Anatomy - Eye Flashcards
Eyelid
- 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
Conjunctiva
- mucous membrane covering eyelids and cornea
- keep the cornea moist
Tears
- produced by lacrimnal gland (lateral orbit)
- tear production
- tear flow is across the eye, to canals, sac, duct and cavity
External eye clinical issues
- eyelid cyst
- canal block
- infections: conjunctivitis
The globe: external tunic
2 parts
Sclera
Cornea
The globe, external tunic
1) Sclera
- 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
The globe: external tunic
2) cornea
- continuous with sclera
- anterior is transparent because of hydration
- avascular/lymph-free
- nourished by aqueous humour
FUNCTION
- lets light in
- focus light on retina
The globe: middle tunic
3 parts
- choroid
- ciliary body
- iris
The globe: middle tunic
1) Choroid
- highly vascular
- very pigmented
- sclera is loose, retina is tight
FUNCTION
- blood supply to retina
- abosrb light
Clinical issues with external tunic of globe
- 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
Middle tunic of globe
2) Ciliary body
- Continuous with choroid anteriorally and iris posteriorally
- ciliaris muscle
- suspensory ligament
FUNCTION
- suspend lens (accomodation) through suspensory ligaments
- makes aqueous hymour
Middle tunic of globe: iris
- 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
Clinical issue of middle tunic of globe
- 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
Reflexes for different parts of brainstem
- reflex for medulla: gag reflex
- reflex for pons: corneal reflex (V, VII)
- reflex for midbrain: pupillary reflex (II, III)
Internal tunic: retina
- part of the CNS, direct outgrowth of thalamus
- light sensitive: photoreceptors
Inner core of globe: 3 parts
- aqueous humour
- vitreous humor
- lens
- Inner core: 1) aqueous humor
- anterior-posterior chambers
- fluid full of aa, glucose and ascorbic acid
FUNCTION
- nourish avascular bits and lens
- maintain intraocular pressure
- inner core of globe
2) vitreous humour
- in vitreal chamber
- transparent gel made of water, salts and glycoprotein
FUNCTION
- structurally supports lens/retina
Inner core of globe
2) lens
- 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)
Clinical issues for inner core of globe
- lens becomes less elastic
- cataracts
- vitreal detachment - problematic if takes retina with it
3 types of muscles in the eye
- recti
- obliques
- levator
REcti muscles
- Superior, inferior, medial and lateral recti
- origin: common tendinous ring (attach to sphenoid bone)
- insertion: globe
Oblique muscles
SUPERIOR OBLIQUE
- origin: sphenoid
- insertion: upper lateral globe
INFERIOR OBLIQUE
- origin: maxilla
- insertion: globe (lower-lateral)
Levator muscles
- levator palpebran superior
- on top of all
- origin: sphenoid
- insertion, eyelid
Individual muscle movement
- SR
- IO
- LR
- MR
- IR
- SO
- LPS
- SR: up, intorsion, adduction
- IO: up, extorsion, abduction
- LR: abduction
- MR: adduction
- IR: down/extorsion/adduction
- SO: down/intorsion/abduction
- LPS: raise eyelid
Clinical issue of eye muscles
- 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
Motor nerve supply
- oculomotor
- trochlear
- abducent
- oculomotor: SR, IR, MR, IO, LPS
- trochlear: SO
- abducent: LR
Sensory nerve supply
- optic: retina
- ophtalmic (V1): eye and surrounds
Autonomic innervation
- parasympathetic
- sympathetic
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
