Ear:
    The ear is the sensory organ for auditory (cochlear system) and motion (vestibular system) information for the body and is buried within the temporal bone of the skull.  Special sense information is carried by a single nerve, CN VIII, the Vestibulocochlear Nerve.  There are three components to the system; the outer ear, the middle ear, and the inner ear.

  Outer Ear - The auricle makes up the visible portion of the ear on the lateral side of the head.  This mainly cartilaginous structure serves only to pick up air waves from the environment and direct them toward the middle ear which is at the terminus of the external auditory meatus.  This s-shaped cartilage and bone passage runs in an anterior-medial direction through the temporal bone and ends at the tympanic membrane, which marks the beginning of the middle ear.  The external auditory meatus is lined by ceruminous and sebaceous glands which produce cerumen, a waxy secretion which acts to clean and protect the ear.

  Middle Ear - The middle ear sits within a hollow space in the petrous portion of the temporal bone, the tympanic cavity and the epitympanic recess (a space superior to the membrane), the borders of which are the following:
    Laterally -  the tympanic membrane
    Medially - the inner ear which sits within the mass of the temporal bone
    Anteriorly - the pharyngotympanic (Eustachian) tube, which opens into the nasopharynx, and the canal of the internal carotid artery
    Posteriorly - the aditus leading to the mastoid air cells
    Inferiorly - the jugular fossa containing the internal jugular vein
Therefore, the only means to enter the tympanic cavity without damage to the internal structures is through the floor of the middle cranial fossa.
    The timpanic cavity serves as a transmission site from the environment to the inner ear, the function of which is to translate sound waves into mechanical motion.  The ear does this through the association of the tympanic membrane and the three ossicles; the malleus (hammer), incus (anvil), and stapes (foot).  The handle of the malleus is attached to the surface of the tympanic membrane at a small depression (toward the inner ear) called the umbo.  As the membrane vibrates with sound waves, the malleus physically vibrates translating its motion to the incus and further along to the stapes where the vibratory motions of the three small bones are converted to motion waves in the inner ear (cochlea) through the oval window.
    Associated with these three bones of the middle ear are two muscles, the tensor tympani muscle and the stapedius muscle.  The tensor tympani muscle inserts on the malleus and acts to tense the tympanic membrane reducing the effectiveness of sound transmission, protecting the inner ear during loud sounds.  This muscle receives its motor innervation from a branch of the mandibular nerve (V3 of CN V).  The stapedius muscle is the smallest voluntary muscle of the body and enters the tympanic cavity via the pyramidal eminence inserting on the neck of the stapes.  This muscle functions to hold the stapes to the cochlea and is innervated by a branch of the Facial Nerve (CN VII).
    The Facial Nerve (CN VII) is closely associated with the ear as it passes through the temporal bone. Chorda tympani arises from CN VII and travels in an posterior-anterior direction, running between the malleus and incus, entering the petrotympanic fissure to the infratemporal fossa.  In addition, on the promontory of the tympanic cavity (inferior to the oval window), the tympanic plexus of nerves exists which is a junction of parasympathetic fibers, sympathetic fibers, and general sensory fibers.  Here, the Tympanic Nerve of Jacobsen (CN IX) becomes the lesser petrosal nerve.  With an infection of the middle ear, a lack of taste to the anterior 2/3 of
the tongue and excessive salivation can possibly be found.
    Placed on the inferior, lateral, anterior wall of the timpanic cavity is the opening to the pharyngotympanic tube.  This bony and cartilaginous tube opens in the nasopharynx and serves as a pressure equalizer between the middle ear and the environment allowing free movement of the tympanic membrane.  Opening and closing of this space is controlled by the motions of the tensor veli palatini and levator veli palatini muscles (“popping one’s ears”).

  Inner Ear - Within the petrous portion of the temporal bone is the vestibulocochlear organ a collection of sacs, ducts, and a bony labyrinth where sound waves are interpreted and balance is maintained.  Through the oval window, the stapes communicates to the vestibule.  Anteriorly, the vestibule communicates to the cochlea and posteriorly, the vestibule communicates to the semicircular canals.
    The cochlea is a shell-shaped structure containing a spiral canal wound around a bony core, called the modiolus which contains the nerve endings of the cochlear nerve (CN VIII).  It is the winding of this structure that produces the promontory on the medial wall of the middle ear.  The semicircular canals are a series of three structures that lie perpendicular to each other and end at an ampulla.  Within each canal is a suspended membrane separating an inner, endolymph fluid, and an outer, perilymph fluid.  Within the ampulla are sensory endings from the vestibular nerve (CN VIII) that can be translated to motion and balance of the head.

Reference Netter 87 - 93.

Larynx:
    The larynx is located at the superior end of the trachea and communicates to the pharynx superiorly.  A skeleton, muscular system, and system of nerves permit the creation of sound through the vibration of two vocal folds.

  Skeleton - The larynx is supported by a cartilage framework composed of nine pieces (the cricoid, thyroid, arytenoid (2), corniculate (2), cuneiform (2), and epiglottal cartilages) and the hyoid bone.  The cricoid cartilage forms the inferior border of the larynx articulating with the trachea through a membrane.  Two surfaces on the cricoid can be identified; a ring which is similarly shaped to the rings of the trachea and a lamina, or vertical plate.  The thyroid cartilage (laryngeal eminence) is a bilaminar v-shaped structure that makes up the bulk of the laryngeal cartilage.  Inferiorly, the thyroid cartilage is connected to the cricoid cartilage via the cricothryoid membrane.  It also indirectly connects with the hyoid bone through the thyrohyoid membrane.  On the internal-anterior surface, the heart-shaped epiglottal cartilage articulates with the thyroid cartilage.  It is the pyramidal shaped arytenoid cartilage that is associated with the vocal ligament (true vocal cord) at its vocal process and a muscular process where the muscles of phonation insert permitting the rotation and adjustment of the
vocal ligament tension.  This body sits superior to the cricoid cartilage and posterior to the thyroid cartilage.  The corniculate cartilages sit superior to the arytenoid cartilage and can be seen as projections into the vocal area.
    The conus elasticus, also known as the cricothyroid membrane, is a sheet of elastic connective tissue that is anchored to three sides within the laryngeal space:
  Anteriorly - it is anchored to the thyroid cartilage
  Posteriorly - to the arytenoid cartilage
  Inferiorly - to the cricoid cartilage
The free edge created at the center creates the vocal ligament.  Between these vocal ligaments is a space called the rima glottidis.  Superior to these “true” vocal cords is a set of “false” vocal folds which are formed by the vestibular fold of the free edge of the quadrate membrane.  Between these “true” and “false” vocal cords is a vertical space called the ventricle.  The space from the vestibular folds to the epiglottis is the vestibule.

  Muscles - Muscles adjust the tension and position of the vocal ligaments across the laryngeal space.  These muscles can be combined into three categories: adductors, abductors, and modulators.
  Adductors - these muscles bring the vocal ligaments together
    Transverse Interarytendoids - slide the arytenoid cartilages together
    Oblique Interarytenoids - bring the arytenoid cartilages together via sliding
    Lateral Cricoarytenoids - brings the vocal ligaments together via rotation of the arytenoid cartilages
  Abductors- this set of muscles separate the vocal ligaments
    Posterior Cricoarytenoids - rotate the arytenoid cartilages laterally opening the space between the ligaments
  Modulators - these muscles can tighten, loosen, or stretch the vocal cords to adjust the tone of the sound produced
    Thryoarytenoids - relax the vocal cords by pulling the arytenoid cartilage anteriorly (lateral muscle fiber of the true vocal cord)
    Cricothyroid - lengthens and tenses the vocal cords by pulling the thyroid cartilage anteriorly and inferiorly stretching the cords
    Vocalis - the most medial part of thyroarytenoid, relax the vocal cords by pulling the arytenoid cartilage anteriorly (medial muscle fiber of the true vocal cord)

  Nerves - All of the laryngeal muscles are innervated by branches of the recurrent laryngeal nerve which is a branch of the Vagus Nerve (CN X) with the exception of the cricothyroid muscle which is innervated by the external branch of the superior laryngeal branch of the vagus.  The recurrent laryngeal nerve is also sensory to the mucosa below the vocal cords.  The internal laryngeal nerve (from the superior laryngeal branch of CN X) is sensory to the mucosa above the vocal cords.

Reference Netter Plates 71 - 75

Orbit:
The orbit is a bony compartment of the skull that contains the eye, the orbital muscles, nerves, retroorbital fat, and the lacrimal
gland.  The roof of the orbit is made of the orbital surface of the frontal bone.  The floor of the orbit is made of the orbital surface of the maxilla and the orbital surface of the zygomatic bone.  The medial wall is composed of the lacrimal bone, the orbital plate of the ethmoid bone, and the orbital plate of the palatine bone.  Along this wall are the anterior and posterior ethmoidal foramena.  The lateral wall is formed by the orbital surface of the zygomatic bone.  The posterior wall is composed of the orbital surfaces of the greater and lesser wings of the sphenoid bones.  This wall contains the optic canal and the superior and inferior orbital fissures.

  Muscles - a series of small muscles are used to move the orbit in a variety of directions as well as control the motions of the eyelid.  All of the muscles have their origin in the common tendinous ring at the posterior of the orbit:
  Levator Palpebrae Superiorus
  Superior Rectus Muscle
  Superior Oblique Muscle
  Inferior Oblique Muscle
  Lateral Rectus Muscle
  Medial Rectus
  Inferior Rectus

  Nerves - Four cranial nerves are devoted solely to the eye with support from a branch of an additional nerve:
  CN II (Optic) - special sensory for the sense of vision
  CN III (Oculomotor) - motor to levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, and inferior oblique.
  CN IV (Trochlear) - motor to the superior oblique muscle
  CN VI (Abducens) - motor to the lateral rectus muscle
  Opthalmic Division of CN V (V1) - multiple branches arise from V1 which is a pure sensory nerve.
    Lacrimal Nerve - runs along the lateral superior wall of the orbit to the lacrimal gland which it pierces and continues as a sensory nerve to the eye.  Picks up parasympathetic fibers from the zygomatic nerve (V2 branch) which regulate the gland’s secretions
    Frontal Nerve - Supratrochlear and Supraorbital branches which exit as sensory to the forehead.
    Nasociliary Nerve - divides into three branches
      Infratrochlear Nerve - sensory around the medial corner of the eye
      Ethmoidal Branches - sensory to the nasal cavities and mucosa of the ethmoidal sinuses (pass through the anterior and posterior ethmoidal foramena)
      Ciliary Branches - carry sympathetic and parasympathetic information on long and short branches.  Parasympathetic fibers originate from the Edinger Westphal Nucleus and travel with CN III to the orbit.  On CN III is the ciliary ganglion (parasympathetic ganglion).  Postganglionic fibers travel along the short ciliary branches to the sphincter pupillae muscles that control the size of the pupil.
  Long Branches - carry sensory information away from the eye and sympathetic information to the eye
  Short Branches - carry sensory information from the eye and sympathetic and parasympathetic information to the eye (only means of parasympathetic information getting to the eye).
The optic canal transmits the optic nerve and the opthalmic artery.
The superior orbital fissure transmits the oculomotor nerve, the trochlear nerve, the opthalmic division of CN V, the abducens nerve, and the superior opthalmic vein.

  Lacrimal Gland - The lacrimal gland produces tears under parasympathetic stimulation.  Tears lubricate the cornea and prevent it from dessication.  The gland is located along on the superior-lateral wall of the orbit.  The tears travel in an inferior-medial direction to the medial corner of the eye where lacrimal canaliculi collect the secretions and transport them to the lacrimal sac.  This sac communicates to the nasal cavity via the nasolacrimal duct and opens to the inferior nasal meatus.

  Cavernous Sinus - The cavernous sinus is a common junction point of many dural venous sinuses of the brain located lateral to the sella turcica.  It is within this plexus of veins that the nerves of the orbit and the internal carotid artery pass.  Cranial nerves III, IV, V1 of V, and V2 of V travel through this space along the lateral wall of the sinus.  However, CN VI travels through the center of this venous plexus.  With pressure in the cavernous sinus, the Abducens nerve can be compressed and motor innervation is lost to the lateral rectus muscle of the orbit (this can occur on one or both sides) and the eye cannot be moved laterally (Lateral Rectus Palsy).  The internal carotid artery also passes through the middle of the cavernous sinus and similar conditions can be seen in CN VI if there is an internal carotid artery aneurysm.

Reference Netter Plates 76 - 86