Posterior Triangle and Suboccipital Region


Left-left subclavian, left common carotid Branches of Subclavian Artery



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Left-left subclavian, left common carotid



Branches of Subclavian Artery

(Netter 29A, 29B)







Subclavian artery: 3 parts: medial, posterior, or lateral to the anterior scalene muscle

(Observe brachiocephalic vein branching into subclavian and jugular)\







Thyrocervical trunk

branches posteriorly to:



  • inferior thyroid artery

  • ascending cervical artery

variable branches:

  • transverse cervical a.

  • suprascapular a.

  • dorsal scapular a.





Vertebral artery

  • ascends through transverse foramena starting with C6 enters skull via foramen magnum characteristic relationship with longus colli and anterior scalene

Internal thoracic (mammary) artery

  • branches anteriorly & inferiorly

Costocervical trunk

  • branches posteriorly from 1st part on the left

  • branches from 2nd part on the right

  • branches:

    • 1)superior intercostal artery

    • 2)deep cervical artery















Veins of Root of Neck

(Moore 8.8)







Brachiocephalic vein

  • Internal jugular vein in carotid sheath

  • Subclavian vein continues as axillary vein

  • External jugular vein drains face and scalp

  • Anterior jugular vein may only be 1

Both brachiocephalic veins drain into the superior vena cava

Muscles of the Anterior Neck

(Netter 25) (the obligatory chart)



MUSCLE

INNERVATION

FUNCTION

Cervical Muscles

Platysma

VII (cervical branch)

Depresses lower jaw, lip, and angle of the mouth, wrinkles skin of neck.

Sternocleidomastoid

XI

Singly, turns face toward opposite side.

Together, flexes head, raises thorax.



Suprahyoid Muscles

Digastric

2 Bellies:

  • Posterior Belly- VII

  • Anterior Belly- Nerve to the mylohyoid (V3)

Elevates hyoid and floor of mouth, depresses mandible.

Mylohyoid

Mylohyoid n. (V3)

Elevates and protracts hyoid.

Stylohyoid

VII (cervical branch)

Elevates and retracts hyoid.

Geniohyoid

C1

Protracts hyoid.

Infrahyoid Muscles (Strap Muscles)

Sternohyoid

C1, C2, C3 (Ansa cervicalis)

Depresses and stabilizes hyoid.

Sternothyroid

C2 and C3 (Ansa cervicalis)

3 functions:

  • Depresses hyoid (indirectly).

  • Depresses thyroid cartilage (directly).

  • Lengthens vocal cords.

Thyrohyoid

C1 (which runs with the hypoglossal nerve)

Depresses hyoid OR elevates larynx.

Shortens vocal cords.



Omohyoid

C1, C2, C3 (Ansa cervicalis)

Depresses and retracts the hyoid.

Draws hyoid laterally when turning the head



Important Points:

  • Suprahyoid muscles elevate the hyoid bone, infrahyoid muscles depress the hyoid bone.

  • The dual innervation of the digastric muscle (due to the embryological origin of the anterior and posterior bellies from the 1st and 2nd pharyngeal arches, respectively).

  • Landmark: the digastric muscle almost always passes through the middle of the stylohyoid muscle


Face, Scalp, and Parotid Region

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Trigeminal Nerve (Cranial Nerve 5)

Has 3 branches



CN#

Name

Sensory

Motor

Special Sensory

Parasymp.

Cranial Exit

V1

Ophthalmic

Cornea, skin of forehead & ant. scalp, eyelids, nose










Superior orbital fissure

V2

Maxillary

Skin over maxilla (includes upper lip), maxillary teeth










Foramen rotundum

V3

Mandibular

Skin over mandible, incl. lower lip mandibular teeth, anterior 2/3 of tongue

Muscles of mastication, mylohyoid, ant. belly of digastric, tensor veli palatini, tensor tympani







Foramen ovale



Facial Nerve (Cranial Nerve 7)

It emerges from the skull through the stylomastoid foramen and gives off its posterior auricular branch, which ascends behind the auricle to supply the auricularis posterior and occipitalis muscles. Here, it also gives off branches to the posterior belly of the digastric and stylohyoid, and receives postganglionic parasympathetic secretomotor fibers for the parotid gland from the otic ganglion via the auriculotemporal nerve (parasym. hitchhike on this nerve). Gee, that was a mouthful. It then enters the parotid gland, supplying it with postganglionic parasympathetic secretomotor fibers as it forms a plexus within its substance. The temporal, zygomatic, buccal, marginal mandibular, and cervical branches emerge along the borders of the parotid gland and innervate the facial muscles.



High Yield

  • CN VII is motor to ALL muscles of facial expression

  • To be redundant (it helps), CN VII emerges from Stylomastoid Foramen and runs through Parotid Gland. Thus, post surgical complications involving the parotid gland may include facial paralysis.





  • Branches: “To Zanzabar By Motor Car, Please”

    • Temporal

    • Zygomatic

    • Buccal

    • Marginal Mandibular

    • Cervical

    • Posterior Auricular

  • Don’t confuse the buccal branch of CN VII with the buccal n. off of V3 (sensory to buccal mucosa of cheeks)

  • With the use of a permanent marker, you can roughly draw the branches on your friends’ faces as shown here.



Muscles of Facial Expression

  • Lower yield

  • These muscles are all innervated by the 7th cranial nerve (facial).

  • They all insert into the skin and are derived from the 2nd branchial arch.

  • buccinator m.- One of my favorites. Without this m. we would be constantly biting our cheek while eating.

Muscle

Origin

Insertion

Main Action

Notable Nerve Supply

Notes

Frontal belly of occipitofrontalis (frontalis) - Forehead

Epicranial aponeurosis

Skin of forehead and eyebrows

Raise eyebrows, wrinkle forehead

Temporal branch of facial n

No bony attachments

Orbicularis oris

Median plane of maxilla (superiorly) and mandible (inferiorly), deep skin

Mucous membrane of lips

Oral sphincter – whistling & sucking – speech, chewing (holding food against teeth)




1st sphincter of the GI, fibers are in lips

Dilator mm: zygomaticus minor, zygomaticus major, levator labii superioris alaque nasi, buccinator, depressor labii inferioris, depressor anguli oris, buccinator, mentalis

Lips

Various

Used to open mouth very wide, in mimicry (actors, mimics)







Levator labii superioris alaque nasi

Frontal process of maxilla, infratemporal region

Skin of upper lip and alar cartilage of nose

Raise lip, flair nostril, raise angle of mouth




Divides into 2 attaching to the cartilage of nose & upper lip to elevate them

Mentalis

Incisive fossa of mandible

Skin at the angle of the mouth

Elevates and protrudes lower lip – doubt







Buccinator

Mandible, pterygomandibular raphe, alveolar processes of maxilla and mandible

Angle of mouth

Presses cheek against molars for chewing/ blowing/ whistling/ sucking facial expression




Smiling, chewing (holds cheeks against molars

Depressor anguli oris




Angle of mouth

Frowns (helped by posterior platysma)







Levator anguli oris

Infraorbital margin

Angle of mouth

Raise corners of mouth







Zygomaticus major

Zygomatic bone

Angle of mouth

Smiling/laughing







Zygomaticus minor

Zygomatic bone

Obicularis oris

Contempt/sadness







Levator labii superioris

Infraorbital margin

Upper lip

Raise and evert upper lip, deepen nasolabial sulcus w/Z. minor - sadness







Depressor labii inferioris

Mandible

Obicularis oris

Pulls lip inferolaterally – impatience

Buccal branch of facial n (inferior part)

Lateral to mentalis

Risorius

Platysma, fascia of masseter

Fascia over parotid, angle of mouth

Pull mouth laterally – grinning

Marginal branch of facial n




Platysma

Superficial fascia off deltoid and pectoral region

Mandible, skin of cheek, angle of mouth, obicularis oris

Inferior attachment: depresses mandible (grimace), superior attachment: tenses skin of lower face and neck

Cervical branch of facial n




Orbicularis oculi

Medial orbital margin, medial palpebral ligament, and lacrimal bone

Skin around margin of orbit, tarsal plate

Wrinkles forehead, closes eyelids: palpebral does lightly, orbital does tightly

Zygomatic branch of facial n (inferior part); Temporal branch of facial n (superior part)

Fibers sweep concentrically around eyelid, 3 parts: lacrimal (drains lacrimal fluid – part of/deep to palpebral), palpebral (closer to orbital fissure), orbital (outside palpebral)

Corrugator supercilii - You’ve got to love the name!

Orbital part of obicularis oculi, nasal prominence

Skin of eyebrow

Wrinkles medial forehead - concern







Procerus

Continuous with frontalis

Bridge of nose (contralaterally)

Makes transverse wrinkles across nose

Buccal branch of facial n




Depressor septi

Maxilla superior to incisor

Mobile part of nasal septum

Widens nostril during deep breathing

Buccal branch of facial n




Nasalis

*Superior part of canine ridge of maxilla **Above compressor naris

Nasal cartilage: *dorsum **alar cartilage

Draws ala (side) of nose towards the septum: *closes nostril **flares nostril

Buccal branch of facial n

Main muscle of the nose *Compressor naris **Dilator naris



Glossopharyngeal Nerve (Cranial Nerve 9)

  • Parasympathetic Innervation to the Parotid Gland

  • Pathway: glossopharyngeal n. (preganglionic fibers) tympanic branch lesser petrosal n. otic ganglion auriculotemporal n. (V3) (postganglionic fibers) parotid gland



Blood Supply

external carotid

facial a - mm facial expression

superior and inferior labial a - upper lip, nose side & septum, lower lip and chin (inf)

angular a - superior cheek, lower eyelid




superficial temporal - facial mm, skin

transverse temporal - parotid, facial mm, skin







inferior alveolar

mental - facial mm of chin
















internal carotid

opthalmic a

supraorbital and supratrochlear - forehead / scalp skin, facial mm




Some extra facts mentioned in your lectures this year:
1. A baby's cranium is disproportionately large when compared to the face. This changes with the development of the maxilla, mandible, paranasal sinuses, and the eruption of the teeth.
2. As we age, we wrinkle in lines that are perpendicular to the facial mm that are deep to the area. So, be sure to suture in the wrinkle line!
3. Superficial Scalp wounds do not bleed as much as deep scalp wounds. This is because in a deep scalp wound the apeuronosis is cut. Further, the frontal and occiptal bellies of the occipitofrontalis mm. pull the wound open and this allows for heavy bleeding. Be sure to suture deep scalp wounds.
4. Black eyes (Ecchymosis) can arise from injury to the scalp or the forehead. This is because the frontalis inserts on the skin. The blood can't go towards he neck because that area is protectd by the occipital belly of the occipital frontalis mm.
5. Emissary Viens" have the potential to spread infection.
6. To Zanzabar By Motor Car. The first letter of each word stands for the 5 branches of the facial nerve: temporal, zygomatic, buccal, marginal mandibular, and cervical.
7.Blepherospasm- the forceful involuntary contraction of mm around the eye.
8. Hemifacial spasm- the forceful contraction of the facial mm. ipsilaterally.
9. Scalp lacerations- remember that when you see a scalp laceration that all of the vasculature to that area is ciming up (from the face). If you flap the scalp superiorly then you are removing it from its innervation and blood supply (don't do this). Instead, flap the skin inferioly.
10. When you speak you are squishing the partoid gland between the ramus of the mandible and the mastoid processes. Thus, an infection here is painful.
11. The lymphatics of the face, scalp and parotid region all eventually drain into the deep cervical nodes along the internal jugular vien.

Infratemporal Region and Muscles of MasticationFrom MNMedWiki

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Learning Objective #1

Review bony anatomy of the temporal fossa:

The Temporal Fossa (N4, N12, check out your skull)



  • It is bounded superiorly and posteriorly by the temporal lines and anteriorly by the frontal and zygomatic bones.

  • The temporal fascia stretches over the temporal fossa and the temporalis muscle.

  • Inferiorly, the temporalis fascia splits into two layers, superficial and deep.

  • The superficial layer is attached to the superior margin of the zygomatic arch.

  • The deep layer passes medial to the arch to become continuous with the fascia deep to the masseter muscle.

  • The floor of the temporal fossa which gives origin to the temporalis muscle, is formed by portions of the four bones: parietal, frontal, greater wing of sphenoid, and squamous part of the temporal bone.

  • The area where the bones meet is called the pterion.

Clinical Correlation: This is an important landmark because the bone is exceptionally weak and is superior to the middle meningeal artery and cause an epidural hematoma.

  • The temporal fossa contains the fan-shaped temporalis muscle, the "handle" of which passes deep to the zygomatic arch.

  • The temporal fossa is deepest where the temporalis muscle is thickest (anteroinferiorly).

Learning Objective #2

To be able to define the boundaries and contents of the infratemporal fossa, with special emphasis on the bony foramina that allow entrance and exit into this region.

The Infratemporal Fossa (N4, N12, your skull)



  • This is an irregularly shaped space inferior and deep to the zygomatic arch and posterior to the maxilla.

  • It communicates with the temporal fossa through the interval between the zygomatic arch and the skull, which is traversed by the temporalis muscle and the deep temporal nerves and vessels.


Bones and Walls of the Infratemporal Fossa (N4, N12, your skull)

  • Lateral wall: ramus of the mandible.

  • Medial wall: lateral pterygoid plate of the sphenoid bone.

  • Anterior wall: infratemporal surface of the maxilla. This wall is limited superiorly by the inferior orbital fissure and medially by the pterygomaxillary fissure.

  • Posterior wall: the condylar process of the mandible and the styloid process of the temporal bone.

  • Roof (superior): this is formed by the flat inferior surface of the greater wing of the sphenoid bone. It is separated from the temporal fossa by a ragged edge called the infratemporal crest.

  • The foramen ovale (through which V3 travels) and spinosum (through which the middle meningeal artery passes) open into the roof of the infratemporal fossa.

  • Inferior boundary: the point where the medial pterygoid muscle attaches to the medial aspect of the mandible near the angle.


First word of warning: you will want to know what comes out of each of the small foramen in the base of the skull for the test; this should be highlighted in the cranial nerves lecture.


Contents of the Infratemporal Fossa

  • This fossa contains the inferior part of the temporalis muscle, the medial and lateral pterygoid muscles, the maxillary artery, the mandibular and chorda tympani nerves, the otic ganglion, and the inferior alveolar, lingual and buccal nerves.


The Maxillary Artery (N36, 30)

  • This vessel is the larger of the two terminal branches of the external carotid artery.

  • It arises posterior to the neck of the condylar process of the mandible and passes anteriorly, deep to the neck, and traverses the infratemporal fossa.

  • It passes superficial to the lateral pterygoid muscle and then disappears in the infratemporal fossa.

  • The middle meningeal artery, the largest of the meningeal artery, a branch of the maxillary artery, ascends between the two roots of the auriculotemporal nerve and enters the skull through the foramen spinosum to supply the dura and the interior of the cranium.


The Mandibular Nerve (V3) (N42)

  • All nerves in the infratemporal region (auriculotemporal, inferior alveolar, lingual and buccal nerves) are branches of the mandibular nerve, except for the chorda tympani which is a branch of the facial nerve (CNVII).

  • The mandibular nerve descends from the middle cranial fossa through the foramen ovale into the infratemporal fossa.

  • The anterior division includes the masseteric n., several deep temporal n., medial and lateral pterygoid nn., and the buccal n.

  • The posterior division includes the ariculotemporal n., inferior alveolar n., and the lingual n. More to come below!


The Otic Ganglion (N128, N125)

  • This parasympathetic ganglion is located in the infratemporal fossa, just inferior to the foramen ovale.

  • It is medial to the mandibular nerve, and posterior to the medial pterygoid muscle.

  • Preganglionic parasympathetic fibers are mainly derived from the glossopharyngeal nerve (CN IX).

  • The postganglionic fibers, which are secretory to the parotid gland, pass from this ganglion to the auriculotemporal nerve.

Learning Objective #3

Understand the function and innervations of the muscles of mastication.

Muscles of Mastication that act on the Temporomandibular Joint (Learning Objectives 4 and 5 will further elucidate on the TMJ)



  • Movements of the temporomandibular joint are chiefly from the action of the muscles of mastication.

  • The temporalis, masseter, and medial pterygoid muscles produce biting movements.

  • The lateral pterygoid muscles protrude the mandible with the help from the medial pterygoid muscles and retruded largely by the posterior fibers of the temporalis muscle.

  • Gravity is sufficient to depress the mandible, but if there is resistance, the lateral pterygoid, suprahyoid and infrahyoid, mylohyoid and anterior digastric muscles are activated.

Actions

Muscles

Depression (Open mouth)

Lateral pterygoid, Suprahyoid, and Infrahyoid

Elevation (Close mouth)

Temporalis, Masseter, and Medial pterygoid

Protrusion (Protrude chin)

Masseter (superficial fibers), Lateral pterygoid, and Medial pterygoid

Retrusion (Retrude chin)

Temporalis and Masseter (deep fibers)

Side-to-side movements (grinding and chewing)

Temporalis on same side, Pterygoid muscles of opposite side, and Masseter


The Temporalis Muscle (N42, N50, N143)

  • This is an extensive fan-shaped muscle that covers the temporal region.

  • It is a powerful masticatory muscle that can easily be seen and felt during closure of the mandible.

  • Origin: floor of temporal fossa and deep surface of temporal fascia.

  • Insertion: tip and medial surface of coronoid process and anterior border of ramus of mandible.

  • Innervation: deep temporal branches of mandibular nerve (CN V3).

  • The temporalis elevates the mandible, closing the jaws; and its posterior fibers retrude the mandible after protrusion.

The Masseter Muscle (N50, N51)

  • This is a quadrangular muscle that covers the lateral aspect of the ramus and the coronoid process of the mandible.

  • Origin: inferior border and medial surface of zygomatic arch.

  • Insertion: lateral surface of ramus of mandible and its coronoid process.

  • Innervation: mandibular nerve via masseteric nerve that enters its deep surface.

  • It elevates and protrudes the mandible, closes the jaws and the deep fibers retrude it.


The Lateral Pterygoid Muscle (N50, N51) HIGH YIELD!

  • This is a short, thick muscle that has two heads or origin.

  • It is a conical muscle with its apex pointing posteriorly.

  • Origin: superior head—infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone, inferior head—lateral surface of lateral pterygoid plate.

  • Insertion: neck of mandible, articular disc, and capsule of temporomandibular joint.

  • Innervation: mandibular nerve via lateral pterygoid nerve from anterior trunk, which enters it deep surface.

  • Acting together, these muscles protrude the mandible and depress the chin.

  • Acting alone and alternately, they produce side-to-side movements of the mandible.


The Medial Pterygoid Muscle (N50, N51) HIGH YIELD!

  • This is a thick, quadrilateral muscle that also has two heads or origin.

  • It embraces the inferior head of the lateral pterygoid muscle.

  • It is located deep to the ramus of the mandible.

  • Origin: deep head—medial surface of lateral pterygoid plate and pyramidal process of palatine bone, superficial head—tuberosity of maxilla.

  • Insertion: medial surface of ramus of mandible, inferior to mandibular foramen.

  • Innervation: 'mandibular nerve via medial pterygoid nerve.

  • It helps to elevate the mandible and closes the jaws.

  • Acting together, they help to protrude the mandible.

  • Acting alone, it protrudes the side of the jaw.

  • Acting alternately, they produce a grinding motion.


Second word of warning: When at lab, make sure you can identify the Lateral and Medial Pterygoid Muscles at all angles (i.e. lateral view, posterior view, etc.)

Learning Objectives #4 & #5



Understand the bony anatomy of the mandible and temporomandibular joint region. The temporomandibular joint is very complex. The goal is to understand the articulation at this joint and the movements of this joint.

The Temporomandibular Joint (N14)



  • This articulation is a modified hinge type of synovial joint.

  • The articular surfaces are: (1) the head or condyle of the mandible inferiorly and (2) the articular tubercle and the mandibular fossa of the squamous part of the temporal bone.

  • An oval fibrocartilaginous articular disc divides the joint cavity into superior and inferior compartments. The disc is fused to the articular capsule surrounding the joint.

  • The superior synovial cavity is responsible for protrusion of the mandible and the inferior synovial cavity is where jaw depression takes place.

  • The articular disc is more firmly bound to the mandible than to the temporal bone.

  • Thus, when the head of the mandible slides anterior on the articular tubercle as the mouth is opened, the articular disc slides anteriorly against the posterior surface of the articular tubercle.


The Articular Capsule

  • The capsule of this joint is loose.

  • The thin fibrous capsule is attached to the margins of the articular area on the temporal bone and around the neck of the mandible.

Ligaments of the Joint (N14)



  • The fibrous capsule is thickened laterally to form the lateral (temporomandibular) ligament. It reinforces the lateral part of this capsule.

  • The base of this triangular ligament is attached to the zygomatic process of the temporal bone and the articular tubercle.

  • Its apex is fixed to the lateral side of the neck of the mandible.

  • Two other ligaments connect the mandible to the cranium but neither provides much strength.

  • The stylomandibular ligament is a thickened band of deep cervical fascia.

  • It runs from the styloid process of the temporal bone to the angle of the mandible and separates the parotid and submandibular salivary glands.

  • The sphenomandibular ligament is a long membranous band that lies medial to the joint.

  • This ligament runs from the spine of the sphenoid bone to the lingula on the medial aspect of the mandible.


Translation of the Temporomandibular Joint (p. 731)

  • The two movements that occur at this joint are anterior gliding and a hinge-like rotation.

  • When the mandible is depressed during opening of the mouth, the head of the mandible and articular disc move anteriorly on the articular surface until the head lies inferior to the articular tubercle.

  • This permits simple chewing or grinding movements over a small range.

  • Movements that are seen in this joint are: depression, elevation, protrusion, retraction and grinding.

Learning Objective #6

Start learning the branches off the maxillary artery in this region. The rest of this artery will be learned later.

Study Plate 36 on Netters (3rd Edition) and be able to identify at least the major branches of the maxillary artery: The inferior alveolar artery, the deep temporal artery, and the middle meningeal artery. Remember that the auriculotemporal nerve (V3) splits around the middle meningeal artery. If you can draw out the branches of arteries by memory at least 3 times, you’re good to go.

Learning Objective #7

To be able to have a good 3-D understanding of the complex courses of nerves in this region. They are complex, but very important. A good understanding of the nerves in this region is critical to anesthetic use in this region.

Alright. This is the part where you should take out your skulls and wires and be able to know where all the nerves course, enter, etc. Focus on the Maxillary and Mandibular regions of the Trigeminal nerve as shown on Netters Plates 41, 42, and 116.




The Maxillary Nerve (CN V2) (N41, 116)

  • This is the intermediate division of the trigeminal nerve and is purely sensory.

  • It arises from the trigeminal ganglion and runs anteriorly in the inferior part of the cavernous sinus, inferior to the ophthalmic nerve.

  • This nerve leaves the middle cranial fossa through the foramen rotundum.

Branches of the Maxillary Nerve



  • The meningeal branches arise from this nerve which it is still in the middle cranial fossa. These nerves supply the dura.

  • Ganglionic branches arise within the pterygopalatine fossa and enter the pterygopalatine ganglion as its sensory root.

  • The zygomatic nerve supplies the skin of the temple and the prominence of the cheek; and brings parasympathetic fibers to the lacrimal gland.

  • Superior alveolar nerves (posterior, middle, anterior); the nasal branches; greater and lesser palatine nerves.


The Mandibular Nerve (CN V3) (N41, 116)

  • This is a mixed nerve (sensory and motor) and contains all the motor fibers of the trigeminal nerve.

  • This nerve descends to the foramen ovale and then passes through this opening in the middle cranial fossa.

  • Just outside the foramen, the motor and sensory roots of the mandibular nerve unite and then CN V3 divides into anterior and posterior divisions.

Branches of the Mandibular Nerve



  • From the nerve; nerve to medial pterygoid, tensor tympani and tensor veli palatini.

  • From anterior trunk; buccal nerve, sensory, supplies cheek and mandibular buccal gingiva; and the motor branches to the muscles of mastication.

  • From the posterior trunk; inferior alveolar nerve, lingual nerve (sensory and taste of anterior 2/3 of the tongue-taste fibers from chorda tympani) and auriculotemporal nerve (encircles the middle meningeal artery and with postsynaptic fibers of CN IX pass to the parotid gland).

Learning Objective #8

To define the venous drainage pattern.

Dr. McLoon just wants you to know that there’s a pterygoid plexus of veins (N66) that surrounds the lateral pterygoid and drains into the maxillary vein (and internal jugular v.), the deep facial vein to facial vein (to internal jugular v.), connections around mandibular nerve through the foramen ovale to cavernous sinus in the skull, and the middle meningeal through foramen spinosum into the skull. I think the most important thing to get out of here is that veins connect with sinus and know how they do it.




Clinical Correlation: As Dr. Mcloon mentioned, infections from the sinuses can travel into the cavernous sinus via the facial vein.

Learning Objective #9



To begin to think about the use of nerve blocks: where the nerve is and where the anesthesia will be.

Basically know that if you want to repair or remove the mandibular teeth, you have to perform an inferior alveolar nerve block. The site of the anesthetic injection is at the entrance to the mandibular canal at the mandibular foramen. This should numb all the mandibular teeth, skin and mucosa of the lower lip, and the mucosa, gingival, and skin of the chin. In Moore and Daly (p. 861 blue box), they caution NOT to insert the needle too far posteriorly, or else you’ll enter the parotid gland, anesthetize the branches of the facial nerve, and cause transient unilateral facial paralysis. Not good. On the other hand, if you inject superiorly in a mandibular nerve block, administered superior to the inferior alveolar nerve block, the entire distribution of the mandibular nerve will be blocked.

Also, be sure to know the difference between a mandibular nerve block and a maxillary nerve block. There were some excellent slides in lecture illustrating which areas are numbed when you do each of these blocks. These are favorite sources for exam questions.

Skull and Intracranial Fossa 1 and 2

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Holes in the Head

CranialFossa

Bone

Hole

Contents

Anterior

Ethmoid

Foramina of Cribiform Plate

Olfactory (CNI) nerve bundles

Middle

Sphenoid

Optic Canal

CN II

Ophthalmic Artery



Sphenoid

Superior Orbital Fissure** (All nerves to eye except CN II)

CN III

CN IV
Lacrimal, frontal, and nasociliary branches of CN V1


CN VI
Ophthalmic Veins

Sphenoid

Foramen Rotundum

CN V2

Sphenoid

Foramen Ovale

CN V3

Lesser Petrosal Nerve


Accessory Meningeal Artery

Sphenoid

Foramen Spinosum

Middle Meningeal Artery, Vein, and Nerve

Temporal (ish)

Foramen Lacerum

EMPTY (sort of—see below)

Temporal

Carotid Canal

Carotid Artery

Sympathetic Nerves



Temporal

Hiatus of the …

Lesser Petrosal Nerve

Temporal

Hiatus of the …

Greater Petrosal Nerve

Posterior

Temporal

Internal Acoustic Meatus

CN VII

CN VIII
Labyrinthine Artery



Occipital

Jugular Foramen

CN IX

CN X
CN XI


Internal Jugular Vein
Sigmoid Sinus

Occipital

Hypoglossal Canal

CN XII

Occipital

Foramen Magnum

Medulla of Brain Stem

CN XI
Vertebral Arteries



Bones of the skull and corresponding landmarks

The skull is a total of 21 fused bones in the skull + the 1 mandible + 6 auditory ossicles

8 Cranial Bones (calvarial)

These bones enclose the brain.

1) Frontal — Supraorbital Notch, sinus


2) Occipital — External Occipital Protuberance and Foramen Magnum
3) Ethmoid — Middle and Superior Concha, and Cribiform Plate
4) Sphenoid— Great and Lesser wings, Sella turcica, Sphenoid sinus, Medial and Lateral plates of pterygoid process, pterygoid hamulus
5) and 6) Paired Temporal — Squamous and Petrous parts, Zygomatic Process, External acoustic meatus, Mastoid process, Mandibular Fossa, Styloid Process
7) and 8) Paired Parietal

14 Facial Bones

1) and 2) Paired Lacrimal


3) and 4) Paired Nasal
5) and 6) Paired Palantine — Perpendicular and Horizontal plates
7) and 8) Paired Inferior Turbinate (Nasal Concha)
9) and 10) Paired Maxillary — Incisive Fossa, Incisive Canal, Palantine Process, Alveolar Process, Zygomatic Process, Frontal Process
11) and 12) Paired Zygomatic
13) Vomer
14) Mandible — Mental Foramen

Skull Development



  • Fontanels are the areas of membrane in babies where the skull bones have not yet fused together. When they fuse together, they form the sutures in the adult skull.

  • Know the following fontanels:

    • Anterior Fontanel

    • Posterior Fontanel

    • Sphenoid Fontanels (2)

    • Mastoid Fontanels (2)



Other Important Skull Features

Sutures



  • Sagittal - defined in the midline of the body

  • Coronal - between the frontal and parietal bones

  • Lambdoid - between the parietal bones and occipital bone

Other landmarks

  • Bregma - junction of the coronal and the saggital sutures

  • Lambda - junction of the saggital and occipital sutures(looks like a greek letter Lambda)

  • Pterion - thin part of the cranium over the middle meningial artery

Skull and Meninx Layers

The following are in order from most superficial to deepest.

1. Outer lamina (compact bone)


2. Diploe (spongy bone)-site of potential spread of infection from scalp to brain
3. Inner lamina (compact bone)
4. Potential epidural space
5. Dura Mater (periosteal and meningeal spaces)-contains venous sinuses between layers and septa
6. Potential subdural space
7. Arachnoid-layers connected by cisterns and trabeculae (avascular)
8. Subarachnoid Space (contains CSF and arachnoid trabeculae)
9. Pia Mater-large cerebral arteries and veins found here (vascular)
10. Brain surface

Arteries of the cranium (Circle of Willis)

Branches of the internal carotid artery



  • Hypophyseal a.

  • ophthalmic a.

  • anterior choroidal a.

  • posterior communicating a.

  • anterior cerebral a.

  • anterior communicating a.

  • middle cerebral a. - remember the location under the pterion and the ease of trauma due to the thin bone

Branches of the vertebral artery

  • Anterior and posterior spinal arteries

  • posterior inferior cerebellar artery

  • basilar a.

    • Posterior Cerebral arteries



The cavernous sinus

  • Is perforated by (i.e., what passes through):

    • Interior Carotid Artery

    • Abducens Nerve (CN VI)

  • Contains within the wall:

    • CN III

    • CN IV

    • CN V1

    • CN V2

Other vessels

  • Ophthalmic Artery = Optic Canal

  • Ophthalmic (optic) Vein = Superior Orbital Fissure



Dural Septa and Venous Sinuses

  • Septa: Falx cerebri (separates hemispheres) , tentorium cerebelli (separates cerebellum from cerebral cortex), falx cerebelli (separates cerebellar hemisheres), diaphragma sella (covers the pituitary gland)

  • Venous Sinuses (drain into internal jugular vein):



Flow of CSF

  • Cerebral Spinal Fluid (from Choroid Plexus)

  • → Subarachnoid space

  • → Arachnoid granulations

  • →Dural Venous Sinuses

  • →Cerebral Veins

  • →Emissary Veins



Other Helpful Hints

  • Divisions of Trigeminal exit the skull according to “Standing Room Only”

    • S = Superior Orbital Fissure

    • R = Foramen Rotundum

    • O = Foramen Ovale

  • No cranial nerves of the Middle Cranial Fossa exit any bone except the sphenoid (CN II—VI)

  • CN XI passes through two foramina (Enters and leaves skull):

    • Foramen Magnum = Spinal roots of accessory nerves

    • Jugular Foramen = Exit of CN XI

Lecture material for the second lecture is a review of the cranial nerves





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