General and Special Senses: Eye and Ear Anatomy and Pathways

Comprehensive vocabulary flashcards covering the anatomical structures, receptor cells, and neural pathways of the auditory, vestibular, and visual sensory systems.

Auricle

The external elastic cartilage structure of the ear that funnels sound vibrations into the external acoustic meatus.

External acoustic meatus

The canal entering into the skull that directs sound vibrations to the tympanic membrane.

Tympanic membrane

A connective tissue membrane situated at the end of the external acoustic meatus that transmits vibrations to the auditory ossicles.

Auditory ossicles

Three small bones in the air-filled middle ear—the malleus, incus, and stapes—that transmit vibrations to the oval window.

Tensor tympani and stapedius

Middle ear muscles that function to stabilize the auditory ossicles.

Eustachian tube

A passage connecting the middle ear to the pharynx that regulates the flow of air and fluid into or out of the middle ear cavity.

Bony labyrinth

The compact bone maze of the internal ear that encloses perilymph fluid.

Membranous labyrinth

A network of tubes suspended within perilymph inside the bony labyrinth that is filled with endolymph.

Perilymph

The fluid located within the bony labyrinth surrounding the membranous labyrinth, also filling the vestibular and tympanic ducts.

Endolymph

The fluid contained within the membranous labyrinth, including the cochlear duct and semicircular canals.

What are the 2 ear regions of internal ear?

1. cochlea

2. vestibule

Cochlea

A snail-shell-shaped tube in the inner ear that narrows, coils approximately $2.5$ times, and functions in hearing.

Oval window

The opening at the large end of the cochlea that contacts the stapes to transmit vibrations into the inner ear.

Organ of Corti

The sensory receptor organ located along the basilar membrane between the cochlear and tympanic ducts that detects sound vibrations.

Hair cells

Mechanoreceptor cells with stereocilia projecting into endolymph that depolarize when their stereocilia are bent.

Tectorial membrane

A firm membrane suspended above the hair cells in the Organ of Corti that bends stereocilia when the basilar membrane vibrates.

Auditory pathway

The ascending hearing route: Hair cells → 1st order neuron → CN VIII → Cochlear nucleus → 2nd order neuron → Inferior colliculi → 3rd order neuron → Thalamus (medial geniculate) → 4th order neuron → Auditory cortex. sound is then percieved.

What is the vestiblue made up of?

• 3 semicircular canals with ampullae

• Utricle and saccule

Semicircular canals

Three fluid-filled inner ear canals oriented anteriorly, laterally, and posteriorly to detect rotational head movement in different directions.

Ampulla

An expanded structure found at the base of each semicircular canal housing a crest and a cupula.

Cupula

A connective tissue cone resting upon a crest within an ampulla that gets knocked over by fluid movement to detect head acceleration.

Macula

A sensory receptor spot within the utricle and saccule that detects stationary head position in either vertical or horizontal orientations.

Otolithic membrane

A gelatinous disc embedded with calcium carbonate crystals inside the macula of the utricle and saccule that sags with gravity to bend hair cell stereocilia.

Equilibrium pathway

The vestibular route: Hair cells → 1st order neuron → CN VIII → Vestibular nucleus → 2nd order neuron → Thalamus → 3rd order neuron → Vestibular cortex. then equilibrium is preceived

What is the 3 tunic layers of the eye

• fiberous tunic- providing structure and protection

• Vascular tunic- blood vessels, pigment

• Nerual tunic- nuerons , neuroglia, and photoreceptors

Palpebare

structures that form the eyelids, protecting the eye and helping to moisten it. Eyelashes line the edge of the tarsal glands to keep them from sticking together,

Conjunctiva

A thin protective vascularized mucus membrane lining the inner eyelid surface (palpebral) and the visible surface of the eye (bulbar).

Lacrimal gland

A gland situated on the superior-lateral corner of the eye that produces tears to moisten the eye, eliminate debris, and provide nutrients to the conjunctiva.

What is the pathway of tears through the lacrimal apparatus?

The lacrimal gland, located in the upper outer corner of the eye, produces tears to moisten and clean the eye. Tears travel across the eye toward the inner corner (lamcrimal ducts) and drain through the lacrimal puncta and canaliculi into the lacrimal sac, then pass down the nasolacrimal duct into the nasal cavity.

What are the two cavities of the eye?

• Anterior and posterior chambers

• Vitreous chamber

Aqueous humor

A watery fluid secreted by the ciliary body into the anterior and posterior chambers that circulates and is reabsorbed through the scleral venous sinus.

Vitreous humor

A gelatinous mass filling the vitreous chamber posterior to the lens that provides structural support for the retina.

Sclera

The dense irregular connective tissue layer forming the firm 'white' of the eye within the fibrous tunic.

Cornea

The transparent anterior layer of the fibrous tunic overlaying the iris and pupil.

Choroid

A highly vascularized layer of the vascular tunic between the sclera and neural tunic containing melanocytes that provide melanin.

Iris

A pigmented ring of the vascular tunic consisting of the sphincter pupillae and dilator pupillae smooth muscles that regulate pupil diameter.

Ciliary zonules

Protein fibers extending from the ciliary body to the lens that adjust lens tension and curvature when ciliary smooth muscles contract.

Pigment layer of Nueral tunic

layer of epithelium where melanocytes depoist melanin

Rods

Photoreceptor cells in the neural tunic specialized for detecting light-dark values.

Cones

Photoreceptor cells in the retina responsible for color vision across three distinct types: red, green, and blue.

Fovea

A depression on the retina with the highest concentration of cones where incoming light is primarily focused.

Horizontal cells

Retinal neurons that inhibit photoreceptors to enhance visual contrast.

Bipolar cells

Intermediate retinal neurons that synapse directly between photoreceptors and retinal ganglion cells.

Amacrine cells

Short neurons in the retina that facilitate light adaptation.

Ganglion cells

Retinal neurons that synapse with bipolar cells and whose axons exit the eye at the optic disc to form cranial nerve II.

Optic disc

The blind spot of the retina where ganglion cell axons converge and exit the eye to begin cranial nerve II.

Visual pathway

The neural pathway for sight: Photoreceptors → Bipolar cells → 1st order neuron (ganglion cells) → CN II → Optic chiasm → Thalamus (lateral geniculate) → 2nd order neuron → Visual cortex.