Head and Neck 2: Face and Skull Flashcards
What is CN V? What is its purpose?
Trigeminal nerve - conveys cutaneous sensation from the face and forehead
How many divisions of CN V are there?
3 divisions - each of which carries sensation from a particular area of the face/anterior scalp
What are the 3 divisions of the trigeminal nerve?
- CN V1 : opthalmic nerve
- CN V2 : maxillary nerve
- CN V3 : mandibular nerve
Which division of the trigeminal nerve innervates which area of skin?
Red - Ophthalmic Nerve
Blue - Maxillary Nerve
Green - Mandibular Nerve
What should clinical examination of the sensory innervation of the face involve?
involve testing pinprick and light touch sensations over each of these regions
What may lesions of these branches of the trigeminal nerve lead to?
lesions of any of these branches may lead to loss of sensation over the corresponding anatomical division.
What are the 3 important groups of muscles in the head?
- The muscles of facial expression
- The muscles of mastication
- The extraocular muscles
Info about muscles of facial expression:
Some of these, act as sphincters and dilators controlling the various openings, they support the angles of the eyes and mouth, and they prevent secretions dribbling on to the face. They all insert into the skin of the face and are thus very superficial.
What are the 6 most important muscles of facial expression?
- Occipitofrontalis
- Orbicularis oculi
- Orbicularis oris + Buccinator
- Orbicularis oris
- Dilators of the mouth
- Platysma
Label this diagram showing the most important muscles of facial expression
The right 6: (top to bottom)
- Occipitofrontalis (frontal belly)
- Obicularis oculi
- Dilators of the mouth
- Orbicularis oris + buccinator
- Orbicularis oris
- Buccinator
Left 2 (top to bottom):
- Occipitofrontalis (occipital belly)
- Platysma
Orbicularis Oculi:
- Location?
- Action?
- Innervation?
- Location: The orbicularis oculi muscle surrounds the eye socket and extends into the eyelid.
- Action:
- Closes the eyelids
- Acts to draw the eyebrows together, creating vertical wrinkles on the bridge of the nose.
- Innervation: facial nerve CN VII
Occipitofrontalis:
- Location?
- Action?
- Innervation?
- Location: Covers parts of the skull. It consists of two bellies: The occipital belly, near the occipital bone, and the frontal belly, near the frontal bone
- Action:
- Frontal part: This part of the muscle pulls the scalp anteriorly; wrinkles the forehead and elevates eyebrows
- Occipital part: This part pulls the scalp posteriorly (retracts)
- Innervation: Facial nerve CN VII
Orbicularis oris:
- Location?
- Action?
- Innervation?
- Location: The fibres of the orbicularis oris enclose the opening to the oral cavity.
- Action: Sphincter of the mouth. Purses the lips.
- Innervation: Facial nerve CN VII
Buccinator:
- Location?
- Action?
- Innervation?
- Location: This muscle is located between the mandible and maxilla, deep to the other muscles of the face.
- Action: The buccinator pulls the cheek inwards against the teeth, preventing accumulation of food in that area. Keeps cheeks taut when whistling etc
- Innervation: Facial nerve CN VII
Platysma:
- Location?
- Action?
- Innervation?
- Location: Lies superficially within the anterior aspect of the neck.
- Action: Tenses the skin of the inferior face and neck
- Innervation: Facial nerve CN VII
Which nerve innervates the muscles of facial expression?
Facial nerve CN VII
The facial nerve has motor, sensory and autonomic functions. What are the sensory and autonomic functions?
- Sensory:
- A small area around the concha of the external ear.
- Special Sensory – provides special taste sensation to the anterior 2/3 of the tongue via the chorda tympani
- Autonomic: supplies many of the glands of the head and neck including:
- Submandibular and sublingual salivary glands.
- Nasal, palatine and pharyngeal mucous glands.
- Lacrimal glands.
The orbicularis oculi, is the circular muscle that acts as a sphincter around the eye. Which two muscles act as dilators of the eyelids?
Levator palpebrae superioris and superior tarsal muscles both act to open the eyelid. They are only present in the upper eyelid.
Paralysis of orbicularis oculi can lead to a serious complication – what is it?
- Exposure keratitis: The eye cannot shut – this can cause the cornea to dry out.
- Ectropion: The lower eyelid droops. Lacrimal fluid pools in the lower eyelid and cannot be spread across the surface of the eye. This can result in a failure to remove debris, and ulceration of the corneal surface.
Which muscle acts as the sphincter of the mouth?
Orbicularis oris
What is the action of orbicularis oris opposed by?
A number of dilator muscles (You do not need to know the names of individual dilator muscles)
What is the function of the buccinator muscle?
a) in neonates?
b) in adults?
- Neonates: It is used to suckle (is one of the first muscles in infants to be activated)
- Adults: The buccinator compresses the cheeks against the teeth and is used in acts such as blowing. It is an assistant muscle of mastication (chewing).
What is the parotid gland?
the largest of the paired salivary glands
Location of the parotid gland?
It occupies the interval between the mastoid process posteriorly, and the ramus of the mandible (covered by the masseter muscle) which it overlaps, anteriorly.
What does the parotid gland lie within?
The parotid gland lies within the fascial parotid sheath, which is continuous with the investing fascia of the neck.
In some conditions the parotid gland may become swollen. Such swelling is extremely painful. Name one such condition and suggest why it is so painful.
Parotitis:
- Inflammation of the parotid gland, usually as a result of an infection. The parotid gland is enclosed in a tough fibrous capsule. This limits swelling of the gland, producing pain.
- The pain produced can be referred to the external ear. This is because the auriculotemporal nerve provides sensory innervation to the parotid gland and the external ear.
How do secretions from the parotid gland get to the mouth?
The parotid duct carries secretions from the parotid gland into the mouth
Describe course of parotid duct
During its course it travels anteriorly over the masseter muscle to pierce the buccinator muscle and open (drain) into the mouth.
Where does the parotid duct open in the mouth?
It opens out into the oral cavity near the second upper molar.
An important cranial nerve divides into its five terminal branches within the substance of the parotid gland. Which nerve is this? What are these 5 branches called?
The facial nerve (cranial nerve VII), gives rise to five terminal branches within the parotid gland. These terminal branches emerge from the anterior border of the gland and innervate the muscles of facial expression.
5 branches:
- Temporal branch
- Zygomatic branch
- Buccal branch
- Marginal mandibular branch
- Cervical branch
Why is the facial nerve vulnerable to damage in the parotid gland?
Lies superifically in the gland
Think of at least two situations in which the facial nerve nerve is at risk?
- The most common cause of an intracranial lesion of the facial nerve is infection related to the external or middle ear.
- Parotid gland pathology – e.g a tumour, parotitis, surgery.
What other structures lie within the substance of the parotid gland?
- the retromandibular vein
- the external carotid artery - which divides into its two terminal branches
How is the retromandibular vein formed?
formed by the union of the superficial temporal vein and the maxillary vein
Label the anterior branches of the external carotid artery
Left top to bottom:
- Superficial temporal
- Maxillary
- Facial
- Lingual
- Superior thyroid
What is the middle meningeal artery a branch of?
The maxillary artery
What does the middle meningeal artery supply?
the dura mater and the calvaria