SS

Question 1

List the bones that make up the skull

Answer 1

Temporal, Frontal, Occipital, Parietal, Maxillary, Zygomatic, Nasal, Lacrimal, Ethmoid, Sphenoid, Mandible

Question 2

Describe sutures and the main ones found on the skulls

What are fontanelles?

Answer 2

Sutures are immobile fibrous joints found only in the skull. In adults the sagittal suture is found between the 2 parietal bones superiorly and it meets with the coronal suture anteriorly and the lambdoid suture posteriorly. The coronal suture travels across the skull in the coronal plane separating the frontal bone from the parietal bones and the lamdoid suture runs across posteriorly separating the pariteal bones from the occipital bone.
The meeting point of the lambdoid sutures and sagittal suture is the lambda, and the meeting point of the coronal suture and sagittal suture is the bregma.
In babies the sutures are not yet fused and they are fontanelles instead. These are thin membranes which join the bones of the skull and become ossified throughout development. Typically the anterior fontanelle ossifies within 1-2 years while the posterior and lateral fontanelles ossify earlier.

Question 3

Describe the mastoid process and its significance

Answer 3

The posterior belly of digastric and sternocleidomastoid muscle attaches to the mastoid process of the temporal bone.
The facial nerve runs deep to the process and therefore it is important to consider when removing the parotid gland.
The mastoid process doesn’t develop til around 10 years of age.

Question 4

What is the pterion and where is it located?

What is its significance?

Answer 4

The pterion is an H-shaped suture formed by the joining of the temporal, parietal, sphenoid and frontal bones.
It is located 2.5cm superior to the zygomatic arch and 2.5cm posterior to the lateral margin of the orbit.
The pterion is the weakest part of the skull which can often become damaged due to trauma and often the anterior branch of the middle meningeal artery runs deep to it. Therefore damage to the pterion often results in extradural haemorrhage which may be fatal.

Question 5

Where are these foramina located and what structures pass through them?

• Foramen ovale
• Foramen spinosum
• Carotid canal
• Jugular foramen
• Foramen magnum
• Hypoglossal canal
• stylomastoid foramen
• Optic canal
• Foramina of cribriform plate
• Superior orbital fissure
• Foramen rotundum
• Internal acoustic meatus

Answer 5

• Foramen ovale is located on the posterolateral border of the greater wing of sphenoid on the base of the skull and the mandibular division of the trigeminal nerve (V3) and lesser petrosal nerve run through it
• The foramen spinosum is posterolateral to the foramen ovale in the greater wing of the sphenoid bone and the middle meningeal artery runs through it
• The carotid canal is in the petrous part of the temporal bone on the base of the skull and contains the internal carotid artery and its associated nerve plexus
• The foramen magnum is a large opening in the base of the skull surrounded by occipital bone which contains the brainstem, vertebral arteries and nerve plexuses, spinal arteries, meninges and the roots of CN XI
• The hypoglossal canal sits anterior and superior to the occipital condyles in the occipital bone and contains the hypoglossal (XII) nerve and vessels
• The jugular foramen sits lateral to the hypoglossal canal in the occipital bone and contains the IJV and CN IX, X and XI
• The sytlomastoid foramen is located between the mastoid and styloid processes at the base of the skull and carries the Facial (VII) nerve
• The optic canals sit anterior to the anterior clinoid processes in the lesser wing of the sphenoid in the anterior cranial fossa. The Optic (II) nerve and ophthalmic artery run through here to enter the orbit.
• The olfactory foramina of the cribriform plate are small perforations in the anterior cranial fossa allowing the passage of Olfactory (I) nerve fibres from the olfactory bulb sitting on the cribriform plate of the ethmoid bone and into the nasal mucosa
• The superior orbital fissure sits just lateral to the optic canals and separates the greater and lesser wings of the sphenoid bone allowing passage of CN III, IV, V1, VI and the ophthalmic vein between the middle cranial fossa and the orbit
• The foramen rotundum is located posterior to the medial end of the superior orbital fissure within the middle cranial fossa and allows the passage of V2 into the pterygopalatine fossa
• The internal acoustic meatus is located in the petrous part of the temporal bone within the posterior cranial fossa and it allows the passage of CN VII and VIII and the labyrinthine artery

Question 6

Describe the external ear, its main components and structure, its innervation and its clinical relevance

Answer 6

The external ear is made up of the auricle and external acoustic meatus. The concha is the deepest part of the auricle forming the external boundary of the external acoustic meatus which extends approximately 2.5cm to the tympanic membrane, although it does not have a straight course. The lateral third of the external acoustic meatus is cartilaginous and the medial two thirds are bony and it is lined by a mucous membrane.

The external ear may be effected by allergy, swimmer’s ear in which there is infection of the mucosa, or surfer’s ear in which there is growth of the bony part which occludes the canal.

The auricle is supplied by the lesser occipital, greater auricular and a branch of V3, so infection of the auricle may cause head and neck pain. The deeper parts of the auricle may also be supplied by CN VII and X.
The external acoustic meatus is supplied by CN V3, X, VII
The tympanic membrane is supplied by V3, VII, X and IX on its outer surface and IX on its inner surface.

Question 7

Describe the middle ear and its main features as well as its main clinical relevance

Answer 7

The middle ear is an air-filled cavity stretching from the tympanic membrane to the inner ear which sits in the petrous part of the temporal bone and is lined by mucosa.
Has 2 parts: tympanic cavity and epitympanic recess and is connected to the nasal cavity by the pharyngotympanic tube.
The middle ear is clinically important due to the high prevalence of middle ear infections in children and babies which have potential to spread intracranially via venous drainage systems. Middle ear infection may also spread to the mastoid antrum via an aditus in the posterior wall of the middle ear and this can lead to mastoiditis which is an emergency situation in which prevention of meningitis must occur through antibiotics, pus drainage, and surgery.

Question 8

Middle ear: Roof/Tegmental wall

Answer 8

The tegmen tympani bone separates the middle cranial fossa and the middle ear and care should be taken not to go through here in surgery

Question 9

Middle ear: Floor/Jugular wall

Answer 9

The floor of the middle ear separates the middle ear from the internal jugular vein which sits below. In the medial aspect of the floor of the middle ear the tympanic branch of CN IX (which travels through the jugular foramen along with the IJV) emerges and joins the tympanic plexus over the promontory on the medial wall.

Question 10

Middle ear: Lateral wall/Tympanic membrane

-Clinical relevance (ear examination)

Answer 10

The lateral wall of the middle ear is formed mainly by the tympanic membrane which separates the middle ear from the external acoustic meatus.

The external acoustic meatus and tympanic membrane can be assessed with an otoscope in an ear examination. It is important to avoid damaging the chorda tympani nerve which runs superiorly behind the tympanic membrane within the middle ear as this supplies taste to the anterior two thirds of the tongue.
When examining the external acoustic meatus the ear should be lifted up in adults and down in babies in order to straighten the canal.
We can then observe the tympanic membrane to determine whether someone has a middle ear infection. We should normally be able to see the lateral process and handle of the malleus and the cone of light and should be able to distinguish the pars flacida. With infection we may not be able to see some of these structures and the membrane may lose its translucence.

Question 11

Middle ear: Medial wall/Labyrinthine wall

Answer 11

The medial wall of the middle ear has many features. The promontory is a prominence of the cochlea of the inner ear which bulges into the middle ear and is lined by mucosa and covered by the tympanic plexus.
The sympathetic chain which travels with the internal carotid artery gives off a branch from the internal carotid plexus which runs through the anterior wall of the middle ear to join the tympanic plexus. The tympanic branch of CN IX joins the tympanic plexus via the medial floor of the middle ear. The lesser petrosal nerve comes off the tympanic plexus and exits the middle ear via the anterior wall.

The round and oval windows connect the middle and inner ears.

The prominence of the facial (VII) nerve is a bony canal which exits through the medial wall. CN VII gives off the chorda tympani before entering this canal and this enters through the posterior wall before running superiorly in the middle ear, deep to the tympanic membrane and going on to supply taste to the tip of the tongue.
The prominence of the lateral semi-circular canal runs just superior to this prominence.

Question 12

Middle ear: Anterior wall/Carotid wall

Answer 12

The anterior wall separates the middle ear from the internal carotid artery.
The lesser petrosal nerve comes off the tympanic plexus and leaves the middle ear via the anterior wall.
The branch of the internal carotid plexus which joins the tympanic plexus enters through the anterior wall.
The chorda tympani nerve leaves through the anterior wall.
The tensor tympani muscle runs through this wall.
The pharyngotympanic tube connects the nasopharynx and middle ear via this wall. This tube has a bony part and soft gelatinous part and is not well developed in babies. It is responsible for equalising air pressure between the oral cavity and middle ear and can become blocked leading to trapping of bacteria in the middle ear.

Question 13

Middle ear: Posterior wall/Mastoid wall

Answer 13

The posterior wall separates the middle ear from the mastoid air cells inferiorly and connects the middle ear to the mastoid antrum superiorly via an aditus.
The continuation of the mucosa between the middle ear and mastoid antrum via the aditus means that middle ear infection may spread and cause mastoiditis.
The tendon to the stapedius muscle and the chorda tympani nerve enter the middle ear via the posterior wall.

Question 14

What are some of the contents of the middle ear and what is the main neurovascular supply?

Answer 14

The malleus, incus and stapes bones form the ossicular chain and are all joined at synovial joints.
The tensor tympani muscle and stapedius are in the middle ear.
Nerves within the middle ear include the chorda tympani (branch of CN VII), tympanic plexus (formed by branch of CN IX, and the caroticotympanic nerves of the internal carotid plexus.
The external carotid artery gives branches to the external acoustic meatus and middle ear.

Question 15

Describe the basic organisation of the cranial dura mater

Answer 15

Made up of 2 layers, an outer periosteal layer and an inner meningeal layer. The periosteal layer seals the whole skull covering the internal and external surface. Only the inner meningeal layer continues down to cover the spinal cord, so the dura mater of the spinal cord differs to that of the cranium.

Question 16

Describe the dural partitions

Answer 16

The dura partitions the different parts of the brain. The falx cerebri separates the 2 cerebral hemispheres.
The tentorium cerebelli separates the cerebrum from the cerebellum.
The falx cerebelli divides the 2 cerebellar hemispheres.
The infundibulum is a membrane which partially covers the pituitary gland

Question 17

Blood supply to the cranial dura mater

Answer 17

The meningeal arteries run in grooves on the interior surface of the skull within the outer periosteal layer of the dura mater.
The main arterial supply to the dura comes from the meningeal arteries, mainly the middle meningeal, which travels through the foramen spinosum and divides into anterior and posterior branches. The anterior branch crosses the pterion.

Question 18

Innervation of cranial dura mater

Answer 18

Falx cerebri innervated by V1
Tentorium cerebelli innervated by V1
Dura mater innervated by V1, V2 and V3, X and C1-C3

Question 19

Intracranial venous sinuses

Answer 19

These sinuses form between the periosteal and meningeal layers of the dura
The inferior sagittal sinus drains into the straight sinus that meets the superior sagittal sinus at the confluence of the sinuses.
From the confluence the transverse sinuses extend out laterally and become the sigmoid sinuses.
The sigmoid sinus eventually becomes the IJV which exits the skull through the jugular foramen

Question 20

Contents, location and clinical relevance of the cavernous sinus

Answer 20

The internal carotid artery and Abducent (VI) nerve run within the cavernous sinus.
CN III, IV, V1 and V2 run along the wall of the cavernous sinus.
The cavernous sinuses are located either side of the sella turcica and are important due to their contents.
An infection in the orbit may be carried back to the cavernous sinus via the ophthalmic vein. Therefore it is important to consider a baby that presents with periorbital cellulitis as this infection may pass into the cavernous sinus, causing a thrombus which may compromise the internal carotid artery or other cranial nerve structures in the sinus.

Question 21

Where does blood accumulate in racoon eyes?

Answer 21

A skull fracture may result in a patient presenting with racoon eyes. This occurs when blood accumulates between the periosteal layer of the dura and the skin of the eyelids

Question 22

Venous drainage of the skull

Answer 22

small venous networks drain into larger veins which drain into venous sinuses which eventually lead to the IJV
Emissary veins run through the bony skull connecting the outside of the skull and dural venous sinuses (this means a laceration of the skull can cause infection which can enter the cranial cavity via the emissary veins)
Diploic veins drain the bony part of the skull into the sinuses
Cerebral veins drain from the cerebrum into the sinuses.

Question 23

Briefly describe the arachnoid and the pia mater

Answer 23

The arachnoid mater is a thin, avascular membrane which has trabeculae and a subarachnoid space beneath it.
It does not enter grooves or fissures of the cerebrum.
The arachnoid granulations in the subarachnoid space drain CSF into the venous sinuses.
The cerebral arteries and veins run in the subarachnoid space

The pia mater is a thin layer which invests around the surface of the brain and down all the grooves of the cerebrum.

Question 24

Extradural haemorrhage

• Where it occurs
• Likely damaged vascular structure
• Likely cause
• CT appearance

Answer 24

Extradural haemorrhage typically occurs due to damage of the meningeal arteries, usually the middle meningeal, resulting in a bleed between the periosteal layer of the dura mater and the skull.
It is usually associated with skull fracture and appears more discrete and lens-shaped on the CT scan.

Question 25

Subdural haemorrhage

Answer 25

Subdural haemorrhage occurs within the meningeal layer of the dura mater. It often results due to damage to venous structures, typically the cerebral veins which cross the meningeal layer of the dura as they travel from the subarachnoid space to the venous sinuses. They require relatively little force to occur, may occur in patients with cerebral atrophy or who are on anti-coagulants. Chronic subdural haemorrhage is more common but acute cases can occur following high velocity trauma.

Question 26

Subarachnoid haemorrhage

Answer 26

Subarachnoid haemorrhage occurs within the subarachnoid space typically due to damage of the cerebral arteries which run in the subarachnoid space (but cerebral veins can also cause subarachnoid haemorrhage). They usually occur due to a cerebral artery aneurysm within the circle of willis. It results in sudden severe headache, vomiting, and frequent loss of consciousness, A subarachnoid haemorrhage appears more diffuse on CT scan.

Question 27

List the bones making up the orbit

Answer 27

``` Frontal bone Zygomatic bone Maxillary bone Lacrimal bone Ethmoid bone Sphenoid bone Palatine bone ```

Question 28

List the bones making up the roof, floor and walls of the orbit

Answer 28

Roof = Frontal bone Floor = Maxilla and zygomatic bones Lateral wall = Frontal and zygomatic bones Medial wall = Lacrimal, ethmoid and maxilla

Question 29

List the layers of the eyelids from superficial to deep

Answer 29

``` skin subcutaneuous tissue orbicularis oculi orbital septum tarsus conjunctiva ```

Question 30

Describe the significance of the skin and subcutaneous tissue of the eyelids

Answer 30

There is the presence of a potential space in the subcutaneous tissue which can accumulate blood. A skull fracture may damage the periosteal layer of the dura leading to bleeding into this potential space between the dura and skin of the eyelids, leading to racoon eyes

Question 31

Describe the voluntary muscle of the eyelids and its clinical significance

Answer 31

The orbicularis oculi muscle has an orbital part and a palpebral part which goes to the eyelid. It is innervated by the facial (VII) nerve. Therefore any damage to the facial (VII) nerve will cause inability of the upper eyelid to close/blink on the ipsilateral side, and the lower eyelid will droop away. This is associated with corneal ulcers and spillage of tears. Therefore it is important to consider the facial nerve in surgical procedures to ensure it is not damaged.

Question 32

Orbital septum

Answer 32

A continuation of the periosteal layer of the cranial dura which runs in the upper and lower eyelids

Question 33

Tarsus, Levator Palpebrae Superioris and Superior Tarsal muscles

Answer 33

The tarsus is a fibrocartilage structure on the eyelid. The LPS and superior tarsal muscle both attach to the tarsus but have different innervation. LPS is innervated by CN III The superior tarsus is a smooth muscle and is innervated by SNS fibres The LPS and superior tarsus muscle are involved in raising the eyelid. Therefore a loss of function in either of these muscles may result in drooping of the upper eyelid. A partial ptosis results if superior tarsus function is lost, while a complete ptosis results if LPS function is lost Patient's often present with Horner's syndrome with partial ptosis when the SNS chain is cut in some procedures

Question 34

Tarsus glands

Answer 34

Glands embedded in tarsus which secrete oily substance Glands at base of eyelashes in eyelids are sweat glands Blockage or infection of these glands can cause bumps in the eyelid Stye/hordeolum may occur due to blockage of sweat glands at base of eyelashes and is usually painful. Chalazion occurs when the duct draining the oily secretions of the tarsus glands is blocked and it usually doesn't cause pain

Question 35

Conjunctiva

Answer 35

Protected by inner surface of eyelid but may be effected in conjunctivitis Supplied by ophthalmic, facial and superficial temporal arteries Supplied by V1 to upper eyelids and V2 to lower eyelids

Question 36

List the extrinsic muscles of the eye

Answer 36

Superior, medial, lateral and inferior rectus muscles | Superior and inferior oblique muscles

Question 37

Common tendinous ring and structures passing through it

Answer 37

A ring formed from the periorbital part of the dura where the superior, inferior, medial and lateral rectus muscles attach which surrounds the optic canal and part of the superior orbital fissure. The structures passing through the common tendinous ring include: the ophthalmic artery and optic (II) nerve (in the optic canal), the superior and inferior divisions of CN III, CN VI, Nasociliary nerve. These structures may all be affected as a result of infection causing narrowing of the ring

Question 38

Lacrimal apparatus

Answer 38

Lacrimal gland sits superolaterally in the orbit around the tendon of LPS and secretes tears Lacrimal sac sits in lacrimal fossa medially and drains the tears The puncta acts as a pump which pumps the tears through the lacrimal canaliculi into the lacrimal sac which leads to the nose

Question 39

Arterial supply and venous drainage in orbit

Answer 39

Ophthalmic artery with many branches (to lacrimal gland, lacrimal duct and retina) Ophthalmic veins

Question 40

Innervation in orbit

Answer 40

CN II, III, IV, V1, VI - intracranial injury such as trauma, increased ICP, infection may effect these nerves. - An increase in ICP will affect CN VI first causing medial deviation of eyes and inability to move eyes laterally from midline - damage to CN IV means you cannot look down and in CN III supplies all extrinsic eye muscles except Lateral rectus which is supplied by CN VI and superior oblique which is supplied by CN IV The superior branch of CN III supplies LPS and superior rectus The inferior branch supplies inferior and medial rectus, inferior oblique and ciliary ganglion If there is no ptosis this indicates the superior branch of CN III should be fine CN V1 has 3 branches - lacrimal, frontal, nasociliary

Question 41

Danger triangle of face

Answer 41

From commisures of mouth on nasion Ophthalmic vein communicates with facial veins and cavernous sinus and therefore this provides a pathway for spread of infection from the face to the cranial cavity The existence of communications between the facial vein and cavernous sinus and direction of blood flow is important for the spread of infection from the face

Question 42

Describe the superficial cervical fascia

Answer 42

The superficial cervical fascia lies between the skin and the investing layer of the deep fascia. It contains fatty subcutaneous tissue and the platysma muscle, a thin sheet of skeletal muscle originating from the thorax and blending with the mandible and lower facial muscles. It is innervated by the cervical branch of the facial (VII) nerve.

Question 43

Investing layer of deep fascia

Answer 43

Lies deep to the superficial fascia being the most superficial layer of the deep fascia surrounding the neck. It invests around the peripheral muscles of the neck including the trapezius, SCM and infrahyoid muscles.

Question 44

Pretracheal layer of deep fascia

Answer 44

Middle layer of deep fascia enclosing the larynx/trachea, pharynx/oesophagus and the thyroid gland

Question 45

Prevertebral layer of deep fascia

Answer 45

Deep layer of deep fascia which encompasses the vertebral column and paravertebral muscles. Anterior to the vertebral bodies the fascia splits into 2 layers.

Question 46

Carotid sheath

Answer 46

Sheath formed by contributions from the investing, pretracheal and prevertebral layers of the deep cervical fascia which covers the internal carotid artery, internal jugular vein and vagus (X) nerve

Question 47

Pretracheal space

Answer 47

The potential space between the investing layer of the deep fascia and the pretracheal layer which extends from the pharynx down to the anterior mediastinum

Question 48

Retropharyngeal space

Answer 48

Potential space between posterior border of pretracheal fascia and the prevertebral fascia extending from base of skull to upper part of posterior mediastinum

Question 49

Prevertebral space

Answer 49

Potential space where the prevertebral fascia has split into 2 anterior to the vertebral bodies which extends from the base of the skull to the diaphragm.

Question 50

Boundaries of posterior triangle of neck (region V of neck)

Answer 50

Anterior boundary = posterior border of SCM Posterior boundary = anterior border of trapezius Base = superior border of middle 1/3 of clavicle Apex = base of skull at superior nuchal line Roof = Investing layer of deep fascia and superficial fascia (involving skin, fatty tissue, platysma muscle, superficial nerves and veins) Floor = Prevertebral fascia covering the splenius capitus, levator scapulae, anterior and middle scalene muscles

Question 51

Describe the contents of the roof of the posterior triangle of the neck

Answer 51

There is the posterior external jugular vein, superficial veins and cutaneous nerves. Transverse cervical nerve (hooks anteriorly) Greater auricular nerve (posterior and ant. to ear) Lesser occipital nerve (To occipital area of skull) Supraclavicular nerve (over clavicle at base) These superficial nerves provide sensation to the neck and all come from the cervical plexus, emerging together as a bundle from the posterior boundary of SCM. The point where they emerge together before splitting off is called Erb's point

Question 52

Arteries of posterior triangle

Answer 52

3 arteries are present at the base of the posterior triangle. The suprascapular artery and transverse cervival artery which both come off the thyrocervical trunk of the subclavian artery. The 3rd part of the subclavian artery also runs at the base.

Question 53

Nerves within the posterior triangle

Answer 53

``` The accessory (XI) nerve runs one plane deep to Erb's point and innervates the SCM and trapezius muscles. It is a spinal accessory nerve entering through the foramen magnum and exiting through the jugular foramen. There is no surface marking for the nerve and there is significant variation on its location in the posterior triangle. ``` The brachial plexus also sits at the base of the posterior triangle and a brachial plexus block can be performed through here.

Question 54

Muscle running within the posterior triangle

Answer 54

Omohyoid muscle (inferior belly)

Question 55

Significance of lymphatics of posterior triangle

Answer 55

There are many lymphatics in the posterior triangle which are closely associated with the accessory (XI) nerve, running one plane deep to it. When performing a lymph node biopsy the accessory (XI) nerve may become damaged causing a loss of arm abduction in the patient.

Question 56

Contents of floor of posterior triangle

Answer 56

Splenius Capitus Levator scapulae Scalene muscles (ant, mid, post) These muscles are covered in the prevertebral layer of the deep fascia

Question 57

Lymph nodes of head and neck

Answer 57

There are many superficial lymph nodes at the base of the skull and in the neck. These run with the external jugular vein and typically drain into the deep cervical lymph nodes which run with the internal jugular vein. Therefore when a patient has a deep cervical lymphadenopathy it is more difficult to determine the site of the cancer.

Question 58

Where would you approach for central vein catheterisation

Answer 58

Can go through the posterior border of SCM below the level of the accessory nerve and into the IJV through the carotid sheath

Question 59

Boundaries of the anterior triangle

Answer 59

Anterior triangle is bounded by the anterior border of SCM laterally, the mandible superiorly and the midline of the neck medially

Question 60

Infrahyoid muscles | -What and where are they?

Answer 60

The first structures deep to the superficial fascia of the anterior triangle, inferior to the hyoid bone and covered in investing fascia are the infrahyoid muscles. When perfroming a tracheostomy we are usually dealing with these muscles first. There are 4 infrahyoid/strap muscles: 1) Sternohyoid: most superficial and longest strap muscle, extending from sternum to hyoid bone. 2) Omohyoid: posterior belly which runs in post triangle and anterior belly which runs in ant triangle 3) Thyrohyoid: is deep to sternohyoid and is smaller, extending from the thyroid to the hyoid 4) Sternothyroid: is also deep to sternothyroid and is smaller, extending from the sternum to the thyroid

Question 61

Describe the cervical plexus and its relation to the infrahyoid muscles

Answer 61

Cervical plexus formed by C1 - C4 and has sensory and motor components. Cervical plexus forms a loop called the ansa cervicalis with C1 - C3 roots. C1 forms the superior root of the loop and this innervates only the thyrohyoid muscle. C2 and C3 form the inferior root of the loop and this innervates the sternohyoid, sternothyroid and omohyoid muscles. The motor components of the cervical plexus all come from the ansa cervicalis. The cervical plexus also gives off the suprascapular, transverse cervical, lesser occipital and greater auricular superficial sensory nerves which emerge from the post. border of SCM at Erb's point. The phrenic nerve also receives contribution from the cervical plexus.

Question 62

Suprahyoid muscles

Answer 62

The suprhayoid muscles are located superior to the hyoid bone and form the floor of the mouth and include the digastric, mylohyoid, geniohyoid and stylohyoid muscles. The digastric has an anterior belly and posterior belly. The mylohyoid muscle is deep to the anterior belly of digastric. The geniohyoid is the deepest muscle, lying in the midline. The stylohyoid muscle runs laterally with the posterior belly of digastric.

Question 63

Innervation of suprahyoid muscles

Answer 63

The posterior belly of digastric attaches to the mastoid process along with SCM and is innervated by CN VII The stylohoid originates from the styloid process and is also innervated by the CN VII The CN VII comes out of the stylomastoid foramen closely associated with the styloid and mastoid processes to innervate the stylohyoid and posterior belly of digastric. The anterior belly of digastric and mylohyoid are innervated by V3 The geniohyoid is innervated by C1

Question 64

Describe the general structure and location of the thyroid gland

Answer 64

It is an endocrine gland which sits anteriorly in the neck within the pretracheal layer of the deep fascia. It has lateral lobes which are connected by an isthmus which sits over the 2nd and 3rd tracheal cartilage. The lateral lobes extend up to the thyroid cartilage. The lower border of the isthmus sits on the jugular notch but moves up higher with head extension.

Question 65

Arterial supply of thyroid Venous drainage of thyroid Lymphatic drainage of thyroid Innervation of thyroid

Answer 65

Superior thyroid artery (1st branch of external carotid artery) Inferior thyroid artery (comes off thyrocervical trunk of subclavian artery) Superior and middle thyroid veins drain into IJV, inferior thyroid vein drains into left bracheocephalic vein Drains into paratracheal lymph nodes and deep cervical lymph nodes Sympathetic supply from middle cervical ganglion PNS supply from recurrent laryngeal nerves branching from vagus (X) and run in groove between trachea and oesophagus.

Question 66

Relations of thryoid

Answer 66

Thyroidectomy is very difficult due to the structures surrounding the thyroid. The thyroid is associated with the trachea, common carotid artery, internal jugular vein, vagus nerve, recurrent laryngeal nerves. Damage to the recurrent laryngeal nerve can cause hoarseness of the voice or inability to breathe if both sides are damaged.

Question 67

Embryology of thyroid and its clinical relevance

Answer 67

Thyroid grows down from foramen caecum at base of tongue as the thyroglossal duct. Thyroid tissue may become stuck anywhere along this duct producting ectopic thyroid tissue or accessory thyroid tissue. It can be termed cervical thyroid if it is larger and pyramidal thyroid may sit on the lateral lobes. This can impair swallowing or protrude the tongue.

Question 68

Course of vagus (X) nerve in neck

Answer 68

Exits skull via jugular foramen along with CN IX and XI. It travels within the carotid sheath along with the internal jugular and internal carotid. It stays close to the midline at the root of the neck and passes between the subclavian artery and vein to enter the mediastinum

Question 69

Course of glossopharyngeal (IX) nerve

Answer 69

Exits skull via jugular foramen with CN X and XI. It then travels down and forward between the external and internal carotid arteries, hooks around stylopharyngeus and continues anteriorly to reach the base of the tongue to supply taste to the posterior 1/3 of the tongue. It runs deep to the stylohyoid and posterior belly of digastric.

Question 70

Course of accessory (XI) nerve

Answer 70

Exits via jugular foramen with CN X and IX. It runs posterolaterally along with IJV crossing the transverse process of the atlas vertebra, passing medial to the styloid process and posterior belly of digastric to pierce SCM and enter the posterior triangle of the neck. It also innervates trapezius.

Question 71

Course of hypoglossal (XII) nerve

Answer 71

Exits via hypoglossal canal. It then passes between internal carotid and internal jugular crossing 3 arteries deep to the posterior belly of digastric and stylohyoid to reach the tongue. It runs superficial to the carotid arteries and is accompanied by a branch of C1 which innervates the thyrohyoid and geniohyoid muscles.

Question 72

Describe the borders of the infratemporal fossa

Answer 72

It is bounded anteriorly by the posterior surface of the maxilla It is roofed by the squamous part of the temporal bone and the inferior surface of the greater wing of the sphenoid. Medially it is bordered by the lateral plate of the pterygoid process, pharnyx and soft palate muscles. Laterally it is bordered by the medial surface of the ramus of the mandible.

Question 73

Contents of infratemporal fossa

Answer 73

- Pterygoid muscles - lateral and medial - Sphenomandibular ligament - Maxillary artery (which gives off middle meningeal artery and inferior alveolar artery) - CN V3: enters infratemporal fossa via foramen ovale and gives off anterior and posterior bundles. The posterior bundle gives off the lingual nerve, inferior alveolar nerves, mental nerves, auricotemporal nerve. The lingual nerve runs with the chorda tympani (a branch of CN VII) to supply taste sensation in the tongue. - CN VII: gives off chorda tympani nerve which comes from middle ear and travels with lingual nerves in infratemporal fossa supplying taste to anterior third of tongue. The lesser petrosal nerve runs with the auriculotemporal nerve and is the PNS supply to the parotid gland. - Pterygoid venous plexus

Question 74

Temporomandibular Joint

Answer 74

- A common source of head and neck pain - Formed by the articulation of the condylar portion of the mandible and the mandibular fossa of the temporal bone - Joint is stabilised by lateral, sphenomandibular and stylomandibular ligaments - The joint is an atypical synovial joint as the condyle of the mandible is covered in fibrocartilage as opposed to hyaline cartilage - The joint is also divided in 2 parts by a disc and has muscles attached to it

Question 75

List the muscles involved in different movements of the TMJ

Answer 75

``` Elevation = Temporalis, Masseter, Medial pterygoid Depression = gravity, digastric, geniohyoid, mylohyoid Protrusion = lateral pterygoid, assisted by medial pterygoid Retraction = Posterior fibres of temporalis, deep part of masseter, geniohyoid, digastric ```

Question 76

Muscles of mastication

Answer 76

These muscles are innervated by V3 Temporalis muscle: originates in temporal region and extends down to coronoid process and ramus of mandible Masseter muscle: originates from lower border of zygomatic and maxilla and extends to angle of mandible Pterygoid muscles: Have medial and lateral groups which lie deep to the ramus of the mandible. The lateral pterygoid muscles attach to the TMJ

Question 77

Borders of pterygopalatine fossa

Answer 77

Sits directly behind maxilla and orbit below middle cranial fossa and lateral to posterior nasal cavity. The palatine bone forms most of medial parts of fossa Roof is formed by sphenoid bone and foramen rotundum sits in roof of fossa where CN V2 emerges

Question 78

Contents of pterygopalatine fossa

Answer 78

Inferior orbital fissure Foramen rotundum Sphenopalatine foramen: carries sphenopalatine artery (a branch of maxillary artery) which supplies posterior part of nasal cavity and this is the artery affected in posterior epistaxis CN V2 enters via foramen rotundum Hay Fever/Pterygopalatine ganglion runs in fossa and receives SNS input from internal carotid plexus and PNS input from greater petrosal nerve Pterygoid plexus

Question 79

List the layers of the scalp and any significant features about them

Answer 79

Skin Connective tissue (dense) Aponeurotic layer Loose CT Pericranium -the 1st 3 layers are very tightly adherent and inseparable -the dense CT layer is where the neurovascular structures lie -The loose CT is visibly attached to the skull and allows movement of the scalp and is the typical site of infection

Question 80

List the nerves supplying the scalp and face

Answer 80

``` Supratrochlear nerve Supraorbital nerve Zygomaticotemporal nerve Auriculotemporal nerve Greater occipital nerve Third occipital nerve Lesser occipital nerve Greater auricular nerve C4 ``` - Greater occipital and third occipital come from the posterior rami of C2-C3 supplying the posterior part of the skull - Lesser occipital and greater auricular come off the cervical plexus and supply around the ear

Question 81

Describe the blood supply to the face and scalp

Answer 81

Comes from branches of the external and internal carotid arteries - although ICA does not give any direct branches at neck it gives branches which exit skull (ophthalmic) which give off the supratrochlear and supraorbital arteries supplying anteriorly - the ECA supplies the rest of the skull giving off the superficial temporal, posterior auricular and occipital arteries - the venous drainage follows a similar pattern to the arteries

Question 82

Describe the lymphatic drainage of the skull

Answer 82

occipital, mastoid, submental, submandibular, pre-auricular and parotid nodes all drain into upper deep cervical lymph nodes

Question 83

List the main muscles of facial expression - describe any of their significant features or clinical relevance - what nerve are they supplied by?

Answer 83

1) Platysma 2) Auricularis (surround ear) 3) Orbicularis Oculi - has an orbital part (allows squeezing of eyes shut) and palpebral part (allows gentle closing of eyes). If there is damage to the facial nerve the patient will therefore be unable to close their eyes. The nerve which supplies orbicularis oculi is relatively vulnerable to injury. 4) Occipitofrontalis 5) Upper and lower lip muscles - upper lip muscles elevate upper lip, lower lip muscles depress lower lip. The nerve supplying the lower lip muscles is relatively vulnerable. 6) Buccinator - on lateral side of face, becomes perforated by parotid duct The muscles of facial expression are all supplied by the facial (VII) nerve. Therefore it is important to avoid damage to the facial nerve with any surgical procedure

Question 84

Describe the location of the parotid gland

Answer 84

The parotid gland is located on the lateral aspect of the face and has a superficial and deep part. The superficial part sits on the ramus of the mandible The deep part wraps under the margin of the ramus in behind the ramus of mandible.

Question 85

Describe the innervation of the parotid gland

Answer 85

Sensory supply: - V3 supplies parotid gland (so pain will be referred to area supplied by V3 - C2 supplies parotid fascia (an extension of the investing fascia. So pain is referred to C2 dermatome around neck) Secretomotor supply: - parasympathetic supply from V3 and IX - sympathetic supply from superior cervical ganglion travelling with ECA and MMA

Question 86

Describe the pathway of the parotid duct

Answer 86

Many small ducts drain the serous secretions of the parotid gland in the deep part and drain into a large common duct in the superficial part. The duct emerges from the anterior border of the parotid gland and runs along the masseter muscle. Once it reaches the anterior border of masseter it hooks 90 degrees toward buccinator and perforates the muscle. It then opens into the oral cavity roughly near the 2nd upper molar.

Question 87

Describe the surface anatomy of the parotid duct and why this is important

Answer 87

The parotid duct lies within the line running from anterior to the tragus to the oral commissure. It usually lies within 1.5cm above or below this line in the middle third of the line and 3mm deep to the skin. The surface anatomy of the parotid duct is very important to consider when a patient presents with a laceration on their face in this region, or if a surgical procedure will occur in this region. If the diagnosis of a damaged parotid duct is missed it can be very costly and will result in a fistula developing in which saliva will drain onto the cheek.

Question 88

Describe the path and the branches of the facial nerve Which branches are most vulnerable? Why is this important?

Answer 88

The facial nerve exits the skull via the stylomastoid foramen between the mastoid and styloid processes and then hits the parotid gland running between the deep and superficial parts. It then moves into the superficial part of the gland where it will usually divide into 2 large bundles, the temporozygomatic and cervicofacial nerves. 5 nerves will end up emerging from the parotid gland which have branched off the facial nerve. The temporozygomatic gives off the temporal, zygomatic and buccal nerves. The cervicofacial gives off the marginal mandibular and cervical nerves. These 5 nerves then go on to supply different muscles of the face. The temporal nerve and marginal mandibular nerve are the most vulnerable as they are superficial, are not covered by fat pads and have relatively high variability. They are the most likely nerve to be damaged by surgical procedures or traumatic lesions and therefore care should be taken when the regions they run in are damaged (lateral part of face and margin of mandible)

Question 89

Describe the relations of the facial nerve

Answer 89

The facial nerve exits the skull from the stylomastoid foramen between the mastoid and styloid processes. It then runs down and hits the border between the superficial and deep parts of the parotid gland and then runs into the superficial part giving off 2 bundles which eventually give off 5 branches. There are important structures running behind the facial nerve. The retromandibular vein and external carotid artery run posterior to the facial nerve, therefore if the patient is bleeding you know you have already gone too far and damaged the facial nerve. The masseter muscle and mandible are also posterior to the nerve.

Question 90

List the structures we would see on the floor of the mouth if we pulled up the tongue

Answer 90

The frenulum connects the inferior surface of the tongue to the floor of the mouth Lingual veins run along the floor of the mouth and lingual arteries, nerves and veins run in the inferior aspect of the tongue. We can see the sublingual glands overlied by the sublingual folds. There are the sublingual caruncles and the opening to the sublingual ducts also. The submandibular gland is palpable and the opening to the submandibular ducts is at the base of the frenulum

Question 91

Describe the main features of the tongue and its surface

Answer 91

The tongue is divided into an oral part and a pharyngeal part by the terminal sulcus. The oral part forms the anterior two thirds and the pharyngeal part extends into the pharynx. The tongue is covered in 3 types of papillae - fungiform, filliform and vallate papillae The foramen cecum where the thyroid embryologically migrates from is also located between the oral and pharyngeal parts of the tongue

Question 92

Roof of oral cavity: - Hard palate - soft palate - neurovascular supply

Answer 92

The hard palate is formed by the palatine process of the maxilla, the horizontal plates of the palatine bone and has a small contribution from sphenoid. There are palatine rugae seen on the hard palate. The soft palate is formed by the tensor veli palatini, levator veli palatini, palatopharyngeus and musculus uvulae. These muscles are all innervated by vagus with the exception of tensor veli palatini which is innervated by V3. The palatoglossal and palatopharyngeal arches are formed by their muscles and the palatine tonsil sits between these. Blood supply is from the facial, lingual, greater palatine and lesser palatine arteries Nerve supply is from greater palatine, lesser palatine and nasopalatine nerves

Question 93

What forms the lateral wall of the oral cavity?

Answer 93

The cheeks, consisting of: | Skin, the buccinator muscle and the oral mucosa lining the oral cavity

Question 94

What forms the floor of the oral cavity?

Answer 94

The suprahyoid muscles form the floor of the oral cavity. Mylohyoid extends from the mylohyoid line anteriorly to the hyoid bone posteriorly. The posterolateral border of mylohyoid is a free edge. Geniohyoid sits on top of mylohyoid extending from the inferior mental spines on the mandible to the hyoid bone posteriorly.

Question 95

Triangular aperture

Answer 95

The triangular aperture is a gap formed by the free edges of the mylohyoid and superior and middle constrictors of the pharynx which allows the passage of neurovascular structures to the oral cavity

Question 96

Muscles of the tongue

Answer 96

The tongue is made up of extrinsic muscles and intrinsic muscles. The extrinsic muscles form important gaps which allow passage of neurovascular structures and include: -Palatoglossus, styloglossus, hyoglossus and genioglossus. The genioglossus muscles sits on top of geniohyoid and runs from the superior mental spines of the mandible to the hyoid bone. Intrinsic muscles have their origin and insertion within the tongue and include the superior longitudinal, inferior longitudinal, vertical and transverse muscles. All muscles of the tongue are supplied by CN XII with the exception of palatoglossus which is supplied by vagus [X]

Question 97

Describe the spaces created by the extrinsic tongue muscles and the structures running through them

Answer 97

``` The 1st potential space runs between the mylohyoid and hyoglossus muscles. The Hypoglossal (XII) nerve, Lingual nerve (along with chorda tympani) and deep lingual vein run in this space. ``` ``` The 2nd potential space lies between hyoglossus and genioglossus. The Glossopharyngeal (IX) nerve, Lingual artery and Dorsal lingual vein run in this space. ```

Question 98

Describe the nerve supply to the tongue

Answer 98

Anterior 2/3: general sensation supply from lingual nerve (V3) Taste sensation from chorda tympani (VII) Posterior 1/3: General + taste sensation from glossopharyngeal (IX) Motor: Hypoglossal (XII) (exception of palatoglossus supplied by vagus [X])

Question 99

Which regions of the neck does the oral cavity lymph drain to?

Answer 99

Regions I and II | Always ensure to examine oral cavity if there is lymph node pathology in these regions of the neck

Question 100

Submandibular gland

Answer 100

Has a deep and superficial part and wraps around the free posterior edge of mylohyoid. The submandibular ducts exit from the deep part of the gland and drain into the oral cavity either side of the base of the frenulum in the floor of the cavity. The deep part of the submandibular duct lies in the 1st potential space between mylohyoid and hyoglossus and therefore the structures in this space are at risk (CN XII, lingual nerve, deep lingual vein) When removing the superficial part of the submandibular gland the marginal mandibular nerve is at risk (as it runs superficial to mylohyoid)

Question 101

List the 3 main regions of the nasal cavity

Answer 101

Olfactory region Respiratory region Nasal vestibules

Question 102

Describe the external nose

Answer 102

The part of the nose we can see Made up of the nasal bones and external nasal cartilage Cartilage structures include septal cartilage (superior margin and lateral processes), major alar and minor alar cartilages

Question 103

Describe the floor of the nasal cavity

Answer 103

Formed by the same structures which form the roof of the oral cavity i.e. the hard and soft palate -Palatine process of maxilla, horizontal plates of palatine bone, soft palate muscles

Question 104

What structures form the roof of the nasal cavity?

Answer 104

``` Nasal bone Nasal spine of frontal bone Cribriform plate of ethmoid bone Sphenoid Little bit of articulation between vomer and medial pterygoid plate of sphenoid ```

Question 105

What structures form the medial wall of the nasal cavity?

Answer 105

1) Septal cartilage - septal cartilage is clinically important due to the arteries closely associated with it. If the septal cartilage is damaged this can result in nasal septal haematoma which can cause the external nose to drop 2) Perpendicular plate of ethmoid bone 3) Vomer

Question 106

What structures make up the lateral wall of the nasal cavity?

Answer 106

1) Lateral process of septal cartilage 2) Major alar cartilage 3) Minor alar cartilages 4) Nasal bone 5) Frontal process of maxilla 6) Lacrimal bone 7) Superior and middle chonchae (of ethmoid bone) 8) Inferior choncha 9) Perpendicular plate of palatine bone 10) Medial pteryoid plate of sphenoid Remember there are several gateways closely associated with and deep to the chonchae which allow drainage of the paranasal sinuses

Question 107

List the paranasal sinuses

Answer 107

Frontal sinuses Ethmoidal cells (anterior, middle and posterior) Maxillary sinuses Sphenoidal sinuses

Question 108

Describe the drainage of the paranasal sinuses

Answer 108

- The sphenoidal sinus opens above the superior choncha into the spheno-ethmoidal recess. - The posterior ethmoidal cells drain through an opening between the superior and middle chonchae - The middle ethmoidal cells drain via an opening on the ethmoidal bulla between the middle and inferior chonchae - The frontal sinus and anterior ethmoidal cells drain via the frontonasal duct into the semilunar hiatus between the middle and inferior choncae - The maxillary sinus also opens into the semilunar hiatus between the middle and inferior chonchae -The nasolacrimal duct coming from the orbit drains deep to the inferior chonca

Question 109

List the main gateways in the nasal cavity

Answer 109

- The sphenopalatine artery (terminal branch of maxillary artery) travels from the pterygopalatine fossa through the sphenopalatine foramen into the nasal cavity. - Foramen cecum carries nasal vein. - Cribriform plate has many foramina where olfactory nerves run through - Incisive canal where greater palatine artery and vein and nasopalatine nerve comes through

Question 110

Describe the blood supply of the nasal cavity

Answer 110

The sphenopalatine artery is the terminal branch of the maxillary artery which comes from the pterygopalatine fossa and into the nasal cavity via the sphenopalatine foramen. It then gives off several branches which anastomose with arteries anteriorly. The sphenopalatine artery is very clinically important as it is the source of posterior epistaxis which can potentially be fatal. The anterior and posterior ethmoidal arteries are branches from the ophthalmic artery (from the ICA) which give off branches in the nasal cavity. They come forward to anastamose anteriorly with the greater palatine and superior labial arteries and the area of this anastamosis is called the 'little area'. This is the source of anterior epistaxis which accounts for the majority of nasal bleeding.

Question 111

Venous drainage and lymphatics of the nasal cavity

Answer 111

Lymphatics drain into the submandibular gland and then into the deep cervical nodes typically (so submandibular gland may become enlarged as result of nasal cavity infection or cancer. Several veins but the nasal vein drains through the foramen cecum and therefore has potential to carry infections intracranially.

Question 112

Innervation in the nasal cavity

Answer 112

Olfactory bulb with the olfactory nerves running into the olfactory region of the nasal cavity Anterior ethmoidal nerve nasopalatine nerve various branches of trigeminal nerve

Question 113

Describe the skeletal framework/attachments of the pharynx

Answer 113

The upper part of the pharynx is attached to the base of the skull. It attaches along the pterygomandibular raphe extending from the ramus of the mandible to the medial pterygoid plate. It runs across the medial pterygoid plate across the scaphoid fossa, across the cartilaginous part of the pharyngotympanic tube, over the petrous part of the temporal bone and then hooks across the pharyngeal tubercle on the basilar part of the occipital bone to complete its C-shaped attachment at the base of the skull. The middle part of the pharynx is attached to the lower part of the stylohyoid ligament and the greater and lesser horns of the hyoid bone The lower part of the pharynx attaches to the thyroid cartilage along the oblique line and extends to the cricoid cartilage.

Question 114

Describe the muscles of the pharynx

Answer 114

3 Constrictor muscles: Superior, middle and inferior constrictors of the pharynx. Superior constrictor attaches to pterygomandibular raphe and base of skull. Middle constrictor attaches to stylohyoid ligament and hyoid bone. Inferior constrictor attaches along oblique line of thyroid cartilage and cricoid cartilage. Note only the upper parts of the muscles are attached to these structures so their attachments are unstable. The muscles meet posteriorly in the midline at the pharyngeal raphe. The overlap of the muscles creates gaps through which structures can pass. 3 longitudinal muscles: Salpingopharyngeus, Palatopharyngeus, Stylopharyngeus These run between and assist/stabilise the constrictor muscles

Question 115

Describe the fascia of the pharynx

Answer 115

Fascia surrounding the pharynx is continuation of pretracheal fascia of the neck but is given a different name when enclosing the pharynx above the level of C6. Posteriorly the pharynx is covered by buccopharyngeal fascia. Behind the buccopharyngeal fascia there is the retropharyngeal space where many lymphatics run and thus pathology of the pharynx will often present in this space. The pharyngobasilar fascia runs between the mucosa of the pharynx and the constrictor muscles of the pharynx

Question 116

Describe the 3 main gaps between the pharynx and the structures that run through them

Answer 116

Oropharyngeal triangle: Gap formed between the free borders of mylohyoid, superior constrictor and middle constrictor. Muscles (stylopharyngeus), nerves (CN IX, XII) and vessels (lingual artery and vein) pass through the oropharyngeal triangle to get to the oral cavity. Gap between lower border of middle constrictor and upper border of inferior constrictor: Internal laryngeal nerve and vessels run in this gap Gap under lower border of inferior constrictor: Recurrent laryngeal nerve and inferior laryngeal vessels run through this gap

Question 117

Describe some of the features of the mucosal part of the pharynx

Answer 117

The pharyngotympanic tube connects the nasopharynx and middle ear The pharyngeal tonsil sits in the roof of the nasopharynx The palatine tonsil sits in the oropharynx between the palatoglossal and palatopharyngeal arches The lingual tonsil sits in the oropharynx posterior to the tongue

Question 118

Blood supply to the pharynx

Answer 118

Supplied by branches of the external carotid artery (e.g. lingual, maxillary, facial) and some branches of subcalvian inferiorly. Palatine tonsil supplied by facial artery.

Question 119

Venous drainage and lymphatics of pharynx

Answer 119

Drains into facial vein and IJV inferiorly. Some drainage into pterygoid plexus superiorly which can carry infection intracranially. Lymph drainage is into deep cervical lymph nodes

Question 120

Innervation of pharynx

Answer 120

``` All muscles of pharynx innervated by vagus except stylopharyngeus which is innervated by IX Sensory supply= V2 supplies nasopharynx IX supplies oropharynx X supplies laryngopharynx ```

Question 121

List the main cartilaginous structures forming the larynx

Answer 121

``` Epiglottis Thyroid cartilage Cricoid cartilage Arytenoid cartilage Corniculate cartilage Cuneiform cartilage ```

Question 122

List some of the ligaments making up the larynx

Answer 122

Thyrohyoid membrane Cricothyroid ligament Vestibular ligament Quadrangular membrane

Question 123

Key muscle of the larynx | -clinical importance

Answer 123

Cricothyroid muscle Most important muscle is posterior crico-arytenoid muscle as it abducts the vocal cords allowing breathing to occur. It is supplied by recurrent laryngeal nerves so if both of these become damaged the posterior crico-arytenoid will close and patient will go into respiratory distress.

Question 124

Blood supply, Lymphatic drainage and innervation of larynx

Answer 124

Blood supply comes from superior and inferior laryngeal arteries which branch off the superior and inferior thyroid arteries. Venous drainage is via superior and inferior laryngeal veins into thryoid veins into IJV/left bracheocephalic Lymphatics run with the arteries Innervation: Sensory supply from superior and inferior laryngeal nerves. Muscles all supplied by recurrent laryngeal nerve (except cricothyroid which is supplied by internal laryngeal)