior thyroid vv > L brachiocephalic v
  • lymph > thoracic duct, R lymphatic duct

variants

  • pyramidal lobe (40%; usually L sup-med; thyroglossal duct remnant)
  • thyroidea ima (3%, anterior to trachea) artery < innominate a/ao.arch
  • lingual thyroid (failed descent)
  • ectopic thyroid tissue along thyrogossal tract or mediastinum, pericardium, myocardium
  • persistent thyroglossal duct (> isthmus)
  • thyroglossal cyst/sinus

Parathyroid Glands

  • superior and inferior pairs of parathyroid glands (5 x 3 x 1mm; posterior to thyroid within its sheath in 90%; 80% have four glands, 20% 3-6 glands)
  • A – thyroid lobes; P = longus colli; medial = trachea; lateral = carotid sheath
  • < inferior thyroid a
  • ectopic inferior parathyroid glands (V, from maldescent; below lower poles thyroid, above superior parathyroids, posterior to oesophagus, posterior mediastinum). superior glands seldom ectopic.

Neck Muscles, Spaces and Layers

Triangles

  • submandibular triangle (betw ant and post digastric bellies, mandible)
  • carotid triangle (posterior digastric, omohyoid, SCM)
  • anterior muscular triangle (ant to omohyoid, SCM)
  • occipital triangle (SCM, inf omohyoid, trapezius
  • subclavian triangle (SCM, inf omohyoid, clavicle)

Superficial spaces

  • infratemporal space (lat = temporalis, zygomatic arch, mandible, coronoid process; medial = lateral pterygoid plate; posterior = parotid, styloid, carotid sheath; S = temporal fossa; pterygoid mm)
  • buccal space (buccal fat pad, facial a&v, terminal parotid duct, buccinator m) – extends between maxilla and masticator space.

deep spaces

  • pharyngeal mucosal space (sup and middle constrictor mm, salpingopharyngeal m, levator palatini, adenoids, lingual tonsils, torus tubarius)
  • parapharyngeal space (P = styloid, carotid sheath, medial = middle layer of deep cervical fascia, lateral = superficial/investing layer of deep cervical fascia; fat, maxillary a, ascending pharyngeal a, pharyngeal v.plex, mandibular nerve branches of  V3)
  • masticator space (lat to parapharyngeal space, investing layer; pterygoids, masseter, temporalis, ramus and body of mandible, V3)
  • parotid space (parotid gland and duct, facial n, ECA, maxillary a, retromandibular v, intraparotid LNs)
  • carotid space (carotid fascia [skull base > aortic arch]; ICA/CCA, IJV, CNIX,X,XI,XII, sympathetic plexus, LNs)
  • retropharyngeal space (between pharynx buccopharyngeal fascia and prevertebral fascia; contains the alar fascia fat, retropharyngeal LNs)
  • prevertebral space (posterior to prevertebral fascia; prevertebral mm [longus colli], vertebra a&v, phrenic n, brachial plex, scalenes)
  • submandibular space (submandibular gland and duct, facial a&v, CNXII)

Muscles and Fascial Layers

  • superficial cervical facia
  • platysma (> body of mandible)
  • superficial LNs
  • investing/superficial layer of deep cervical fascia (> thorax)
  • sternocleidomastoid (SCM, clavicular and sternal heads)
  • muscular layer of deep cervical fascia
  • anterior strap muscles
    • sternohyoid
    • omohyoid (superior and inferior bellies; hyoid > clavicle via deep fascia to central tendon > upper border scapula just med to suprascapular notch, 1st rib)
    • thyrohyoid and sternothyroid
  • visceral/middle/pretracheal layer of deep cervical fascia (ant border of retropharyngeal space = buccopharyngeal fascia)
  • larynx, thyroid gland, trachea, oesophagus
  • prevertebral/deep layer of deep cervical = alar fascia
  • vertebrae, paraspinal mm, brachial plexus

 

carotid sheath

  • temporal petrous and occipital bones around carotid and jugular foramen > adventitia of arch
  • innominate a, CCA, ICA, IJV, CNIX,X,XI,XII, sympathetic nn, deep cervical nodes

relations:

  • A = investing and visceral layers, thyroid gland, omohyoid, SCM, thymus
  • P = prevertebral layer, prevertebral mm, sympathetic chain
  • S = temporal petrous and occipital bones
  • I = aortic arch
  • medial = pharynx, oesophagus, trachea, recurrent laryngeal n
  • lateral = parotid, styloid process and mm

Orbit

Compartments

  • subperiosteal compartment
  • periorbita = periosteum of bony orbit (->dura)
  • preseptal/anterior compartment (eyelids, lacrimal apparatus, soft tissues)
  • orbital septum – reflection of periorbita from orbital rim -> medial and lateral palpebral ligaments, superior and inferior tarsal plates
  • globe
  • posterior/postseptal compartment = retrobulbar space
    • intraconal space (optic nerve, arteries and veins, retrobulbar fat, ciliary ganglion)
    • muscle conal space = orbital muscles – the rectus muscles are connected by intermuscular fibrous membranes.
    • extraconal space (fat, vessels, nerves)

Osseous Anatomy

  • sup, inf, med, and lateral orbital margins/rims
  • frontal process/anterosuperior angle of maxilla
  • lacrimal bone
  • anterior and posterior lacrimal crests
  • lacrimal sac
  • lamina papyracea = orbital plate of ethmoid
  • orbital process of palatine bone
  • orbital surface of frontal bone
  • orbital surface of greater and lesser wings of sphenoid
  • orbital surface of zygomatic bone
  • orbital plate/surface of the maxilla
  • infraorbital groove/fissure -> canal -> foramen (infraorbital n [<V2], infraorbital a [<max a], inferior ophthalmic vv; posterior > pterygopalatine fossa, anterior > infratemporal fossa; closed by periorbita)
  • frontozygomatic suture
  • superior orbital fissure
  • optic canal/foramen (<7 mm, mean 5mm di)
  • separate foramen or keyhole for opthlamic a (V)
  • supraorbital notch/foramen

Eye

(Ocular globe). ~25mm diameter.

  • anterior and posterior poles
  • equator = midcoronal plane
  • conjunctiva (covers anterior eye, inner eyelids, fuses with limbus)
  • anterior segment of globe (between cornea and lens)
  • cornea
    • anterior and posterior chambers divided by iris
    • aqueous body/humour continuous through pupil = aperture of iris)
  • lens capsule and nucleus
    • Zonular fibers = suspensory ligament of lens
    • ciliary body (muscle and processes)
  • posterior segment of globe (behind lens)
    • vitreous body/humour – bounded by vitreous/hyaline membrane
    • subhyaloid space – between hyaline membrane and retina
    • retina – inner sensory layer (photoreceptor rods and cones, ganglion cells, neuroglia) and outer layer (retinal pigment epithelium); lies on basal lamina of choroid (Bruch’s membrane); anterior limit = ora serrata
    • subretinal space – between inner sensory and outer retinal pigment layers
    • uveal tract = choroid + ciliary body + iris
    • suprachoroidal space
    • cornea -> limbus = corneoscleral junction -> sclera. Canal of Schlemm near limbus collects aqueous humour from anterior chamber into veins.
  • Tenon’s capsule (covers sclera from limbus to optic n, -> fascia of extrinsic ocular mm at their insertions)
  • fovea centralis of the macula (temporal to optic disc)
  • optic disc and nerve

Extraocular Muscles

LR6(SO4)3 = nerve supply

striated muscles

  • annulus of Zinn = common tendinous ring (-> around optic canal and inner superior orbital fissure)
  • medial (III), inferior (III, with slip to lower lid), lateral (VI) and superior (III) recti (annulus of Zinn -> anterior to equator)
  • inferior oblique (III; ant-med floor orbit > inf-lat globe posterior to equator)
  • superior oblique (IV; sphenoid sup-med to optic foramen –> trochlear [->frontal bone] –> sup-lat globe posterior to equator)
  • levator palpebrae superioris (III; inferior lesser wing > superior tarsal plate)

smooth muscles

  • capsulopalpebral muscle of Hesser
  • Muller’s muscle = superior tarsal muscle

Lacrimal Pathways

  • orbital (larger, in lacrimal fossa) and palpebral parts of lacrimal gland, separated by levator palpebrae aponeurosis; tears -> upper fornix [betw upper eyelid and eye]
  • superior and inferior lacrimal papilla and puncta -> canaliculi -> common canaliculus -> lacrimas sac -> nasolacrimal duct -> opening in the inferior nasal meatus
  • lacrimal caruncle (betw lacrimal papillae)
  • valve of Hasner = plica lacrimalis (distal nasolacrimal duct to prevent reflux)

Vessels

Arteries

  • ophthalmic artery – lateral to optic nerve in orbital canal, then crosses superiorly to medial orbit
    • central retinal artery (runs in optic n)
    • lacrimal artery
    • long and short posterior ciliary arteries
    • muscular arteries –> anterior ciliary arteries)
    • posterior and anterior ethmoidal arteries (-> sup to cribriform plate)
    • superior palpebral arteries
    • supraorbital artery
    • supratrochlear artery
    • dorsal nasal artery
    • recurrent lacrimal artery -> middle meningeal artery
  • superficial temporal a. and anterior temporal branch of the internal maxillary a -> transosseous branches to lateral wall orbit
  • transverse facial a + zygomaticofacial/zygomaticomalar a -> inferior palpebral aa
  • infraorbital artery
  • facial artery -> angular artery >anast with supraorbital, supratrochlear, dorsal nasal aa

Veins

  • supraorbital and angular vv -> superior ophthalmic vein (sup-med angle of orbit -> superior orbital fissure -> cavernous sinus)
  • vortex/vorticose veins (<-post globe)
  • inferior ophthalmic vein (-> pterygoid plexus and joins cavernous sinus or with superior ophthalmic v to form ophthalmic v)

Ear

Auricle = External Ear

  • helix (outer) > crus (ant-sup)
  • antihelix and crura (sup-ant)
  • concha (adj to ext auditory meatus)
  • tragus (ant) and antitragus (inf)
  • lobule

External Auditory Meatus (35mm)

  • cartilaginous (outer 1/3) and osseous (inner 2/3) parts
  • isthmus of the external auditory meatus
  • pars flaccida (sup to malleus between anterior and posterior mallear folds)
  • superior recess of the tympanic membrane = Prussak’s space (between pars flaccida and malleus neck)
  • pars tensa
  • tympatic ring (around tympanic membrane)
  • scutum (sup portion of ring, lateral wall of epitympanum)

Middle Ear

  • tympanic cavity
  • epitympanum = attic, mesotympanum and hypotympanum
  • protympanum (ant), mesotympanum and post-tympanum
  • tegmen tympani = roof of tympanic cavity
  • Eustachian/pharyngotympanic tube (35mm, bony then fibrocartilaginous; >ant-med)
  • bony canal for tensor tympani muscle > malleus (sup to Eustachian tube)

medial wall

  • aditus = mastoid antrum (opening on posterior wall of attic > mastoid air cells)
  • Koerner’s septum (V, dividing mastoid antrum)
  • prominence of lateral semicircular canal
  • tympanic segment of the facial nerve (>post to stylomastoid foramen)
  • oval window = fenestra ovalis (sup)
  • stapedius (pyramidal eminence [post-med] > stapes neck)
  • sinus tympani (med to pyramidal eminence)
  • promontory (over basal turn of cochlea)
  • round window = fenestra cochlea/rotunda

auditory ossicles

  • malleus (head, neck, anterior process, lateral process, handle/manubrium)
  • umbo (handle > tympanic membrane)
  • incudomallear articulation
  • incus (body, short limb, long limb > lenticular process > stapes)
  • posterior (>short limb) and superior (>body) ligaments of incus
  • incudostapedial joint
  • stapes (head, anterior and posterior limbs, footplate; >oval window)

Inner Ear

bony labrynth = otic capsules

  • vestibule (middle)
  • lateral/horizontal semicircular canal
  • anterior/superior semicircular canal (90° to petrous, forming arcuate eminence of superior petrous bone)
  • posterior semicircular canal (parallel to petrous)
  • common crus/limb (of anterior and posterior canals)
  • cochlear (with basal turn; perpendicular to petrous)
  • cupola (apex of chochlear spiral; points ant-lat)
  • modiolus (central canal) > spiral lamina
  • scala vestibuli
  • helicotrema (meeting of scala tympani and vestibule)
  • scala tympani (<round window)
  • perilymph (in vestibule, scala vestibuli/tympani; cont with CSF)
  • cochlear duct/aqueduct (perilymph; near round window –> inferior to IAM)
  • vestibular duct/aqueduct (-> betw IAM and groove for jugular v)

membranous labyrinths

  • utricle (posterior; > semicircular duct)
  • utricosaccular duct
  • saccule (anterior; > cochlear ducts)
  • endolymph (in ducts, saccule, utricle)
  • semicircular ducts (w ampullae)
  • endolymphatic duct (in vestibular duct; utricosaccular duct > endolymph sac post-lat to internal acoustic meatus)

inner cochlear (2½-2¾ turns)

  • scala vestibuli (->vestibule)
  • vestibular/Reissner’s membrane
  • cochlear duct (>saccule)
  • organ of Corti = spiral organ; spiral lamina and basilar membrane
  • scala tympani (>round window)

Internal Auditory Meatus/Canal (IAM; 10mm)

  • porus acousticus internus = opening of IAM
  • external IAM covered by perforated plate of bone
  • crista falciformis (horizontal dividing IAM)
  • anterosuperior quadrant (facial and intermediate nerves)
  • anteroinferior quadrant (cochlear branch CNVIII)
  • posterior quadrants (sup and inferior vestibular branches CNVIII)
  • labyrinthine artery (<basilar a)

Facial (VII) Nerve

  • intracranial/cisternal segment
  • meatal/IAC segment (in internal auditory canal)
  • labyrinthine segment (canal > geniculate fossa and ganglion, anterior/1st genu)
    • greater petrosal nerve (>middle cranial fossa >nerve of the pterygoid canal [with deep petrosal nerve] > pterygopalatine ganglion; palate taste, lacrimal gland)
    • lesser petrosal nerve (>middle cranial fossa > foramen ovale > otic ganglion > parotid gland)
  • tympanic segment (ganglion > pyramidal eminence; between lateral semicircular canal and oval window/stapes; posterior/2nd genu)
    • chorda tympani nerve and canal (betw incus and malleus > taste anterior 2/3 tongue, submandibular and sublingual glands)
    • nerve to stapedius
  • mastoid segment (inf > stylomastoid foramen)
  • extratemporal segment (after stylomastoid foramen, divides into 5 main branches in parotid gland)
    • (posterior auricular n)
    • temporal/frontal branch
    • zygomatic branch
    • buccal branch
    • marginal mandibular branch
    • cervical branch

‘snake eyes’ (coronal CT with facial nerve above cochlea medial eye =labyrinthine segment; lateral = tympanic segment)

fallopian/facial canal (IAM>stylomastoid foramen)

Arteries

Common Carotid Artery (CCA)

  • common carotid artery bifurcation ~C3-4 ~angle of mandible
  • carotid sinus at bifurcation (contain baroreceptors)

Relations:

  • A/med = thyroid gland; A/lat = SCM, strap mm
  • P = sympathetic trunk, prevertebral mm, transverse processes C4-C6
  • medial = recurrent laryngeal n, trachea, oesophagus, larynx/pharynx
  • lateral = IJV; P/lat = vagus n

External Carotid Artery (ECA)

ECA > upper cervical, facial, scalp, dura; 4-12 branches

Relations:

  • A = thyroid, submandibular gland, mandible ramus
  • P = styloglossus, CNIX, ICA [lat>med]
  • medial = pharynx, greater horn hyoid
  • A/lat = SCM, posterior belly digastric, stylohyoid, retromandibular v

Branches (‘Some angry lady figured out PMS’):

  • superior thyroid artery (ant, -> thyroids, pharynx, larynx, infrahyoid m)
  • ascending pharyngeal artery (post)
    • anterior/pharyngeal branch -> larynx, post-lat pharynx, palatine tonsil, soft palate, auditory tube
    • middle/neuromeningeal and posterior branches -> meninges (via foramen lacerum), middle ear, lower CNs
  • lingual artery (ant, characteristic hook; -> pharynx, tongue, submandibular gland, mandible)
  • facial artery (ant; -> submandibular gland, soft palate, tonsils)
    • superior and inferior labial aa
    • lateral nasal a
    • angular a (terminal branch)
  • occipital artery (post; -> upper posterior neck mm incl SCM and posterior belly digastric, skull, scalp, dura)
    • stylomastoid a -> middle and inner ear
  • posterior auricular artery (post; between styloid and parotid; -> parotid, auricle, scalp, tympanic cavity)
    • supplies stylomastoid a in 33%
  • terminal branch bifurcation in parotid gland
  • maxillary artery (terminal branch of ECA)
    • 1st/mandibular part of maxillary a (deep to mandibular neck)
      • middle meningeal artery (->foramen spinosum; anterior/frontal and posterior/parietal branches)
      • accessory meningeal artery (from maxillary or middle meningeal a; -> foramen ovale -> trigeminal ganglion)
      • inferior dental/alveolar artery (->mandibular foramen -> mental foramen)
    • 2nd/pterygoid part of maxillary a (betw temporalis and lateral pterygoid;-> mastication mm)
      • deep temporal aa (under zygomatic arch; -> orbital aa)
    • 3rd/pterygopalatine part of maxillary a (pterygopalatine fossa; -> maxilla, palate, orbit, nasal cavity)
      • superior dental/alveolar artery (->upper jaw)
      • infraorbital a (->inf orbital fissure- > infraorbital canal -> facial a)
      • greater/descending palatine artery (->palatine canal ->greater palatine foramen; -> tonsil, palate, gums, mucous membrane roof of mouth)
      • sphenopalatine artery (->sphenopalatine foramen -> nasal cavity; ->nose, sinuses)
      • vidian artery = artery of pterygoid canal
  • superficial temporal artery (terminal branch of ECA, post-lat to TMJ; -> anterior 2/3 scalp, parotid, TMJ, outer ear, anast with occipital a, lacrimal and palpebral branches of ophtlamic a)
    • transverse facial a -> facial a

Variations:

  • high/low bifurcation of CCA
  • common lingulofacial trunk (20%)
  • superior thyroid a from CCA

Veins

Veins Primary Draining the Brain

internal jugular v (IJV) > innominate vv

  • sigmoid sinus
  • inferior petrosal sinus
  • occipital v
  • pharyngeal vv
  • common trunk of facial/retromandibular/lingual vv
  • superior and middle thyroid vv

superior (in jugular fossa) and inferior (just above SVC) jugular bulbs of IJV

internal jugular valve (just above inferior jugular bulb)

subcutaneous part between clavicular heads of SCM

pterygoid plexus (over buccinators and superior pharyngeal constrictor) >maxillary vv (+superficial temporal v)> retromandiular vein > common trunk for facial (<supraorbital, supratrochlear vv), retromandibular and lingual vv > internal jugular v (IJV)

thoracic duct and right lymph duct > junction IJV and SCV

Veins with No Cerebral Drainage

  • external jugular v (EJV, superficial to platisma, SCM, pieces deep fascia above clavicle) > subclavian v (<post external cervical, transverse cervical, suprascapular, anterior jugular vv)
    • double external jugular vein (V)
  • posterior auricular vein + posterior branch from retromandibular v > EJV
  • anterior jugular vv (<superior submandibular v; > EJV)
  • jugular arch (U-shaped comm between anterior jugular vv above manubrium)
  • vertebral vv (brachiocephalic v; <mm of neck)
  • inferior thyroid vv (>L brachiocephalic)
  • deep cervical vv (>vertebral vv; <post mm of neck

Lymphatics

  • submandibular and jugulodigastric <1.5cm, the rest are <1cm
  • jugulodigastric nodes (post to angle mandible)
  • internal jugular nodes = deep cervical chain
  • jugulo-omohyoid node (at junction IJV and omohyoid)
  • supraclavicular nodes
  • jugular trunk > thoracic duct

Lymph node levels exclude intraparotid and retropharyngeal nodes:

  • Level 1 – Below myohyoid anterior to hyoid. Level 1a submental, 1b submandibular.
  • Level 2 (jugulodigastric) – base of skull to hyoid.
  • Level 3 (deep cervical) – hyoid to cricoid.
  • Level 4 (Virchow) – cricoid to manubrium/clavicle.
  • Level 5 (acessory spinal/posterior triangle) – 5a superior half , 5b inferior half.
  • Level 6 (prelaryngeal/pretracheal/Delphian)
  • Level 7 (superior mediastinal) – between CCAs below manubrium.