Anatomy and Physiology of the Human Eye and Ear

: What is the outer layer of the eye called and what structures does it include?

: The fibrous tunic; includes the sclera (white, protection, muscle attachment) and cornea (transparent, refracts light).

: What is the middle layer of the eye called and what structures does it include?

: The vascular tunic; includes the choroid (blood supply, absorbs stray light), ciliary body (produces aqueous humor, controls lens), and iris (controls pupil size).

: What is the inner layer of the eye called and what does it contain?

: The neural tunic (retina); contains photoreceptors (rods and cones) that detect light.

: What is the optic disc and why is it called the blind spot?

: It is the region where the optic nerve exits the retina; contains no photoreceptors.

: What is the fovea centralis and its function?

: A small region of the retina with the highest density of cones; provides the sharpest vision.

: What changes occur in the lens for close vision?

: Ciliary muscles contract, suspensory ligaments loosen, lens becomes rounder.

: What changes occur in the lens for distant vision?

: Ciliary muscles relax, suspensory ligaments tighten, lens flattens.

: What fluid fills the anterior cavity of the eye and what is its function?

: Aqueous humor; nourishes cornea and lens, removes wastes, maintains intraocular pressure.

: What fluid fills the posterior cavity of the eye and what is its function?

: Vitreous humor; gel-like fluid that maintains eye shape and holds retina in place.

: What type of photoreceptor functions in dim light and black-and-white vision?

: Rods; located mainly in the retina periphery, detect movement and low light.

: What type of photoreceptor functions in bright light and color vision?

: Cones; concentrated in the fovea centralis, provide sharp detail and color vision.

: What ligaments connect the ciliary body to the lens and adjust lens shape?

: Suspensory ligaments.

: What enzyme in tears destroys bacteria?

: Lysozyme; produced by the lacrimal gland.

: What part of the eye controls pupil size and regulates light entering?

: The iris.

: What protein in the lens maintains transparency and refraction?

: Crystallin.

: What tube connects the middle ear to the nasopharynx and equalizes pressure?

: The auditory (Eustachian) tube.

: What three small bones transmit sound vibrations in the middle ear?

: The auditory ossicles: malleus, incus, and stapes.

: What spiral-shaped structure in the inner ear is responsible for hearing?

: The cochlea; contains the organ of Corti with hair cells.

: What structures in the inner ear detect rotational head movements?

: The semicircular canals; provide dynamic equilibrium.

: What part of the inner ear detects linear acceleration and head position?

: The vestibule; contains utricle and saccule for static equilibrium.

: What structure in the cochlea contains hair cells that transduce sound?

: The organ of Corti; located on the basilar membrane.

: What is the sequence of events for hearing?

: Sound waves → tympanic membrane vibrates → ossicles transmit → stapes pushes oval window → fluid waves in cochlea → basilar membrane vibrates → hair cells bend → signals sent via cochlear nerve.

: What cranial nerve branch carries hearing signals?

: The cochlear branch of the vestibulocochlear nerve (CN VIII).

: What cranial nerve branch carries balance signals?

: The vestibular branch of the vestibulocochlear nerve (CN VIII).

: How do the semicircular canals detect dynamic equilibrium?

: Endolymph movement bends the cupula and hair cells in the ampulla, signaling rotation.

: How does the vestibule detect static equilibrium?

: Otoliths in the utricle and saccule shift with head tilt or linear acceleration, bending hair cells.