Muscular and Senses

Special senses The special senses are vision, hearing, smell, taste, and touch; they detect specific stimuli using specialized receptors

Chemical receptors Receptors that respond to chemicals (smell, taste)

Physical receptors Receptors that respond to physical energy like light and sound (vision and hearing)

Sight Electromagnetic energy detected by the eyes

Hearing Mechanical energy (sound waves) detected by the ears

Smell and taste Chemical senses using chemoreceptors

Touch General sense using mechanoreceptors, thermoreceptors, nociceptors

Orbit Bony cavity (eye socket) that holds the eyeball

Extraocular muscles Muscles that move the eyeball within the orbit

Eyebrows Hair above the eye that protects from sweat and debris

Eyelids Movable folds that protect the eye and spread tears

Eyelashes Hairs that protect eye from debris and trigger blinking

Conjunctiva Mucous membrane lining eyelids and covering front of eye

Lacrimal glands Produce tears to lubricate and clean eye

Lacrimal sac Collects and stores tears before drainage

Lacrimal ducts Channels that carry tears from gland to eye area

Nasolacrimal duct Drains tears from eye into the nasal cavity

Sclera White outer layer of eye that maintains shape

Cornea Transparent front layer that refracts most light

Choroid Vascular layer that supplies blood to eye

Ciliary body Controls lens shape for focusing (accommodation)

Lens Transparent structure that focuses light onto retina

Iris Pigmented muscle that controls pupil size

Pupil Opening in iris that lets light into eye

Retina Light-sensitive layer containing rods and cones

Optic nerve Carries visual signals from retina to brain

Aqueous humor Fluid in anterior chamber that nourishes cornea/lens

Vitreous humor Gel-like fluid that maintains eye shape

Photoreceptors Retinal cells that detect light (rods and cones)

Rods Detect black, white, and low-light vision

Cones Detect color and sharp detail

Fovea centralis Area of sharpest vision in retina

Optic disc Blind spot where optic nerve exits retina

Refraction Bending of light as it passes through eye structures

Accommodation Eye adjusting lens shape for near/far vision

Hyperopia Farsightedness (difficulty seeing near objects)

Myopia Nearsightedness (difficulty seeing far objects)

Presbyopia Age-related loss of near focusing ability

Astigmatism Irregular cornea/lens curvature causing blurred vision

Conjunctivitis Infection/inflammation of conjunctiva (pink eye)

Keratitis Inflammation of cornea (often from injury/infection)

Dacryocystitis Infection of lacrimal sac

Blepharoptosis Drooping eyelid

Ectropion Eyelid turns outward

Entropion Eyelid turns inward

Hordeolum Stye; infection of eyelash oil gland

Xerophthalmia Dry eyes (often vitamin A deficiency)

Glaucoma Increased intraocular pressure damaging optic nerve

Cataract Clouding of the lens causing vision loss

Ophthalmoscope Instrument used to view interior of eye

LASIK Laser surgery to reshape cornea and correct vision

Scleral buckle Silicone band used to repair retinal detachment

Ophthalmology Medical specialty dealing with eye diseases

Ophthalmologist Physician who treats eye disease and performs surgery

Optometrist Doctor of optometry who prescribes glasses/contacts

Optician Makes and fits eyeglasses and lenses

External ear Outer portion that collects sound

Middle ear Air-filled chamber with ossicles

Inner ear Contains cochlea and balance structures

Auricle (pinna) Visible outer ear structure

External acoustic meatus Ear canal leading to eardrum

Tympanic membrane Eardrum that vibrates with sound

Ceruminous glands Produce earwax (cerumen)

Tympanic cavity Space in middle ear containing ossicles

Malleus Hammer-shaped ossicle

Incus Anvil-shaped ossicle

Stapes Stirrup-shaped ossicle

Auditory tube (Eustachian tube) Equalizes pressure in middle ear

Labyrinth Inner ear structure for hearing and balance

Cochlea Converts sound waves into nerve impulses

Vestibule Balance center of inner ear

Semicircular canals Detect rotational movement for balance

Hearing process Sound → eardrum vibrates → ossicles amplify → cochlea converts to nerve impulses → brain interprets

Impacted cerumen Buildup of earwax blocking ear canal

Otalgia/Ear pain Pain in the ear

Conductive hearing loss Problem in outer/middle ear blocking sound

Sensorineural hearing loss Damage to inner ear or auditory nerve

Presbycusis Age-related hearing loss

Anacusis Total deafness

Otitis externa Outer ear infection

Otitis media Middle ear infection

Otitis interna Inner ear infection

Myringitis Inflammation of tympanic membrane

Mastoiditis Infection of mastoid bone

Labyrinthitis Inner ear inflammation causing dizziness/hearing loss

Otosclerosis Abnormal bone growth fixing stapes

Ménière’s syndrome Inner ear disorder causing vertigo/hearing loss/tinnitus

Vertigo Sensation of spinning dizziness

Tinnitus Ringing in ears

Otoplasty Surgical repair of outer ear

Mastoidectomy Removal of mastoid bone

Myringectomy Removal of part/all of eardrum

Myringotomy Incision in eardrum to drain fluid/tubes

Tympanoplasty Eardrum reconstruction

Stapedectomy Removal of stapes bone

Labyrinthotomy Incision into inner ear labyrinth

Audiology Study of hearing and hearing disorders

Audiologist Specialist who tests hearing and treats hearing loss

Otoscope Instrument used to examine ear canal and eardrum

Otology Study of the ear