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Anatomy2 Eye and Ear
| Term | Definition |
|---|---|
| Auricle/Pinna | outer elastic cartilage funnel used to collect sound waves and direct them toward the external acoustic/auditory meatus |
| helix | the rime of the auricle |
| anithelix | elevation internal and parallel to the helix |
| concha | deep cavity bordered by anithelix |
| tragus | dorsal projections anterior to concha and over orifice of meatus |
| antitragus | a small tubercle opposite the tragus |
| lobule/ear lobe | directly below the antitragus, lacks cartilage |
| external acoustic meatus | about 1 inch in length, extending from the concha to the tympanic membrane/eardrum |
| cerumen | a waxy substance secreted by the small hairs and sweat glands in the ear |
| tympanic cavity | air filled space in the temporal bone |
| auditory tube | connects the tympanic cavity to the nasopharynx |
| Ossicles | 3 small bones which transmits vibrations from the tympanic membrane to fluid in the inner ear |
| malleus | the hammer-shaped outermost ossicle; it has a handle embedded in the tympanic membrane. vibrations of the tympanic membrane are transmitted to the malleus via the handle |
| incus | the anvil-shaped middle ossicle, recieves vibrations from the malleus and transmits them to the stapes |
| stapes | the stirrup-shapped innermost ossicle articulating with the oval window |
| oval window | opening on medial wall leading from the tympanic cavity into the vestibule of the inner ear, it receives the base of the stapes |
| round window | membrane-covered hole in medial wall |
| tensor tympani | inserts into the malleus and innervated by mandibular division of the trigeminal nerve. the muscle increase the tension on the tympanic membrane thereby decreasing vibrations- acts as a damper to prevent damage |
| stapedius | inserts into stapes and is innervated by facial nerve. the muscle decreases vibration, preventing excessive movement of the stapes |
| chorda tympani nerve | a branch of the CN 7 (facial) passing through the middle ear just medial of the malleus. the nerve conducts taste from the anterior 2/3 of the tongue; it also sends some autonomics to the salivary glands |
| Osseous Labyrinth | hollowed out, fluid filled passageway in the petrous portion of the temporal bone. the walls of the tunnel are made of compact bone- all surrounding bone is spongy |
| Vestibule | ceteral portion of osseous labyrinth made of the oval window and round window |
| oval window | recieves the foot plate of the stapes |
| round window | covered with a membrane which accommodates changes in the fluid pressure of the perilymph by moving in and out in synchrony with movements of the stapes at the oval window |
| semicircular canals | 3 canals branching posterolateral from the vestibule |
| cochlea | branching anteromedial in the shape of the snails shell from the vestibule. the cochlea has two osseous chambers along its length: scala vestibuli and scala tympani |
| scala vestibuli | attached to vestibule and running to the helicotrema at the apex of the cochlea |
| scala tympani | from the heliocotrema to the round window |
| membranous labyrinth | represents a tubular fluid filled passageway with membranous walls positioned inside the osseous labyrinth |
| Saccule and utricle | located in the vestibule and innervated by the vestibular nerve (CN 8- vestibulocochlear nerve) |
| semicicular ducts | 3 ducts attached to the utricle and located inside the semicircular canals. At the base of each semicircular duct is a dilated area- the ampulla. the semicircular ducts are also innervated by vestibular nerve |
| cochlear duct | attached to the saccule and located inside the chochlea, between the scala vestiuli and the scala tympani. the duct is innercated by the chochlear nerve (CN 8) |
| endolymphatic duct | blind ending sac, expands under dura mater lining posterior part of the temporal boe. endolymph produced by cell of the membranous laburinth passes through the endolympahtic duct and into numerous blood bessels at the dialted terminal end of the duct |
| Conjunctiva | mucous membrane lining the inner surface of the eyelids and covering the surface of the eye |
| Lacrimal Gland | located in the lateral aspect of the roof of the orbit; it has both superior and inferior parts; secretions (tears) from this gland pass through 6-12 ducts which open onto the conjunctiva |
| Superior and Inferior Lacrimal Puncta | small openings into superior and inferior lacrimal canaliculi |
| Superior and Inferior Lacrimal Canaliculi: | small tubular ducts leading to lacrimal sac |
| Lacrimal Sac | enlarged cavity located in fossa for lacrimal sac |
| Nasolacrimal Duct | duct running from lacrimal sac and opening into nasal cavity |
| Lacrimal Caruncula | small reddish conical body of skin containing sebaceous and sweat glands; it is the source of the whitish secretion that collects in this area |
| Plica Semilunaris | a semilunar fold of conjunctiva |
| Lacrimal Lake | a triangular space at the medial angle of the eye where tears collect |
| Route of Tears | lacrimal gland —> lacrimal lake —> lacrimal puncta —> lacrimal canaliculi —> lacrimal sac —> nasolacrimal duct —> nasal cavity |
| Sclera: | outer layer of the eyeball |
| Choroid: | middle layer of the eyeball |
| Retina: | inner layer of the eyeball |
| Optic Nerve | contains axons leading from the retina (containing rod and cone receptors) to the brain; they outer surface is covered by dura mater |
| Optic Disk | point of exit for fibers forming optic nerve; lacks rod and cone receptors = insensitive to light (“blind spot”) |
| Macula Lutea and Fovea Centralis | macula lutea is a yellow spot about o.5 millimeter in diameter consisting only of cone receptors; in the center of the macula lutea is a small pit = the fovea centralis - the macula is the point of critical vision (sharp focus) |
| Lens: | situated between the iris and the vitreous body; crystalline, transparent, elliptical lens acts to focus light on the retina |
| Suspensory Ligaments | act to suspend the lens via attachment to the ciliary body |
| Ciliary Body | contains the ciliary muscle (smooth muscle) - contraction of the ciliary muscle reduces tension on the suspensory ligaments, thus causing the shape of the lens to change (become thicker) for near distance focus (accommodation to distance) |
| Aqueous Humor: | watery fluid secreted by the ciliary body and contained within the anterior and posterior chambers of the eye |
| Vitreous Body | transparent semi-gelatinous substance filling the vitreous chamber |
| Iris: | colored part of eye just anterior to the lens and surrounding the pupil; consists of an inner circular layer of smooth muscle which reduces pupil diameter (bright) and an outer radiating layer of smooth muscle that increases pupil diameter (low light) |
| Pupil: | opening for entrance of light into the eye |
| Cornea: | clear, transparent extension of sclera over anterior 1/6 of eye |
| Posterior Chamber | between iris and lens |
| Anterior Chamber | between iris and cornea |
| Vitreous Chamber | posterior to lens containing the vitreous body |
| Trabeculae: | minute small cavities at junction of iris and cornea; drain aqueous humor from the anterior chamber |
| Scleral Venous Sinus (Canal of Schlemm): | drains aqueous humor from the trabeculae and delivers it to small veins in the immediate area |
| Route of Aqueous Humor: | ciliary body —> posterior chamber —> pupil —> anterior chamber —> trabeculae —> scleral venous sinus (canal of Schlemm) —> vein |
| Levator Palpebrae Superioris | raises upper eyelid; direct antagonist of the orbicularis oculi |
| Four Recti Muscles | all arise from a common tendinous ring that surrounds the optic foramen and part of the superior orbital fissure 1. Superior Rectus: elevates, adducts 2. Inferior Rectus: depresses, adduct 3. Medial Rectus: adducts 4. Lateral Rectus: abducts |
| Two Oblique Muscles | 1. Superior Oblique: depresses, abducts; its tendon passes through a cartilaginous loop called the trochlea 2. Inferior Oblique: elevates, abducts |
Created by:
karisak
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