Orbit and Face Anatomy Notes

Orbit and Face

TBL Pre-class Assignment

• Read Moore’s Clinically Oriented Anatomy 9e Ch 8, p 861-883, 907-934 by Dalley and Agur.

• Read Moore’s Essential Clinical Anatomy 6e Ch 8, p521-551 by Agur and Dalley.

• Lecture notes and slides: Orbit and Contents, Muscles of Facial Expression

TBL Pre-class Learning Objectives

1. Bony Orbit Anatomy

• Identify the bones forming the bony orbit and describe their three-dimensional anatomy including foramina.

• Shape/Orientation: pyramid-shaped cavities that house and protect the eyes.

  • The medial wall of the orbit is parallel to the median sagittal plane.

  • The lateral wall is at a 45° angle from the median sagittal plane.

  • The anterior to posterior axis of the orbit is therefore directed toward the midline of the head.

• Walls of the Orbit:

  • Roof: separates orbital contents from frontal lobes of the brain. Formed by the orbital plate of the frontal bone.

  • Floor: orbital surfaces of maxilla and zygomatic bone and to a small extent the orbital process of palatine. Very thin, can be damaged in blow-out fracture causing the eye to sink into the maxillary sinus.

  • Medial Wall: very thin—delicate. Formed by the frontal process of the maxilla, lacrimal bone, ethmoid, and a small part of the body of the sphenoid.

  • Lateral Wall: orbital process of zygomatic bone and orbital surface of the greater wing of the sphenoid.

  • Posterior Wall: primarily sphenoid bone.

2. Lacrimal Apparatus

• Lacrimal Gland:

  • Supplied by the lacrimal n. over the superolateral part of the orbital fossa.

  • Produces tears.

  • Responsible for secretion and drainage of tears, preventing drying of the cornea and conjunctiva improving the optical quality of the cornea.

  • Secretions contain lysozyme—a bactericidal enzyme.

  • Tears are swept from lateral to medial.

• Lacrimal Puncta: tears drain across eyes to puncta.

• Lacrimal Canaliculi: from puncta to sac.

• Lacrimal Sac: at the inferomedial corner of orbital fossa, the dilated end of the nasolacrimal duct.

• Nasolacrimal Duct: membranous canal from lacrimal sac to inferior meatus in the lateral wall of the nose.

3. Orbital Septum and Tarsal Plates

• Orbital Septum: Separates the subcutaneous tissue of the face and scalp from structures in the orbit.

• Tarsal Plates: Dense fibrous tarsal plates give support to the thin eyelids and are connected to the medial and lateral palpebral ligaments.

• Levator Palpebrae Superioris: Does not move eyeball.

  • Most superficial muscle.

  • O: lesser wing of sphenoid

  • I: upper eyelid

  • A: raises upper lid

  • N: oculomotor (III) supplies the striated muscle fibers and sympathetic fibers supply the smooth muscle fibers

• Fascial Specializations

  • Periorbita

  • Fascial Sheath

  • Suspensory ligament

  • Check ligaments

    • Medial

    • Lateral

4. Extraocular Muscles

• Describe the anatomy, innervation, and action of each extraocular muscle:

  • Superior and inferior oblique mm.

  • Superior, lateral, medial, and inferior rectus mm.

  • Levator palpebrae superioris m.

• Muscles of the Eye

  • Superior Rectus

    • O: common annular tendon

    • I: superior part of sclera

    • A: elevates and adducts eyeball to look superomedially, intorsion (medial rotation to align both eyes)

    • N: CN III, Oculomotor

  • Medial Rectus

    • O: common annular tendon

    • I: medial sclera

    • A: adducts eyeball

    • N: CN III

  • Inferior Rectus

    • O: common annular tendon

    • I: inferior part of sclera

    • A: depresses and adducts eyeball to look inferomedially, extorsion (lateral rotation to align both eyes)

    • N: CN III

  • Lateral Rectus

    • O: common annular tendon

    • I: lateral surface of sclera

    • A: abducts eyeball

    • N: abducens (VI) (only muscle abducens supplies)

  • Inferior Oblique

    • O: maxilla, anterior part of floor of orbit

    • I: posterior lateral aspect of sclera

    • A: elevates and abducts eyeball to look superolaterally, extorsion

    • N: CN III

  • Superior Oblique

    • O: body of sphenoid

    • I: posterior and lateral sclera

    • A: depresses and abducts eyeball to look inferolaterally, intorsion

    • N: trochlear (IV)

5. Clinical Relevance

• Abducens Nerve Palsy: CN VI, lateral rectus.

  • At rest, eye going medially when eye is supposed to look forward; cannot look laterally. If eye is told to go laterally, then the eye that is staring forward is the one affected.

• Trochlear Nerve Palsy: CN IV, superior oblique.

  • At rest, the eye is elevated and looking medially.

• Occulomotor Nerve Palsy: eye can only look down and laterally, also present with Ptosis (droopy eyelid).

6. Nerves of the Orbit

• Describe the course and innervations of the following nerves:

  • Optic nerve (CN II)

  • Oculomotor n. (CN III)

  • Trochlear n. (CN IV)

  • Abducent n. (CN VI)

  • Frontal n.

  • Supraorbital n.

  • Trigeminal Nerve

    • Ophthalmic division travels through the superior orbital fissure.

    • Purely sensory to skin of forehead, eye, and conjunctiva (somatic sensory).

    • Several branches within the orbit

      • Frontal N: largest branch of V1, branches form supraorbital and supratrochlear Nn

      • Lacrimal nerve: supplies the lacrimal gland. Receives PSNS fibers from CN VII.

      • Nasociliary n. branches:

        • Long ciliary- sensory to eyeball

        • Anterior and posterior ethmoidal: supply sensory to the mucosa of the ethmoid air cells, sphenoid sinus, and nasal cavity

        • Infratrochlear- sensory to the bridge of the nose

  • Oculomotor (III): supplies superior rectus, levator palpebrae superioris, medial rectus, inferior rectus, and inferior oblique. Runs through the superior orbital fissure. Carries PSNS fibers to the ciliary muscle. Sends preganglionic fibers to the ciliary ganglion.

    • Sphincter pupillae muscles: contraction of this circular muscle decreases the size of the pupil (miosis), involved in the pupillary light reflex

    • Ciliary muscle: changes the shape of the lens for accommodation

    • An abnormally constricted pupil: Unopposed parasympathetic constriction due to a block of the sympathetic dilation.

    • An abnormally dilated pupil: Unopposed sympathetic dilation due to a block of the parasympathetic constriction.

  • Trochlear (IV): supplies the superior oblique M

  • Abducens (VI): supplies the lateral rectus

  • Optic (II): surrounded by extensions of the 3 meninges and by common annular tendon. The central A of retina enters optic N about 1/2 way along its length, posterior side of eyeball, through optic canal

7. Arteries of the Orbit

• Describe the course and distribution of the following arteries:

  • Ophthalmic art.

  • Supraorbital art.

  • Ophthalmic A and V: from the internal carotid, passes through the optic canal.

  • Central A of retina: branch of the ophthalmic artery that runs in the center of the optic nerve and supplies the retina. Branch of the internal carotid a.

  • Also muscular, lacrimal, and br that follow Nn

  • Vv parallel Aa—important anastomotic connections w/ brs of the facial V and pterygoid plexus.

  • In geriatric patients, macular degeneration may result from the decreased blood supply to the retina.

8. Superficial Fascia of the Face

• Describe the anatomy and location of structures within the superficial fascia of the face.

  • Parotid gland

  • Parotid duct

    • Parotid Gland:

      • Largest of the paired salivary glands, located on the side of the face in front of the ear

    • Parotid Duct: emerges from the anterior border of the gland that crosses the masseter. At the anterior border, it pierces the buccal fat pad and subsequently the buccinator muscle. The parotid duct opens into the vestibule of the oral cavity opposite the 2nd molar tooth. Think about SOUR strawberry or sour pickles for two seconds, then are you feeling the salivatory action over the vestibules inside your mouth.

    • Parotid Capsule: the superficial layer of deep cervical fascia splits to enclose the parotid gland. Viral and/or other types of infection cause inflammation and edema w/in the capsule. The increase in pressure may cause associated paralysis of muscles of facial expression by compressing the facial nn branches, which run through the middle of the gland.

    • Infection, inflammation, or a tumor of the parotid gland may cause compression to the facial nerve.

9. Scalp Anatomy

• Describe the anatomy, attachments, and layers of the scalp from superficial to deep.

• 5 layered structure w/ its own acronym (SCALP)

  • S—Skin—thin w/ numerous sebaceous and sweat glands, firmly attached to the next layer

  • C—Connective tissue—thick w/ feltwork of connective tissue fibers and fat intermixed -contains ends of hair follicles, Aa, Vv and Nn. Collagenous fibers connect top two layers w/ aponeurosis. All 3 layers move together when scalp wrinkles. Bleeding into this space caused by blow to head will lead to localized damage; the blood and edema will not spread.

  • A—Aponeurosis and muscle—(occipitofrontalis) layer

  • L-- Loose connective tissue w/ small blood vessels—loose nature allows for movement of upper 3 layers and for spread of fluid. Bleeding into this space caused by blow to head can lead to bilateral black eyes. The blood flows under the occipitofrontalis and orbicularis oculi and accumulates around the eyes (Raccoon’s eyes)

  • P—Periosteum/pericranium—periosteum of cranial bones—adheres loosely except along suture lines where it passes deeply to become continuous w/ periosteum of inner surface

Clinical Correlation

• Hit by a rock will cause a lump over your head may indicate injury in “C of SCALP” above aponeurosis; while Raccoon’s eyes may indicate the injury in “L of SCALP” below aponeurosis.

• Cuts thru scalp bleed profusely for 2 reasons

  • Occipitofrontalis pulls sides of wound apart

  • Dense connective tissue holds cut vessels open

10. Facial Muscles

• Describe the anatomy, innervation, and function of:

  • Buccinator

  • Orbicularis oculi

  • Levator labii superioris

  • Zygomaticus major

  • Orbicularis oris

  • Depressor anguli oris

  • Occipitofrontalis

    • Platysma: superficial sheet of muscle over the upper thorax, clavicles, and neck

      • O: superficial fascia of upper thorax, inferior to the level of the 2nd rib

      • I: lower border of mandible, skin of lower face and musculature of angle and lower part of the mouth

      • A: expression of surprise, horror

    • Occipitofrontalis: occipital belly and anterior frontal belly connected by a long aponeurosis—epicranial aponeurosis or galea aponeurotica. Wrinkles forehead.

      • Occipitalis

        • O: lat 2/3 of the supreme nuchal line of occipital bone and mastoid process of temporal

        • I: epicranial aponeurosis

      • Frontalis

        • O: anterior margin of epicranial aponeurosis

        • I: fibers merge with the orbital part of orbicularis oculi and w/ muscles and connective tissue over the bridge of the nose

        • A: elevates eyebrows

    • Orbicularis Oculi: flat sheet of muscle surrounding palpebral fissure (palpebra- eyelid)—2 parts:

      • Orbital—sphincter of eye

        • O: nasal part of frontal bone and frontal process of maxilla (between these two sites—medial palpebral ligament)

        • I: fibers pass around the orbit in concentric loops

        • A: forced closure

      • Palpebral—central part confined to eyelids

        • O: medial palpebral ligament

        • I: lateral palpebral raphe

        • A: blinking—closing eyes w/o effort

    • Orbicularis Oris: sphincter of mouth. “Kissing muscle.”

      • Fibers are in the upper and lower lips and encircle the mouth. Many fibers from other muscles of facial expression join the muscle. These muscles act in concert to produce changes in the shape of the mouth.

      • A: closure, protrusion, and pursing of lips

    • Mentalis

      • O: incisive fossa of mandible

      • I: skin over chin

      • A: wrinkles skin of chin and protrudes lower lip

    • Zygomaticus Major: lateral to zygomaticus minor

      • O: lateral surface of zygomatic bone

      • I: fibers blend with orbicularis oris at the corner of mouth

      • A: pulls the corner of the mouth up as in laughing

    • Zygomaticus Minor

      • O: lower portion of zygomatic bone

      • I: fibers blend with orbicularis oris just medial to angle of mouth

      • A: helps elevate upper lip

    • Levator Labii Superioris

      • O: maxilla at inferior margin or orbit

      • I: skin of lat upper lip and some fibers blend with orbicularis oris

      • A: elevates upper lip

    • Levator Labii Superioris Alaeque Nasi: in sulcus between nose and cheek, runs laterally to nose

      • O: superior part of frontal process of maxilla

      • I: ala of nose and skin of lat upper lip

      • A: elevates the upper lip and dilates nares

    • Levator Anguli Oris: elevates the upper lip

    • Risorius (laugh or grin)

      • O: fascia over parotid gland

      • I: skin at the angle of the mouth

      • A: assists in widening mouth—grin

    • Depressor Anguli Oris

      • O: external oblique line of mandible

      • I: skin at the corner of the mouth and some fibers blend with orbicularis oris

      • A: depresses corner of mouth—frown

    • Depressor Labii Inferioris: depressed lower lip

    • Buccinator: forms musculature of cheek; primarily a muscle of mastication; deeper than other muscles of facial expression; covered by buccal fat pad

      • O: pterygomandibular raphe, alveolar margins (lateral to molar teeth) of maxilla and mandible in regions of molars.

      • I: fibers blend with orbicularis oris

      • A: aids in chewing by maintaining food between molars; involved in sucking and blowing air

    • Buccal fat pad: superficial to buccinator muscle at the anterior border of masseter—is thought to aid in sucking—relatively large in infants, gives shape to face

11. Major Nerves of the Face

• Describe the anatomy and distribution of the major nerves of the face region:

  • Facial nerve (CN VII)

    • Temporal branch

    • Zygomatic branch

    • Buccal branch

    • Mandibular branch

    • Cervical branch

  • Trigeminal nerve (CN V)

    • Ophthalmic (V1)

      • Supraorbital n

    • Maxillary (V2)

      • Infraorbital n

    • Mandibular (V3)

Motor Nerves of the Face

• Facial nerve (VII)

  • Emerges from the base of the skull through the stylomastoid foramen. Gives off branches to occipitofrontalis, posterior belly of the digastric, stylohyoid, and some muscles that wiggle the ear. The motor portion gets to the face by passing through the parotid gland. As it passes through it divides 5 components that are named according to the region of the face they project to:

    • Temporal

    • Zygomatic

    • Buccal

    • Marginal mandibular

    • Cervical

  • Bell’s palsy: a relatively common condition in which the facial nerve is compromised and results in weakness of muscles of facial expression. Typically, one side of the face is paralyzed.

Cutaneous Nerves of the Face

• All are branches of the Trigeminal N. (V). The trigeminal ganglion is in the cranial vault –all Nn exit via named foramina.

  • Ophthalmic division (V1)—supplies forehead, upper eyelid, superior portion of nose—has 5 named branches named by position

    • Supraorbital—largest V1 branch, it emerges from the orbit by supra orbital notch (foramen) and supplies most of the forehead and upper eyelid

    • Supratrochlear—located medial to supraorbital and supplies medial forehead and upper eyelid

  • Maxillary division (V2)—supplies the skin of the lower eyelid, prominence of cheek, ala of nose, part of the temple, and upper lip. It has three main branches, one that you need to be aware of:

    • Infraorbital—through Infraorbital foramen. Supplies skin over the maxilla, lower eyelid, and lateral aspect of the nose

  • Mandibular division (V3)—skin over mandible, lower lip, fleshy part of cheek, part of auricle, and part of the temple. There are 3 named branches, two you need to know.

    • Auriculotemporal—emerges to the face by the superior margin of the parotid gland and travels anterior to the ear with the superficial temporal vessels. It supplies skin of the temporal region and the anterior aspect of the ear, along with the temporomandibular joint, the skin of the external acoustic meatus, some of the tympanic membrane, and a portion of the parotid gland.

    • Mental N—continuation of inferior alveolar nerve; through the mental foramen on the mandible—it supplies the skin of the lower lip and over some of the mandible

PSNS to Parotid gland: CN IX, GLOSSOPHARYNGEAL NERVE

• Lesser petrosal n: Fibers from the tympanic nerve and plexus become the lesser petrosal nerve.

• Synapses in otic ganglion (on V3), then joins the auriculotemporal n.

• Parasympathetic fibers to parotid gland

12. Major Vessels of the Face

• Describe the anatomy and branching pattern of the major vessels within the region:

  • Facial a. and v.

  • Superficial temporal a. and v.

    • Facial A and V: curls around the inferior border of the mandible, it then follows a twisted course toward the bridge of the nose

    • Superficial temporal A: a terminal branch of the external carotid that supplies the lateral aspect of the scalp

      • Clinical correlation: temporal arteritis (or giant cell arteritis): related to this artery; indolent onset of pain over the temporal area, worse at night, most unilateral. Common over 50 years old. Jaw claudication during chewing or talking over 50% of patients.

    • Occipital A: a branch of the external carotid that pierces trapezius and supplies the posterior aspect of the head

    • Arteries arising from the internal carotid system—inside the cranial cavity, the internal carotid gives rise to the ophthalmic a. Two branches of the ophthalmic A supply the face and travel w/ nerves already mentioned

      • Supraorbital A—traverses the supraorbital notch (foramen). Supplies the upper eyelid, forehead, and scalp.

      • Supratrochlear A—traverses the frontal notch. Supplies the medial aspect of the upper eyelid, forehead, and scalp

    • *Veins of the same name accompany the arteries listed above

    • *Important feature: facial, angular, and ophthalmic veins have no valves—blood can pass in either direction. Supraorbital and Supratrochlear Vv unite to form angular V, which communicates w/ superior ophthalmic.

    • Some clinically important anastomotic connections that are valve-less occur in the face. They connect the following veins:

      • Facial V and the Superior Ophthalmic V (via the communication of the angular and supratrochlear Vv)

      • Facial V and Pterygoid Plexus of veins (via the communication of the buccal V with both of these venous systems)

    • *Both the superior ophthalmic V and the pterygoid plexus of veins drain into the cavernous venous sinus. Therefore, venous blood can pass from the face into the cranial cavity via these anastomotic connections—infections from facial area can spread to the cranial vault. Infection on the face, especially the “Dangerous Triangle” between nose and mouth angle may cause infection into brain tissue secondary to the non-filtered (no-valves) venous communication