VISION part II Flashcards by Kimberly Cambia

the act of seeing, is extremely important to human survival
more than half the
sensory receptors in the human body are located in the eyes, and a large part of the cerebral
cortex is devoted to processing visual information

VISION

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what are the accessory structures of the eye

eyelids, eyelashes, eyebrows, lacrimal apparatus, extrinsic eye muscles

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protect the eyes from foreign objects, from
perspiration and direct rays from the
sun

EYEBROWS AND EYELASHES

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shades the eyes
during sleep
also, it protect the eyes
from excessive light and foreign
objects, and spread lubricating
secretions over the eyeballs.

UPPER AND LOWER EYELIDS (PALPEBRAE)

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LEVATOR PALPEBRAE SUPERIORIS MUSCLE

PALPEBRAL FISSURE - lateral and medial commissure
TARSAL PLATE

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narrower and closer to the temporal bone

LATERAL COMMISSURE

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s broader and nearer the nasal bone

MEDIAL COMMISSURE

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small, reddish elevation
contains oil and sweat glands

LACRIMAL CARUNCLE

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thick fold of connective tissue that gives form and
support to the eyelids

TARSAL PLATE

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row of elongated modified sebaceous glands that secrete a fluid that helps keep
the eyelids from adhering to each other

TARSAL GLANDS or MEIBOMIAN GLANDS

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thin, protective mucous membrane composed of nonkeratinized stratified squamous epithelium with numerous goblet cells that is supported by
areolar connective tissue

CONJUNCTIVA

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lines the inner aspect of the eyelids

PALPEBRAL CONJUNCTIVA

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passes from the eyelids onto the surface of the eyeball, where it covers the sclera but not the cornea

BULBAR CONJUNCTIVA

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is a group of structures that produces and drains lacrimal fluid or tears

LACRIMAL APPARATUS

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production of tears of lacrimal fluid is a process called

LACRIMATION

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It is about the shape & size of an almond, secretes lacrimal
fluid which drains into 6-12 excretory lacrimal ducts.

LACRIMAL GLAND

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opening
These are 2 small openings in each of
the papilla of the eyelid at the midline commissure of the eye

LACRIMAL PUNCTA/PUNCTUM

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These are 2 small ducts connected with to each
lacrimal punctum

LACRIMAL CANALS/CANALICULI

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It is the expanded portion of the nasolacrimal duct

LACRIMAL SAC

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It carries the lacrimal fluid into the nasal cavity

NASOLACRIMAL DUCT

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produced is a watery solution containing salts, some mucus, and lysozyme

LACRIMAL FLUID

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protective bactericidal enzyme

LYSOZYME

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each gland produces __ ml of lacrimal fluid per day

1 ML

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PHYSIOLOGY OF TEAR PRODUCTION

STRONG EMOTIONS/IRRITATING SUBSTANCES
increases parasympathetic
stimulation
Stimulates production of lacrimal fluid by the lacrimal gland
passes thru the lacrimal ducts
spills over the eyelids
spreads over the surface of the eyeball
enters the lacrimal punctum
passes thru the superior and inferior lacrimal
canal
lacrimal sac
nasolacrimal duct
nasal cavity

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- eyes sit in the bony depressions of the skull called

ORBITS

6 EXTRINSIC EYE MUSCLES

- 4 STRAIGHT RECTI MUSCLES - 2 OBLIQUE MUSCLES

turns the eye upward

- SR (superior rectus) - OCULOMOTOR

turns the eye downward

- IR (inferior rectus) - OCULOMOTOR

turns the eye toward midline

MR (midline rectus) - OCULOMOTOR

turns the eye towards lateral side

LR (lateral rectus) - ABDUCENS

they preserve rotational stability of the eyeball

2 oblique muscles

rotates the eyeball so the cornea turns in a downward & outward direction

superior oblique (trochlear)

rotates the eyeball so the cornea turns in a upward & outward direction

inferior oblique (oculomotor)

EYEBALL is also called as

BULBUS OCULI

spherical in shape - It measures about 2.5 cm (1 inch) in diameter - Of its total surface area, only the anterior 1/6 is exposed

EYEBALL

the bony pyramidal shaped cavity of the skull that holds the eyeball

ORBIT

3 LAYERS OF EYEBALL

- FIBROUS TUNIC - VASCULAR TUNIC (UVEA) - NERVOUS TUNIC (RETINA)

- is the superficial layer of the eyeball and consists of the anterior cornea and posterior sclera outer layer - It is AVASCULAR

FIBROUS TUNIC

is a transparent coat that covers the colored iris. It is located on the anterior portion and has no capillaries

CORNEA

outer surface of cornea consists of

nonkeratinized stratified squamous epithelium

middle surface of cornea consists of

collage fibers, fibroblasts

inner surface of cornea consists of

squamous simple epithelium

- is the “white” of the eye, is a layer of dense connective tissue made up mostly of collagen fibers and fibroblasts

SCLERA

- opening located at the junction of the sclera and cornea. - Aqueous humor (a fluid), drains into this sinus

CANAL OF SCHLEM

FIBROUS TUNIC has 3 parts

- cornea - sclera - canal of schlem

is the middle layer of the eyeball. It contains lots of blood vessels

VASCULAR TUNIC/UVEA

posterior portion of the vascular tunic, lines most of the internal surface of the sclera. Its numerous blood vessels provide nutrients to the posterior surface of the retina

CHOROID

Choroid contains ____________ that produce pigment for melanin

MELANOCYTES

absorbs stray light rays, which prevents reflection and scattering of light within the eyeball.

MELANIN

is the anterior portion of the vascular layer. It is the thickest portion of the vascular tunic which extends from the ORA SERRATA

CILLIARY BODY

- the jagged anterior margin of the retina

ORA SERRATA

protrusions or folds on the internal surface of the ciliary body

CILIARY PROCESS

what do you call the suspensory ligaments that attach to the lens

ZONULAR FIBERS

circular band of smooth muscle. Contraction or relaxation of the ciliary muscle changes the tightness of the zonular fibers, which alters the shape of the lens, adapting it for near or far vision

CILIARY MUSCLE

DISTANT VISION

lens are relatively flat

DISTANT VISION - physiology

When the ciliary muscles are relaxed, the suspensory ligaments of the ciliary body maintain elastic pressure on the perimeter of the lens, keeping it relatively FLAT, allowing for distant vision

NEAR VISION

lens bulges/increases in its curvature

NEAR VISION - PHYSIOLOGY

When an object is brought closer than 20 ft to the eyes, the ciliary muscles contract as a result of parasympathetic stimulation, pulling the ciliary body toward the lens - this reduces tension on the suspensory ligaments of the lens, allowing the lens to assume a more spherical form

It is flexible, biconvex, transparent disc (crystal-clear). It is located just posterior to the pupil and iris.

LENS

- the lens is made up of

65% of water 35% of CHON

proteins found in the lens, arranged like the layers of an onion, make up the refractive media of the lens, which normally is perfectly transparent and lacks blood vessels

CRYSTALINS

MAIN FUNCTION OF LENS

PRINCIPAL REFRACTIVE MEDIUM

THE ANTERIOR CAVITY OF LENS IS FILLED WITH ______

AQUEOUS HUMOR

ANTERIOR CAVITY consists of two chambers

1. anterior chamber - lies between cornea and iris 2. posterior chamber - lies behind the iris and in front of the zonular fibers and lens

what if the normal IOP

16mmHg

PRODUCTION and DRAINAGE of the AQUEOUS HUMOR

 It is produced by the CHOROID PLEXUS (a network of capillaries)  Aqueous humor continually filters out of blood capillaries in the ciliary processes of the ciliary body and enters the posterior chamber.  It then flows forward between the iris and the lens, through the pupil, and into the anterior chamber.  From the anterior chamber, aqueous humor drains into the scleral venous sinus (canal of Schlemm) and then into the blood.  Normally, aqueous humor is completely replaced about every 90 minutes.

- LARGE CAVITY OF EYEBALL

POSTERIOR CAVITY

POSTERIOR CAVITY IS FILLED WITH

VITREOUS HUMOR

composed of 99% water, it is transparent, jelly-like substance. Also, contains phagocytic cells that remove debris, keeping the post cavity clear

VITREOUS HUMOR

narrow channel that runs thru the vitreous body from the optic disc to the posterior aspect of the lens

HYALOID CANAL

colored portion of the eyeball, is shaped like a flattened donut

IRIS

IRIS IS MADE UP OF CONTRACTILE MUSCLES THAT SURROUND AN OPENING CALLED

PUPIL

PRINCIPAL FUNCTION OF IRIS

regulate the amount of light entering the eyeball through the pupil, the hole in the center of the iris

2 TYPES OF MUSCLES IN THE IRIS

1. CIRCULAR MUSCLES or SPHINCTER PUPILLAE 2. RADIAL MUSCLES or DILATOR PUPILLAE

if bright light, which muscles contract?

the circular muscles contract, thus constriction of pupils

if dim light, which muscles contract?

the radial muscles contract, thus dilation of the pupils

as light intensity increases, the pupil _____

decreases in diameter/CONSTRICTS

as light intensity decreases, the pupil ______

increases in diameter/DILATES