📚 Question Bank

The given image shows the subclavian triangle marked. Dorsal scapular nerve/nerve to rhomboideus is a content of the occipital triangle and not the subclavian triangle.

Contents of the subclavian triangle:

• 3rd part of subclavian artery and vein
• Suprascapular artery and vein, transverse cervical artery
• Supraclavicular lymph node
• Trunks of the brachial plexus
• Branches from upper trunk of the brachial plexus – nerve to subclavius, suprascapular nerve

The structure marked above is the spinal accessory nerve. The spinal accessory nerve enters the posterior triangle passing deep to the sternocleidomastoid muscle and runs in an oblique direction within the triangle to supply the trapezius.

Option A: Phrenic nerve is seen related to the anterior surface of scalenus anterior, and supplies the diaphragm.

Option C: The greater auricular nerve supplies the skin over the angle of the jaw, skin over the mandible, and lower 1/3rd of the auricle, greater auricular nerve (C2,3).

Option D: The suprascapular nerve (C5, C6) arises from the upper trunk of the brachial plexus. It supplies the supraspinatus and infraspinatus muscles

Clinical note:

There are three types of modified radical neck dissection (MRND). Structures preserved are:

• MRND 1 - Only spinal accessory nerve
• MRND 2 - Accessory nerve and internal jugular vein
• MRND 3 i.e., functional neck dissection - Accessory nerve, sternocleidomastoid, and internal jugular veins.

The given region is the suboccipital triangle. It does not contain the occipital artery. The suboccipital triangle is bounded by:

• Superomedially - rectus capitis posterior major
• Superolaterally - obliquus capitis superior
• Inferiorolaterally - obliquus capitis inferior
• Roof - dense adipose tissue deep to semispinalis capitis, longissimus capitis muscle, and sometimes splenius capitis.
• Floor -posterior atlantooccipital membrane and the posterior arch of the atlas.
• Contents:
• 3rd part of the vertebral artery
• suboccipital nerve (dorsal ramus of C1)
• suboccipital venous plexus.

The muscle marked in the image is the temporalis and its main action is elevation of the mandible.

Other actions are:

• It helps in the side-to-side grinding movements of the mandible.
• The posterior fibres which are horizontal, help in the retraction of the mandible.

Rotatory movements of the jaw take place in the joint space below the articular disc of the temporomandibular joint.

The temporomandibular joint is adapted to accommodate both sliding and rotation movement in a sagittal plane.

The capsular ligament that surrounds the upper joint compartment is loose and hence allows the sliding or translation movements.

The capsular ligament that surrounds the lower joint compartment is tight and hence allows only the rotatory movements.

The structure marked in the image is the superior oblique muscle. It is supplied by the trochlear nerve (CN IV).

The superior oblique muscle helps in looking downwards and inwards. In cases of palsy of the trochlear nerve, the muscle is paralysed and the patient is unable to perform the same movement.

There are seven extraocular muscles present in the eye. They are:

• Levator palpebrae superioris - Which elevates the upper eyelids
• Four recti muscles - Superior, inferior, medial, and lateral recti
• Two obliques - Superior and inferior oblique

The muscles originate from the back of the orbit in a common tendinous ring called the annulus of Zinn and are inserted into the sclera.

All the extraocular muscles are innervated by the oculomotor (III) nerve except:

• Lateral rectus which is supplied by abducens (VI) nerve
• Superior oblique which is supplied by trochlear (IV) nerve

The bifurcation of the common carotid artery is at the level of the upper border of thyroid cartilage (C3-C4 junction). Carotid body tumors present at the bifurcation of the CCA and cause the external carotid artery (ECA) and internal carotid artery (ICA) to spread out, or splay, which is called 'Lyre sign' as seen on carotid angiography.

The course of the common carotid artery (CCA):

• The right and the left common carotid arteries differ in their origin:
• The right CCA arises from the brachiocephalic artery
• The left CCA arises directly from the arch of the aorta.
• In the neck, it is enclosed within the carotid sheath along with the internal jugular vein and vagus nerve.
• It ascends upwards up to the upper border of the thyroid cartilage (C3-4 junction) and divides into internal and external carotid arteries

Clinical significance of carotid bifurcation:

• Chassaignac/carotid tubercle/transverse process of C6 vertebra: The pulsations of the common carotid artery can be felt by compressing the artery against this tubercle.
• Site of carotid body tumor
• The most common site for carotid atherosclerosis. It can lead to stroke or transient ischaemic attack (TIA).
• In carotid endarterectomy, the presence of high bifurcation predisposes to injury to the cranial nerves, commonly the hypoglossal nerve or marginal mandibular nerve. In such patients, carotid stenting is usually preferred to carotid endarterectomy.

The only branch of the external carotid artery which is given from its medial side is ascending pharyngeal artery.

The external carotid artery is a branch of the common carotid artery which begins at the upper border of the thyroid cartilage at the level between third and fourth cervical vertebrae.

Branches of the external carotid artery are:

• Superior thyroid artery
• Ascending pharyngeal artery
• Lingual artery
• Facial artery
• Occipital artery
• Posterior auricular artery
• Maxillary artery and superficial temporal artery (terminal branches)

The internal carotid artery does not give any branch in the cervical region.

The internal carotid artery is a terminal branch of the common carotid artery which begins at the level of the upper border of thyroid cartilage.

The dorsal nasal artery will not be affected in this case, as is not a branch of the facial artery. It is a branch of the ophthalmic artery which is a branch of the ICA.

The facial artery is a branch of the external carotid artery which arises in the carotid triangle, above the origin of the lingual artery. In runs upwards in the neck and curves around the anteroinferior border of the masseter to enter the face.

Branches of facial artery in th e neck

Ascending palatine artery Tonsillar branch

Submental artery

Branches to submandibular g land

Branches of facial artery in th e face

Premasseteric artery

Superior and inferior labial a rteries

Lateral nasal artery Angular artery

The structure marked A is the pterygoid canal. The artery of the pterygoid canal is a branch of pterygopalatine part of the maxillary artery.

Pterygopalatine branches of maxillary artery are (mnemonic PIGPAS):

• Posterior superior alveolar artery
• Infraorbital artery
• Greater palatine artery
• Pharyngeal artery
• Artery of pterygoid canal
• Sphenopalatine artery

The triangular area from the corners of the mouth to the bridge of the nose, including the nose and maxilla is considered as the danger triangle of the face or dangerous area of the face.

The blood from these area drains through the facial vein. The facial vein is valveless and connects with the cavernous sinus through the superior ophthalmic vein and with the pterygoid venous plexus through the inferior ophthalmic and deep facial veins. Hence any infection of the face may spread to the cavernous sinus and pterygoid venous plexus and lead to cavernous sinus thrombophlebitis.

The anteromedial surface of the parotid gland is related to the medial pterygoid muscle.

The parotid gland is the largest salivary gland. It is usually in the shape of an inverted pyramid and has a superior surface, apex, superficial surface, anteromedial surface, and posteromedial surface.

Relations of the parotid gland:

• Superior surface - the external acoustic meatus and posterior part of the temporomandibular joint.
• Apex - directed downwards and is related to the posterior belly of the digastric and carotid triangle.
• Superficial surface - skin, superficial fascia, greater auricular nerve, parotid lymph nodes, and platysma.
• Anteromedial surface - posteroinferior part of the mandibular ramus, masseter, medial pterygoid, and temporomandibular joint.
• Posteromedial surface i- mastoid process, posterior belly of the digastric, styloid process, and
• the muscles attached to it.

The parotid nodes lie on the superficial surface of the parotid gland.

The false capsule which covers the parotid gland is derived from the investing layer of deep cervical fascia.

Structures present in the parotid gland from superficial to deep are the facial nerve, retromandibular vein, and external carotid artery.

The parotid gland is derived from the ectoderm.

The facial artery is not present within the parotid gland The parotid gland contains:

Arteries:

• External carotid artery, which terminates into the maxillary artery and superficial temporal artery.
• The transverse facial artery, which is a branch of the superficial temporal artery.

Sometimes the external carotid artery may also give posterior auricular artery within the gland.

Veins:

Maxillary vein and superficial temporal vein, which unite to form the retromandibular vein.

Nerves:

Facial nerve and its branches and parotid lymph nodes

The given image shows foramen ovale marked. The lesser petrosal nerve passes through this foramen. It derives preganglionic fibres from the tympanic nerve, also known as Jacobson's nerve.

Note: Mandibular division of trigeminal nerve also passes through the foramen ovale. However, it does not have any parasympathetic pre-ganglionic fibres.

The parotid duct or the Stensen's duct opens opposite to the 2nd upper molar tooth. It pierces the buccinator at the level of the 3rd upper molar tooth.

Structures pierced by the parotid duct are shown in the image below:

Clinical significance:

Sialolithiasis is the presence of stones in the salivary ducts. It is more commonly seen in the submandibular gland than the parotid gland. Parotid duct stones are usually radiolucent and rarely visible on plain radiography, therefore contrast is given to perform sialography to visualize the stones on X-rays.

The accessory parotid gland is present between the parotid duct and zygomatic arch.

It is usually a detached part of the parotid gland. They have their own blood supply and a secondary duct that drains into the main parotid duct.

Clinical significance:

• They can be missed during complete parotidectomy.
• They can present as mid-cheek masses.
• The histological characteristics of accessory glands can differ from that of main gland and hence tumors arising from them can show different clinical course.

Frey's syndrome occurs due to the aberrant innervation of the auriculotemporal nerve. It is also known as gustatory sweating or auriculotemporal syndrome.

It commonly develops after parotid surgery or any trauma where there is an injury to the parotid capsule.

During the regrowth, an aberrant connection develops between the parasympathetic fibres supplying the parotid gland (auriculotemporal nerve) and the sweat glands.

This results in sweating, warmth, and redness of the face during the salivary stimulation by the smell or taste of food.

Management:

• Antiperspirants - aluminum chloride
• Tympanic neurectomy
• Botulinum toxin injection into the affected skin

The lingual nerve is susceptible to injury during excision of the submandibular gland.

Lingual nerve loops around the submandibular duct, and hence is susceptible to injury during the procedures involving the submandibular region.

Superficial to the hyoglossus muscle, the submandibular duct lies between lingual and hypoglossal nerves. As it reaches the anterior border of the hyoglossus, it is crossed by the lingual nerve.

In the given case, the swelling is present in the submandibular region, involving

the submandibular gland. The gland is seen to wrap around the posterior border of the mylohyoid.

The submandibular gland is made up of large superficial and smaller deep parts, which are continuous with each other around the posterior border of the mylohyoid.

Option B: The facial artery is related to the superficial part of the gland.

Option C, D: Lingual nerve loops around the submandibular duct. Damage to it causes loss of sensation in the anterior 2/3rd of the tongue.

Preganglionic fibres to the submandibular ganglion arise from the superior salivatory nucleus..

The structure marked X is the isthmus of the thyroid gland. It overlies 2nd, 3rd, and 4th tracheal rings.

Isthmus connects the lower parts of both the lobes of the thyroid gland. It is usually present anterior to the 2nd and 3rd tracheal cartilages, but the position may vary according to its size.

Recurrent laryngeal nerve is related to the posterior branch of the inferior thyroid artery near the lobes of the thyroid gland. Therefore, during ligation of the artery, it is ligated close to the gland to prevent injury to it.

External laryngeal nerve is related to the superior thyroid artery. Superior thyroid artery pierces the thyroid fascia and supplies the upper part of the gland. The superior thyroid artery is ligated close to the gland to prevent injury to this nerve.

Inferior thyroid artery is a branch of the thyrocervical trunk of the subclavian artery.