ANAPHY MT 100 LEC - Special Senses (EYE)

Special Senses

senses whose receptors are confined to specialized

organs located primarily in the head

Head

Where are the receptors of the Special Senses confined in?

Vision (eye);

Hearing (ear);

Equilibrium/balance (vestibular apparatus);

Smell (olfaction);

Taste (Gustation)

Enumerate the five special senses:

environmental stimulus; sensory pathways; cerebral cortex

Each receptor converts an _____ into electrical impulses that travel through specific ____ __ to designated areas of the ____

Eye

responsible for detecting light, focusing images, and converting light energy into nerve impulses that are interpreted by the brain as vision

Eyebrows

- Divert sweat away from the eyes

- Provide some protection from sunlight

- Assist in facial expression

Eyelids (Palpebrae)

- Protect the anterior surface of the eye from injury

- Spread tears evenly across the cornea during blinking

- Prevent drying of the corneal surface

- Remove dust and foreign particles

Eyelashes

Trap dust and airborne particles before they reach the eye

Blink Reflex

touching an eyelash initiates the ____

Conjunctiva

A thin, transparent mucous membrane that lines:

• Inner surface of the eyelids (palpebral conjunctiva)

• Anterior sclera (bulbar conjunctiva)

palpebral conjunctiva

Inner surface of the eyelids

bulbar conjunctiva

Anterior sclera

Conjunctiva

- Produce mucus to lubricate the eye

- Helps reduce friction during blinking

Conjunctivitis

An inflammation in the conjunctiva

Lacrimal apparatus

Responsible for tear production and drainage

Tear (Lacrimal Apparatus)

- Lubricate the eye

- Wash away debris

- Prevent corneal drying

- Provide oxygen and nutrients to the cornea

- Contain lysozyme, an antibacterial enzyme

Extrinsic Eye Muscles

Six skeletal muscles move the eyeball while keeping both eyes focused on the same object

Lateral rectus (VI - Abducens)

which muscle, and cranial nerve Moves the eye laterally

Medial rectus (III - Oculomotor)

which muscle, and cranial nerve Moves the eye medially

Superior rectus (III - Oculomotor)

which muscle, and cranial nerve Elevates eye and turns it medially

Inferior rectus (III - Oculomotor)

which muscle, and cranial nerve Depresses eye and turns it medially

Inferior Oblique (III - Oculomotor)

which muscle, and cranial nerve Elevates eye and turns it laterally

Superior Oblique (IV - Trochlear)

which muscle, and cranial nerve Depresses eye and turns it laterally

Fibrous Layer, Vascular Layer, Nervous Layer

Enumerate the three layers the eyeball wall consists of:

Cornea and Sclera

the Fibrous Layer consists of:

Sclera (White of the eye)

protects internal eye structures, maintains eyeball shape, serves as the attachment site for extrinsic eye muscles

Sclera (White of the eye)

tough, dense connective tissue, opaque layer of the eyeball

Cornea

transparent anterior continuation of the sclera

Cornea

allows light to enter the eye, provides most of the eye's refractive power

Cornea

avascular, richly supplied with sensory nerve endings, highly sensitive to pain layer of the eyeball

Corneal Abrasion

a scratch on the clear, protective outer surface (epithelium) of your eye, painful due to abundant sensory innervation

Vascular Layer (Uvea)

Contains numerous blood vessels that nourish the eye.

Choroid, Ciliary Body, Iris, and Pupil

The Vascular Layer (Uvea) consists of:

Choroid

- supplies oxygen and nutrients to the retina

- contains melanin pigment that absorbs scattered light

- prevents internal reflection of light

Ciliary Body

Contains the ciliary muscle, ciliary processes, suspensory ligaments (ciliary zonule)

Ciliary Body

Functions: produces aqueous humor, changes lens shape during accommodation

Near Vision, Distance Vision

Enumerate the two accommodation mechanism of the Ciliary Body

Near Vision

ciliary muscle contracts, suspensory ligaments relax, lens becomes thicker and more convex

Distance Vision

ciliary muscle relaxes, ligaments tighten, lens flatten

Iris

the colored portion of the eye

Iris

Functions: regulates the amount of light

entering the eye by adjusting pupil size

Circular Muscle, Radial Muscle

Enumerate the two smooth muscles in the Iris

Circular Muscle

Muscle that constricts the pupil during Parasympathetic

Radial Muscle

Muscle that dilates the pupil during Sympathetic

Pupil

the central opening of the iris that controls the entry of light into the eye

Dilates

When the lights are dim, the pupil _______

Constricts

When the lights are bright, the pupil _______

Nervous Layer (Retina)

contains the photoreceptors that convert light into electrical impulses.

Rods, Cones

Enumerate the to major receptor cells in the retina

Rods

Receptor for night vision, black-and-white vision, peripheral vision

Rods

Receptor that is extremely sensitive to light, poor visual acuity, more numerous (~120 million)

Cones

receptor for daylight vision, color discrimination, fine detail

Receptor that is less sensitive to dim light, high visual acuity, concentrated in the fovea centralis, approximately 6 million

Macula Lutea, Fovea Centralis, Optic Disc, Lens, Chambers and Humors

Enumerate the parts of the retina:

Macula Lutea

Yellow central region of the retina responsible for detailed central vision

Fovea Centralis

Located at the center of the macula that only contains cones.

Fovea Centralis

Site of the sharpest and clearest vision, focusing images

Optic Disc

also called the blind spot

Optic Disc

exit point of the optic nerve, contains no rods or cones, cannot detect light

Lens

transparent, flexible, biconvex structure suspended by suspensory ligaments

Lens

fine adjustment of image focusing, changes shape during accommodation

Presbyopia

loss of elasticity with aging in the lens of the retina

Anterior Cavity, Posterior Cavity

Enumerate the Chambers and Humors

Anterior Cavity

contains aqueous humor

Anterior Cavity

nourishes the cornea and lens, maintains intraocular pressure

trabecular meshwork → Canal of Schlemm → venous circulation

Enumerate the drainage pathway of the Anterior cavity

Glaucoma

poor drainage increases intraocular pressure

Posterior Cavity

contains vitreous humor

Posterior Cavity

maintains globe shape, holds retina firmly against the choroid, does not circulate or regenerate