TBL25 - Scalp and Face

Question 1

What does the scalp cover?

Answer 1

The scalp covers the neurocranium from the external occipital protuberance to the supraorbital margins and laterally to the zygomatic arches

Question 2

Define the five layers of the scalp.

Answer 2

Outer to inner:

1) Skin
2) Connective tissue (Dense)
3) Aponeurosis
4) Loose connective tissue
5) Pericranium

Question 3

Why is the loose connective layer the “danger area of the scalp”?

Answer 3

1) Loose areolar tissue: a sponge-like layer including potential spaces that may distend with fluid as a result of injury or infection
2) The loose connective tissue layer (layer four) of the scalp is the danger area of the scalp because pus or blood spreads easily in it
3) Infection in this layer can also pass into the cranial cavity through small emissary veins, which pass through parietal foramina in the calvaria, and reach intracranial structures such as the meninges

Question 4

What is each pair of pharyngeal arches supplied by (nerve)? What is the first pharyngeal arch supplied by (nerve)?

Answer 4

1) Each pair of pharyngeal arches is supplied by a cranial nerve
2) The 1st pharyngeal arch is supplied by CN V

Question 5

What is the viscerocranium derived from? What do the three divisions of the trigeminal nerve provide cutaneous (somatic sensory) innervation to?

Answer 5

1) The viscerocranium is derived from the 1st pharyngeal arch
2) The three divisions of the trigeminal nerve provide cutaneous (somatic sensory) innervation to the face and the scalp anterior to the ear

Question 6

What forms the sensory root of CN V to the brain? What are the peripheral projecting fibers of the trigeminal ganglion organized into and what do they each innervate, respectively?

Answer 6

1) The trigeminal ganglion has central projecting axons that form the sensory root of CN V to the brain
2) The peripheral projecting fibers are organized into the ophthalmic nerve (CN V1), maxillary nerve (CN V2), and mandibular nerve (CN V3), which are cutaneous nerves to the frontonasal, maxillary, and mandibular prominences, respectively

Question 7

When CN V1 enters the orbit, what does it generate, where does this nerve traverse, and what does this nerve terminate as? What does this nerve innervate? What supplies the skin of the neck and scalp posterior to the ear?

Answer 7

1) CN V1 enters the orbit where it generates the frontal nerve that terminates as the supraorbital nerve, which traverses the supraorbital foramen
2) The supraorbital nerve innervates the upper eyelids and scalp anterior to the ear
3) The cervical plexus supplies the skin of the neck and scalp posterior to the ear

Question 8

What nerves does CN V3 generate and what do these nerves innervate?

Answer 8

CN V3 generates the auriculotemporal and buccal (aka long buccal) nerves, which innervate the scalp superior to the ear and the lateral cheek, respectively

Question 9

What is the infraorbital nerve a branch of and where does it enter and course? What does this nerve innervate?

Answer 9

1) The infraorbital nerve, a branch of CN V2, enters the orbit and courses along the orbital floor to the infraorbital foramen
2) The infraorbital nerve innervates the lower eyelids, nose, central cheek below the eyelids, and upper lip

Question 10

Which peripheral branch of the trigeminal ganglion is most commonly affected by neuralgia and what are proposed causes, clinical symptoms, and possible treatment? (Clean this up)

Answer 10

1) Trigeminal neuralgia or tic douloureux is a sensory disorder of the sensory root of CN V that occurs most often in middle-aged and elderly persons
2) CN V2 is most frequently involved, then CN V3, and least frequently, CN V1
3) In trigeminal neuralgia, demyelination of axons in the sensory root occurs. In most cases this is caused by pressure of a small aberrant artery
4) Other scientists believe the condition is caused by a pathological process affecting neurons in the trigeminal ganglion
5) It is characterized by sudden attacks of excruciating, lighteninglike jabs of facial pain. A paroxysm (sudden sharp pain) can last for 15 minutes or more. The pain may be so intense that the person winces; hence the common term tic (twitch). In some cases, the pain may be so severe that psychological changes occur, leading to depression and even suicide attempts
6) Medical or surgical treatment or both are used to alleviate the pain. In cases involving the CN V2, attempts have been made to block the infra-orbital nerve at the infra orbital foramen by using alcohol. This treatment usually relieves pain temporarily. The simplest surgical procedure is avulsion or cutting of the branches of the nerve at the infra-orbital foramen

Question 11

When are infraorbital nerve blocks typically employed and what is a probable consequence of a careless injection?

Answer 11

1) For treating wounds of the upper lip and cheek or, more commonly, for repairing the maxillary incisor teeth, local anesthesia of the inferior part of the face is achieved by infiltration of the infra-orbital nerve with an anesthetic agent
2) Because the orbit is located just superior to the injection site, a careless injection could result in passage of anesthetic fluid into the orbit, causing temporary paralysis of the extra-ocular muscles

Question 12

What is an ophthalmic herpes zoster and what are its symptoms?

Answer 12

1) A herpes zoster virus infection may produce a lesion in the cranial ganglia
2) The infection is characterized by an eruption of groups of vesicles following the course of the affected nerve
3) Usually, the cornea is involved, often resulting in painful corneal ulceration and subsequent scarring of the cornea

Question 13

What supplies the 2nd pharyngeal arch? What are the facial muscles and the platysma derived from and what are they innervated by?

Answer 13

1) The facial nerve (CN VII) supplies the 2nd pharyngeal arch
2) The facial muscles and the platysma, which are derived from myoblasts of the 2nd pharyngeal arch, are innervated by CN VII (ignore its named branches) after the nerve exits the neurocranium

Question 14

Locate the mastoid process. What lies anterior to it? What is this structure the exit site for from the neurocranium?

Answer 14

1) Anterior to the mastoid process lies the stylomastoid foramen
2) The stylomastoid foramen is the site where CN VII exits the neurocranium

Question 15

Why is the facial nerve susceptible to injury during forceps delivery of a newborn? (Don’t completely understand this)

Answer 15

1) Because there are no mastoid processes at birth, the facial nerves are close to the surface when they emerge from the stylomastoid foramina
2) As a result, the facial nerves may be injured by forceps during a difficult delivery

Question 16

Where do the facial muscles attach proximally to? What do the muscles attach distally to? Within what layer do the facial muscles reside?

Answer 16

1) The facial muscles attach proximally to the periosteum of the facial skeleton
2) The muscles attach distally to the dermis
3) Thus, the muscles reside in the superficial fascia of the face

Question 17

What muscles are used to close the eyelids and lips, respectively? Where does the buccinator muscle reside? Define its role during chewing.

Answer 17

1) The orbicularis oculi and orbicularis oris muscles are involved in closure of the eyelids and lips, respectively
2) The buccinator muscle resides in the lateral cheek
3) The buccinator, active in smiling, also keeps the cheek taut, thereby preventing it from folding and being injured during chewing

Question 18

Observe the epicranial aponeurosis (aka aponeurosis of the scalp) and the occipital and frontal bellies of the occipitofrontalis muscle. Describe the facial expression that results when the two muscle bellies contract simultaneously.

Answer 18

1) Acting simultaneously, the occipital belly, with bony attachments, works as a synergist with the frontal belly, which has no bony attachments, to elevate the eyebrows and produce transverse wrinkles across the forehead
2) This gives the face a surprised look

Question 19

Why do patients with Bell’s palsy frequently dab the affected eye and corner of the mouth and have difficulty chewing and speaking?

Answer 19

1) Injury to the facial nerve (CN VII) or its branches produces paralysis of some or all facial muscles on the affected side (Bell palsy)
2) The affected area sags, and facial expression is distorted, making it appear passive or sad
3) They frequently dab their eyes and mouth with a handkerchief to wipe the fluid (tears and saliva), which runs from the drooping lid and mouth; the fluid and constant wiping may result in localized skin irritation

Question 20

What is the most common nontraumatic cause of facial nerve palsy and when is recovery from facial paralysis remote?

Answer 20

1) The most common nontraumatic cause of facial paralysis is inflammation of the facial nerve near the stylomastoid foramen, often as a result of a viral infection. This produces edema (swelling) and compression of the nerve in the facial canal
2) If the nerve is completely sectioned, the chances of complete or even partial recovery are remote

Question 21

Where does the occipital artery arise from? What supplies the scalp superior and posterior to the ear?

Answer 21

1) The occipital artery arises from the external carotid near its terminal bifurcation into the superficial temporal and maxillary arteries
2) The superficial temporal and occipital arteries supply the scalp superior and posterior to the ear

Question 22

What supplies the scalp anterior to the ear? What is the origin of the facial artery? Where does the facial artery course and what does it terminate as?

Answer 22

1) The supraorbital artery (its origin will be studied later) supplies the scalp anterior to the ear
2) The facial artery originates from the external carotid artery
3) It courses over the mandible onto the face and terminates as the angular artery

Question 23

Why can scalp lacerations be fatal?

Answer 23

These wounds bleed profusely because the arteries entering the periphery of the scalp bleed from both ends owing to abundant anastomoses

Question 24

Where is pressure best applied to stop bleeding from lip lacerations?

Answer 24

In lacerations of the lip, pressure must be applied on both sides of the cut to stop the bleeding

Question 25

Which vein drains the face? Where does this vein terminate?

Answer 25

1) The facial vein provides venous drainage of the face

2) The facial vein terminates in the IJV

Question 26

Where does lymph from the scalp anterior to the ear, the eyelids and face drain into? Where does lymph from the scalp superior and posterior to the ear drain into?

Answer 26

1) Lymph from the scalp anterior to the ear, the eyelids and face drains into the parotid lymph nodes
2) Lymph from the scalp superior and posterior to the ear drains into the mastoid and occipital lymph nodes

Question 27

Define lymph drainage into the submandibular and submental lymph nodes.

Answer 27

1) Lymph from the upper lip and lateral parts of the lower lip drains to the submandibular lymph nodes
2) Lymph from the chin and central part of the lower lip drains to the submental lymph nodes

Question 28

What is the principal cause of squamous cell carcinoma of the lip and which lip is usually involved? When does metastasis occur to the submental or the submandibular lymph nodes?

Answer 28

1) Overexposure to sunshine over many years, is a common factor in these cases
2) Chronic irritation from pipe smoking is also a contributing cause
3) Squamous cell carcinoma (cancer) of the lip usually
involves the lower lip
4) Cancer cells from the central part of the lower lip, the floor of the mouth, and the apex of the tongue spread to the submental lymph nodes, whereas cancer cells from lateral parts of the lower lip drain to the submandibular lymph nodes

Question 29

Where does all efferent lymph from the aforementioned nodes (parotid, mastoid, occipital, submandibular, & submental) drain into? These nodes form a chain along which vein?

Answer 29

All efferent lymph from the aforementioned nodes drains into the deep cervical lymph nodes, which form a chain along the IJV

Question 30

Where else does lymph drain from into the deep cervical nodes? Where do the deep cervical nodes drain into? Where do these ducts return lymph to?

Answer 30

1) Lymph from the thyroid and parathyroid glands also drains into the deep cervical nodes, which empty into the thoracic duct and right lymphatic duct
2) The two ducts return lymph to the bloodstream at the left and right venous angles

Question 31

Where does the parotid gland rest on and what does this muscle cover? What does resistance to swelling by the connective tissue sheath surrounding the gland cause and what condition does this parallel with?

Answer 31

1) The parotid gland rests on the masseter muscle that covers the ramus of the mandible (assessed below)
2) Resistance to swelling by the connective tissue sheath surrounding the gland causes severe pain as occurs with parotiditis

Question 32

After CN VII traverses the stylomastoid foramen, where does it immediately enter and what is found here?

Answer 32

After CN VII traverses the stylomastoid foramen, it immediately enters the parotid gland where the plexus of branches are formed to innervate the facial muscles

Question 33

Why is the facial nerve susceptible to injury during parotidectomy?

Answer 33

1) Because the parotid plexus of CN VII is embedded in the parotid gland, the plexus and its branches are in jeopardy during surgery
2) An important step in parotidectomy is the identification, dissection, isolation, and preservation of the facial nerve