Anatomy - Eye

Question 1

Eyelid

Answer 1

• upper and lower
• upper is larger and contains a muscle: levator palpebral superior

CONTENTS

• tarsal plate: fibrocartilaginous
• tarsal glands: secrete oily substances to prevent tears from overflowing
• eyelashes: protect cornea

Question 2

Conjunctiva

Answer 2

• mucous membrane covering eyelids and cornea

- keep the cornea moist

Question 3

Tears

Answer 3

• produced by lacrimnal gland (lateral orbit)
• tear production
• tear flow is across the eye, to canals, sac, duct and cavity

Question 4

External eye clinical issues

Answer 4

• eyelid cyst
• canal block
• infections: conjunctivitis

Question 5

The globe: external tunic

2 parts

Answer 5

Sclera

Cornea

Question 6

The globe, external tunic

1) Sclera

Answer 6

• posterior white fibrous tissue
• lamina cribrosa: where all the optic nerves go through sclera
• Canal of schelmm -> drains aqueaous humor to ciliary veins

FUNCTION

• maintain form of globe
• drain aqueous humor through canal of schlemm

Question 7

The globe: external tunic

2) cornea

Answer 7

• continuous with sclera
• anterior is transparent because of hydration
• avascular/lymph-free
• nourished by aqueous humour

FUNCTION

• lets light in
• focus light on retina

Question 8

The globe: middle tunic

3 parts

Answer 8

• choroid
• ciliary body
• iris

Question 9

The globe: middle tunic

1) Choroid

Answer 9

• highly vascular
• very pigmented
• sclera is loose, retina is tight

FUNCTION

• blood supply to retina
• abosrb light

Question 10

Clinical issues with external tunic of globe

Answer 10

• blocked canal of schlemm can result into increase pressure and glaucoma
• corneal transplants
• corneal reflex can test integrity of nerves V and VII
• retinal detachments between choroid and retina

Question 11

Middle tunic of globe

2) Ciliary body

Answer 11

• Continuous with choroid anteriorally and iris posteriorally
• ciliaris muscle
• suspensory ligament

FUNCTION

• suspend lens (accomodation) through suspensory ligaments
• makes aqueous hymour

Question 12

Middle tunic of globe: iris

Answer 12

• continous with ciliary body, the other and is free -> pupil
• divides front space into anterior and posterior chambers
• angle of the division is called the iridocorneal angle
• pigment because looking to posterior chooid
• sphinctor pupillae is parasympathetic innervation
• dilatator pupillae is sympathetic innervation

FUNCTION
- light control

Question 13

Clinical issue of middle tunic of globe

Answer 13

• iridocorneal angle is sometimes collapsed and blocks canal of Schlemm -> “closed angle glaucoma:
• albino - no pigment in coroid on iris
• Pupillary reflex: II and III

Question 14

Reflexes for different parts of brainstem

Answer 14

• reflex for medulla: gag reflex
• reflex for pons: corneal reflex (V, VII)
• reflex for midbrain: pupillary reflex (II, III)

Question 15

Internal tunic: retina

Answer 15

• part of the CNS, direct outgrowth of thalamus

- light sensitive: photoreceptors

Question 16

Inner core of globe: 3 parts

Answer 16

• aqueous humour
• vitreous humor
• lens

Question 17

• Inner core: 1) aqueous humor

Answer 17

• anterior-posterior chambers
• fluid full of aa, glucose and ascorbic acid

FUNCTION

• nourish avascular bits and lens
• maintain intraocular pressure

Question 18

• inner core of globe

2) vitreous humour

Answer 18

• in vitreal chamber
• transparent gel made of water, salts and glycoprotein

FUNCTION
- structurally supports lens/retina

Question 19

Inner core of globe

2) lens

Answer 19

• avascular
• suspended by suspensory ligament (attach to ciliary process)

FUNCTION

• focus on retina - accomodation - by ciliary muscle
• when suspensory ligaments pull - flat lens -> see in distance
• when suspensory ligament relaxes -> fat lens (short distance)

Question 20

Clinical issues for inner core of globe

Answer 20

• lens becomes less elastic
• cataracts
• vitreal detachment - problematic if takes retina with it

Question 21

3 types of muscles in the eye

Answer 21

• recti
• obliques
• levator

Question 22

REcti muscles

Answer 22

• Superior, inferior, medial and lateral recti
• origin: common tendinous ring (attach to sphenoid bone)
• insertion: globe

Question 23

Oblique muscles

Answer 23

SUPERIOR OBLIQUE

• origin: sphenoid
• insertion: upper lateral globe

INFERIOR OBLIQUE

• origin: maxilla
• insertion: globe (lower-lateral)

Question 24

Levator muscles

Answer 24

• levator palpebran superior
• on top of all
• origin: sphenoid
• insertion, eyelid

Question 25

Individual muscle movement - SR - IO - LR - MR - IR - SO - LPS

Answer 25

- SR: up, intorsion, adduction - IO: up, extorsion, abduction - LR: abduction - MR: adduction - IR: down/extorsion/adduction - SO: down/intorsion/abduction - LPS: raise eyelid

Question 26

Clinical issue of eye muscles

Answer 26

- hard to test individually - the trick is to get the muscle to act by itself by aligning the axes 1) adduct or abduct eye 2) test up and down

Question 27

Motor nerve supply - oculomotor - trochlear - abducent

Answer 27

- oculomotor: SR, IR, MR, IO, LPS - trochlear: SO - abducent: LR

Question 28

Sensory nerve supply

Answer 28

- optic: retina | - ophtalmic (V1): eye and surrounds

Question 29

Autonomic innervation - parasympathetic - sympathetic

Answer 29

PARASYMPATHETIC - oculomotor preganglion synapse into ciliary ganglion: sphincter pupillae, ciliary body - facial preganglion synapse into pterygopalatine ganglion: lacrimal gland SYMPATHETIC - superior cervical ganglia: dilatator pupillae, LPS, lacrimal gland