Anatomy and Physiology of the Eye and Ear

Conjunctiva

Transparent mucus membrane that covers the inner surface of the eyelid and anterior surface of the eye, except for the cornea.

Lacrimal Apparatus

Includes the Lacrimal Gland, Lacrimal Punctum, Lacrimal Canals, and Lacrimal Sac, which drain tears into the Nasolacrimal Duct.

Lacrimal Gland

Produces tears.

Lacrimal Punctum

Tiny openings at the medial canthus of the eyes.

Lacrimal Canals

Drain tears into the Lacrimal Sac.

Eyelids

Known as palpebrae, they block foreign objects, aid in sleep by providing darkness, spread tears over the eye surface, and clear debris from the surface of the eye.

Extrinsic Eye Muscles

Six muscles that control the movement of the eye in various directions.

Sclera

The white, dense collagenous connective tissue that shapes the eye and anchors the extrinsic muscles.

Cornea

The transparent anterior region that admits light, covering the pupil and iris.

Choroid

Highly vascular, pigmented layer behind the retina that helps absorb light and provide nutrients.

Ciliary Body

Includes the Ciliary Muscle and Ciliary Processes.

Ciliary Muscle

Alters the shape of the lens.

Ciliary Processes

Extensions that hold the suspensory ligaments attached to the lens.

Iris

The colored part of the eye, controlling the diameter of the pupil to regulate the amount of light entering the eye.

Retina

Contains sensory receptors sensitive to light.

Pigmented Layer

Absorbs light and prevents scattering.

Neural (Sensory) Layer

Includes photoreceptors (rods and cones).

Rods

Respond to low light levels and provide black and white vision.

Cones

Require bright light and detect color.

Bipolar Cells

Transmit signals from rods and cones.

Ganglion Cells

Their axons form the optic nerve, which exits through the optic disc.

Macula Lutea

Contains a high concentration of cone cells for sharp central vision.

Fovea Centralis

The area of highest visual acuity.

Anterior Cavity

Contains Aqueous Humor and is divided into Anterior Chamber and Posterior Chamber.

Anterior Chamber

Located between the cornea and iris.

Posterior Chamber

Located between the iris and lens.

Posterior Cavity

Contains Vitreous Humor which helps maintain the shape of the eyeball and hold the retina in place.

Accommodation

The process by which the lens changes shape to focus light on the fovea.

Ciliary Muscles

Control the tension on the suspensory ligaments to flatten for distant vision or to bulge for near vision.

Emmetropic Vision

Normal vision where the eye can focus on both distant and near objects.

Myopia (Nearsightedness)

Difficulty focusing on distant objects.

Hyperopia (Farsightedness)

Difficulty focusing on near objects.

Astigmatism

Irregular curvature of the lens or cornea causing blurred vision.

Presbyopia

Age-related decline in the lens's elasticity, leading to difficulty focusing on close objects.

Snellen Eye Chart

Used to test visual acuity by having subjects read letters at various distances.

Astigmatism Test

Identifies irregularities in the lens or cornea by how subjects perceive lines on a chart.

Near Point of Accommodation

Measures the closest point at which one can see an object clearly, used to test lens flexibility.

Auricle (Pinna)

Funnels sound into the external auditory canal.

External Auditory Canal

Leads from the auricle to the tympanic membrane (eardrum).

Tympanic Membrane

Transmits vibrations to auditory ossicles.

Auditory Ossicles

Malleus (hammer), Incus (anvil), and Stapes (stirrup) that amplify sound vibrations and transmit them to the inner ear.

Pharyngotympanic (Auditory) Tube

Equalizes pressure between middle and outer ear.

Bony Labyrinth

Contains perilymph and houses the membranous labyrinth filled with endolymph.

Cochlea

Converts sound vibrations into neural signals via hair cells in the spiral organ of Corti.

Semicircular Canals and Vestibule

Detect rotational and linear movements for balance.

Vestibule

Contains the utricle and saccule, which have maculae for detecting gravitational pull.

Vestibulocochlear Nerve

Sends electrical signals from the cochlea to the brain.

Balance Maintenance

Maintained through the semicircular canals and vestibule sending position data to the brain.