Anatomy & Branchial Arches Flashcards
BRANCHIAL ARCHES Definitions - epidemiology
Defintion A congenital anomaly of the neck due to disturbances in the complex development of the branchial apparatus of the foetus
Btwn weeks 4-7 of development
Epidemiology 17% paediatric neck masses
Definitions:
Arch- mesoderm
Cleft- ectoderm
Pouch- endoderm
Branchial membrane- cleft and pouch in contact. Only preserved in 1st arch (i.e. TM)
BRANCHIAL ARCHES Theories
Theories of development:
- Branchial remnant
- Salivary gland inclusion in a lymph node
- Squamous metaplasia of a LN
- Thymopharyngeal theory (persistent connection between thymus and its pharyngeal origin)
BRANCHIAL ARCHES Embryology
Embryology:
4/40- 4 arches arise at lateral pharynx and grow forward to meet in midline - V and VI are rudimentary
5/40- development of cervical sinus (2nd arch grows over 2, 3, 4, clefts)
6/40- 6 Hillocks of His develop to form pinna (1, 2, 3- 1st arch, 4, 5, 6- 2nd arch)
7/40- skin smooth over anterior neck
BRANCHIAL ARCHES Pathology
Pathology:
Thin-walled cystic structures. 90% contain squamous epithelial lining. 10% contain respiratory epithelium (ciliated columnar)
Nodular or diffuse lymphoid infiltrate often with germinal centres
Cyst fluid contains cholesterol crystals
BRANCHIAL ARCHES Syndromes associated
Syndromic associations:
- Treacher-Collins Syndrome
- Goldenhar
- Di George
- Pierre-Robin Sequence
- Branchio-Oto-Renal
1st BRANCHIAL ARCH CYSTS Work type 1
Work Type 1:
Ectodermal - Doesn’t communicate with EAC - Presents as mass around lower ear - Runs parallel to EAC. Involves parotid tissue, superior to VII
1st BRANCHIAL ARCH CYSTS Work Type 2
Work Type 2:
Ectoderm and mesoderm - Cartilage + skin adnexa (hair follicles, sebaceous glands, sweat glands) - Present as mass around ear, AoM / SCM / otorrhoea - Duplication anomaly of membranous and cartilagenous EAC - More intimately assoc with VII (may run through main trunk) - Myringeal band- floor of hypotympanum to umbo - Pathognomonic - MRI will demonstrate its tract - High recurrence rate - ave 2.4 procedures/pt
8-10% of all branchial arch anomalies
Cysts twice as common as sinuses/fistulae
1st BRANCHIAL ARCH CYSTS Clinical & radiological findings Recurrence rate % of all BA anoms
- Myringeal band- floor of hypotympanum to umbo
- Pathognomonic
- MRI will demonstrate its tract - High recurrence rate - ave 2.4 procedures/pt
8-10% of all branchial arch anomalies
Cysts twice as common as sinuses/fistulae
2nd ARCH FISTULA TRACT AND CYSTS Classification
Classification of 2nd arch cysts:
Type 1- superficial at border of SCM
Type 2- between SCM and IJV
Type 3- in the carotid bifurcation
Type 4- in the pharyngeal wall
2nd ARCH FISTULA TRACT AND CYSTS Describe
External: lower 1/3 of neck, anterior border SCM
Fistula tract: - caudal to platysma, through deep fascia to carotid sheath - below stylohyoid and above (superficial) IX and XII - between ICA, ECA
Enters pharynx- anterior aspect of posterior faucial pillar
2nd ARCH FISTULA TRACT AND CYSTS Recurrence
Recurrence rates in 2nd arch surgery (Mayo clinic, n=208):
- Prior surgery = 21%
- Prior infection = 14%
- No infection/surgery = 3%
3rd ARCH FISTULA TRACT Describe & course
Fistula tract:
External: as for 2nd arch fistula - lower 1/3 of neck, anterior border SCM
Course: inferior to CN IX, superior to CN XII, posterior to ICA
Internal: pierces thyrohyoid membrane to open in upper piriform fossa
4th ARCH FISTULA TRACT Describe & course
Fistula tract:
External: as for 2nd/3rd arch fistulae - lower 1/3 of neck, anterior border SCM
Course: deep to platysma, loops over CN XII, turns caudally in carotid sheath, loops around 4th arch artery (R SCA, L arch of aorta)
Internal: pierces cricothyroid membrane, opens to piriform apex
PARAPHARYNGEAL SPACE Boundaries
An inverted pyramid shape
Potential space lateral to upper pharynx, filled with fat and areolar tissue
Boundaries
Superior (base) - base of skull (temporal/sphenoid) Inferior (apex) - junction of digastric tendon with lesser horn of hyoid
Anterior - Pterygomandibular raphe and medial pterygoid fascia
Posterior - Pre-vertebral fascia
Medial - Buccopharyngeal fascia overlying sup constrictor and pharyngobasilar fascia. Fascia from TVP to medial pterygoid
Lateral - Fascia overlying medial pterygoid, mandibular ramus, PBD and deep lobe of parotid
PARAPHARYNGEAL SPACE Divisions
Division is by the Styloid process tensor-vascular-styloid fascia
- Prestyloid - Fat, deep lobe parotid, LNs, Styloglossus, Stylopharyngeus, V3 branches, TVP, LVP, IMA, asc palatine a, asc pharyngeal a
- Post-styloid - Cartoid sheath (ICA, IJV, X), SNS trunk, IX, XI, XII, IMA, paraganglionic tissue
PARAPHARYNGEAL SPACE Communcations xxxx x
Communications
Medial - peritonsillar space
Anterolateral - Masticator space
Posteromedial - Retropharyngeal space
Inferomedial - Submandibular space
Lateral - Parotid space
Posterior - Carotid sheath contents
Superior - ITF
Pathology: 80% benign, 20% malignant (mostly salivary)
TEMPORAL FOSSA Boundries
Boundaries:
Superiorly - by the superior temporal line.
Inferiorly - zygomatic arch (arbitrary designation)
Floor - bones of the lateral aspect of the skull, including a portion of the frontal, GW sphenoid, the temporal, and the parietal bones
Separated inferior from infratemporal fossa by the infratemporal crest of the greater wing of sphenoid
TEMPORAL FOSSA Contents
Contents: Temporalis muscle - attaches superiorly to inferior temporal line
TEMPORAL FOSSA Superior Temporal Line
Superior temporal line:
Anteriorly - Zygomatic process of the frontal bone
Arches posteriorly over the parietal bone before descending to the temporal bone, where it blends into the zygomatic process
Attachment of temporalis fascia
Vertical groove on squamous temporal bone = superficial temporal vessels
INFRATEMPORAL FOSSA Boundaries
A space lying beneath the base of skull between side wall of pharynx and ramus of mandible
Boundaries
Superior - IT surface of greater wing of sphenoid, Squamous temporal bone - Continous with temporal fossa laterally (infratemporal crest marks this transition)
Inferior - Opens into the neck
Anterior - Posterior surface of maxilla and IOF
Posterior - Upper carotid sheath
Medial - Lateral surface of lateral pterygoid plate, TVP/LVP/superior constrictor, pterygomaxillary fissure (connects to PPF)
Lateral - Ramus of mandible and its coronoid process
INFRATEMPORAL FOSSA Contents xxxx
Contents: Medial pterygoid Lateral pterygoid Insertion of temporalis into coronoid process Internal maxillary artery Pterygoid venous plexus V3 and branches (+ otic ganglion, chorda tympani) PSAN (of V2)
MUSCLES OF MASTICATION xxxxxx x
1. Medial pterygoid
- Origin - Deep head: Medial surface LPP, fossa between MPP/LPP - Superficial head: maxillary tuberosity and pyramidal process of palatine bone
- Insertion - Angle of mandible (broad insertion)
2. Lateral pterygoid
- Origin - Upper head - Infratemporal surface of skull (GW sphenoid) - Lower head - Lateral surface of LPP - Insertion - Pterygoid fovea (beneath medial end of mandibular head) - Articular disc and capsule of TMJ 3. Temporalis - Origin - Temporal fossa
- Insertion - Coronoid process and down ramus to buccinator insertion
4. Masseter
- Origin - Zygomatic arch
- Insertion - 3 heads of masseter fuse anteriorly - Posteriorly they diverge from one another - Superficial - broad attachment - body, angle, ramus - Intermediate - ramus - Deep - ramus - Between the heads: sup / intermed = masseteric artery, intermed / deep = masseteric nerve
PTERYGOPALATINE FOSSA Def & boundries
Lies between back of maxilla and pterygoid process of sphenoid
Boundaries:
- Posterior - sphenoid bone - a. root of pterygoid process (incl Vidian Canal), b. greater wing (incl Foramen Rotundum)
- Medial - palatine bone (incl notch for SP foramen)
- Anterior - posterior wall of maxilla - leads to IOF
- Roof - a. body of sphenoid, b. orbital process of palatine bone
- Lateral - pterygomaxillary fissure (leads to ITF)
PTERYGOPALATINE FOSSA Contents
Contents:
1. V2 - Meningeal branch (to MCF) - Zygomatic Nerve (arises in PPF and runs to IOF above V2), takes the secretomotor fibres from the ganglion (pass to lacrimal gland via Lacrimal branch of V1) - Post Sup Alveolar N - Exits via Pterygomaxillary Fissure to posterior surface of maxilla - V2 exits through IOF to become ION - Ganglionic branch
2. Pterygopalatine Ganglion - Connected to V2 by short trunk (inf/med to V2) - Only cell bodies are PSNS (SNS and sensory fibres ‘relay station’) - Autonomic root is Vidian N (PSNS- GSPN, SNS- ICA plexus via DPN) - Fibres arise in Superior Salivary Nucleus 3. Maxillary Artery 5 branches accompany the 5 nerves of the PPG - Vessels lie in front of nerves
PTERYGOPALATINE Ganglion Branches
Branches of the Pterygopalatine Ganglion:
1. Nasopalatine N - SP foramen - Septum + incisive gum of hard palate (descends down incisive foramen)
2. Lat Post Sup Nasal Ns - SP foramen - Postersup quadrant of LNW
3. Greater Palatine N - GP foramen/canal (junction of maxilla and palatine bone) - Mucosa of hard palate - Nasal branches - posteroinf quadrant LNW + med wall max sinus
- Lesser Palatine Ns - Lesser palatine foramina (behind GPN) - Soft palate and tonsil mucosa
- Pharyngeal N - Palatovaginal canal - Nasopharynx mucous membrane
- Orbital branches - IOF - Orbital periosteum, orbitalis muscle - Sphenoid/ethmoid sinuses
TONGUE xxxx
Mass of skeletal muscle with midline fibrous septum covered by mucous membrane - Keratinising stratified squamous epithelium Parts of the tongue: - Dorsum, tip, ventral surface, base (BOT is oropharynx not oral cavity)
Papillae:
- Filiform- velvety appearance
- Fungiform- discrete pink pinheads (bears the taste buds)
- Circumvallate- 12, form a V in front of sulcus terminalis (marks division of oral cavity and oropharynx
Folds: Median glossoepiglottic, lateral glossoepiglottic
Muscles:
- Intrinsic x4 shape no bony attachments - longitudinal (sup/inf), vertical, transverse
- Extrinsic x 4 position - Genioglossus - bulk of tongue. Genial tub to mucous memb + hyoid (i.e. geniohyoglossus) - Hyoglossus - length of greater horn/body of hyoid (free ant + post borders) - Styloglossus - low/ant styloid to interdig with hyoglossus - Palatoglossus - undersurface of palate to interdig with styloglossus
TONGUE Parts
Mass of skeletal muscle with midline fibrous septum covered by mucous membrane - Keratinising stratified squamous epithelium Parts of the tongue:
- Dorsum, tip, ventral surface, base (BOT is oropharynx not oral cavity)
TONGUE Papillae
Papillae:
- Filiform- velvety appearance
- Fungiform- discrete pink pinheads (bears the taste buds)
- Circumvallate- 12, form a V in front of sulcus terminalis (marks division of oral cavity and oropharynx
TONGUE Folds & Muscles
Folds:
Median glossoepiglottic, lateral glossoepiglottic
Muscles:
- Intrinsic x4 shape no bony attachments - longitudinal (sup/inf), vertical, transverse
- Extrinsic x 4 position - Genioglossus - bulk of tongue. Genial tub to mucous memb + hyoid (i.e. geniohyoglossus) - Hyoglossus - length of greater horn/body of hyoid (free ant + post borders) - Styloglossus - low/ant styloid to interdig with hyoglossus - Palatoglossus - undersurface of palate to interdig with styloglossus
TONGUE Blood & nerve supply
Blood supply: Lingual A. - above greater horn of hyoid - Dorsal lingual branches to posterior tongue Asc Pharyngeal, tonsil branches of Facial- small contributions Lingual v. - tributaries run with Lingual a. Deep Lingual v. (visible in FOM) + sublingual v. — vena comitants of XII
Nerve supply: Anterior 2/3 - sensation- Lingual N., Taste- chorda tympani Posterior 1/3 - IX (sensation + taste), X (internal branch of SLN- ant valleculla) Motor - all CN XII except palatoglossus (pharyngeal plexus)
** taste travels to nucleus tractus solitarius
TONGUE Embryology
Embryology:
Appears during Week 4 - as the tuberculum impar.
2 lateral swellings appear either side of the tuberculum —> fuse to form the midline fibrous septum (Arch I)
Base of tongue is formed from the hypobranchial eminence (Arch III). This joins with the lateral swellings at the sulcus terminalis to form the tongue
Tongue muscles derived from suboccipital myotomes (ie not supplied by branchial arch nerves - XII instead)
Migrate forward into the sac of mucous membrane derived from arches I, III, IV
PHARYNX Def Layers
BOS to C6 (12cm), open anteriorly
Divided to Naso-, Oro-, Hypo- - Free edge of soft palate - Tip of epiglottis (level of hyoid)
Layers of Pharynx
- Mucosa
- Submucosa- thickened superiorly as the Pharyngobasilar Fascia
- Muscle - 3 constrictors, 3 other
- Buccopharyngeal Fascia (thickening of the epimysium of the muscle layer)
PHARYNX Attachments
Attachments of the Pharyngobasilar Fascia
- Pharyngeal tubercle (occipital bone) - Laterally across longus colli, anterior to carotid canal/foramen lacerum, drapes off ET - Medial Pterygoid plate down to hamulus
PHARYNX Constrictors
Constrictor muscles insert to the pharyngeal raphe (midline posteriorly) and fan out from there to the following attachments:
- Superior - Hamulus, pterygomandibular raphe, mandible
- Middle - Angle between Stylohyoid (at lesser horn) and hyoid bone
- Inferior - 2 parts: - Thyropharyngeus - Oblique line of thyroid and fibres spanning CT muscle - Cricopharyngeus - Cricoid cartilage (full ring of muscle) - Killian’s dehiscence between TP and CP
PHARYNX Structures entering & relationship to constrictors
Structures enter pharynx from outside:
Above SC - Eustachian tube
Between SC/MC - IX, Lingual N, Stylopharyngeus
Between MC/IC - IBSLN, SL vessels (thyrohyoid membrane)
Under IC - RLN
PHARYNX Innervation
Innervation - All pharyngeal plexus (IX, X, SNS fibres) - SNS fibres are vasoconstrictor - Arise in Nucleus Ambiguus - Except Stylopharyngeus - IX
TONSIL ANATOMY Def and parts
Paired lymphoid aggregates in the lateral oropharyngeal wall forming part of Waldeyer’s Ring
- Specialized lymphoid aggregates with external lining of stratified squamous epithelium
2 borders - Anterior - Palatoglossal arch - Posterior - Palatopharyngeal arch
2 poles - Upper - Soft palate - Lower - Tongue base
2 surfaces - Medial - Pharyngeal mucosa (stratified squamous epithelium) with crypts (up to 20 in number) - Lateral - Covered by capsule ( a thickening of the submucosa/extension of PB fascia) - Connective tissue septae extend to tonsil from capsule (not easily separated)
TONSIL ANATOMY Relations
Relations of the tonsil
- SC
- Stylopharyngeus, Styloglossus, Stylohyoid lig, Styloid process
- ICA (2cm posterolateral to tonsil bed)
- IX
TONSIL ANATOMY Blood sup
Blood supply:
5 arterial sources, tonsillar branches of
- Ascending pharyngeal a.
- Lesser palatine a. (3rd part IMA)
- Ascending palatine a. (branch of Facial a.)
- Facial a.
- Lingual a.
Venous drainage
- Venous plexus forms around capsule then drain to tonsil branch of Lingual v.
- Accessory Tonsil v. (drains to pharyngeal plexus)
- External palatine v. (superior pole)
TONSIL ANATOMY Embrology
Embryology:
Begins 12 weeks
Derived from 2nd pharyngeal pouch endoderm
Lymphocytes migrate into the area (mesoderm)
8-10 buds of pharyngeal squamous epithelium grow into the pharyngeal walls —> crypts formed
TONSIL ANATOMY Histo & epithelium
Embryology:
Begins 12 weeks
Derived from 2nd pharyngeal pouch endoderm
Lymphocytes migrate into the area (mesoderm)
8-10 buds of pharyngeal squamous epithelium grow into the pharyngeal walls —> crypts formed
TONSIL ANATOMY Zones
Zones:
- Specialised squamous epithelium (epithelium invaginates as the crypts- increase surface area to compensate for lack of afferents) - Lymphoepithelium = epithelium + lymphocytes + macrophages + dendritic cells (APC) - Captures foreign material from the epithelial surfaces
- Parafollicular (T-cell rich) - Dendritic cells present antigens on their cell surface via MHC-II molecules, interacting with CD4+ T cells (assisted by co-stimulatory molecules e.g. CD80)
- Mantle zone = lymphocytic cap around the germinal centre (B-cell predominant) - Primed T cells interact with naive B cells with co-stimulatory CD-40 —> B cell proliferation and differentiation - B cells migrate to the lymphoid follicle (forming germinal centres)
- Germinal centres (B-cell rich) - B cell proliferation, high affinity mutation, isotype switching and maturation - Produces Plasma cells and memory B cells
TONSIL ANATOMY Difference from lymph node
Differences from lymph nodes:
- Non-encapsulated
- No afferent lymphatic channels
Front-line defense at mucosal site
- Secretory Ig regulation
SOFT PALATE Innervation
Innervation
- All pharyngeal plexus (IX, X, SNS fibres)
- SNS fibres are vasoconstrictor
- Arise in Nucleus Ambiguus
- Except TVP - Nerve to Medial Pterygoid (V3)
Palatopharyngeal sphincter:
Level of hard palate (C1)
Forms Passavant’s ridge
SOFT PALATE Muscles
Made up of 5 paired muscles:
- Tensor Veli Palatini Arises outside pharynx - 2 triangles converge on the pterygoid hamulus - Vertical (muscular) - arises from scaphoid fossa (med pterygoid plate), lateral cartilagenous ET, spine of sphenoid - Horizontal (aponeurotic) - attaches to other side, hard palate. Posterior edge is free
- Levator Veli Palatini Arises inside pharynx - Arises from petrous apex (ant. to ICA) and medial cartilagenous ET - Inserts to nasal surface of aponeurosis (interdigitates with other side to form a V-shaped sling)
- Palatopharyngeus (Palatolaryngeus) post faucial pillar - Arises from 1. nasal surface of aponeurosis and 2. hard palate - Inserts to superior horn of thyroid cartilage and thyroid lamina
- Palatoglossus Ant faucial pillar - Arises from under surface of aponeurosis - Interdigitates with Styloglossus
- Musculus uvulae - unimportant
SOFT PALATE Histology
Histology: Oral surface = stratified squamous epithelium Nasal surface = respiratory epithelium
SOFT PALATE What form’s passavant’s ridge?
Palatopharyngeal sphincter:
Level of hard palate (C1)
Forms Passavant’s ridge
OESOPHAGUS Def Parts Relations in thorax
Cricoid cartilage to cardiac orifice of stomach (C6-T10), 25cm long
2 portions
Cervical - Slightly to L of midline, then enters thorax in midline
Thoracic - Slightly to L of midline against vertebral bodies, behind L main bronchus, passes in front of descending aorta (i.e. off vertebrae) in contact with pericardium (L atrium)
Relations in thorax
Crossed by aortic arch on left and azygos vein on right
Crossed anteriorly by L main bronchus and R pulmonary artery
Thoracic duct crosses behind oesophagus (R to L) L atrium
OESOPHAGUS Constrictions
Constrictions
15cm - Cricopharyngeus
22cm - Aortic arch
27cm - Left main bronchus
38cm - Diaphragm
OESOPHAGUS Structure
Structure
Epithelium- stratified squamous
Muscularis mucosae- thick
Submucosa- sparse mucous glands
Muscular wall- inner circular, outer longitudinal - Skeletal in upper 1/3, visceral in lower 2/3
No serosa (except the short intra-abdominal course)
OESOPHAGUS Blood supply
Arterial supply
Upper- Inferior thyroid artery
Middle- Oesophgeal branches of aorta
Lower- Oesophageal branches of L gastric artery Venous drainage
Upper - Brachiocephalic veins
Middle - Azygos veins
Lower - L gastric vein (to Portal vein)
OESOPHAGUS Nerve supply Lymph drainage
Nerve supply
Upper - RLN
Middle - Unnamed CN X branches
Lower - Oesophageal plexus (CN X branches Lymph Follows arteries
BRONCHIAL BRANCHING Overall structure Blood supply
Trachea — Mainstem Bronchi (Primary) — Lobar Bronchi (Secondary) — Segmental bronchi (Tertiary) — Bronchioles — Alveolar duct
Lobar bronchi:
- 3 on right
- 2 on left (upper includes lingula segmental bronchi)
Segmental bronchi: Each segmental bronchus enters a pyramid shaped bronchopulmonary segment with its apex pointing towards the hilum
Blood supply:
Artery - bronchial a. from aorta
Venous - Right —> Azygos, Left —> Hemiazygos
BRONCHIAL BRANCHING Left segmental brochi
Left side: ASIA ALPS (or ASIA SAMPL)
- Upper - Apical - Sup Lingula - Inf Lingula - Anterior
- Lower - Anterior - Lateral - Posterior - Superior
BRONCHIAL BRANCHING Right segmental brochi
Right side: A PALM Seed Makes Another Little Palm (or A PALM SAMPL)
- Upper - Apical - Posterior - Anterior
- Middle - Lateral - Medial
- Lower - Superior - Medial - Anterior - Lateral - Posterior
THYROID Def Surroundings Immediate relations
2 symmetrical lobes +/- pyramidal lobe
- Joined by the isthmus which attaches to 2nd-4th tracheal rings
Surrounded by visceral portion of MLDCF
- Thickened as Berry’s ligament (attachment to trachea) Upper pole is limited by sternothyroid thus goitre extends retrosternally rather than superiorly
3 Surfaces:
- Lateral - Under sternothyroid/sternohyoid
- Medial - Against larynx/trachea
- Posterior - Carotid sheath/parathyroids
- Tubercle of Zuckerkandl (remnant of Ultimobranchial Body) - Posterolateral projection. RLN Nearly always behind this.
- Sup PT nearly always cranio-posterior to TZ
THYROID Course of RLN
Recurrent Laryngeal Nerve:
Ascent - Left - in tracheo-oesophageal groove - Right - at an angle (20 degrees) to trachea
Relationship to ITA - Left - more likely behind - Right - 50/50 in front/behind
Always behind pretracheal fascia and therefore Berry’s Ligament
May divide above isthmus - anterior branch will be motor (larger)
THYROID Non-recurrent laryngeal nerve
Non recurrent RLN
- Due to anomalies of branchial arteries
- Come off ~ level with cricoid, behind CCA to CTJ
- Right - 1% associated with retro-oesophageal subclavian artery (arises from left aortic arch)
- Left - very rare - assoc with situs inversus & anomalous left SCA
THYROID Blood supply
Arterial supply
- STA - 1st branch ECA - Divides on the gland (ant/post branches)
- ITA - thyrocervical trunk, 1st part of SCA - Divides outside the fascia, then multiple branches enter capsule
- Thyroid ima artery- present in 3% - Variably arises from Brachiocephalic a., R CCA, arch of Aorta
Venous drainage - STV- drains to IJV or Facial v. - MTV- direct to IJV - ITV- Brachiocephalic v.
SUPERIOR LARYNGEAL NERVE Anatomy
Anatomy
- Arises from inferior (Nodose) Ganglion
- Medial to ICA (bifurcates into ext (motor) & int (sensory & autonomic) branch)
- Internal - Pierces thyrohyoid membrane (with SL artery & vein), divides into upper & lower branch
- External runs inferiorly over inferior constrictor
- EBSLN variable couse - Type 1 stays superficial to IC to CT, Type 2 pierces lower IC, Type 3 pierces upper IC
- Type 3 rarely identified but is protected by IC
- Type 1 commonly seen over superior pole thyroid (Cernea 2b) - most at risk
SUPERIOR LARYNGEAL NERVE Locating ext Br SLN
Finding EBSLN (Friedman et al)
- Remove medial 5mm Sternothyroid to ecpose IC & CT
- Nerve stimulator to identify EBSLN as inserts into CT
- If runs over IC (type 1) it is followed to preserve it over superior pole (Cernea 2b)
- If dives into IC low (type 2) no further dissection required (IC protects)
- Type 3 usually not seen (~20%)
SUPERIOR LARYNGEAL NERVE Joll’s Triangle boundaries Finding nerve within
Joll’s Triangle:
- Lateral = superior thyroid pole and superior thyroid artery/vein
- Superior = Hyoid bone (attachment of fascia and sternothyroid)
- Medial = midline
- Floor = cricothyroid membrane Identifying the EBSLN within Joll’s triangle: - Retract gland laterally and develop avascular plane between gland and larynx - EBSLN passes medialy across this space
SUPERIOR LARYNGEAL NERVE Cernea EB-SLN types
Cernea EBSLN types: Aina & Hisham ANZJ Surg, 2001
Type 1: >1cm from upper pole (17%)
Type 2a: <1cm from upper pole (56%)
Type 2b: in contact with upper pole (27%)
Asymmetry in 53% - Increased Type 2a/2b configuration in MNG (superior enlargement of gland) - Preservation still results in 5% voice change (cricothyroid affects pitch) - Loss of high tone and pitch volume and fatigue after extensive use
SUPERIOR LARYNGEAL NERVE SLN palsy - rates - Symptoms - exam findings
SLN Palsy - Conflicting - up to 20% when not looked for - Bilateral CT paralysis rare (often needs EMG to confirm)
Symptoms - Hoarse / breathy voice - Lack of projection / loudness - Vocal fatigue - Difficulty singing (loss of high pitch control)
Appearance - Shortened cord - Bowing - Height mismatch (inferior displacement) - maybe compensatory muscle tension dysphonia
PARATHYROID ANATOMY xxxx
Paired superior & inferior glands
35-40mg, 3-8mm 87% 4 glands, 6% 3 glands, 6% 5 glands
Embryology - starts in 5th week
- Superior PT (PT IV)- 4th pouch endoderm with C cells of thyroid
- Inferior PT (PT III)- 3rd pouch endoderm with thymus - Position more variable in ectopia, because of longer descent course
Location of the glands Symmetrical in 80%
- Inferior PT - superficial to RLN. within 1cm inf/post/lat to inferior pole (50%) - Carotid bifurcation to thymus - Identifying branches of ITA is an excellent technique
- Superior PT - deep to RLN, in a 2cm diameter area centred above crossing of the ITA and RLN, within 1cm of CT joint - More likely to be intrathyroidal (joint origin with C cells) - Very rare to be below main trunk of ITA (i.e. cephalad to ITA) - On or just above RLN at junction of upper/middle 1/3s of gland (when thyroid retracted medially)
Blood Supply
- Both glands usually receive supply from ITA
- Occ superior PT receives blood from STA
FLOOR OF MOUTH Muscles inc courses
Muscles of the FOM:
- Mylohyoid - Mylohyoid line to hyoid bone (only the posterior fibres) and midline raphe (most fibres)
- Geniohyoid - midline, genial tubercle to hyoid body (lies on top of mylohyoid)
Mylohyoid divides the neck and the mouth
FLOOR OF MOUTH Structures between mylohyoid and hyoglossus
Structures between mylohyoid and hyoglossus:
1. SM duct - Passes fwd from superficial gland. Opens at sublingual papilla
- CN XII - Passes fwd on lower border of hyoglossus - At the anterior border of hyoglossus it becomes flat and gives off branches to the tongue
- Lingual Nerve - Enters mouth passing under sup constrictor (at its attachment to PM raphe) - Runs fwd on mylohyoid, dips under SM duct then runs fwd on hyoglossus above the duct - Lingual N runs lat-med, Wharton’s duct runs med-lat - In the FOM the nerve is flattened rather than round
FLOOR OF MOUTH Structures deep to hyoglossus:
Structures deep to hyoglossus:
- Lingual artery - Runs just above greater horn of hyoid (level with CN XII)
- CN IX - Disappears under upper part of hyoglossus - Much thinner than CN XII
- Stylohyoid ligament - Styloid process to lesser horn of hyoid - Angle between lig and hyoid is the origin of middle constrictor which fans out posteriorly
STYLOID APPARATUS Def parts
Part of temporal bone, ossifies in cartilage
Embryologically derived from 2nd branchial arch
2 Ligs
3 Muscles
Stylohyoid ligament - Runs from styloid tip to lesser horn of hyoid - Persistence of perichondrium of Reichert’s cartilage - Styloid process has a variable length
Stylomandibular ligament - Thickening of deep lamina of parotid fascia (SLDCF) - Vaginal process of tympanic bone to angle of mandible - Forms the stylomandibular tunnel (skull base and mandible) where parotid tumours dumb-bell
STYLOID APPARATUS Ligaments
Stylohyoid ligament - Runs from styloid tip to lesser horn of hyoid - Persistence of perichondrium of Reichert’s cartilage - Styloid process has a variable length
Stylomandibular ligament - Thickening of deep lamina of parotid fascia (SLDCF) - Vaginal process of tympanic bone to angle of mandible - Forms the stylomandibular tunnel (skull base and mandible) where parotid tumours dumb-bell
STYLOID APPARATUS Muscles
Muscles: all have different innervation
- Stylopharyngeus- Deepest (medial) and highest (CN IX) Inserts: posterior border of the thyroid lamina and side wall of pharynx
- Stylohyoid- arises posteriorly, high up (CN VII) Inserts: splits around digastric tendon, inserts base of greater cornu
- Styloglossus- Arises in front and low down (CN XII) Inserts: lateral aspect of tongue, interdigitates with hyooglossus
TEMPOROMANDIBULAR JOINT Def Nerve supply Features
Definition: Synovial joint between mandibular head and mandibular fossa (squamous TB)
Features:
- Interarticular fibrocartilagenous disc (attaches to capsule)
- Capsule
- No Hyaline cartilage
- Lateral TM lig - Oblique down and back - Tightened by movements away from resting position
- Sphenomandibular lig axis of rotation - Spine of sphenoid to lingula of mandible
Nerve supply: Auriculotemporal Nerve (Hilton’s law)
TEMPOROMANDIBULAR JOINT Movement & Stabilisers
Stability: Greatest when occluded
- Preventing forward movement: - Posterior temporalis fibres - Prominence of articular tubercle
- Preventing backward movement: - Lateral pterygoid contraction - Obliquity of lateral ligament
Movements:
Protraction (LP) / Retraction (Temporalis)
Depression (LP + Digastric) / Elevation (Masseter/MP/Temporalis)
Side-to-side LP on one side, MP on the other
ROOT OF THE NECK CONTENTS Relationship to Scalenus Anterior
Scalenus Anterior: Key to the root of the neck
- Anterior tubercles of transverse process - C3-6 —> scalene tubercle (1st rib, upper surface)
- In line with longus capitis
Relations:
- Anterior - Phrenic N (5) - Ascending Cervical A. (Branch of ITA or thyrocervical trunk (15) - Transverse cervical (4) / suprascapular aa (8) - CN X (incl RLN) (14) - IJV - Subclavian V.
- Posterior - 2nd part SCA - Scalenus Medius
- Lateral - 3rd part SCA - Brachial Plexus
ROOT OF THE NECK Scalenus Muscles
Scalenus Anterior: Key to the root of the neck - Anterior tubercles of transverse process - C3-6 —> scalene tubercle (1st rib, upper surface) - In line with longus capitis
Scalenus Medius: - Posterior tubercles of transverse process - all Cx vertebrae —> quadrangular area btw neck + subclavian groove of 1st rib
Scalenus Posterior: - Posterior tubercles of transverse process - C4-6 —> 2nd rib
ROOT OF THE NECK Chassaignac’s triangle - boundries - contents
Chassaignac’s triangle: Apex TP C6 - compress CCA here
- Scalenus Anterior (lat)
- Lower fibres of longus colli (med)
- Subclavian Artery (base)
Contents - Vertebral art, vein, Stellate Ganglion
SUBCLAVIAN ARTERY Parts
3 parts related to the Scalenus Anterior muscle: Remember VITamin C + D 1st part before scalenus anterior
- Vertebral a.
- Thyrocervical trunk - Transverse cervical and suprascapular a. (laterally) - Inferior thyroid a. and Ascending Cervical a. (superiorly)
- Internal Thoracic a.
2nd part behind scalenus anterior 4. Costocervical trunk - Superior Intercostal a. - Deep Cervical a.
3rd part beyond scalenus anterior 5. Dorsal Scapular a.
AXILLARY ARTERY BRANCHES xxxxxx
Described in 3 parts related to Pec Minor:
- Before
- Behind
- Beyond
Mnemonic: Sixties Teens Love Sex And Pot
1st part: 1. Superior Thoracic a.
2nd part: 1. Thoracoacromial a. — pierces clavipectoral fascia — clavicular/deltoid/acromial/pectoral branches 2. Lateral thoracic a.
3rd part: 1. Subscapular a. 2. Ant circumflex humeral a. 3. Post circumflex humeral a.
CERVICAL SYMPATHETIC TRUNK Course Ganglia
Course:
- Ascends from thorax in front of prevertebral fascia
- Medial to Vertebral a. and medial to CN X
- Behind carotid sheath
- Ends at superior cervical ganglion
Cervical ganglia:
- Superior - Lat mass of atlas (grey rami to C1-4)
- Middle - Med to carotid tubercle (grey rami to C5-6) - In front of vertebral artery
- Inferior - Behind commencement of Vertebral A. (grey rami to C7-8 ie brachial plexus) - Inf and middle connect via the ansa subclavia in front of SCA
CERVICAL SYMPATHETIC TRUNK Visceral efferents
Visceral Efferents:
- Cardiac Plexus
- Vascular
- Superior - ICA (Int Carotid N, PPG and eyeball), ECA (pharyngeal plexus, otic/SM ganglia)
- Middle - Subclavian a. (local branches), ITA (larynx, trachea, hypopharynx, upper oesophagus)
- Inferior - Vertebral a. - to its branches
VASCULAR ANATOMY OF THE NOSE (INTERNAL) Supply
Internal Carotid Artery System: AEA - branch of Ophthalmic PEA - branch of Ophthalmic
External Carotid Artery System: Facial artery branches - Superior labial artery Internal Maxillary artery branches - SPA. Divides to a septal branch and conchal branch - Greater Palatine artery - descends via GP foramen then ascends through Incisive foramen
Intranasal plexuses: - Kiesselbach’s - anterior septum - Woodruff’s - posterior LNW
Septum distribution: Upper septum - AEA + PEA Posterior / inferior septum - SPA Ant / inferior septum - GPA Caudal septum/columella - Sup labial art
Lateral nasal wall: Superior - AEA Posterior - SPA Anterior - nasal br of facial a (check)
VASCULAR ANATOMY OF THE NOSE (INTERNAL) Plexuses
Intranasal plexuses: - Kiesselbach’s - anterior septum - Woodruff’s - posterior LNW
VASCULAR ANATOMY OF THE NOSE (INTERNAL) Septum distribution
Septum distribution:
Upper septum - AEA + PEA
Posterior / inferior septum - SPA
Ant / inferior septum - GPA
Caudal septum/columella - Sup labial art
VASCULAR ANATOMY OF THE NOSE (INTERNAL) Lateral wall
Lateral nasal wall:
Superior - AEA
Posterior - SPA
Anterior - nasal br of facial a (check)
HARD PALATE Parts Foramina
Make-up:
- Palatal process of maxilla - Pitted surface are insertion of Sharpey’s fibres)
- Horizontal process of palatine bone (smooth surface) - Mucous glands between bone and mucosa
Foramina:
- Greater palatine - between palatine and maxilla
- Lesser Palatine - multiple foramina behind GPF
- Incisive - midline anteriorly (GPN/GPA enter nose)
HARD PALATE Blood & Nerve supply
Blood supply: Greater Palatine A.
Nerve supply:
- Greater Palatine N.
- Nasopalatine N. (anterior)
DURAL VENOUS SINUSES xxxx
Torcular Herophili or Torcula is the confluence of the sinuses
CAVERNOUS SINUS Description
Spindle-shaped dural venous sinus Volume = 1.5mL
- No valves in the veins — bidirectional blood flow possible
Extends orbital apex —> petrous apex
Intersected by fibrous bands = tiny ‘caves’ (contrasts with all other dural venous sinuses)
Lies between 2 layers of dura - Outer layer = periosteum of sphenoid bone - Inner layer = covering of temporal lobe
CAVERNOUS SINUS Relations
Relationships:
Medial = sphenoid bone and pituitary fossa
Lateral = Temporal lobe + Meckels’ cave (post/inf)
Anterior = orbital apex (medial end of SOF)
Posterior = cerebral peduncle (PCF contents)
Roof = ICA + uncus of temporal lobe
Floor = greater wing of sphenoid
CAVERNOUS SINUS Inputs Outputs Contents
3 sources:
- Orbit (sup/inf ophthalmic veins)
- Bony vault (sphenoparietal sinus)
- Cerebral hemispheres (superficial middle cerebral vein)
3 outputs:
- Superior petrous sinus
- Inferior petrosal sinus
- Vein of Vesalius (to pterygoid plexus either via FO or own foramen medial to FO)
Contents: - ICA - III, IV, V1, V2 (lateral wall, top to bottom) - VI (medial side, below ICA)
SCALP Layers
5 layers of the scalp:
SCALP pnemonic Skin- thickest in the body (3-7mm)
- mostly firmly attached by the CT layer to aponeurosis/muscle
Connective tissue - a dense layer
Aponeurosis - includes muslce at either end (occipitalis/frontalis)
Loose areolar tissue - really a subaponeurotic layer (scalping can occur through this layer)
Pericranium - loosely applied to bone but firmly applied to the sutures - Carries blood supply to the cranium
SCALP Blood supply
Blood supply: free anastomosis between all branches
ECA branches - Occipital a. (runs with greater occipital N, Post auricular a. runs with lesser occipital N.) - Superficial Temporal a.
ICA branches branches of Ophthalmic a. - Supraorbital a. - Supratrochlear a.
TEMPORAL FASCIA Layers - fascia - all tissue layers (ext to internal)
There are 3 fascial layers in the temporal region:
- Temporoparietal fascia (also known as superficial temporal fascia) - Continuous with SMAS below zygoma)
- Deep Temporal fascia, subdivided to: - Superficial layer DTF - Deep layer DTF - These layers surround the temporal fat pad
Layers of the temporal region
Skin
Subcutaneous tissue
Temporoparietal fascia (aka superfical temporal fascia) - continuous with SMAS below, galea aponeurotica above superficial temporal line
Loose areolar tissue
Temporalis muscle fascia (aka deep temporal fascia) - continuous with pericranium. Has 2 lamina which fuse 2 cm above zygomatic arch. (superficial temporal fat pad between lamina) T
emporal muscle
Pericranium Bone
SMAS LAYER xxxx
Layers of the face:
Skin
Subcutaneous fat
SMAS - superficial musculoaponeurotic system
Muscles
Deep facial fascia (parotidomasseteric fascia - continuous with SLDCF in neck)
Retaining ligaments
Key features of the SMAS:
- Divides subcutaneous fat of the face into 2 layers - Non-septate fat (muscles to SMAS) - Septate fat (SMAS to dermis)
- Has a consistent relationship with neurovascular structures of the face
- Acts as a distributor of force - Attaches to nasolabial fold, perioral and periorbital regions to transmit the forces of facial expression
Relationship of SMAS to VII branches: - Lower face: VII branches are deep to SMAS - innervate facial muscles from undersurface (except levator anguli oris, buccinator and mentalis) - Upper face: nerves penetrate SMAS and thus run superficial to SMAS - sub-SMAS dissection to avoid nerves - Temporal branch of VII: runs within the SMAS
*** NEW STUDY in PRS suggests all branches are deep to SMAS
MUSCLES OF THE FACE Functional groups
Form part of the panniculus carnosus - attached in part to dermis, thus wrinkles the skin
Consist of 3 functional groups- eyelid, nose, lips/cheeks
MUSCLES OF THE FACE Eyelid
Eyelid - Sphincter = Orbicularis oculi - Palpebral - confined to lids. Med palpebral lig to lateral palpebral raphe - Orbital - anterior lacrimal crest and frontal process of maxilla - Dilator = Levator palpebrae superiorus and occipitofrontalis
MUSCLES OF THE FACE Nose
Nose - Sphincter = compressor naris (transverse component of nasalis) - Dilator = dilator naris - Elevator = procerus, lev labii sup alequae nasi - Depressor = depressor septi
MUSCLES OF THE FACE Lips/cheek
Lips/cheeks
- Sphincter = orbicularis oris - Mental + incisive slips attach to bone, rest forms from Buccinator via the modiolus
- Buccinator - upper to lower jaw + PM raphe + pterygomaxillary lig
- Dilators = form the ‘spokes of a wheel’ - Lev labii sup alequae nasi = frontal process maxilla to LLCs + upper lips - Lev labii sup = inferior orbital margin to upper lip - Lev anguli oris = canine fossa to modiolus - Zygomaticus minor = zygomaticomaxillary suture to modiolus - Zygomaticus major = zygomatic bone to modoilus - Risorius = upward extension of platysma to modiolus - Depressor anguli oris = oblique line of mandible to modiolus - Depressor labii inferioris = deep to DAO to lower lip - Mentalis = mental symphysis to skin
MUSCLES OF THE FACE VII supplies which muscles?
Distribution of VII branches:
- Temporal — Frontalis
- Zygomatic - Upper —> above eye (frontalis and upper 1/2 of orbicularis oculi) - Lower —> below eye (lower 1/2 of orbicularis oculi and muscles below orbit
- Buccal — Buccinator and upper lip muscles (OO, LLSAN, LLS, ZMin, Zmaj, LAO, Ris)
- Marginal mandibular — Lower lip muscles (OO, DAO, DLI, Mentalis)
- Cervical — Platysma
NERVE SUPPLY OF THE FACE Motor
Motor Supply: CN VII
VII divides to temporozygomatic and cervicofacial divisions in parotid - Pes anserinus Emerges as 5 branches
- Temporal- Frontalis
- Zygomatic- - Upper branch- upper 1/2 of orbicularis oculi - Lower branch- lower half of orbicularis oculi and muscle below orbit
- Buccal- buccinator and upper lip muscles (upper 1/2 orbicularis oris and elevators)
- Marginal mandibular- Muscles of lower lip
- Cervical- platysma
NERVE SUPPLY OF THE FACE Sensory
Sensory supply: CN V branches (except over Ao mandible - GAN)
- Ophthalmic - Lacrimal - Upper lateral eyelid - Supraorbital - forehead and scalp to vertex - Supratrochlear - midline forehead - Infratrochlear - medial upper eyelid - External Nasal - middle of external nose down to tip
- Maxillary - Infraorbital - - Palpebral- lower eyelid and cheek - Nasal- nasal sidewall and alar - Labial- upper lip and labialgum to 2nd premolar - Zygomaticotemporal - hairless part of the temple - Zygomaticofacial - over zygomatic arch
- Mandibular - Auriculotemporal - - Auricular- EAM, surface of TM, pinna above EAM - Temporal- hairy skin over temple - Buccal - ‘thumbprint’ area of skin below zygomatic arch - Mental - skin/mucous membrane of lower lip/gum midline to 2nd premolar
VENOUS DRAINAGE OF THE FACE xxx
Venous drainage face
Supraorbital, supratrochlear veins → angular vein → facial vein → pierces investing layer of deep fascia → joined by anterior branch of retromandibular vein → IJV → brachiocephalic vein
Superficial temporal vein → joined by maxillary veins (from pterygoid plexus) → becomes retromandibular vein → anterior branch joins facial vein, posterior branch joined by posterior auricular vein → EJV → subclavian vein
Deep venous anastomoses:
B/W facial vein and cavernous sinus (via ophthalmic veins at medial canthus)
B/W facial vein and pterygoid plexus (via deep facial vein in front of masseter)
PAROTID GLAND Def Relations
Paired glands on either side of face between ear and mandibular ramus
Surrounded by thick capsule derived from SLDCF
Superficial/deep portions arbitrarily divided by CN VII
Relations:
Superior - TMJ, zygomatic arch
Inferior - upper border of SCM (‘parotid tail’)
Lateral - subcutaneous, GAN - GAN branches to anterior and posterior (supplies ear lobe)
Anterior - MP, ramus, masseter
Deep - Mastoid tip (with assoc muscles esp SCM, PBD), styloid (assoc muscles- stylohyoid, stlyoglossus, stylopharyngeus), ECA
PAROTID GLAND Landmarks VII in Parotid
Landmarks for CN VII in Parotid
- Posterior belly of digastric (just above its superior border, bisects digastric-mastoid angle)
- Tympanomastoid suture
- Tragal pointer- 1cm inferior, deep
PAROTID GLAND Stensen’s duct - size - course
Stensen’s duct:
5cm long - along a line from intertragal notch to philtrum
Passes fwd across masseter and turns to pierces buccinator
- Passes submucosal in buccinator before pierces mucous membrane opposite upper 2nd molar
- Provides a ‘valve’ function
PAROTID GLAND Histology
Histology: predominantly a serous gland
Serous secretory units (acini) drain to intercalated (terminal) ducts
Intercalated ducts converge to form striated (intralobular) ducts which in turn converge to form secretory (interlobular) ducts
Interlobular ducts empty to main parotid duct
SUPERIOR ORBITAL FISSURE Boundries
SOF forms between greater and lesser wings of sphenoid, tendinous ring = Ligament of Zinn
ORBITAL APEX Muscle & ligament attachments
Lig of Zinn attaches to bone, origin of recti
LR separates SOF into medial & lateral compartments
LPS arises from LWoS inserts sup tarsal plate & skin upper lid
SO arises from narrow tendon body sphenoid, thru trochlea into postero-superior sclera
IO - arises orbital floor beneath trochlea (maxilla) - passes obliquely back to post-inf sclera
All nerves stay within / outside cone except anterior ethmoid / posterior ethmoid / infratrochlear (all branches of nasocilary (V1))
LACRIMAL APPARATUS Parts
Consists of:
- Lacrimal gland
- Lacrimal canaliculi
- Lacrimal sac
- Nasolacrimal duct
LACRIMAL APPARATUS Describe lacrimal gland - parts - location - Nerve supply
1. Lacrimal gland
- A serous gland made up of two components- orbital (large) and palpebral (small)
- Lacrimal gland fossa sits in orbital portion of frontal bone - In the lateral part of orbital roof, supported by lateral edge of apopneurotic tendon of LPS
- Approx 12 ducts lead from palpebral component to superior fornix of conjunctiva
Nerve supply: Sup Salivatory Nucleus —> NI —> GG –> GSPN –> Vidian Nerve –> PPG v—> Zygomatic Nerve (V2) —> lacrimal nerve (v1) —> lacrimal gland
SNS - Sup cervical ganglion
LACRIMAL APPARATUS Describe lacrimal Canaliculi - parts - location - Nerve supply
Lacrimal canaliculi puncta lie 6mm from medial canthus
- Each canaliculus has a 2mm vertical portion and 8mm horizontal portion
- Superior and inferior join to form the common canaliculus
- Valved ducts (Valve of Rosenmuller) prevent reflux of tears from the lacrimal sac
LACRIMAL APPARATUS Describe lacrimal sac - parts - location - Nerve supply
-
Lacrimal sac 12mm x 5mm
- Lies in its fossa formed by lacrimal grooves of maxilla and lacrimal bone - Relatively higher than previously appreciated — affects surgical approach - 9mm above middle turbinate axilla
- Crossed in front by medial palpebral ligament and palpebral fibres of OO
- Muscle contraction causes tears to be ‘sucked’ through the puncta (i.e. during blinking)
- When the muscle relaxes the lacrimal sac recoils and pumps its contents to the NLD
LACRIMAL APPARATUS Describe nasolacrimal duct - parts - location - Nerve supply
Nasolacrimal duct -
2cm long, slopes downward and laterally to open to inferior metaus - 2cm behind nostril, Hasner’s valve
- Internal diameter = 3.5mm
- Mucous membrane is raised into several folds which act as valves to prevent air entering the NLD
ORBITAL SEPTUM Structure of eyelid
Structure of the eyelids: superficial to deep
- Loose skin
- Orbicularis oculi muscle
- Skeletal framework: orbital septum (thickened at the lid margins to form the tarsal plates)
- Conjunctiva
ORBITAL SEPTUM Structure of Tenon’s capsule
Tenon’s Capsule:
- Applied to the back of the eye - Extends forward encasing the muscles - Thickenings lateral and medial: - Lateral/medial check ligaments - Joined as the suspensory ligament of Lockwood —> supports the eye
ORBITAL SEPTUM Description Attachments
Orbital septum:
Attached to the anterior lacrimal crest and margins of the orbit - Wide ‘buttonhole’: the palpebral fissure between the lids
Thickened superiorly and inferiorly - Superior/inferior tarsal plates (dense fibrous tissue)
Septum thickened medially in its attachment to anterior lacrimal crest (medial palpebral ligament) - Lat palp lig is much thinner, fusing with lat palpebral raphe of OO
Contain the tarsal (Meibomian) glands
OLFACTORY ANATOMY Epithelium - type - cell types - thickness - % airflow reaching cleft
Epithelium = pseudo stratified columnar neuroepithelium
- 70microm thick vs 30microm for resp, Area = 1cm2 (cilia — 22cm2)
10-15% of airflow reaches olfactory cleft
Olfactory epithelium - 5 cell types:
- Olfactory neurons- bipolar neurons - One end = knobs for detecting odour (immotile cilia- lack dynein arms) - Other end = projection to olfactory bulb. Synapses in glomerular layer
- Microvillar cells - Receptor function (poorly understood)
- Sustentacular cells - Maintains ionic milieu. Deactivates odourants. Insulates adjacent receptor cells from each other
- Basal cells - deepest layer. Regenerative (3-7 weeks) - Globose cells —> neuron replacement, Horizontal cells —> replace all cell types
- Bowman’s glands - Mucus secretion for odour absorption
OLFACTORY ANATOMY Olfactory nerve supply
Unmyelinated axons converge into 15-20 fila (myelinated) to traverse cribriform plate
- Synapse in glomerular layer (mitral + tufted cells). Convergence
OLFACTORY ANATOMY Olfactory bulb anatomy & cell types supply
Olfactory bulb anatomy:
Divided into 2 layers
- Internal plexiform layer = glomerular layer. Mitral/tufted cells
- External plexiform layer = granular layer. Granular cells
Olfactory bulb cell types:
- Mitral - glomerular layer — lateral olfactory tract
- Tufted - glomerular layer. Function unclear
- Periglomerular - relay between glomerular cells and granular cells for feedback loops
- Granular - inhibitory cells
2nd order neurons project to ipsilateral olfactory cortex (temporal lobe)
OLFACTORY ANATOMY Olfactory physiology
Olfactory physiology:
Largest gene family in the human genome
Codes for > 1000 G-protein receptor type. 7 transmembrane domains with binding site for specific odorants
Vomeronasal Organ: - Anteroinferior septum. Reproductive behaviours in animals. Unknown function in humans
Accessory Inhalant Chemosensory Pathway - V1 and V2 detect irritant stimuli —> Substance P and Calcitonin GRP —> nasal oedema and secretion
SINONASAL ANATOMY NUMBERS Max sinus - accessory ostium - most common adjacent cell Ethmoid - Roof thickness of bone (fovea ethmoidalis) - % with agger nasi - % with ono - % AEA on mesentery
Maxillary Sinus:
- Accessory ostium in 25% — defect in mucosal coverage of posterior fontanelle
- Haller cell most common additional cell
Ethmoid sinus:
- Roof thickness of bone (fovea ethmoidalis) - Lateral = 0.5mm (orbital plate of frontal bone) - Medial = 0.2mm thick (cribriform plate of ethmoid bone) - 0.05mm at site of AEA canal — thinnest portion of skull base
- Agger Nasi cell = 90%
- Onodi cell = 30%
- AEA on a mesentery + 35%
- Suprabullar cell = Cell originating in suprabullar region but doesn’t reach frontal sinus
- Frontal bulla cell = Suprabullar cell that enters the frontal sinus
SINONASAL ANATOMY NUMBERS Sphenoid sinus - % with ICA dehis - ICA % septum inserts into canal -ICA % with >90’ bony exposure - % optic nerve Dehis
Sphenoid sinus:
- ICA: 20% dehiscent, 40% septum inserts to its canal, >50% have >90 degrees bony exposure
- Optic nerve: 15% dehiscent, 30% septum inserts to canal
SINONASAL ANATOMY NUMBERS Sphenoid sinus - landmarks of ostium
Finding the sphenoid ostium: medial to superior turbinate in 83%
- Junction of upper 2/3 and lower 1/3 of superior turbinate
- 12mm above bony choana
- 7cm at 30 degree angle from anterior nasal spine
- Trans-septal and raised mucosa off front face of sphenoid
- Level of roof of the antrum
SINONASAL ANATOMY NUMBERS Uncinate - insertions %
Uncinate process insertions:
- Lamina papyracea 54%
- Middle turbinate 34%
- Skull base 7%
NASAL SEPTUM Components xxxx
Components: - Cartilage - Perpendicular plate of ethmoid - Vomer - Rostrum of sphenoid contributes small amount - Maxillary crest and crest of palatine bone
NASAL SEPTUM Blood supply
Blood supply:
- Posterior nasal artery - branch of SPA
- Incisive branch - Greater Palatine artery
- Superior labial artery - Facial artery
- Anterior ethmoidal artery - Ophthalmic artery
- Posterior ethmoidal artery - Ophthalmic artery
NASAL SEPTUM Nerve supply
Nerve supply:
- Nasopalatine nerve - branch of PPG
- Anterior ethmoidal nerve - from Nasociliary N (V1)
- Posterior ethmoidal nerve - from Nasociliary N (from V1)
NASAL SEPTUM Cottle’s area of septum
Cottle’s areas of the septum:
I = external nasal valve
II = internal nasal valve
III = attic of nasal cavity
IV = anterior middle turbinate
V = posterior middle turbinate
ANTERIOR ETHMOIDAL ARTERY Course inc terminal branches
3rd branch of Ophthalmic artery
Exits orbit through anterior ethmoid foramen (at or above fronto-ethmoidal suture- marks floor of ACF)
Traverses roof of sinus (anteromedial) in the orbitocranial canal to enter the ACF - 30% on a mesentery
Enters ACF at lateral lamella of lamina cribrosa (lateral wall of olfactory fossa)
Curves anteriorly in ethmoidal sulcus (gives off branch to anterior meningeal artery)
Then exits ACF back into nose via cribroethmoidal foramen
Terminal branches are:
- Anterior nasal artery (sup/med/lat branches)
- Posterior branch
- Small meningeal branches
Area of supply: - Previously thought it supplied all of MT (watershed between AEA and SPA territories) - Now thought to supply less of MT
ANTERIOR ETHMOIDAL ARTERY Landmarks for artery Retractor for AEA ligation
Locating artery in orbit, distances from anterior lacrimal crest (24,36,42)
- AEA - 24mm
- PEA- 12mm
- Orbital apex - 6mm
Use a Ferris-Smith retractor for the Lynch Howarth incision
Area of supply: - Previously thought it supplied all of MT (watershed between AEA and SPA territories) - Now thought to supply less of MT
NERVE SUPPLY OF EXTERNAL NOSE xxxx
Nerve:
- V1 branches - Frontal —> supraorbital and supratrochlear - Nasociliary —> infratrochlear and external nasal (terminal branch of AEN)
- V2 branches - ION terminal branches —> palpebral, nasal, labial - ASAN
Also motor supply from CN VII
BLOOD SUPPLY OF EXTERNAL NOSE xxxx
Blood:
- AEA derived - Dorsal Nasal artery
- Facial artery derived - Angular artery (terminal branch of facial artery) - Lateral nasal artery - Columellar artery (branch from superior labial artery)
CSF ANATOMY - parts of Ventricular system
Anatomy of the ventricular system:
2 lateral ventricles –> Foramen of Monro –> 3rd ventricle –> cerebral aqueduct of Sylvius –> 4th ventricle — 2x Foramen of Luschka and 1 x Foramen of Magendie —> subarachnoid space
- Luschka — subarachnoid space via the pontine cisterns
- Magendie — subarachnoid space via the cerebello-medullary cistern
Arachnoid villi - situated along the cerebral convexities
- Project into the dural sinuses and act as one-way valve
- Valve will close when pressure <1.5 cm H2O
CSF Physiology - volume - Produced/day - where made - constituents
CSF Physiology:
Production = 450mL/day,
Total volume = 150mL — turned over 3x/day
Produced in choroid plexus 50% and walls of lat/3rd/4th ventricles 50%
Filtrate of venous blood, modified by ependymal cells - Slightly higher NaCL, Lower K+, Glu, Ptn
Normal ICF pressure = 5-15 cmH2O
Absorbed by arachnoid villi (90%) and direct to cerebral venules (10%)
CSF B2 tranferrin
B-2 transferrin:
Produced by desialisation of B1 transferrin (by cerebral neuraminidase)
Found in CSF, perilymph, vitreous humour
High sensitivity and specificity for CSF from nasal secretions - Stable at room temperature for 7 days (Bleier et al)
