Anatomy & Physiology: Special Senses (Eyes, Ears, Smell & Taste)

Comprehensive vocabulary flashcards covering the anatomy and physiology of the special senses, including the structural tunics, photoreceptors, and visual pathway of the eye; auditory and equilibrium mechanisms of the ear; and the receptors and cranial nerves mediating olfaction and gustation.

Conjunctiva

A thin membrane that lines the inner surface of the eyelids and covers the anterior surface of the sclera (does not cover the cornea) to protect and lubricate the eye.

Palpebral conjunctiva

The specific portion of the conjunctiva that lines the inner surface of the eyelids.

Bulbar conjunctiva

The specific portion of the conjunctiva that covers the anterior surface of the sclera.

Lacrimal gland

A gland located above the lateral portion of the eye that produces tears to lubricate, cleanse, and protect the eye.

Tarsal glands (Meibomian glands)

Glands located in the eyelids that produce an oily secretion that helps prevent tears from evaporating too quickly.

Sclera

The white, tough outer portion of the fibrous tunic that protects the eyeball and helps maintain its shape.

Cornea

The clear, transparent anterior portion of the fibrous tunic that allows light to enter and provides the major refraction (bending) of incoming light.

Choroid

The highly vascular middle layer (vascular tunic) of the eye that supplies nutrients and oxygen and contains pigment to absorb excess light.

Retina

The innermost neural layer (neural tunic) of the eye containing photoreceptors (rods and cones) that convert light stimuli into nerve signals.

Rods

Photoreceptors in the retina that allow vision in dim light, essential for night/low-light vision, peripheral vision, and seeing shades of gray.

Cones

Photoreceptors in the retina that function mainly in color vision, bright-light vision, and sharp, detailed vision.

Fovea Centralis

A small depression in the retina with the highest concentration of cones that provides the sharpest vision, most detailed central vision, and best visual acuity.

Optic Disc

The point where the optic nerve leaves the eye; it contains no rods or cones and is known as the blind spot.

Lens

A transparent, biconvex structure located behind the iris that focuses light onto the retina and adjusts focus for near and far objects.

Accommodation

The ability of the eye to focus on near objects, achieved by ciliary muscle contraction, relaxation of suspensory ligaments, lens thickening/rounding, and increased refractive power.

Refraction

The bending of light as it passes through different transparent structures of the eye, provided mostly by the cornea and fine-tuned by the lens.

Visual Pathway

The sequence of structures through which light information travels to the brain: Retina → Optic nerve → Optic chiasma → Optic tract → Thalamus → Optic radiation → Occipital lobe.

Aqueous Humor

The clear fluid in the anterior portion of the eye that maintains intraocular pressure, nourishes the cornea and lens, and drains through the trabecular meshwork into the Canal of Schlemm.

Glaucoma

Damage to the optic nerve commonly associated with increased intraocular pressure, often caused by impaired drainage of aqueous humor.

Color Blindness

A deficiency in distinguishing certain colors due to non-functioning cones, with the common red-green type being X-linked recessive and more prevalent in males.

Auricle (Pinna)

The visible external part of the ear that collects sound waves and directs them into the external acoustic meatus.

External Acoustic Meatus

The auditory canal that conducts sound toward the tympanic membrane; it contains hairs and ceruminous glands.

Ceruminous Glands

Glands located in the external auditory canal that produce cerumen, commonly known as earwax.

Tympanic Membrane

The eardrum; a membrane that separates the outer ear from the middle ear and vibrates when struck by sound waves, transferring vibrations to the ossicles.

Ossicles

Three tiny middle-ear bones (Malleus, Incus, Stapes) that receive, amplify, and transfer sound vibrations from the tympanic membrane toward the oval window.

Pharyngotympanic Tube (Auditory / Eustachian Tube)

A tube connecting the middle ear to the nasopharynx that equalizes air pressure on both sides of the tympanic membrane.

Cochlea

The major snail-shaped organ of the inner ear responsible for hearing.

Spiral Organ of Corti

The receptor organ inside the cochlea containing sensory hair cells that detect sound vibrations and convert them into nerve signals.

Static / Linear Equilibrium

The maintenance of balance detecting head position, gravity, and linear acceleration, monitored by receptors within the vestibule (utricle and saccule).

Otoliths

Tiny calcium carbonate crystals located in the utricle and saccule that shift with head position to stimulate sensory hair cells for static equilibrium.

Semicircular Canals

Inner ear structures responsible for dynamic/angular equilibrium by detecting rotational movement of the head (such as spinning or turning).

Crista Ampullaris

The sensory receptor located in the ampulla of each semicircular canal that detects rotational or angular acceleration of the head.

Vestibulocochlear Nerve (CN VIII)

Cranial nerve VIII that transmits sensory information from the inner ear to the brain; contains a cochlear division for hearing and a vestibular division for balance/equilibrium.

Ménière's Disease

An inner-ear disorder affecting both hearing and balance, characterized by episodic vertigo, fluctuating hearing loss, tinnitus, and a sensation of fullness or pressure in the ear.

Conductive Hearing Loss

Hearing impairment resulting from mechanical interference with sound conduction through the outer or middle ear (e.g., cerumen impaction, otitis media, ossicle problems).

Sensorineural Hearing Loss

Hearing impairment caused by damage to the inner ear, cochlear hair cells (such as from loud noise exposure), or the auditory nerve pathway.

Presbycusis

Age-related sensorineural hearing loss that typically affects both ears and primarily involves higher-frequency sounds.

Olfactory Receptors

Chemoreceptors located in the olfactory epithelium of the upper nasal cavity that detect airborne odor molecules.

Chemoreceptors

Sensory receptors that respond to chemical stimuli; used for both the sense of smell (olfaction) and taste (gustation).

Papillae

Small projections on the surface of the tongue, some of which contain taste buds (distinct from taste buds themselves).

Fungiform papillae

Mushroom-shaped tongue projections found mainly on the anterior portion of the tongue that contain taste buds.

Circumvallate (Vallate) papillae

Large tongue projections arranged near the back of the tongue that contain many taste buds.

Foliate papillae

Tongue projections located along the lateral sides of the tongue that contain taste buds.

Filiform papillae

The most numerous tongue projections that provide friction to help manipulate food; they do not contain taste buds.

Gustatory receptor cells

Specialized sensory receptor cells within taste buds that possess gustatory hairs and respond to dissolved chemical stimuli in saliva.

Facial Nerve (CN VII)

The cranial nerve responsible for transmitting taste sensations from the anterior two-thirds ($\frac{2}{3}$) of the tongue.

Glossopharyngeal Nerve (CN IX)

The cranial nerve responsible for transmitting taste sensations from the posterior one-third ($\frac{1}{3}$) of the tongue.

Vagus Nerve (CN X)

The cranial nerve responsible for transmitting taste sensations from the epiglottic and pharyngeal regions.

Umami

One of the five basic taste sensations (along with sweet, sour, salty, and bitter), commonly associated with savory or protein-rich flavors.