Face and Neck Flashcards
What are the boundaries of the infratemporal fossa?
The infratemporal fossa can be said to have a wedge shape.
Located deep to the masseter muscle and zygomatic arch (to which the masseter attaches). The fossa is closely associated with both the pterygopalatine fossa, via the pterygomaxillary fissure, and also communicates with the temporal fossa, which lies superiorly (figure 1.0).
The boundaries of this complex structure consists of both bone and muscle:
Lateral – condylar process and ramus of the mandible bone
Medial – lateral pterygoid plate; tensor veli palatine, levator veli palatine and superior constrictor muscles
Anterior – posterior border of the maxillary sinus
Posterior – carotid sheath
Roof – greater wing of the sphenoid bone
Floor – Medial pterygoid muscle
The roof of the infratemporal fossa, formed by the greater wing of the sphenoid bone, provides an important passage for the neurovascular structures transmitted through the foramen ovale and spinosum. Among these are the mandibular branch of the trigeminal nerve and the middle meningeal artery.
What are the contents of the infratemporal fossa?
Acts as a pathway for neurovascular structures passing to and from the cranial cavity, pterygopalatine fossa and temporal fossa.
Lateral pterygoid splits the fossa contents in half – the branches of the mandibular nerve lay deep to the muscle, while the maxillary artery is superficial to it.
Muscles
The infratemporal fossa is associated with the muscles of mastication. The medial and lateral pterygoids are located within the fossa itself, whilst the masseter and temporalis muscles insert and originate into the borders of the fossa.
Nerves
Important passage for a number of nerves originating in the cranial cavity
Mandibular nerve – a branch of the trigeminal nerve (CN V). It enters the fossa via the foramen ovale, giving rise to motor and sensory branches. The sensory branches continue inferiorly to provide innervation to some of the cutaneous structures of the face.
Auriculotemporal, buccal, lingual and inferior alveolar nerves – sensory branches of the trigeminal nerve.
Chorda tympani – a branch of the facial nerve (CN VII). It follows the anatomical course of the lingual nerve and provides taste innervation to the anterior 2/3 of the tongue.
Otic ganglion – a parasympathetic collection of neurone cell bodies. Nerve fibres leaving this ganglion ‘hitchhike’ along the auriculotemporal nerve to reach the parotid gland
Vasculature
The maxillary artery, the terminal branch of the external carotid artery, travels through the infratemporal fossa. Within the fossa, it gives rise to the middle meningeal artery, which passes through the superior border via the foramen spinosum.
The pterygoid venous plexus is directly connected to the cavernous sinus and drains the eye. Infections of the skin and eye socket are able to track back into this plexus within the fossa and up into the cavernous sinus, making meningitis is a substantial risk.
Other veins in the fossa include the maxillary vein and middle meningeal vein.
What are the clinical implications of a fracture of the pterion?
It is the point where the temporal, parietal, frontal and sphenoid bones meet and the skull is at its weakest.
Trauma in this region can lead to an extradural haematoma as the middle meningeal artery (MMA) lies deep to it.
An extradural haematoma causes a dangerous increase in intra-cranial pressure, which can lead to herniation of brain tissue and ischaemia.
The increase in intra-cranial pressure causes a variety of symptoms; nausea, vomiting, seizures, bradycardia and limb weakness.
Treated by diuretics in minor cases, and drilling burr holes into the skull in the more extreme haemorrhages.
What are the mucles of mastication and from which embryological structure are the derived?
The muscles of mastication are a group of muscles associated with movements of the jaw
There are four muscles of mastication – the masseter, temporalis, medial pterygoid and lateral pterygoid.
Embryologically, the muscles of mastication develop from the first pharyngeal arch. Consequently they are innervated by a branch of the trigeminal nerve (CN V), the mandibular nerve.
Describe the anatomy of the masseter muscle
The masseter muscle is the most powerful muscle of mastication.
It is quadrangular in shape, and can be split into two parts; deep and superficial.
The entirety of the muscle lies superficially to the pterygoids and temporalis, covering them.
Attachments: The superficial part originates from maxillary process of the zygomatic bone. The deep part originates from the zygomatic arch of the temporal bone. Both parts attach to the ramus of the mandible.
Actions: Elevates the mandible, closing the mouth.
Innervation: Mandibular nerve (V3).
Describe the anatomy of the temporalis muscle
The temporalis muscle originates from the temporal fossa – a shallow depression on the lateral aspect of the skull.
The muscle is covered by tough fascia which can harvested surgically and used to repair a perforated tympanic membrane (an operation known as a myringoplasty).
Attachments: Originates from the temporal fossa. It condenses into a tendon, which inserts onto the coronoid process of the mandible.
Actions: Elevates the mandible, closing the mouth. Also retracts the mandible, pulling the jaw posteriorly.
Innervation: Mandibular nerve (V3).
Compare and contrast the medial and lateral pterygoid muscles
Medial Pterygoid
The medial pterygoid muscle has a quadrangular shape, with two heads; deep and superficial. It is located inferiorly to the lateral pterygoid.
Attachments: The superficial head originates from the maxilla. The deep head originates from the lateral pterygoid plate of the sphenoid bone. Both parts attach to the ramus of the mandible, near the angle of mandible.
Actions: Elevates the mandible, closing the mouth.
Innervation: Mandibular nerve (V3).
Lateral Pterygoid
The lateral pterygoid muscle has a triangular shape, with two heads; superior and inferior. It has horizontally orientated muscle fibres, and thus is the major protractor of the mandible.
Attachments: The superior head originates from the greater wing of the sphenoid. The inferior head originates from the lateral pterygoid plate of the sphenoid. The two heads converge into a tendon, which attaches to the neck of the mandible.
Actions: Acting bilaterally, the lateral pterygoids protract the mandible, pushing the jaw forwards. Unilateral action produces the ‘side to side’ movement of the jaw.
Innervation: Mandibular nerve (V3).
Describe the osteological features of the mandible
Largest and strongest bone of the face
It forms the lower jaw and acts as a receptacle for the lower teeth.
Articulates on either side with the temporal bone, forming the temporomandibular joint
Anatomical Structure
Consists of a horizontal body (anteriorly) and two vertical rami (posteriorly). The body and the rami meet on each side at the angle of the mandible.
Body
The body of the mandible is curved, and shaped much like a horseshoe.
It has two borders:
Alveolar border (superior) – contains 16 sockets to hold the lower teeth.
Base (inferior) – site of attachment for the digastric muscle medially
Mandibular symphysis in midline - small ridge of bone from fusion of the two halves during development. The symphysis encloses a triangular eminence – the mental protuberance, which forms the shape of the chin.
Lateral to the mental protuberance is the mental foramen (below the second premolar tooth on either side). It acts as a passageway for neurovascular structures.
Rami
Two mandibular rami project perpendicularly upwards from the angle of the mandible.
Head – situated posteriorly, and articulates with the temporal bone to form the temporomandibular joint.
Neck – supports the head of the ramus, and site of attachment of the lateral pterygoid muscle.
Coronoid process – site of attachment of the temporalis muscle
The internal surface of the ramus marked by the mandibular foramen, which acts as a passageway for neurovascular structures.
Foramina
The mandibular foramen is located on the internal surface of the ramus of the mandible. It serves as a conduit for the inferior alveolar nerve and inferior alveolar artery. They travel through the mandibular foramen, into the mandibular canal, and exit at the mental foramen.
The mental foramen is on the external surface of the mandibular body, below the second premolar tooth. Allows the inferior alveolar nerve and artery to exit the mandibular canal. When the inferior alveolar nerve passes through the mental foramen, it becomes the mental nerve (innervates the skin of the lower lip and the front of the chin).
Describe the muscular attachments of the mandible
Mandibular body:
External (lateral) surface – mentalis, buccinator, platysma, depressor labii inferioris, depressor anguli oris. (5 expression mm)
Internal (medial) surface – genioglossus, geniohyoid, mylohyoid and digastric. (4 neck muscles)
Mandibular rami – masseter, temporalis, medial pterygoid and lateral pterygoid (mm of mastication)
The temporalis muscle attaches to the coronoid process, and the masseter attaches to the rami. The lateral pterygoid inserts into the neck of the mandible, and the medial pterygoid inserts into the ramus near the angle of the mandible.
What are the clinical implication of a fractured mandible
A mandibular fracture rarely occurs in isolation. Much like fractures of the pelvic brim, a fracture on one side is frequently associated with a fracture on the contralateral side.
Therefore, if one fracture is observed, another should be searched for. For example, a fractured neck of the mandible is often observed in conjunction with a fracture of the contralateral mandibular body.
The characteristics of mandibular fractures are as follows:
Fractures of the coronoid process are uncommon and usually singular.
Fractures of the neck of the mandible are often transverse and usually accompanied with dislocation of the temporomandibular joint.
Fractures of the angle of the mandible are usually oblique and may involve the alveolus of the 3rd molar.
Fractures of the body of the mandible frequently pass through the canine tooth.
Describe the lymphatic drainage of the head and neck
Lymphatic Vessels
The lymphatic vessels of the head and neck can be divided into two major groups; superficial vessels and deep vessels.
Superficial Vessels
The superficial vessels drain lymph from the scalp, face and neck into the superficial ring of lymph nodes at the junction of the neck and head.
Deep Vessels
The deep lymphatic vessels arise from the deep cervical lymph nodes. They converge to form the left and right jugular lymphatic trunks:
Left jugular lymphatic trunk – joins the thoracic duct at the root of the neck.
Right jugular lymphatic trunk empties into the right lymphatic duct at the root of the neck. The right lymphatic duct enters the venous system at the right venous angle, the junction between the internal jugular vein and subclavian vein
Lymph Nodes
The lymph nodes of the head and neck can be divided into two groups; a superficial ring of lymph nodes, and a vertical group of deep lymph nodes.
Superficial Lymph Nodes
The superficial lymph nodes of the head and neck receive lymph f_rom the scalp, face and neck_. They are arranged in a ring shape; extending from underneath the chin (mental nodes), to the posterior aspect of the head (occipital nodes). They ultimately drain into the deep lymph nodes.
Occipital: There are usually between 1-3 occipital lymph nodes. They are located in the back of the head at the lateral border of the trapezius muscle and collect lymph from the occipital area of the scalp.
Mastoid/Post-auricular: There are usually 2 mastoid lymph nodes. They are located posterior to the ear and lie on the insertion of the sternocleidomastoid muscle into the mastoid process. They collect lymph from the posterior neck, upper ear and the back of the external auditory meatus (the ear canal).
Pre-auricular: There are usually between 1-3 pre-auricular lymph nodes. They are located anterior to the auricle of the ear, and collect lymph from the superficial areas of the face and temporal region.
Parotid: The parotid lymph nodes are a small group of nodes located superficially to the parotid gland. They collect lymph from the nose, the nasal cavity, the external acoustic meatus, the tympanic cavity and the lateral borders of the orbit. There are also parotid lymph nodes deep to the parotid gland that drain the nasal cavities and the nasopharynx.
Submental: These lymph nodes are located superficially to the mylohoid muscle. They collect lymph from the central lower lip, the floor of the mouth and the apex of the tongue.
Submandibular: There are usually between 3-6 submandibular nodes. They are located below the mandible in the submandibular triangle and collect lymph from the cheeks, the lateral aspects of the nose, upper lip, lateral parts of the lower lip, gums and the anterior tongue. They also receive lymph from the submental and facial lymph nodes.
Facial: This group comprises the maxillary/infraorbital, buccinator and supramandibular lymph nodes. They collect lymph from the mucous membranes of the nose and cheek, eyelids and conjunctiva.
Superficial Cervical: The superficial cervical lymph nodes can be divided into the superficial anterior cervical nodes and the posterior lateral superficial cervical lymph nodes. The anterior nodes lie close to the anterior jugular vein and collect lymph from the superficial surfaces of the anterior neck. The posterior lateral nodes lie close to the external jugular vein and collect lymph from superficial surfaces of the neck.
Deep Lymph Nodes
The deep (cervical) lymph nodes receive all of the lymph from the head and neck – either directly or indirectly via the superficial lymph nodes. They are organised into a vertical chain, located within close proximity to the internal jugular vein within the carotid sheath. The efferent vessels from the deep cervical lymph nodes converge to form the jugular lymphatic trunks.
The nodes can be divided into superior and inferior deep cervical lymph nodes. They are numerous in number, but include the prelaryngeal, pretracheal, paratracheal, retropharyngeal, infrahyoid, jugulodigastric (tonsilar), jugulo-omohyoid and supraclavicular nodes.
What is the clinical relevance of Virchow’s node?
Virchow’s node is left supraclavicular node, located in the left supraclavicular fossa. It receives lymph drainage from the abdominal cavity.
The finding of an enlarged Virchow’s node is referred to as Troisier’s sign – and indicates gastric cancer that has spread through the lymph vessels.
What is the clinical relevance of inflamed palatine tonsils?
The palatine tonsils can become inflamed due to a viral or bacterial infection. In such a case, they appear red and enlarged, and are accompanied by enlarged jugulo-digastric lymph nodes.
Chronic infection of the palatine tonsils can be treated with their removal, a tonsillectomy. When performing a tonsillectomy, there may be bleeding primarily from the external palatine vein and secondarily from the tonsilar branch of the facial artery.
If an infection spreads to the peritonsillar tissue, it can cause abscess formation. This can cause deviation of the uvula, known as quinsy. A quinsy is a medical emergency, as it can potentially cause obstruction of the pharynx. It is treated with draining of the abscess and antibiotics.
What is Waldeyer’s Ring?
Waldeyer’s tonsillar ring refers to the collection of lymphatic tissue surrounding the superior pharynx. This lymphatic tissue responds to pathogens that may be ingested or inhaled.
The tonsils that make up the ring are as follows:
Lingual tonsil – located on the posterior base of the tongue to form the antero-inferior part of the ring.
Palatine tonsils – located on each side between the palatoglossal and glossopharyngeal arches. These are the common ‘tonsils’ that can be seen within the oral cavity. They form the lateral part of the ring.
Tubal tonsils – these are located where each Eustachian tube opens into the nasopharynx and form the lateral part of the ring.
Pharyngeal tonsil – also called the nasopharyngeal/adenoid tonsil, located in the roof of the nasopharynx, behind the uvulva and forms the postero-superior part of the ring.
Describe the anatomy of the superficial cervical fascia
Fascia is a layer of fibrous tissue that surrounds muscles, vessels and nerves. In the neck, there are several layers of fascia, which act to support and compartmentalise the structures present.
The superficial cervical fascia lies between the dermis and the deep cervical fascia. It contains various structures:
- Neurovascular supply to the skin
- Superficial veins (e.g the external jugular vein)
- Superficial lymph nodes
- Fat
- Platysma muscle
The platysma muscle is situated on the anterior aspect of the neck. It has two heads, which originate from the fascia of the pectoralis major and deltoid. Fibres from the two heads cross the clavicle, and meet in the midline, fusing with the muscles of the face. Motor innervation to the platysma is via the cervical branch of the facial nerve.
Describe the anatomy of the deep cervical fascia
Fascia is a layer of fibrous tissue that surrounds muscles, vessels and nerves. In the neck, there are several layers of fascia, which act to support and compartmentalise the structures present.
Investing Layer
The investing layer is the most superficial of the deep cervical fascia.
It surrounds all the structures in the neck. Where it meets the trapezius and sternocleidomastoid muscles, it splits into two, surrounding them.
The investing fascia can be thought of as a tube; with superior, inferior, anterior and posterior attachments:
Superior: attaches to the external occipital protuberance and the superior nuchal line.
Inferior: attaches to the spine and acromion of the scapula, the clavicle, and the manubrium of the sternum.
Anterior: attaches to the hyoid bone.
Posterior: attaches along the ligamentum nuchae.
Pretracheal Layer
The pretracheal layer of fascia is situated anteriorly in the neck. It spans between the hyoid bone and the thorax, where it fuses with the pericardium.
The trachea, oesophagus, thyroid gland and infrahyoid muscles are enclosed by the pretracheal fascia. It can be anatomically divided into two parts:
Muscular – encloses the infrahyoid muscles.
Visceral – encloses the thyroid gland, trachea and oesophagus.
The posterior aspect of the visceral fascia is formed by contributions from the buccopharyngeal fascia (a fascial covering of the pharynx).
Prevertebral Layer
The prevertebral fascia surrounds the vertebral column and its associated muscles (scalene, prevertebral, and deep muscles of the back). It has attachments along the antero/posterior and supero/inferior axes:
Superior: attaches to the base of the skull.
Inferior: fuses with the endothoracic fascia of the ribcage.
Anterior: attaches to the transverse processes and vertebral bodies of the vertebral column.
Posterior: attaches along the ligamentum nuchae.
The anterolateral portion of prevertebral fascia forms the floor of the posterior triangle of the neck. It also surrounds the brachial plexus and subclavian artery as they leave the neck, forming the axillary sheath.
Carotid Sheaths
The carotid sheaths are paired structures which enclose important vessels and nerves. They are formed by contributions from the pretracheal, prevertebral, and investing fascia layers.
The contents of the carotid sheath are:
- Common carotid artery (which bifurcates within the sheath into the external and internal carotid arteries).
- Internal jugular vein.
- Vagus nerve.
- Cervical lymph nodes.
The carotid fascia is organised into a column, which runs from the base of the skull to the thoracic mediastinum.
This is of clinical importance as a pathway for the spread of infection.
Clinical Relevance: Spread of Infections
- The neck fascia compartmentalises the structures within the neck. These layers of tough fascia define where infection can spread (e.g a superficial skin abscess is prevented from spreading further into the neck by the investing fascia).*
- Infections that occur deep to the investing fascia have a well-defined spread:*
Posterior to the prevertebral fascia – This can erode through the prevertebral fascia, and drain into the retropharyngeal space (a space between the pretracheal and prevertebral fascial layers). The retropharyngeal space extends into the thorax, and i_nfection can spread to the mediastinal contents_.
Between the investing fascia and visceral part of the pretracheal fascia – This can spread inferiorly into the chest, causing infection of the anterior mediastinum.
