Chapter 22 Eyes and Ears

Chapter 22 Eyes and Ears

Figure 22.1 Anatomy of the eye.

Anatomy of the Eye • Cornea—clear or transparent outer “window” of the eye • Sclera—opaque, white portion around the circumference of the cornea • Conjunctiva—thin, transparent layer that extends from the edge of the cornea to cover the sclera; also lines the inside of the eyelids

Anatomy of the Eye (cont.) • Iris—colored disc visible through the cornea • Pupil—opening in the iris • Lens (crystalline lens)—located directly behind the iris

Anatomy of the Eye (cont.) • Retina—sensory tissue that lines the back of the eye • Optic nerve—visual pathway by which electrical impulses move from the retina to the brain and back • Macula—small, yellowish area in the retina that provides the most central and acute vision

Anatomy of the Eye (cont.) • Vitreous humor—occupies about 80 percent of the interior of the eye; composed mostly of water • Choroid—layer of nourishing blood vessels between the sclera and the retina • Extraocular muscles—regulate the motion of each eye

Figure 22.8 Anatomy of the ear.

Anatomy of the Ear • The outer ear structures are the visible portion of the ear • The middle ear structures include: • Tympanic membrane (eardrum) • Auditory canal • Malleus, incus, and stapes • Eustachian tube

Anatomy of the Ear (cont.) • The inner ear structures include: • Cochlea, snail-shaped organ that contains the nerves required for hearing • Vestibular labyrinth, which contains the sense organs required for balance

Function of the Eye • The function of the eye is sight • In humans, stereoscopic vision creates depth perception

Figure 22.2 The eye as a camera.

Functions of the Ears • The ears have two separate functions: to hear and to govern balance • These functions are not interdependent • One may be deaf and have perfect balance • One may have perfect hearing and have a disrupted sense of balance

Common Diseases of the Eyes • Stye (hordeolum)—localized infection of the sebaceous gland in a hair follicle at the base of an eyelash • Blepharitis—inflammation of the eyelid margins, accompanied by redness, thickening, and possibly the formation of scales and crusts or shallow marginal ulcers

Common Diseases of the Eyes (cont.) • Conjunctivitis—acute or chronic inflammation of the conjunctiva caused by a virus, bacteria, allergy, or irritant such as wind, smoke, or snow • Vascular retinopathy—noninflammatory disease in which the retina has become damaged

Figure 22.3 Bacterial conjunctivitis. (Phototake NYC.)

Table 22.1 Various Topical Ophthalmics Used for Ocular Infections

Table 22.1 (continued) Various Topical Ophthalmics Used for Ocular Infections

Table 22.2 Drugs for Glaucoma with Various Mechanisms of Action

Table 22.2 (continued) Drugs for Glaucoma with Various Mechanisms of Action

Diseases of the Ears • Otitis media—an inflammation and infection of the middle ear • Hearing loss—technically not a disease; there are many types of hearing loss • Earwax buildup—also not a disease; this condition can lead to temporary hearing loss, loss of homeostasis, and irritation of the ear

Chapter 22 Eyes and Ears