Chapter 15: Special Senses (eye anatomy)

palpebral conjunctiva

A

inner layer

M

rods, cones

What are the 2 types of photoreceptors?

offers protection from foreign objects and spreads secretions to moisten eye

What does reflex blinking do for the eye?

sty

inflammation of any of the smaller sebaceous glands

excretory ducts of lacrimal gland

C

lens fibers

form bulk of lens and are filled with transparent protein crystallin

lacrimal punctum

D

photoreceptors to bipolar cells to ganglion cells to optic nerve

How does the signal spread in the neural layer of the retina?

lacrimal canaliculus

E

nasolacrimal duct

F

conjunctival sac

K

-moves eye laterally -moves eye medially

What is the action of the lateral rectus? medial rectus?

-supplies blood to all layers of eyeball; brown pigment absorbs light to prevent scattering light and visual confusion -control shape of lens which allows for accommodation of the eye

What is the function of the choroid? What is the function of the ciliary muscles?

absorbs light and prevents it from scattering, phagocytizes photoreceptor cell fragments, stores vitamin A

What is the function of the pigmented layer of the retina?

-protects and shapes eyeball, anchors extrinsic eye muscles -forms clear window that lets light enter eye and bends light

What is the function of the sclera? cornea?

lens fibers are continually added

Why do lenses become more dense, convex, and less elastic with age?

lens epithelium

anterior region of cuboidal cells that differentiate into lens fiber cells

cornea

transparent anterior fibrous later of eye

-elevates eye and turns it laterally -depresses eye and turns it laterally

What is the action of the inferior oblique? superior oblique?

lens

biconvex, transparent, flexible, and avascular; changes shape to precisely focus light on retina

diplopia (double vision)

occurs when movements of external muscles of two eyes are not perfectly coordinated

sclera

opaque posterior region of eye; can't see through it, "white" of the eye

Lacrimal secretion (tears)

Dilute saline solution containing mucus, antibodies, and lysozyme

-vascular layer -choroid, cilliary body, iris

Middle pigmented layer of eye, also called uvea What are the 3 regions of this layer?

-special sensory receptors vision, taste, smell, hearing, equilibrium

-What type of receptors do special senses use? -What are the different special senses of the body?

-fibrous layer -sclera, cornea

-outermost layer of eyeball; dense avascular connective tissue -What are the 2 regions?

lacrimal sac

A

photoreceptors, bipolar cells, ganglion cells

What 3 types of neurons is the neural layer of the retina composed of?

vision receptors for bright light; high-resolution color vision

What are some facts about cones?

dim light, peripheral vision receptors; more numerous and more sensitive to light than cones; no color vision or sharp images; numbers greater at periphery

What are some facts about rods?

lens epithelium, lens fibers

What are the 2 regions of the lens?

Choroid supplies outer third (photoreceptors) Central artery and vein of retina supply inner two-thirds

What are the 2 sources of blood supply to the retina?

fibrous layer, vascular layer, inner layer

What are the 3 layers of the eyeball?

eyebrow eyelids conjunctiva lacrimal apparatus extrinsic eye muscles

What are the different accessory structures of the eye?

-close vision and bright light; pupils constrict (diameter decreases) -distant vision and dim light; pupils dilate (diameter increases)

What causes the sphincter pupillae to contract? What does this causes? dilator pupillae?

subject matter is appealing or requires problem-solving skills

What causes to pupils to dilate in regards to changes in the emotional state?

secrete fluid for anterior segment of eyeball

What do the capillaries of ciliary processes do?

-contribute to blinking and tearing reflexes -no (no immune system and can be transplanted without risk of rejection)

What do the pain receptors in the cornea do? Does the cornea have blood vessels?

-accessory structures and eyeball -1/6 -1/2 -fat cushion and bony orbit

What does the eye consist of? What fraction of the eye is visible? How much of the cerebral cortex is involved in visual processing? What is the eye protected by?

tears spread toward medial commissure where they enter the lacrimal canaliculi via lacrimal puncta; tears then drain into the lacrimal sac and then into the nasolacrimal duct, which empties into nasal cavity

What happens to tears when a person blinks?

it swells which constricts ducts and prevents tears from draining (causing "watery" eyes)

What happens to the lacrimal mucosa during a cold/nasal inflammation

-retina -millions of photoreceptor cells that transduce light energy, neurons, glial cells -outer pigmented layer, inner neural layer

What is another name for the inner layer of the eye? What does it contain? What are the 2 layers of the membrane?

-elevates eye and turns it medially -depresses eye and turns it medially

What is the action of the superior rectus? inferior rectus?

hairs that project from eyelids (innervated) that triggers reflex blinking when touched

What is the function of eyelashes?

-overlie supraorbital margins -shade eye from sunlight, prevent perspiration from reaching eye, help with communication/expression

Where are the eyebrows and what are their functions?

-originate from bony orbit and insert on eyeball -follow moving objects, maintain shape of eyeball, and hold it in orbit

Where do the extrinsic eye muscles originate and insert? What do they allow the eye to do?

-originates at common tendinous ring then passes through fibrocartilaginous loop called trochlea and inserts in superolateral part of eye -originates from medial surface and inserts on inferolateral surface

Where does the superior oblique muscle originate and insert? inferior oblique muscle?

strabismus ("cross-eye")

congenital weakness of external eye muscles Eye rotates medially or laterally Eyes may alternate focusing on objects, or only controllable eye is used Brain begins to disregard inputs from deviant eye, which can become functionally blind if not treated early

pinkeye

conjunctival infection caused by bacteria or viruses, highly contagious

lacrimal apparatus

consists of lacrimal gland and ducts that drain into nasal cavity

ciliary zonule

extends from ciliary processes to lens and holds lens in position

chalazion

infected tarsal gland resulting in an unsightly cyst

conjunctivitis

inflammation of the conjunctiva resulting in reddened, irritated eyes

humors

internal cavity filled with fluids in the eye

lacrimal gland

located in orbit above lateral end of eye; secretes lacrimal secretions (tears)

lacrimal caruncle

locating at medial commissure; contains oil and sweat glands

bulbar conjunctiva

membrane that covers white of eyes (not cornea) Small blood vessels found in this membrane; seen easily in "bloodshot" eyes

palpebral conjunctiva

membrane that lines underside of eyelids

tarsal glands

modified sebaceous glands that produce oily secretions that lubricates lid and eye

palpebral fissure

opening between eyelids

choroid

posterior portion of vascular layer

ora serrata

serrated junction between the retina and the ciliary body

pigmented layer of retina

single-cell-thick lining next to choroid; extends anteriorly covering ciliary body and iris

conjunctival sac

space between palpebral and bulbar conjunctiva; area where contact lens rests

tarsal plates

supporting connective tissue that give eyelids shape, as well as anchor orbicularis oculi and levator palpebrae superioris muscles

optic disc

the site where the optic nerve leaves the eye; lacks photoreceptors (the blind spot)

Palpebrae (eyelids)

thin, skin-covered folds that protect eye anteriorly

neural layer of retina

transparent layer that runs anteriorly to margin of ciliary body

conjunctiva

transparent mucous membrane that produces a lubricating muscous secretion

lens

separates internal cavity into anterior and posterior segments

iris

colored part of eye that lies between cornea and lens, continuous with ciliary body (E)

ciliary glands between hair follicles

modified sweat glands of the eye

lacrimal gland

B

ciliary body

anteriorly, choroid becomes this; thickened ring of tissue surrounding lens

pupil

central opening of iris that regulates amount of light entering eye (F)

cataract

clouding of the lens; crystallin proteins clump; consequences of aging, diabetes, mellitus, heavy smoking, frequent exposure to intense sunlight; some congenital; lens can be replaced surgically with artificial lens