Head and Neck Flashcards
1
Q
State the innervation of the facial muscles
A
- Facial Nerve (CN VII) supplies the majority of facial muscles
- Trigeminal Nerve (CN V) supplies the muscles of mastication
2
Q
Describe the arterial supply to the face
A
- Branches of external carotid artery
- Main artery is facial artery
- Compress both arteries when lacerated as there are many anastamoses
3
Q
Describe the venous drainage of the face
A
- Facial vein drains into internal jugular vein
- Superficial temporal and maxillary drains into external jugular vein
- Both drain into subclavian vein
4
Q
Describe the layers of the deep cervical fascia of the neck
A
- Investing layer - surrounds whole neck
- Encloses sternocleidomastoid and trapezius
- Pretracheal layer
- Encloses infrahyoid muscles
- Encloses trachea, oesophagus and thyroid gland
- Prevertebral layer
- Encloses vertebrae and associated muscles
5
Q
What are the functions of the deep cervical fascia?
A
- Support
- Limit the spread of abscesses
- Allows fluidity of structures in the neck - move over one another
- Swallowing
- Turning the head and neck
6
Q
What structures does the carotid sheath contain?
A
- Common carotid artery
- Internal jugular vein
- Vagus nerve (CN X)
7
Q
Describe the main routes of spread of infection through the neck
A
- Retropharyngeal space between prevertebral fascia and pharynx fascia
- Runs to diaphragm
- Parapharyngeal space - adjacent to carotid sheath
- More common due to tonsilitis
- Runs to mediastinum
8
Q
State the borders of the anterior triangle of the neck
A
- Roof = Superficial cervical fascia
- Floor = Pharynx, larynx, thyroid gland
- Inferior = jugular notch of manubrium
- Superior = Inferior mandible
- Medial = Midline
- Lateral = Anterior sternocleidomastoid
9
Q
How is the anterior triangle subdivided? What are their main contents?
A
- Submandibular (digastric) triangle
- Submandibular gland
- Submental triangle
- Carotid triangle
- Carotid sheath
- Thyroid gland
- Pharynx and larynx
- External carotid artery
- Muscular (omotracheal) triangle
- Sternothyroid, sternohyoid, thyroid, parathyroid muscles
10
Q
What are the borders of the posterior traingle of the neck?
A
- Roof = Investing layer fascia
- Floor = Muscles covered by prevertebral layer
- Superior = Where SCM and trapezium meet (superior nuchal line of occipital bone)
- Inferior = Middle third of clavicle
- Anterior = Posterior sternocleidomastoid
- Posterior = Anterior trapezius
11
Q
List the suprahyoid muscles and describe their function
A
- Mylohyoid
- Geniohyoid
- Digastric
- Stylohyoid
Elevate hyoid and larynx during swallowing
Consitute the floor of the mouth
12
Q
List the infrahyoid muscles and describe their function
A
- Sternohyoid (superficial)
- Omohyoid (superficial)
- Sternothyroid (deep)
- Thyrohyoid (deep)
Anchor the hyoid, sternum, clavicle and scapula
Depress the hyoid and larynx during swallowing
13
Q
What is the carotid sinus and why is it clinically relevant?
A
- The dilation of the internal carotid artery after the carotid bifurcation at superior thyroid cartilage (C4)
- It contains the baroreceptors that detect changes in arterial blood pressure by detecting stretch
- Can be used to treat Supra-Ventricular Tachycardia (SVT) by gentle rubbing - carotid massage
14
Q
What is the carotid body?
A
The location of the peripheral chemoreceptors which detect changes in arterial pO2
It is located at the bifurcation of the common carotid artery at the superior thyroid cartilage (C4)
15
Q
Why can atheromas in the common carotid artery be dangerous?
A
- The bifurcation is a common site of atheromas
- Rupture of the clot can cause an emboli that travels to the brain to cause a TIA or stroke
16
Q
Describe the main arterial supply of the neck
A
- No branches of common carotid or internal carotid in neck
- Subclavian artery gives rise to thryocervical trunk
- Ascending cervical
- Inferior thyroid
- External carotid gives rise to:
- Superior thyroid
- Ascending pharyngeal
17
Q
List the branches of the external carotid artery
A
- Stop - Superior thyroid
- Alcohol - Ascending laryngeal
- Late - Lingual
- Friday - Facial
- Or - Occipital
- Puke - Posterior auricular
- More - Maxillary
- Saturday - Superficial temporal
18
Q
Describe the vertebral arteries
A
- Arise from subclavian arteries
- Ascend through the transverse foramen of cervical vertebrae 6 to 1
- Supplies the brain (with the internal carotid artery)
19
Q
Describe the arterial supply to the scalp
A
- Internal carotid
- Supra-orbital
- Supra-trochlear
- External carotid
- Superficial temporal
- Posterior auricular
- Occipital
Lies within the dense connective tissue
20
Q
Describe the blood supply to the dura and skull
A
- Middle meningeal artery (branch of maxillary)
- Posterior and anterior branches
- Fracture at the pterion can rupture the anterior branch to cause an extradural haemorrhage
21
Q
List the superficial arteries of the face
A
- Facial artery - supplies mandible
- Superior and inferior labial - supplies lips
- Lateral nasal - nose
- Angular - angle of eye
- Transverse facial
- Maxillary
- Supratrochlear
- Supraorbital
22
Q
Describe the venous drainage of the scalp
A
- Superficial temporal, posterior auricular and occipital accompany corresponding arteries
- Supraorbital + supratrochlear → angular vein → facial vein
- Internal jugular vein
23
Q
What are the dural venous sinuses?
A
- Enothelium-lined spaces between periosteal and meningeal layers of dura that receive blood from veins of the brain
- Drain into internal jugular vein
- Cause of spread of infection from the scalp to the meninges
- E.g. Transverse, sigmoid, cavernous, superior sagittal
24
Q
Describe the venous drainage of the face
A
- Supraorbital, supratrochlear, angular, superior/inferior labial
- Drains into common facial vein
- Drains into internal jugular vein
25
How do you measure JVP?
* Via internal jugular vein
* Direct communication with right atrium
* Through sternocleidomastoid
* Patient at 45º
* Measure height from sternal angle + 5 cm
26
What isthe lymphatic system?
A series of vessels and lymphoid organs that drain tissue fluid from the extracellular compartment to the venous system. It is driven by breathing and muscle contraction and is a low pressure system
27
What is the functions of the lymphatic system?
* Return of plasma proteins from extracellular space
* Immunological function for the body
* Absorbs/transports fats from the digestive system
* Regulate fluid balance of the body
28
List the main regional/superficial lymph nodes of the head and neck
* Occipital
* Post-auricular
* Pre-auricular
* Parotid
* Submandibular
* Submental
* Superficial cervical
* Along external jugular vein
* Anterior/posterior cervical chain
29
List the main terminal/deep lymph nodes of the head and neck
* Deep cervical
* Follows course of internal jugular vein
* Jugulo-digastric (tonsillar)
* Jugulo-omohyoid (lingual)
* Supraclavicular
* Including Virchow's node on the left, associated with gastric cancer
30
Describe the lymphatic ducts of the body
* Right lymphatic duct
* Drains the right upper qudrant of body
* Enters venous system via right venous angle (union of r. internal jugular and r. subclavian)
* Thoracic duct
* Drains the rest of the body
* Enters venous system via left venous angle (union of l. internal jgular and l. subclavian)
* Crosses from right to left at T5 (sternal angle)
31
What are the pharyngeal arches?
A system of mesenchymal ridges that form in the lateral walls of the embryonic pharynx
* Covered by ectoderm externally and endoderm internally
* 5 in total (1-4 and 6)
* Each arch has an associated artery, nerve and cartilage bar
* They lie inferior to frontonasal prominence which overlies the developing brain
32
Describe the devlopment and basic structure of the neural tube
* Forms in week 3
* Notochord signals overlying ectoderm to thicken to from neurectoderm
* Edges curl towards each other to create the tube
* Anterior end forms the brain
* Forebrain, midbrain and hindbrain
* Mid and hindbrain give rise to all cranial nerves (apart from CNI and II)
33
Describe the formation of the facial skeleton
Derived from frontonasal prominence and 1st pharyngeal arch
34
List the muscle derivatives of the pharyngeal arches
* 1st = mastication muscles
* 2nd = muscles of facial expression
* 3rd = stylopharyngeus
* 4th = cricothyroid, levator palantine and pharynx constrictors
* 6th = intrinsic muscles of larynx
35
Describe the cartilage derivatives of the pharyngeal arches
* 1st = Meckel's cartilage
* Template for mandible and malleus and incus of middle ear
* 2nd = Reichart's
* Stapes of middle ear, styloid process, hyoid bone
* 3rd = hyoid bone
* 4th = epiglottis
* 4th-6th = cartilage of larynx
36
List the branchial arch derivatives
* 1st and 2nd = arteries regress
* 3rd = internal carotids
* 4th = arch of Aorta (L) and braciocephalic (R)
* 6th = pulmonary arch
37
List the cranial nerves of the pharyngeal arches and their sensory and motor functions
* 1st = CN V (trigeminal)
* Sensory - skin of face
* Motor - muscles of mastication
* 2nd = CN VII (facial)
* Sensory - taste buds in anterior 2/3rds of tongue
* Motor - muscles of facial expression
* 3rd = CN IX (glossopharyngeal)
* Sensory - posterior 1/3rd of tongue
* Motor - stylopharyngeus
38
Describe what happens to the pharyngeal pouches
* 1st = Eustachian tube and tympanic cavity
* Connects middle ear to pharynx
* 2nd = proliferates and colonised by lymphoid precursors to become the palatine tonsil
* 3rd and 4th pouch divide into dorsal and ventral
* Dorsal of 3rd and 4th = parathyroid gland
* Ventral of 3rd = thymus
39
Describe what happens to the pharyngeal clefts
* 1st cleft remains
* 2nd arch grows down and obliterates remaining clefts
* Cysts or fistulae can occur if cervical sinus isn't obliterated properly
* Occur along anterior border of sternocleidomastoid
40
Name the cranial nerves and whether they are sensory, motor or both
41
Describe CN I including function, test and causes of and consequences of trauma
* Olfactory
* Sensory
* Sense of smell - supplies left and right nasal cavities
* Damaged in fractures of cribiform plate of ethmoid bone
* Trauma causes anosmia
* Test using specific odours
42
Describe CN II including function, test and causes of and consequences of trauma
* Optic
* Sensory
* Sense of vision
* Damaged in direct trauma to eye, fracture to optic canal or pressure on optic nerve pathway
* Trauma causes loss of pupillary constriction and visual fields
* Test using Snellen plates, Ishihara plates and fundoscopy
43
Describe CN III including function, test and causes of and consequences of trauma
* Oculomotor
* Mixed
* Motor - all extraocular muscles (except LR6 and SO4) ciliary muscles and sphincter pupillae
* Sensory (parasympathetic) - constrictor pupillae
* Damaged by fractures of cavernous sinus or aneurysms
* Trauma causes dilated pupil, ptosis and 'down and out' eye due to unooposed action of lateral rectus and superior oblique
* Test using H test and eye torch
44
Describe CN IV including function, test and causes of and consequences of trauma
* Trochlear
* Motor - superior oblique
* Damaged in orbit fractures
* Causes inability to look down when eye is adducted
* Tested with H test
45
Describe CN V including function, test and consequences of trauma
* Trigeminal
* Mixed
1. Opthalmic - sensory sensation of scalp, forehead, upper eylid, dorsum of nose
2. Maxillary - sensory sensation of lower eyelid, cheek, upper lip, nasal cavity, palate, upper teeth
3. Mandibular - sensory sensation to lower cheek, anterior 2/3rds of tongue and lower teeth and motor supply to muscles of mastication
Tested by touching with cotton wool and pinprick and by masseter and pterygoids pushing against resistance
46
Describe CN VI including function, test and causes of and consequences of trauma
* Abducens
* Motor - lateral rectus
* Damaged in fractures to orbit or cavernous sinus
* Causes diplopia on looking laterally
* Test using H test
47
Describe CN VII including function, test and causes of and consequences of trauma
* Facial
* Mixed
* Motor - muscles of facial expression
* Secretomotor to lacrimal, submandibular and sublingual glands and mucous membranes of nasopharynx, paranasal sinuses and palates
* Sensory - taste in anterior 2/3rds of tongue
* Damaged in laceration in parotid region, fracture of temporal bone or intracranial haematoma
* Tests by creasing forehead, keeping eyes closed against resistance, puffing out cheeks and revealing teeth
48
Describe CN VIII including function, test and causes of and consequences of trauma
* Vestibulocochlear
* Sensory
* Vestibular - balance
* Cochlear - hearing
* Damaged by skull fractures of ear infections
* Causes unilateral hearing loss/tinnitus/vertigo
* Test by whispering numbers into ears and Rinne's (mastoid process) and Weber's (forehead) test
49
Describe CN IX including function, test and causes of and consequences of trauma
* Glossopharyngeal
* Mixed
* Motor - stylopharyngeus and parotid gland
* Sensory - Carotid body and sinus, pharynx, middle ear and taste to posterior 1/3rd of tongue
* Damaged in deep laceration to neck
* Test using gag reflex (pharyngeal reflex)
50
Describe CN X including function, test and causes of and consequences of trauma
* Vagus
* Mixed
* Motor - muscles of larynx, pharynx and palate and smooth muscles of bronchi and digestive tract
* Sensory - external ear, auditory canal, ear drum, pharynx, larynx and viscera of thorax and abdomen
* Damaged by bronchial/carcinoma, aortic aneurysm and thryoidectomy
* Causes hoarseness of voice (left recurrent laryngeal nere damage)
* Test by opening mouth and saying 'ah' - uvula should be central
51
Describe CN XI including function, test and causes of and consequences of trauma
* Accessory
* 2 divisions = cranial and spinal
* Motor = sternocleidomastoid and trapezius
* Damaged in lacerations to neck
* Causes shoulder droop
* Test by shrugging shoulders against resistance
52
Describe CN XII including function, test and causes of and consequences of trauma
* Hypoglossal
* Motor - muscles of tongue
* Damaged in neck lacerations and fracture to base of skull
* Causes tongue to deviate to damaged sides
* Test by sticking tongue out and moving side to side
53
Describe how the head and neck is innervated by the sympathetic nervous system
* Via sympathetic trunk (paravertebral chain)
* FIbres 'hitch-hike' on the walls of the carotid arteries but lie outside the carotid sheath
* Preganglionic fibres arise in the first thoracic segment and then synapse in:
* Superior cervical ganglion (C1-C4)
* Middle cervical ganglion (C6)
* Inferior cervical ganglion (C7)
54
Describe what each of the cervical ganglion innervates in the head and heck and how they travel into that region
* Superior: Internal/external carotid arteries
* Somatic - sweat glands
* Visceral - dilator pupillae, nasal and salivary glands, smooth muscle of levator pupillae
* Middle: Inferior thryoid artery
* Lower larynx, trachea, hypo-pharynx, upper oesophagus
* Inferior: Vertebral artery
* May fuse with thoracic ganglion to form the stellate ganglion
55
State which cervical nerves each cervical ganglion gives rise to
* Superior = upper 4 cervical nerves
* Middle = 5th and 6th
* Inferior = 7th and 8th
All three gives branches to cardiac plexus
56
State the cranial nerves that provides parasympathic stimulation to the head and neck and which ganglion they synapse with
* CN III (oculomotor) = ciliary ganglion
* CN VII (facial) = pterygopalatine or submandibular ganglion
* CN IX (glossopharyngeal) = otic ganglion
* CN X (vagus) = no discrete ganglion
57
Describe what parasympathetic stimulation CN III provides and where the preganglionic neurones are located
* Preganglionic neurones in Edinger-Westphal nucleus
* Postganglionic fibres run with short ciliary nerves to enter eye
* Supplies sphincter pupillae and ciliary muscles
58
Describe what parasympathetic stimulation CN VII provides and where the preganglionic neurones are located
* Preganglionic neurones in superior salivatory nucleus
* Postganglionic fibres supply the:
* Lacrimal gland and mucous glands of palate and nose via the pterygopalatine plexus (via greater petrosal nerve)
* Submandibular and sublingual salivary glands via the submandibular plexus (via chorda tympani)
59
Describe what parasympathetic stimulation CN IX provides and where the preganglionic neurones are located
* Preganglionic neurones in inferior salivatory nucleus
* Postganglionic fibres supply the parotid gland and oropharynx
60
Describe what parasympathetic stimulation CN X provides and where the preganglionic neurones are located
* Preganglionic neurones in dorsal vagal motor nucleus
* Postganglionic fibres synapse in wall of target organs to supply the laryngopharynx, larynx, oesophagus and trachea
* Hitch-hike on auriculotemporal nerve (Viii)
61
What is Horner's syndrome?
* Interruption to cervical sympathetic trunk
* Causes:
* Miosis (pupil constriction due to unopposed sphincter pupillae)
* Ptosis
* Vasodilation
* Anhydrosis (lack of sweating)
62
What is the neural crest?
A specialised population of cells that originates within the neroectoderm (lateral border)
The cells become displaced and enter the mesoderm
63
Describe the components of the primitive face and what structures they give rise to
* Frontal nasal prominence
* Forehead, nose, philtrum, upper eyelids
* Stomatadeum
* Buccopharyngeal membrane - mouth
* 1st pharyngeal arch
* Maxillary prominence = middle third of face, cheeks, lateral upper lip and upper jaw
* Mandibular prominence = lower third of face, lower lip and jaw
Prominences consist of mesenchyme covered by ectoderm
64
Describe the development of the nose
* Nasal placodes (ecotdermal thickenings) appear on frontonasal prominence
* Sinks to become nasal pits
* Medial and lateral nasal prominences develop on either side
* Nasal prominences are pushed together in the midline when maxillary prominances grow medially
* Maxillary prominences fuse with medial nasal prominences
* Medial nasal prominences then fuse in the midline
* Oronasal membrane disappears
65
Describe the development of the palate
* Fusion of medial nasal prominences creates the intermaxillary segment
* Gives rise to philtrum, primary palate and 4 incisors
* A palatal shelf develops from the maxillary prominence and grows towards the midline
* It fuses together and with the primary palate to create the secondary palate
* Separates the oral and nasal cavities
* Mandible grows large enough to allow tongue to drop out of the way
* Nasal septum develops as a midline down-growth and fuses with palatal shelves
66
Describe some conditions that occur in malformation of the palate
* Lateral cleft lip = failure of fusion of medial nasal prominence and maxillary prominence
* Can involve the primary palate also
* Cleft lip = failure of the palatal shelves to meet in the midline
67
Describe the development of the eyes
* 4th week
* Develop as out-pocketings of forebrain
* Grow out to make contact with overlying ectoderm to form optic placodes
* Optic placodes then invaginate and pinch off
* Retina derived from forebrain
* The eyes move to the front from the side when the facial prominences grow
68
Describe the development of the external ear
* External auditory meatus from 1st pharyngeal CLEFT
* Auricles from proliferation within 1st and 2nd pharyngeal ARCHES
* 1st = malleus and incus
* 2nd = stapes
* Ears grow to the side of the head from the neck when the mandible grows
69
Describe the development of the inner ear
* Otic placodes develop as thickening of the ectoderm
* They then sink and invaginate to form the auditory vesicles
*
70
What is foetal alcohol syndrome and what are its symptoms?
* Sensitivity to the developing brain to alcohol
* Causes problems with migration of neural crest cells
* Alcohol can freely cross the placenta so no known safe levels
* Symptoms include:
* Small eye/nose opening
* Thin philtrum
* Under developed jaw
71
What does the infratemporal fossa contain?
* Mandibular nerve and branches
* Buccal, lingual, inferior alveolar, auriculotemporal
* Chorda tympani from facial nerve
* Otic ganglion
* Lateral and medial pterygoid and inferior temporalis muscles
* Maxillary, middle meningeal and superficial temporal arteries
* Maxillary and middle meningeal veins
* Pterygoid venous plexus
72
Name some openings in the infratemporal fossa
* Foramen ovale - mandibular nerve
* Foramen spinosum - middle meningeal artery
* Alveolar canal
* Inferior orbital fissure
73
Describe some clinical relevances involving the infratemporal fossa
* Mandibular nerve block - anaesthetic injected near to foramen ovale
* Inferior alveolar nerve block - anaesthetic injected around mandibular foramen which affects mandibular teeth and skin and mucous membranes of lower lip
* Dental procedures
* Potential space for tumour growth
* Hard to detect so likely to be advanced
74
What is the temperomandibular joint?
* Modified synovial hinge joint between cranium and mandible
* It is located anterior and roughly level to the tragus
* Bilaterally symmetrical
75
Name the articulating surfaces of the temporomandibular joint
Superior:
* Mandibular fossa (posterior and concave)
* Articular tubercle (anterior and convex)
Inferior:
* Condyle of mandible
The superior and inferior compartments are created by the articular disc (mensicus)
76
Describe some movements of the temporomandibular joint
Mandible always displaces. Movement in superior compartment = gliding and movement in inferior compartment = hinge
* Flexion (closing mouth)
* Retraction of mandible by temporalis
* Elevation of mandible by temporalis, masseter and medial pterygoids
* Extension (opening mouth)
* Condyles pulled forwards (gliding) by lateral pterygoids
* Chin pulled down (hinge) by digastric
* Gliding (translation)
* Rotation (pivoting)
77
List the features of the temporomandibular joint
* Modified synovial joint
* Lined by fibrocartilage and not hyaline
* Thin and loose fibrous capsule to permit movement
* Articular disc separates bony surfaces from contact
* Upper cavity = sliding joint
* Lower cavity = modified hinge joint
* Both enclosed by its own synovial cavity
78
Describe some features of the capsule in the temporomandibular joint
* Strengthened by extracapsular ligament
* 1 lateral (temperomandibular) - strongest
* 2 medial (accessory ligaments)
Attaches to:
* Superior - circumference of mandibular fossa and articular tubercle
* Inferior - neck of the condyle of the mandible
79
Describe the functions of the accessory ligaments
* Sphenomandibular = prevents inferior dislocation
* Constant in length and tension
* Stylomandibular = separates parotid gland from submandibular gland
* Thickening of deep parotid fascia
80
How does the temporomandibular joint remain stable?
* Posterior glenoid tubercle limits posterior displacement
* Articular tubercle limitis passive anterior displacement
* Sphenomandibular ligament prevents inferior dislocation
* Most stable when closed
* Teeth in occlusal contact
81
Describe some disorders of the temporomandibular joint
* Bruxism = grinding teeth in sleep
* Temporomandibular Pain Dysfunction Disorders (TPDD) = muscle pain
* Mal-occlusion syndrome = muscle pain
* Dislocation = condyle of mandible moves forwards
* Sideways blow to the chin when open
* Excessive contraction of lateral pterygoids when eating or yawning
82
Name which bones makes up the borders of the orbit
* Roof = frontal and sphenoid
* Floor = maxillar, zygomatic (and palatine)
* Medial = ethmoid, lacrimal and maxilla
* Lateral = zygomatic and sphenoid
83
Describe common fractures of the orbit and their consequences
* Involves the thinner medial and inferior walls
* 'Blow out' fractures displaces the orbital walls and contents into nearby sinuses
* Can cause enopthalmus, diplopia and infraorbital bleeding
84
Name some important orbital fissures and what enters/exits through them
* Optic canal - optic nerve (CN II)
* Superior Orbital Fissure - Lacrimal, Frontal, Trochlear (CN IV) Oculolmotor (CN III) Abducens (CN VI) nerves and opthalmic veins
* Large French Teenagers Sit Numb In Anticipation Of Sweets (L to M)
* Inferior Orbital FIssure - infraorbital nerves
85
Describe the optic nerve and clinical importance
* CN II
* Covered by pia, arachnoid and dura mater and is continuous with the brain
* Infection can spread backwards into brain
* Contains a central artery and vein
* Shows signs of raised ICP, venous engorgement and papilloedema
86
Describe the extraocular muscles of the eye, their action and innervation
* Superior rectus - moves eye up
* Oculomotor (CN III)
* Inferior rectus - moves eye down
* Oculomotor (CN III)
* Medial rectus - moves eye medially
* Oculomotor (CN III)
* Lateral rectus - moves eye laterally
* Abducens (CN VI)
* Superior Oblique - moves eye down and in
* Trochlear (CN IV)
* Inferior oblique - moves eye up and out
* Oculomotor (CN III)
87
Describe consequences of palsies to CN III
* CN III (oculomotor)
* Ptosis of superior eyelid due to paralysis of levator palpabrae superioris and unopposed action to orbicularis oculi
* Fully dilated pupil due to paralysis of sphincter pupillae and unopposed action to dilator pupillae
* Eye moves 'down and out' due to unopposed action to lateral rectus and superior oblique
88
Describe consequences of palsies to CN IV
* Trochlear nerve damage
* Paralysis of superior oblique muscle
* Unable to look down and in
* Eg. Diplopia when walking down stairs
89
Describe consequences of palsies to CN VI
* Abducens nerve
* Paralysis of lateral rectus muscle
* Inability to move eye laterally (abduction)
* Pupil is fully adducted due to unopposed pull of medial rectus
90
Describe the arterial supply to the eye
* Opthalmic artery (via internal carotid)
* Through optic canal
* Gives rise to central artery of retina
* Short/long ciliary arteries supply external aspect of eye
* Supraorbital and supratrochlear
* Infraorbital artery (via maxillary artery via external carotid artery)
91
Describe the venous drainage of the eye and clinical relevance
* Superior/inferior opthalmic veins
* Medially
* Drain through superior orbital fissure
* Danger triangle = communication between facial vein to cavernous sinus via the opthalmic veins
* Can spread infection
* Meningitis, brain abscess, cavernous sinus thrombosis
92
What is the function of the eyelids
* Protect from light and injury
* Prevent cornea drying out by spreading lacrimal fluid
* Corneal (blink) reflex
* Controlled by CN Vi and VII
93
Name the muscles that open and close the eye, innervation and consequences of paralysis
* Levator palpabrae superioris = opens eye
* Oculomotor nerve (CN III)
* Paralysis leads to complete ptosis
* Superior tarsal muscles = assists in opening eye
* Sympathetic nerves (from sympathetic trunk)
* Paralysis leads to partial ptosis and Horner's syndrome
* Orbicularis oculi = closes eye
* Facial nerve (CN VII)
* Paralysis leads to Bell's Palsy (failure to close eyes) loss of blink reflex and dry eyes
94
Describe how lacrimation takes place
* Eyes close laterally to medially
* Tears accumulate at lacrimal lake (medial canthus)
* Stimulates by parasympathetic fibres of facial nerve
* Sensory supply via lacrimal branch of Vi
* Lacrimal gland → Lacrimal ducts → Lacrimal canaliculi (medial) → Nasolacrimal duct → Inferior nasal meatus
95
Describe a Meibomian cyst, stye and consequences of raised ICP and papilloedema
* Meibomian cyst = blockage of tarsal gland
* Stye = infection of sebaceous gland at the base of the eylid
* Raised ICP = Compresses optic nerve and blood vessels in optic nerve to cause blindness
* Papilloedema = vein is occluded before artery leading to oedema of the retina before blindness
96
What is Horner's syndrome and describe some common symptoms and causes
Damage to the sympathetic trunk
* Inactivation of dilator pupillae muscle causes miosis
* Unopposed contrictor pupillae
* Inactivation of superior tarsal muscle causing ptosis
* Enopthalmus
* Anhydrosis
* Can be caused by congenital, iatrogenic (thyroidectomy) trauma, tumour of thyroid/lung apex
97
Describe the external ear, including blood supply and sensory innervation
* Consists of pinna/auricle + external auditory meatus
* Elastic cartilaginous skeleton
* Collects sound and funnels it into the external auditory meatus
* Blood supply from posterior auricular and superficial temporal arteries (from external carotid)
* Sensory innervation anterior to EAM is auriculotemporal nerve (from CN Viii)
* The rest of the ear supplied by great auricular nerve (C2-3)
98
Describe the histology of the external auditory canal
* Outer 1/3 is elastic cartilage
* Inner 2/3 is tympanic plate of temporal bone
* Skin lining the outer 1/3 contains hairs, sebaceous glands and ceruminous glands (secrete ear wax)
99
Describe some disorders of the external ear
* Otitis externa = inflammation of external auditory meatus
* Frequently in swimmers who don't dry properly
* Pain and itching
* Pinna haematoma = haematoma between cartilage and perichondrium
* Prevents oxygenation = pressure necrosis
* Tissue undergoes fibrosis = cauliflower ear
* Physical blockage of external auditory meatus due to excess earwax
* Congenital - antihelix deformity, pinna malformation
100
What is the middle ear? List the components
The narrow air-filled chamber in the petrous part of temporal bone. Divided into tympanic cavity proper and epitympanic recess (superior)
* Tympanic membrane
* Ossicles
* Eustachian tube
* Muscles
* Branches of facial and glossopharyngeal nerves
* Mastoid air cells
* Respiratory epithelium
101
What is the function of the middle ear?
Converts sound into mechanical form
* Sound waves vibrate tympanic membrane
* Vibrations transmitted to oval window by ossicles
* Causes vibrations of vestibular and basilar membranes
Also connected to the nasopharynx via Eustachian tube, which allows the pressure to equalise between the middle ear and the throat
102
Describe the ossicles and their function
* Malleus
* Handle attached to tympanic membrane
* Incus
* Stapes
* Articulates with oval window
* Relay vibrations from the tympanic membrane to the inner ear, amplifying and concentrating the sound energy
* Synovial joints
103
Describe the function of muscles of the ossicles
* Tensor tympani - tenses the tympanic membrane to dampen the vibrations of the malleus
* Prevents damage to the inner ear from loud noises
* Stapedius - tightens the anular ligament to prevent excessive movement of the stapes
* Innervated by facial nerve
104
Describe 2 common infections of the middle ear
* Otitis media = infection of the middle ear
* Usually strep pneumoniae
* Secondary to resp infections (Eustachian tube)
* Inflammatory products can clog up cavity and cause a build up of pressure = perforation
* More common in children (shorter and more horizontal Eustachian tubes)
* Mastoiditis = infection of mastoid antrum and mastoid air cells resulting from otitis media
* Swelling behind ear
105
What is cholesteatoma?
A destructive and exanding growth in the middle ear which is formed by a necrotic mass of dead skin cells that have accumulated in pockets formed by negative pressure
* Pressure build up by blockage of Eustachian tube
* Erodes middle ear structures via lytic enzymes
106
Describe the causes and consequences of Eustachian tube blockage
* Swelling of mucous membranes due to infection
* Causes residual air from tympanic cavity to be absorbed into mucosal blood vessels
* Lowers the pressure in cavity
* Causes retraction of tympanic membrane = glue ear (treated with gromits)
* Tympanic membrane can no longer move freely so hearing is affected
* In children, Epstein-Barr virus can cause adenoidal hypertrophy to block the entrance to ET
107
Describe the causes and consequences of perforation of the tympanic membrane
* Caused by trauma, inserting foreign bodies, otitis media and excessive pressure (scuba diving)
* Can be central or subtotal
* Minor ruptures can heal spontaneously
* Large ruptures require surgical repair
* Can lead to deafness
108
Describe the components and function of the inner ear
Cavity in petrous part of temporal bone
* Cochlear = organ of hearing
* Contains cochlear duct and Organ of Corti
* Organ of Corti = contains receptors of the auditory apparatus
* Vestibule = bony chamber sensitive to balance
* Contains saccule and utricle
* Semi-circular ducts contain receptors that respond to rotational acceleration
* Communicates with vestibule
109
What is the difference between conductive deafness and sensorineural deafness?
* Conductive deafness = vibrations do not reach cochlear
* Due to blockage of sound (wax/object)
* Or interference of movement of the oval or round windows (osteosclerosis etc)
* Sensorineural deafness = vibrations not perceived in the cochlear
* Defect in transduction mechanism or nerve
* Treated with cochlear implant
110
Name the sensory innervation of the tympanic membrane
* External surface innervated by
* Auriculotemporal nerve (branch of CN Viii)
* Auricular branch of Vagus nerve (CN X)
* Internal surface innervated by glossopharyngeal nerve (CN IX)
111
Why do some people cough when sticking things in their ear?
* Stimulation of auricular branch of Vagus nerve (CN X)
* The Vagus nerve also supplies the throat (pharyngeal and laryngeal branches)
* This stimulates the cough (sometimes vomit) reflex
* Arnold's Cough Reflex
112
Describe the skeleton (and cartilage) of the external nose
* Bones
* Nasal bones
* Frontal processes of maxilla
* Frontal bone
* Cartilage
* 2 lateral cartilages
* 2 alar cartilages
* 1 septal cartilage
113
Describe the different portions of the nasal septum
* Anterior = cartilagenous
* Middle = perpendicular plate of ethmoid bone
* Posterior = vomer
114
What is a conchae? Describe its function
Curved shelves of bone that project out of the lateral wall
* Creates 4 pathways for air to flow through
* Inferior, middle, and superior meatus
* Spheno-ethmoidal recess
* Increases surface area of nasal cavity to increase humidification and warming of air
* Make air flow slow and turbulent
115
List some functions of the nose
* Olfaction
* Filter and humidify air
* Respiration
* Drain paranasal sinuses
116
Name some openings into the nasal cavity and what vessels exit/enter through them
* Holes in cribriform plate of ethmoid bone - olfactory nerve
* Sphenopalatine foramen - communication from ptreygopalatine fossa
* Sphenopalatine artery, nasopalatine and superior nasal nerves
* Incisive foramen - nasopalatine nerve and greater palatine artery
* Foramen cecum - nasal veins to superior sagittal sinus
117
Describe the arterial supply to the nasal cavity
* Branches of opthalmic artery (anterior/posterior ethmoidal)
* from ICA
* Branches of facial (superior labial) and maxillary arteries (sphenopalatine and greater palatine)
* from ECA
* Form anastamoses with eachother in anterior nose = Kiesselbach's area
118
Describe the venous drainage of the nasal cavity
Veins tend to follow arteries and drain into:
* Pretygoid plexus
* Facial vein
* Cavernous sinus
119
Describe the innervation of the nose
* Special sensory = olfactory nerves from olfactory bulb on superior cribriform plate
* General sensory
* Nasopalatine N (via maxillary Vii) to posteroinferior nasal mucosa
* Anterior and posterior ethmoidal N (via opthalmic Vi) to anterosuperior mucosa
* Trigeminal (infraorbital Vii and external nasal Vi) to external skin
120
What are paranasal sinuses? What is their function?
Air filled extensions of the nasal cavity
* Humidify inspired air
* Reduce weight of the skull
121
Describe the frontal sinus
* Not present at birth
* Drains into middle meatus via frontonasal duct
* Opens out at semilunar hiatus
* Related to anterior cranial fossa and the orbit
122
Decribe the ethmoidal sinuses
Air cells between the orbit and nasal cavity
* Anterior → middle meatus via infundibulum
* Middle → ethmoid bulla (into middle meatus)
* Posterior → superior meatus
123
Describe the sphenoidal sinus
* Present at birth
* Enlarges after puberty
* Drains into the sphenoethmoidal recess
* Important anatomical relationships:
* Access to pituitary gland during surgery (through sphenoid bone)
* Cavernous sinus and ICA
* Posterior cranial fossa and pons
124
Describe the maxillary sinus (including borders)
* Roof = floor of orbit
* Floor = alveolar part of maxilla
* Posterior = pterygopalatine and infratemporal fossa
* Present at birth
* Enlarges after age 8
* Drains into middle meatus via maxillary ostium
* Spread of infection from frontal sinus
125
Name some potential sites of spread of infection from the nasal cavity
* Anterior cranial fossa (via superior openings - foramen cecum, cribriform plate, ethmoidal foramina)
* Middle ear (via Eustachian tube)
* Paranasal sinuses
* Lacrimal apparatus and conjunctiva (via nasolacrimal duct)
126
Describe some disorders of the nasal cavity
* Rhinitis = inflammation of nasal mucosa
* Viral (adenovirus, rhinovirus), allergic, polyps
* Nasal polyps = benign swellings in nasal cavity
* Can cause obstruction → snoring/obstructive sleep apnoea
* Sinusitis = inflammation of mucosal lining of sinuses
* Acute/sub-acute/chronic
* Viral with secondary bacterial (S. pneumoniae or H. influenzae)
127
Describe some disorders and consequences of the paranasal sinuses
* Ethmoidal sinus infection
* Breaks through medial wall of orbit to damage optic nerve and opthalmic artery
* Maxillary sinus infection
* Congestion of mucous membranes in ostia
* Impossible for drainage when upright
128
Describe the different management steps in epistaxis
1. Compression for 10 minutes - lean forward
2. Cautery = burning the ends of the blood vessel to close it off
1. Electro = using a metal probe
2. Chemical = using silver nitrate
3. Nasal tampons (covered in alginate)
4. Posterior packing = occlude the cloacal arch to stop blood trickling inot the nasopharynx
5. Surgical intervention = ligation of palatine/maxillary /external carotid arteries or radiological embolisation
129
Name some risks that increases the chance of epistaxis
* Trauma
* Ethanol
* Coagulation defects
* Vascular abnormalities
* Mucosal drying
* Infections
* NSAIDs
130
Describe the anataomical journey of the trigeminal nerve
131
Describe the general sensation to the face that the trigeminal nerve supplies
* Opthalmic = scalp, forehead, upper eyelid, dorsum of nose, cornea
* Maxillary = lower eyelid, upper cheek, upper lip, nasal cavity, maxillary sinus
* Mandibular = temples, lower cheek, chin, lower lip, anterior 2/3rds tongue, external ear
132
Describe the actions of the trigeminal nerve (not including general sensation)
* Motor from mandibular branch - mastication muscles
* Masseter, pterygoids, temporalis, digastric, mylohyoid
* Carries sympathetic fibres from superior cervical ganglion
* Sweating
* Vasomotor function
133
What is Harlequin Syndrome?
Damage to the trigeminal nerve (specifically pre-ganglionic sympathetic fibres)
* Anaesthesia to face
* Vasomotor dysfunction
* Anhydrosis
134
What does the oculomotor nerve supply?
* 4/6 muscles controlling oculomotion
* Superior, inferior and medial rectus
* Inferior oblique
* Levator palpebrae superioris
* Sphincter pupillae
135
What is the difference between the anatomical and clinical oculomotor nerve?
* Oculomotor nerve proper = anatomical
* Only motor function to eye muscles and LPS
* Begins in oculomotor nucleus
* Does not synapse at ciliary ganglion
* Oculomotor nerve including parasympathetic fibres from Edinger-Westphal nucleus = clinical
* Motor function to eye muscles and LPS as well as innervation to sphincter pupillae (via short ciliary nerve)
* PNS fibres do terminate at ciliary ganglion
136
Describe the consequence of an oculomotor nerve palsy
* Anatomical
* Down and out position of eye due to unopposed action of LR6 and SO4
* Complete ptosis due to denervation of levator palpebrae superioris
* Clinical
* As above
* AND with a dilated pupil due to denervation to sphincter pupillae
137
Describe the difference of a proximal and distal palsy of the oculomotor nerve
* Proximal palsy will have loss of motor function as well as a dilated pupil and loss of accommodation
* Distal palsy will only have loss of motor function with equal pupils
* Pupil-sparing third nerve palsy
138
Describe the anatomical journey of the oculomotor nerve
* Oculomotor nucleus (+/- fibres from Edinger-Westphal nucleus)
* Cavernous sinus
* Uncus
* Tentorial notch
* Exits via superior orbital fissure
* Terminates at/near ciliary ganglion
139
Describe the course of the facial nerve
1. Motor cortex
2. Pons (facial motor nucleus)
3. Internal acoustic meatus (petrous temporal bone)
4. Facial canal
5. Stylomastoid foramen
6. Branches to face and neck
140
Name the branches of the facial nerve (motor portion)
* Temporal
* Occiptofrontalis and superior ocularis oculi
* Zygomatic
* Inferior Ocularis oculi
* Buccal
* Orbicularis oris, buccinator, zygomaticus
* Marginal mandibular
* Mentalis
* Cervical branch
* Platysmus
To Zanzibar By Motor Car
141
Describe the functions of each strand of the CN VII
* Facial nerve = facial expression muscles
* Superior Salivatory Nucleus = visceral efferent parasympathetic to lacrimal, submandibular, sublingual, nasal and palatine glands
* Nucleus Solitarius = special sensory of anterior 2/3rds of tongue (taste)
* Geniculate ganglion = general sensory of auricle of ear
142
How can the facial nerve be damaged?
* Forceps delivery
* Tumours of partoid gland/parotitis/parotidectomy
* Incision or inflammation of facial nerve
* Tympanectomy
* Surgery on infratemporal fossa
143
Describe the consequences of a facial nerve palsy
* Loss of facial expression
* Loss of lacrimation
* Loss of secretomotor function in oral and nasal mucosa
* Loss of action of sphincter muscles
* Orbicularis oculi = complete ptosis and loss of blink reflex
* Orbicularis oris = drooling
144
What is the difference between stroke and Bell's palsy?
* Bell's palsy causes paralysis of all facial expression muscles
* Stroke spares the frontal lobe
* So occipitofrontalis and orbicularis oculi are not paralysed due to bilateral innervation
145
What is the difference between facial nerve palsy and Bell's Palsy?
* Facial nerve palsy = cause of damage can usually be identified
* Usually permenant
* Bell's Palsy = inflammation of the facial nerve where cause sometimes cannot be identified
* Usually temporary
* Both present in the same way
146
Describe the development of the anterior lobe of the pituitary
* Endocrine (from ectoderm)
* Derived from Rathke's Pouch (roof of oral cavity)
* Grows towards infundibulum and differentiates into endocrine cells
* The connection between the oral cavity regresses but remnants can form cysts
147
Describe the development of the posterior lobe of the pituitary gland
* Neuroendocrine (from neuroectoderm)
* Derived from the infundibulum (from the diencephalon of the brain)
* Extends towards oral cavity to meet anterior lobe
* Connection becomes the pituitary stalk, connecting pituitary to hypothalamus
148
Describe each component of the primitive tongue
* 2 lateral lingual swellings from Ph Arch 1
* 3 median lingual swellings
* Ph Arch 1 = tuberculum impar
* Ph Arch 2, 3 and 4 = cupola
* Ph Arch 4 = epiglottal swelling
149
Describe the sequence of steps in the development of the tongue
* Lateral lingual sweelings overgrow the tuberculum impar
* 3rd arch component of cupola overgrows 2nd arch component
* Extensive degeneration (apoptosis) frees the tongue from the floor of the oral cavity
* Connected via lingual frenulum
150
List the sensory innervation of the tongue
* General anterior 2/3rds = lingual branch of CN V3 (from PA 1)
* General posterior 1/3rd = CN IX (PA 3)
* Special sensory anterior = chorda tympani from CN VII (PA 2)
* Special sensory posterior = CN IX (PA 3)
151
List the motor innervation of the tongue
* Hypoglossal nerve (CN XII)
* Myogenic precursors migrate into tongue
* NB: Palatoglossus = Vagus nerve (CN X)
152
Describe the development of the thyroid gland
* Develops in floor of pharynx between tuberculum and cupola
* In adult = foramen cecum
* Bifurcates and descends as a bi-lobed diverticulum
* Connected by the isthmus
* Remains connected by the thyroglossal lobe
* Loses patency after development
153
Describe the origins of the different cells in the thyroid gland
* Follicular cells secrete T3/T4 and are formed from the thyroid diverticulum (Branchial arches 1 and 2)
* Parafollicular cells secrete calcitonin and are formed from the ultimobranchial body of the 4th pharyngeal pouch
154
Describe some disorders of incomplete thyroid development
* Thyroglossal cyst = remnant of the thyroglossal duct
* Fistulae = when a thyroglossal cyst is connected to the exterior by a fistulous canal
* Ectopic thyroid tissue = incomplete descent of the thyroid
155
What is First Arch Syndrome?
Spectrum of defects in development of the eyes, ears, mandible and palate thought to result as a failure of colonisation of 1st Arch with neural crest cells
* Eg: Treacher-Collins Syndrome = hypoplasia of the mandible and facial bones
156
What is Di-George Syndrome?
Congenital thymic aplasia and abscence of parathyroid glands due to abnormal development of neural crest cells
* CATCH 22
* Deletion of chromosome 22
* Cardiac abnormality
* Abnormal facies
* Thymic aplasia
* Celft palate
* Hypocalcaemia/parathyroidism
157
What is CHARGE Syndrome?
A CHD7 mutations essentail for production of multipotent neural crest cells
* Coloboma
* Heart defects
* Choanal atresia
* Growth/development retardation
* Genital apalsia
* Ear defects
158
Name the function, boundaries, epithelum and contents of the nasopharynx
* From skull base to soft palate
* At level of C1
* Respiratory function
* Ciliated pseudostratified columnar epithelium (respiratory)
* Contents = nasopharyngeal tonsil (adenoids) and Eustachian tube orifice
159
Name the function, boundaries, epithelum and contents of the oropharynx
* Digestive function
* From soft palate to superior epiglottis
* At level of C2-C3
* Stratified squamous epithelium
* Contents = palatine tonsils and tonsillar pillars
* Tonsils atrophy after puberty
160
Name the boundaries, epithelum and openings of the laryngopharynx
* From superior epiglottis to inferior cricoid cartilage
* At levels of C3-C6
* Statified squamous epithelium
* Opens into oesophagus (posterior) and larynx (anterior)
161
Describe the pharyngeal musculature
* Superior, middle and inferior constrictors
* Overlap eachother
* Open anteriorly
* Attached posteriorly by the median raphne
Walls of pharynx = outer circular and inner longitudinal layer of muscle which shorten and widen the pharynx during swallowing
162
Name the innervation of the pharynx
* Sensory
* Naso = CN V2 (maxillary of trigeminal)
* Oro = CN IX (glossopharyngeal)
* Laryngo = CN XII (hypoglossal)
* Motor = mainly CN X (vagus) and CN IX (glossopharyngeal)
* Forms the pharyngeal plexus along with sympathetic fibres from the superior cervical ganglion
163
Describe the phases of swallowing
1. Voluntary phase = bolus pushed from oral cavity to oropharynx by the tongue
2. Pharyngeal phase = bolus passes into laryngopharynx by aid of middle and inferior constrictor
* Soft palate elevates to close off nasopharynx
* Pressure receptors in the palate and pharynx signal to the swallowing centre
* Tongue and suprahyoids pull hyoid and larynx up
* Inhibition of breathing
3. Oesophageal phase = peristaltic wave propels bolus into stomach
* Upper 3rd is voluntary striated muscle
* Lower 2/3rds is smooth muscle
164
Describe the arterial and venous supply to the pharynx
* External carotid artery - superior thyroid, ascending pharyngeal, branches of lingual, facial and maxillary
* Internal jugular vein - pharyngeal venus plexus
165
Describe the adenoids and associated pathologies and management
Mass of lymphoid tissue that can enlarge with viral/bacterial infections
* Nasal obstruction - hyponasal speech, feeding difficulty, obstructive sleep apnoea
* Eustachian tube obstruction → otitis media → glue ear and conductive hearing loss
* Managed with adenoidectomy (curettage or suction diathermy)
166
What is Obstructive Sleep Apnoea?
Airway obstruction during sleep that creates turbulent airflow and pauses in breathing
* 30 apnoeic episodes in 7 hours of sleep
167
Describe a test for innervation of the pharynx
* Gag reflex - touching the back of the oropharynx to make the pharyngeal muscles contract
* Afferent - glossopharyngeal nerve (CN IX)
* Efferent - vagus nerve (CN X)
168
Describe the complications and management of tonsillitis
* Palatine tonsils = lymphoid tissues covered by squamous epithelium
* Enlarge with bacterial/viral infection
* Tonsillectomy if recurrent tonsilitis, carcinoma, abscess os obstructive sleep apnoea
* Can cause bleeding from external palatine vein
169
What is the pharyngeal pouch?
Posterior herniation of pharyngeal mucosa that occurs through Killian's dehiscence (between inferiior constrictor and cricopharyngeus)
* Herniates due to weaker area, incoordination of pharyngeal phase of swallowing or cricopharyngeal spasm
170
What is the difference between stridor and stertor
Stertor = noisy breathing caused by partial obstruction of the airways ABOVE the larynx
Stridor = noisy breathing caused by partial obstruction to the aiway AT OR BELOW the larynx
171
Describe the causes, signs and management of acute epiglottitis
* Bacterial infection - H. influenzae type B, staph, ß-haemolytic strep
* Pyrexial (\>38), drooling, tripod position
* Thumb print sign on x-ray
* Management:
* Secure airway - extubation
* Throat swab
* Broad spectrum antibiotics (ceftriaxone)
* Steroids
172
Describe the causes, signs and management of croup (laryngotracheobronchitis)
* Initially viral infection - influenza/parainfluenza
* Presents with stridor and barking cough
* Infective oedema narrows subglottis
* Management:
* Mild - oral antibiotics and steam inhalation
* Moderate - IV antibiotics, humidified oxygen, nebulised adrenaline
* Severe - intubation, tracheostomy
173
Name some common sites for food to get stuck in the pharynx larynx
* Piriform fossa - mucosal recess between the ventral larynx and lateral thyroid cartilage
* Vallecula - mucosal pouch between the base of the tongue and the epiglottis
* Palatine tonsils
* Cricopharyngeus
174
List some functions of the pharynx
* Respiration
* Phonation
* Protecting the trachea during swallowing
175
Describe the components of the laryngeal skeleton
* Epiglottis = leaf shaped plate of elastic fibrocartilage that prevents the aspiration of food into the trachea during swallowing
* Thyroid cartilage
* Cricoid cartilage
* Completely encircles airway
* Paired arytenoid cartilage = pyramid-shaped cartilage that artcultes with the cricoid cartilage and allows vocal cord movement
176
Describe the divisions of the larynx and contents of each
* Supraglottis (inferior epiglottis)
* Vestibular folds
* Glottis
* True vocal cords (+1cm inferiorly)
* Subglottis
* Down to lower cricoid cartilage
177
Describe the laryngeal muscles
* Extrinsic muscles move the entire larynx
* Infrahyoids depress
* Suprahyoids elevate
* Intrinsic muscles act on the vocal cords and aryepiglottic folds
* Cricothyroid - stretches/tenses vocal cords
* Thyroatenoid - relaxes vocal cords
178
Describe the structure of the vocal cords and the muscles that produce movement
* Stratified squamous epithelium → Reinke's space (fluid) → vocal ligament → vocalis muscle
* No submucosa
* Posterior cricoarytenoid = abduction
* Only muscle to open
* Lateral cricoarytenoid = adduction
179
Describe the innervation of the larynx
* Superior laryngeal nerve = cricothyroid muscle
* Deep to carotids
* Recurrent laryngeal nerve = rest of laryngeal muscles
* Left - under arch of Aorta
* Right - under subclavian artery
* Back through tracheo-oesophageal groove
180
Name the arterial and venous supply of the larynx
Arterial - superior and inferior laryngeal arterys
* External carotid → superior thyoid → superior laryngeal
* Subclavian → inferior thyroid → inferior laryngeal
Venous - superior and inferior laryngeal veins
* Superior → superior thyroid vein → internal jugular
* Inferior → inferior thyroid vein → left brachiocephalic
181
Describe the causes of hoarseness of the voice
Pathology in the neck and chest can damage the recurrent laryngeal nerve leading to intrinsic laryngeal muscle weakness
* Laryngeal cancer
* Thyroid hyperplasia/cancer
* Trauma (thyroidectomy etc)
* Cervical lymphadenopathy
* Aortic aneurysm
* Oesophageal cancer
* Apex of lung cancer
182
Describe some causes of acute airway obstruction and emergency management
Causes:
* Oedema due to infection
* Inhalation of foreign body
* Tumour
* Anaphylaxis
Management:
* Cricothyroidotomy - piercing through the cricothyroid membrane
* Tracheostomy
